Energy and the New Reality, Volume 1: Energy Efficiency and the Demand for Energy Services Chapter...

Energy and the New Reality, Volume 1:

Energy Efficiency and the Demand for Energy Services

Chapter 4: Energy Use in Buildings

L. D. Danny Harveyharvey@geog.utoronto.ca

This material is intended for use in lectures, presentations and as handouts to students, and is provided in Powerpoint format so as to allow customization for the individual needs of course instructors. Permission of the author and publisher is required for any other usage. Please see www.earthscan.co.uk for contact details.

Publisher: Earthscan, UKHomepage: www.earthscan.co.uk/?tabid=101807

Overview

• Kinds of buildings, breakdown of energy use in different kinds of buildings in different climates

• Role of building shape, orientation, size and clustering (multi-unit vs single unit, multi-story vs single story, self shading)

• Building thermal envelope (insulation, windows, doors and air tightness)

• Heating • Cooling • HVAC systems

Overview (continued)

• Hot Water• Lighting• Appliances, consumer electronics, office

equipment• Embodied energy• Building design process• Examples of exemplary buildings from around

the world

This Chapter covers all forms of passive solar energy (for heating, cooling, ventilation, and

daylighting), but does not cover active forms of solar energy, namely:

• Photovoltaic (PV) systems mounted on buildings, and building-integrated photovoltaic (BiPV) systems (covered in Volume 2, Chapter 2)

• Solar thermal collectors for heating, hot water, and cooling (covered in Volume 2, Chapter 2)

• Seasonal storage of solar thermal energy as part of district heating and cooling systems (covered in Volume 2, Chapter 11)

OVERVIEW OF ENERGY USE IN BUILDINGS

Figure 4.1a Residential Energy Use in the US in 2001

Figure 4.1b Residential Energy Use in the EU-15 in 1998

Space Heating

57%Water Heating

Lighting and Appliances

Cooking7%

Figure 4.1c Residential Energy Use in China in 2005

Space Heating36%

Water Heating25%

Lighting9%

Cooking6%

Appliances15%

Air Conditioning4%

Other5%

Figure 4.2a Commercial Building Energy Use in the US in 2003

Water Heating8%Cooling

Ventilation7%

Lighting21%

Cooking3%

Refrigeration 6%Space Heating

Office Equipment 1%

Computers2% Other

Figure 4.2b Commercial Building Energy Use in the EU-15 in 1998

Space heating

Water heating

Lighting14%

Cooking5%

Cooling4%

Other16%

Figure 4.2c Commercial Building Energy Use in China in 2005

Space Heating38%

Water Heating18%

Lighting & Other29%

Cooling15%

Supplemental figure: Average energy intensity of commercial buildings in different countries in 1990

U.S. Sweden Japan France Denmark Canada

2 /yr)

District HeatOther FuelsOilGasElectric HeatingCooling (HVAC)LightingOther Electricity

Source: Harvey (2006, A Handbook on Low-energy Buildings and District-Energy Systems, Earthscan, London)

BACKGROUND PHYSICS

Processes of Heat Transfer

• Conduction (transfer of molecular energy)

• Convection (movement of air parcels)

• Exchange of air between inside and outside

• Radiative energy transfer

Conduction and Convection

• Rate of heat flow (W/m2) is given by

Qc = (Temperature Difference) x U-value

Qc = (Temperature Difference)/ Resistance (R-value)

U-value has units of W/m2/K (smaller is better)

R-value is the reciprocal of the U-value (larger is better)

Warning to North American readers:

• Insulation and window manufacturers in Canada and the US use non-metric R-values and U-values

• To distinguish between metric and non-metric R-values, the term “RSI-value” is used in Canada (where the “SI” means “système international”)

• Both R-values and RSI-values are printed on insulation packages in Canada

• In Europe, the term RSI is not used, and R-value means the metric value

• US and Canadian window manufacturers (and sales agents!) invariably quote U-values without giving the units, but the non-metric U-values are 5.7 times smaller than the metric U-values and so would appear to be incredibly good if one thought that they were metric U-values

Computing heat flow through wall and window systems

• In computing heat flow through multiple layers in an envelope component (such as the portion of a wall with a particular amount of insulation), add the resistances of the layers to get the total resistance, then take the reciprocal to get the U-value for that component

• The U-value (W/m2/K) times the area of the component (m2) times T (K) gives the rate of heat flow (watts)

• Rate of heat flow times time (in seconds) gives the heat loss (joules)

• To get the average U-value for the various adjacent components, just compute the area-weighted average of the individual U-values

Heat flow through walls: For layers: add resistancesFor adjacent components: add U values (with area weighting)

T o u t

R = 1 /h1

R = 1 /h61 6

U3=k3/D, U4=k4/D, U34=f3U3+f4U4,

where f3 and f4 are area fractions

R34=1/U34

Rtotal = R1 + R2 + R34 + R5 + R6

U-value = 1/RtotalSource of figures: Sherman and Jump (1997, CRC Handbook of Energy Efficiency, CRC Press, Boca Raton)

Heat flow through a double-glazed window

T o ut

T 1 T 2

h o c h c23R 2

h r23h o r

T 3 T 4

h = h + ho oc o r h = h + h23 o23 r23 h = h + hi ic ir

R = 1 /h1 o R = 1 /h3 23 R = 1 /h5 i

R = R + R + R + R + Rtota l 1 2 3 4 5

U -v a lu e = 1 /R tota l

Here, hr23 and hc23 are added together because both processes act overthe entire surface area – no need for weighting by an areal fraction (as in U3 and U4 in the previous slide)

Exchange of air between inside and outside

• The sensible heat content per unit volume (J/m3) of a parcel of density ρ, specific heat cpa (J/kg/K), and temperature T (K) is ρcpaT

• The net rate of heat flow (W) due to a rate of exchange Q (m3/s) of inside and outside air is

Qe=ρcpaQ (Tindoor-Toutdoor)=ρcpaQT

Emission of radiant energy

• All matter above absolute zero in temperature (0 K) emits electromagnetic radiation

• The maximum possible rate of emission of radiant energy is given by the Stefan-Boltzman law,

F = σT4, where σ=Stefan Boltzman constant =5.67 x 10-8 W/m2/K4

• This rate of emission is called blackbody emission

Notes on temperatures and temperature differences

• Temperatures on the Celsius scale are “degrees Celsius’• However, temperature differences are Celsius degrees or

kelvin• ‘kelvin’ also refers to absolute temperatures on the kelvin

scale, but a difference of 1 on the Celsius scale is the same as a difference of 1 on the kelvin scale – so a difference of one Celsius degree is the same as 1 K

• You should write, for example: 26ºC – 22ºC = 4 K• Thus, the U-value has units of W/m2/K – you are supposed

to know from your physical understanding that the K refers to temperature differences, not absolute temperatures

• However, the Stefan-Boltzman constant has units of W/m2/K4 – here K refers to absolute temperature, because emission of radiation depends on absolute temperature

Notes on temperatures and temperature differences (continued)

• The proper convention is to write ‘kelvin’ with lower-case letters (just like for ‘watts’ and ‘joules’) and to use upper case for the shorthand (oC, K, J, W). The exception is ‘Celsius’, where upper case C is used. Note that it is incorrect to say or write ‘degrees kelvin’.

• The term ‘centigrade’ has long since been abolished

Figure 4.3 Blackbody Radiation

0.1 1.0 10.0 100.0

Wavelength (mm)

Solar Radiation (left scale) Extraterrestrial Surface (1.5 atm)

BlackbodyRadiation(right scale):

RelativeSensitivity of Human Eye 50oC

Emission of radiant energy (continued)

• The sun emits radiation almost exclusively at wavelengths < 4 μm (1 μm=10-6 m)

• Objects at typical Earth-atmosphere temperatures emit radiation almost exclusively at wavelengths > 4 μm

• Actual total emission (W/m2) is given by the blackbody emission times the emissivity ε:

E =εσT4

• The absorption of infrared radiation is equal to the incident infrared flux times the absorptivity, but because absorptivity=emissivity (Kirchoff’s Law), absorption equals incident flux times emissivity

Supplying heat to a room

• Heat is supplied to a room if air entering the room (from a heating vent) is warmer than air leaving the room, or if hot water entering a radiator is warmer than the water leaving the radiator

• The rate at which heat is supplied to the room is equal to the rate at which heat is lost from the ventilation airflow or from the water circulating through a radiator. This is given by

QH=ρcpQ (Tsupply-Treturn)=ρcpQT

where Q is the volumetric rate of flow (m3/s) of air or water• For a given flow rate and temperature drop, 3333 times more heat is

delivered by circulating warm water through a radiator than by circulating warm air

Energy Required to Move Air or Water

• Rate at which energy must be imparted (power) to the moving fluid is:

Pfluid= P Q, but P varies with Q2 for turbulent flow, so

Pfluid α Q3

• Electrical power requirement for fixed-speed motors

Pelec= Pfluid/(ηmηp) α Q3/(ηmηp)

• Electrical power requirement for variable-speed motors

Pelec= Pfluid/(ηVSDηmηp)

Based on the cubic law (whereby the power that must be supplied to a fluid varies with Q3):

• Cutting the flow rate in half would seem to cut the required power by a factor of 8

• However, the efficiencies of motors and pumps decrease at lower flows, so the reduction is more like a factor of 6-7

• This assumes that what the system is trying to do decreases in proportion to the required power input to the fluid (Pfluid)

• However, a common procedure is for a pump or fan system to operate at full power irrespective of the actual requirements, and to throttle (restrict) the flow if less flow is actually needed

Figure 4.6 Variation of fan or pump power with flow, usingvarious methods to reduce the rate of flow

0 10 20 30 40 50 60 70 80 90 100

%Peak Flow

PumpsInlet Vane

Throttle Valve

Outlet Damper

Cubic Law

The ratio of energy used circulating air or water to heat energy released (to a room) by the circulating air or water is

R = ∆P/ρcp∆T

For the given ρ and cp of air and water, and for typical ∆P and ∆T values of air vs hydronic (water-based) systems, it takes about 25 times less energy to deliver a given amount of heat by circulating warm water than by circulating warm air

Definitions• Sensible heat – heat that can be felt as warmth• Latent heat – heat that is released when water vapour

condenses (or that is absorbed when liquid water evaporates)• Absolute vapour pressure (ea) – the partial pressure of the

water vapour in the air• Saturation vapour pressure (es) – the partial pressure of water

vapour in the air when the air is saturated (unable to hold any more water vapour)

• Relative humidity – ratio of actual to saturation vapour pressures (multiplied by 100 to give as a percent). RH(%) = ea/es x 100%

• Mixing ratio – the ratio of mass of water vapour in an air parcel to mass of dry air

Saturation vapour pressure increases sharply with increasing temperature:

0 10 20 30 40

Temperature (oC)

The mixing ratio (mass of water vapour over mass of dry air) is proportional to the ratio of the

pressures of water vapour and dry air,

r = 0.622 ea/(Pa-ea)

(Pa = total atmospheric pressure, Pa-ea is the pressure of the dry air alone) but it is more

convenient to use graphs with r rather than ea on the vertical axis, because r is unchanged when an air parcel cools whereas ea decreases slightly as T

decreases

Supplemental Figure: plot of saturation mixing ratio and mixing ratio at various relative humidities on a T-mixing ratio graph

0 10 20 30 40 50

Temperature (oC)

100%RH 60% RH 40%RH

The sensible and latent heat contents of a parcel of air are given by

H=cpaT+rcpwvT

respecitevly, where cpa and cpwv are the specific heats (J/kg/K) of dry air and water vapour, respectively, r is the water vapour mixing ratio, and Le is the latent heat of condensation (J/kg). The latent plus sensible heat is called the enthalpy.

More definitions:

• Drybulb temperature – the temperature of the air (measured with a dry thermometer)

• Wetbulb temperature – the temperature that the air acquires when liquid water is allowed to evaporate into the air until the air is saturated and the remaining liquid and air have adjusted (equilibrated) to have the same temperature (it is the same as the temperature measured with a wet thermometer)

• Dewpoint temperature – the temperature at which condensation begins when an air parcel is cooled with fixed water vapour mixing ratio

0 5 10 15 20 25 30 35 40 45 50

Dry Bulb Temperature (oC)

100%RH 60%RH 40%RH

Dewpoint Temperature

Wetbulb Temperature

•Drybulb (actual)temperature

Lines of constant enthalpy

••

Figure 4.7 Psychrometric chart

Conventional dehumidification process

0 5 10 15 20 25 30 35 40 45 50

100%RH 60%RH 40%RH

Cooling to the dewpoint temperature

Condensation from over cooling

Reheating

Adaptive Thermal Comfort

• The temperature that appears to be comfortable depends on how hot or cold it is outside (which conditions our expectations)

• Thus, the temperature down to which a building is air conditioned can be increased on hotter days

Figure 4.8 Proposed Range of Thermostat Temperature Settings – varying with the outdoor temperature

0 5 10 15 20 25 30 35 40

Mean Monthly Outdoor Air Temperature (oC)

95867768595041

90% acceptability limits

80% acceptability limits

Source: Brager and de Dear (2000, ASHRAE Journal 42, 10, 21–28)

REDUCING HEATING ENERGY USE

• Reduce the heat load (the amount of heat that needs to be provided)

• Provide the required heat as efficiently as possible

Thermal Envelope

• Insulation

• Windows and doors

• Curtainwalls in commercial buildings

• Air leakage

• Double skin façades

As noted above,

• Heat flow across a window or wall varies with ΔT/R

• R (or RSI) in turn varies with the thickness D of the insulation: R = D/k, where k is the thermal conductivity (W/m/K) of the insulation

• The total R (or RSI) value of a wall is just the sum of the R’s of each layer

• Uoverall=1/Rtotal (has units W/m2/K)

Figure 4.9 Wall and Ceiling Heat Loss

0 10 20 30 40 50 60

R-Value

Walls at R12 (RSI 2.1, U=0.47 W/m2/K)

Walls at R20 (RSI 3.52,U=0.28 W/m2/K)

Roof at R32 (RSI 5.6,U=0.18 W/m2/K)

Walls (R40, RSI 7.0)Roof (R60, RSI 10.6)Advanced House:

RSI-Value

0 2 4 6 8 10

The heating requirement is the residual (or difference) between heat loss, useful passive heat gain, and useful internal heat gain – so a given percentage reduction in heat loss has a disproportionately larger effect in reducing the heating requirement

Greater sensitivity of heating requirement than ofheat loss to changes in the amount of insulation

Source: Danny Harvey

120100 unitsheat loss

Passive Heat Gain

Internal Heat Gain

80 units heatingrequirement

50 unitsheat loss

30 unitsheating requirement

Types of insulation

• Glass fibre (fibreglass) batts• Mineral fibre batts (roxul)• Cellulose – blown in or spray-on• Foam – solid panels or spray-on• Wood fibre (e.g., hemp)• Vacuum insulation panels

Issues with regard to insulation

• Thickness• Cost• Thermal bridges, gaps• Embodied energy (the energy required to make

it – not negligible for all except cellulose and wood-fibre insulation)

• Leakage of halocarbon blowing agents for foam insulation (HFCs vs CO2, H2O, or pentane as blowing agents)

• Degradation over time (for HFC-blown foam insulation)

Figure 4.10 Engineered Wood – reduces thermal bridges, has strength equal to a rectangular

joist with the same outside dimensions

Source: The Engineered Wood Association (www.apawood.com)

Vacuum insulation panels

• Thermal conductivity is ~ 1/10 that of plastic foam, fibreglass, or cellulose insulation (all of which have a similar thermal conductivity)

• Thus, a 1-cm thick panel gives the same resistance to heat flow as 10 cm of regular insulation

• Ideal where space is tight• Large market in Switzerland for insulating roof-top

decks without requiring a step between the inside and outside

• Also used in doors and super-low energy refrigerators and freezers

• Also about 10x the cost of regular insulation

Figure 4.11: Niche application of vacuum-insulation panels in Europe

Normal insulationthickness

Solid foaminsulation

Interiorwallboard

Vacuuminsulation

Cavity forretractedexternal

Retracted external

Triple-glazedwindow

Grundschule am Reidburg, Frankfurt (illustrating external blinds, not necessarily with VIP)

Figure 4.12 Prefabricated VIP Wall

Source: Binz and Steinke (2005, 7th International Vacuum Insulation Symposium, EMPA, Duebendorf, Switzerland, www.empa/ch/VIP-Symposium)

VIPs in prefabricated roof units

Reducing the heat loss through windows

• Extra glazing (glass) layers• Low-emissivity (low-e) coatings• Inert gas between glazings (Ar, Kr, Xe)• Vacuum between glazing layers• Highly insulating frame• Airtight

Benchmark

• A single-glazed, non-coated window has a U-value of about 5 W/m2/K – so the rate of heat loss is 200 W/m2 when the outdoor temperature is -20ºC and the indoor temperature is +20ºC

• The best commercially-available high-performance window will have a centre-of-glazing U-value of 0.5 W/m2/K – so the heat loss will be a factor of 10 smaller!

The normal practice in building design is to place the heaters or warm-air vents below the window. This is because normally there is large heat loss from the window, so heating at the base of the window

• Keeps the window warm, thereby avoiding radiant asymmetry

• Prevents drafts • Prevents condensation on the window

With high performance windows, the heat loss is so low that the heaters can be placed on the side of the room near the core of the building, thereby reducing costs (and reducing heat loss even further)

Figure 4.13 Required window U-value at which perimeter heating can be eliminated as a function

of the coldest designed-for temperature

-30 -20 -10 0 10

Design Temperature (oC)

Perimeter HeatingNot Needed

Perimeter HeatingNeeded

Penetration of solar energy through a window

• Direct transmission of solar radiation• Partial absorption of solar radiation by the glazing layers,

warming up the layer and

- causing re-emission (by the inner glazing surface, toward the inside) of some of the absorbed solar radiation as infrared radiation

- reducing the conduction heat flow from the room to the glazing surface, by reducing the temperature difference the room air temperature and the window glazing temperature (in fact, if the window glazing becomes warmer than the inside air, heat will flow into the room)

Solar heat gain coefficient (SHGC) or g-value (in Europe)

• accounts for both the direct effect (reduced transmission) and indirect effect (re-emission of IR radiation into the room and reduced conductive heat loss) of extra glazing layers or added coatings

• For uncoated double-glazed windows, SHGC = 0.7 and U-value = 2.5 W/m2/K

• Windows can be engineered to have

-a SHGC of 0.23 with a U-value of 0.4 W/m2/K, or

-a SHGC of 0.60 and a U-value of 0.7 W/m2/K

Solar radiation• Divided into three parts - Ultraviolet (minor) - Visible (0.4-0.7 μm wavelength) - Near infrared (NIR) (0.7-4.0 μm)• Roughly half of the solar energy reaching the ground is

in the visible and half in the NIR• Windows having a SHGC of ~ 0.25 have roughly 50%

transmittance in the visible and zero transmittance in the NIR, so there is still plenty of light for daylighting while greatly reducing heat gain and the resulting air conditioning requirements in the summer

Double-skin façades

• Consist of an outer glass façade and an inner façade (which could also be largely glass) separated by an air layer that is not actively heated or cooled

• Contain adjustable shading devices in the gap between the two façades

• Permit passive ventilation (through operable windows) even in very high buildings

• Solve the problem of overheating in highly glazed buildings, especially for west-facing facades

• Do not eliminate the need to limit the glazing (window) fraction (generally to no more than 0.4-0.6) in order to optimize the overall design from an energy point of view

Box window DSF

Source: Oesterle et al (2001), Double Skin Facades, Feustel, Munich

Fish-mouth DSF

Source: Baird (2001), The Architectural Expression of Environmental Control Systems, Spon Press, UK

DSF example from Berlin

Figure 4.14 Daimler Chrysler Bldg

Corridor DSF, Genzyme Headquarters,

Boston

Corridor DSF, Centre for Cellular and Molecular Biology, University of Toronto

Source: Sandy Kiang,Toronto

Impact of Increasing Glazing Fraction• Increasing conductive heat loss in winter – the very best windows

have a U-value of 0.5 W/m2/K, while so-called “energy efficient” windows (double glazed windows, low-e, argon fill) have U ~ 1.5 W/m2/K, compared to 0.25 W/m2/K for typical insulation levels in cold climates and 0.1 W/m2/K or less in super-insulated buildings

• Increasing passive solar heat gain – but useful only up to a point, and more useful if there is thermal mass to absorb the heat by day and slowly release it at night

• Increasing daylight, but useful only up to a point and only if the electric lighting can automatically dim down if there is more daylight

• Increasing problem of heat gains in summer (exacerbated by the usual absence of thermal mass and external shading)

• The negative impacts can only be partly compensated by specifying high-performance glazing

Figure 4.15 Impact of increasing the glazing fraction (shown as the % below each bar) and choice of windows (either “base” or “upgraded”) an energy use in Swedish Offices

30% Base 60% Base 60% Upgraded

100% Base 100% Upgraded

Heating Cooling LightingEquipment Pumps & fans Server rooms

Figure 4.16 Impact of house size on heating requirement in Boston in comparison to thermal envelope characteristics

Small, Poor Small, Moderate

Large, Moderate

Cooling

Heating

Poor: R13 walls, R19 attic, R2.1 doors, SG windows, uninsulated ductsModerate: R19 walls, R30 attic, R4.4 doors, R6 ducts, DG low-e windows

Figure 4.17 Annual heat loss (kWh per m2 of floor area per year) for a detached house or apartment building in Stockholm, and the associated

U-values for different thermal envelope elements

Walls Roof Floor Window frame

Window glass

Envelope average

Reference house, 70 kWh/m2/yr

Single-family house at 20 kWh/m2/yr

Apartment building at 20 kWh/m2/yr

Apartment building at 6.5 kWh/m2/yr

As illustrated in the preceding slides,• The impact of about 50% more insulation in US houses

since the 1950s has been more than offset by the effect of larger houses (at least in Boston)

• Decreasing the heating energy requirement from the typical value of 70 kWh/m2/yr for new detached houses in Stockholm to 20 kWh/m2/yr (a factor of 3.5 times less) can be achieved either by decreasing the overall window and wall U-values by about 40%, or by building apartments instead with slightly less stringent U-values than for the original house

• Conversely, if we apply in an apartment the U-values needed to get the detached house down to 20 kWh/m2/yr, the result is a heating energy requirement of 6.5 kWh/m2/yr – about a factor of 10 smaller than for the typical detached house in Stockholm

Heating Systems

• Passive solar• Furnaces• Boilers• Wood-burning stoves• District heating• Electric resistance heating• Heat pumps• On-site cogeneration

Passive Solar Heating

• Direct gain

• Solar collectors

• Air-flow windows

Not all solar gain is usable – some leads to overheating, requiring the windows to be opened

To maximize the useful solar gain, thermal mass (such as concrete or stone) is needed and should be exposed to the indoor air (so minimize interior finishings) (this is the new look anyway in many buildings now)

With thermal mass, absorbed solar energy goes into storing heat with minimal temperature rise (apart from being uncomfortable, high temperatures result in greater radiant and convective heat loss, and thus less heat available for later)

At night, the heat is slowly released when there is high thermal mass. This is adequate if the building is highly insulated with high-performance windows.

If there is too large a glazing fraction (which typically means > 60%), there will be more solar gain than can be used, and greater heat loss at night

Figure 4.18 Example of fan-assisted passive solar heating in a Japanese school

Source: Yoshikawa (1997, CADDET Energy Efficiency Newsletter June, 8–10)

Figure 4.19 Air-flow windows to preheat incoming ventilation air

Figure 4.20: Triple-glazed air flow window serving as a counterflow heat exchanger

Source: Gosselin and Chen (2008, Energy and Buildings 40, 452-458, http://www.sciencedirect.com/science/journal/03787788)

Figure 4.21 Finnish supply-air window

Source: www.domus.fi

Boilers, Furnaces

• Non-condensing, 75-85% full-load efficiency, lower efficiency at part load (which is achieved through on/off cycling)

• Condensing, 88-95% full-load efficiency, greater at part load (which is achieved through modulation of the fuel and air flow) and with lower return temperatures (because more water vapour can be condensed and used to preheat the return water flow)

Figure 4.22 Efficiency of a condensing boiler vs temperature of the water returning to the boiler from the heating loop, and vs load

20 25 30 35 40 45 50 55 60 65 70 75 80 85

Return water temperature (oC)

25% input

50% input

100% input

Source: Durkin (2006, ASHRAE Journal 48, 7, 51–57)

Pellet-burning boilers

• 86-94% efficiency• Have a maximum output as low as 10 kW and

can operate between 30-100% of maximum output (we want the capability for minimal output in super-insulated houses)

• Largest units have 40 kW peak output• Pneumatic delivery of pellets from trucks to

storage bins in houses • Automatic transfer of pellets to the burner and

removal of ash• Common in Austria

Electric Resistance Heating• 100% efficiency at the point of use• Easily controlled – can supply just the amount of heat required and

no more• In super-insulated houses, about 1/3 of the total heat required

comes from waste heat from lighting, appliances and electronic equipment, so a significant fraction of the heating is already electric

• Overall efficiency – including loss at the electric powerplant (which is typically coal fired) and transmission - can be quite low (30-40%)

• However, if electricity is supplied on the margin by renewable electricity at certain times then, in a superinsulated house, one could use electricity for heating only or mostly at those times and let the temperature drift in between

Heat Pumps

• This is an alternative electric heating system• Electricity is used to transfer heat against its

‘will’, from cold to warm• Typically, 1 unit of electricity can provide 3 units

of heat – so this nullifies the losses associated with the roughly 33% overall efficiency in supplying electricity from coal plants at the typical 35-40% generation efficiency

Heat Pump, Operating Principles

• Heat pumps transfer of heat from cold to warm (against the macro temperature gradient)

• At each point in the system, heat flow is from warm to cold

• Heat pumps rely on the fact that a gas cools when it expands, and is heated when it is compressed, creating local temperature gradients contrary to the macro-gradient

Components of a heat pump

• Compressor

• Evaporator

• Condenser

Figure 4.23a Heat pump in heating mode

Indoor a ir(20 C )

B low er

H eated a ir (30 C )

H igh -p re ssure refrigeran t (60 C )

OE x p a n s i o n d e v ic e

C o m p r e s s o r

R e v e r s in g v a lv e

O u t d o o r a ir ( 0 C )

L o w - p r e s s u r er e f r ig e r a n t ( - 1 0 C )

O u t d o o r c o i l a se v a p o r a t o r

R e j e c t a ir ( -5 C )O

I n d o o r c o i l a s c o n d e n s e r

Figure 4.23b. Heat pump in cooling mode

Indoor a ir(25 C )

B low er

C oo led a ir (15 C )

H igh -p re ssure refrigerant (60 C )

E x p a n s i o n d e v ic e

C o m p r e s s o r

R e v e r s in g v a lv e

O u t d o o r a ir ( 3 0 C )

L o w - p r e s s u r er e f r ig e r a n t ( - 1 0 C )

O u t d o o r c o i l a sc o n d e n s e r

R e j e c t a ir ( 3 5 C )O

I n d o o r c o i l a s e v a p o r a t o r

Heat Pump, Efficiency Principles

• The ratio of heat delivered to energy input is called the coefficient of performance (COP)

• The maximum possible COP (called the Carnot cycle COP) is related to the temperature lift, TH-TL, where TH=condenser temp and TL=evaporator temp

COPcooling,Carnot = TL/(TH-TL) COPheating,Carnot = TL/(TH-TL)+1.0

• The actual COP (in the case of cooling) is given by COPcooling, real = ηc (TL/(TH-TL))

where ηc is the Carnot efficiency

Figure 4.24a: Heat Pump COP in heating mode

-20 -15 -10 -5 0 5 10 15

Evaporator Temperature (oC)

50oC70oC

CondenserTemperature:

nc=0.65

Figure 4.24b: Heat Pump COP in Cooling Mode (or chiller COP)

30 35 40 45 50

Condenser Temperature (oC)

10oC5oC

EvaporatorTemperature:

nc=0.65

-5oC-10oC

Figure 4.25: Heat flow, temperature lifts, and COPs of a heat pump in cooling mode

Thus, to reduce heat pump energy use,

• Distribute heat at the lowest possible temperature (e.g., at 30ºC instead of 60ºC – using radiant floor or ceiling heating)

• Distribute coldness at the warmest possible temperature (e.g., at 20ºC instead of 6ºC – using chilled ceiling or chilled floor slab)

• Minimize ΔTH and ΔTL by- minimizing the required heat flows (which must balance heat loss or heat gain, so this means a super-insulated building with high-performance windows)

- using as large a radiator surface as possible

Sources of heat for a heat pump:

• The outside air (gives an Air-Source Heat Pump)• The ground (gives a Ground-Source Heat Pump,

now quite incorrectly called “geothermal heating” by vendors of this equipment)

• The exhaust air (gives an Exhaust-Air Heat Pump – now standard practice for new houses in Sweden) (extracts more heat from the outgoing exhaust air than a simple heat exchanger)

Figure 4.26a Ground Source Heat Pump, horizontal pipes

S upplyRunouts

ReturnRunouts

30 m x 84 mavailable surface area

Source: Caneta Research Inc (1995, Commercial/Institutional Ground-Source Heat Pump Engineering Manual, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta)

Figure 4.26b Ground Source Heat Pump, vertical pipes

15 m x 46 m available surface area

Foundation Wall SupplyRunouts

Return Runouts

Source: Caneta Research Inc (1995, Commercial/Institutional Ground-Source Heat Pump Engineering Manual, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta)

The ground is a better source of heat than the air because, during the winter, the ground might be at 8-10ºC while the outside air is at -20ºC.

Conversely, during the summer the ground will be cooler than the air and so it is a good heat sink

However, if a ground-source heat pump is mostly used for winter heating, the ground will get progressively colder from one year to the next, while if a ground-source heat pump is used mostly for air conditioning, the ground will get progressively warmer over time, in both cases reducing the COP of the heat pump.

Solutions:

• Try to balance winter heating and summer air conditioning loads (by shifting the priorities in the design of the building)

• Circulate hot water from solar thermal collectors to restore ground temperatures during the summer

• Cool the ground down during the winter by circulating some fluid (with antifreeze) between the ground and some sort of heat exchanger in the outside air

The downside of heat pumps is that they have a high upfront cost, although they often pay for themselves over their lifespan (see the RETScreen heat pump module)

A key economic issue will be the ratio of peak heating requirement to average heating requirement (a lower ratio will be more favourable). This will be affected by the character of the envelope, building thermal mass, and the building surface/volume ratio (which is smaller in multi-unit than in single unit residential buildings)

If a building has a high-performance envelope (so that heat is lost or gained slowly) and a high thermal mass (so that the temperature change for a given heat loss is small), then the heating or cooling system can be turned off for some period of time without an important effect on the building temperature.

Thus, if the heating and cooling are provided by electric heat pumps, then we have an electric load that can be ramped up or down to match variations in the supply of C-free electricity.

If we are running a heat pump when, example, there is excess wind-derived electricity supplied to the grid, and not running it at other times, we are in effect using the building thermal mass to store wind energy in the form of useful heat (or coldness during the summer season when the heat pump is used as an air conditioner).

In summary, a high-performance envelope saves fossil fuel energy in 3 ways

• By reducing the heating load (the amount of heat that needs to be provided)

• By increasing the efficiency of a furnace, boiler or (especially) of a heat pump in providing the required heat

• By providing flexibility as to when heat is provided (this flexibility is amplified if the building has a high thermal mass)

REDUCING COOLING ENERGY USE

• Reduce the amount of heat that a building receives, thereby reducing the cooling load (the amount of the heat that needs to be removed)

• Use passive and low-energy techniques to meet as much of the cooling load as possible

• Use efficient equipment and systems to meet the remaining cooling load

Figure 4.27a Cooling load in a Los Angeles office building

Fans13%

People12%

Office Equipment

Windows21%

Walls3%

Roof8%

Fresh Air10%

Lighting28%

Figure 4.27b Cooling load in a typical Hong Kong building

Lighting18%

Fans10%

People27%

Office Equipment

Windows8%

Walls4%

Roof0%

Fresh Air20%

Reducing Cooling Loads

• Building orientation and clustering• High-reflectivity building materials• External insulation• External shading devices• Windows with low SHGC• Thermal mass• Vegetation (provides shading and evaporative

cooling)• Efficient equipment and lighting to reduce

internal heat gains

Thermal Mass

• By itself, does not reduce the cooling load• High thermal mass means that it takes longer for

the building to warm up, but with a prolonged heat wave, a building with high thermal mass eventually heats up (and then will take a long time to cool down)

• However, thermal mass will greatly reduce the temperature increase from morning to late afternoon, so if the night becomes cool enough, night air can be used to remove heat from the thermal mass – so that it does not build up from day to day (or at least not as much)

To most effective, thermal mass needs to be combined with

• External insulation • Night-time ventilation with cool outside air flowing into

the core of the thermal mass (such as hollow concrete slab ceilings or walls)

• In effect, the coldness of the night air is stored and used to keep the building cool during the day

• This of course reduces total energy use but also reduces required peak rates of mechanical cooling – saving on purchase costs for cooling equipment and electrical transformers, and reducing utility charges to meet peak electricity demand

The traditional materials used to add thermal mass are concrete and stone

However, phase change materials can also be used – either as small spheres in regular plaster or in the ventilation air flow. These are waxes that can be designed to melt at, say, 26ºC, absorbing heat in the process and resisting any further increase in air temperature. If the air temperature drops below 26ºC at night, they will refreeze (releasing heat that is taken away with the night-time air flow), ready to absorb heat again the next day. These would be ideal in arid parts of the world (where nights get cold and days are hot)

Figure 4.28 Micro-encapsulated phase-change material (left) and spheres containing phase

change materials in an air flow pipe (right)

Source: Schossig et al (2005, Solar Energy Materials and Solar Cells 89, 297–306, http://www.sciencedirect.com/science/journal/09270248) & Arkar and Medved (2007, Solar Energy 81, 1078-1087, http://www.sciencedirect.com/science/journal/0038092X)

Double skin facades

• Permit adjustable external shading on tall buildings

• Permit day and night ventilation when it would not otherwise be possible

• In so-doing, they can greatly reduce cooling loads

• Design details are important, however

Figure 4.29a Comparison of double-skin façades (DSF) and single-skin façades (SSF) with moderate or high levels of insulation and normal or

optimal ventilation strategies with regard to heating load in a 5-story office building in Belgium

100000

Moderate, SSF Base

Moderate, SSF Opt

Moderate, DSF Opt

High, SSF Base

High, SSF Opt

High, DSF Opt

Figure 4.29b: Comparison of double-skin façades (DSF) and single-skin façades(SSF) with moderate or high levels of insulation and normal

or optimal ventilation strategies with regard to cooling load in a 5-story office building in Belgium

100000

Moderate, SSF Base

Moderate, SSF Opt

Moderate, DSF Opt

High, SSF Base

High, SSF Opt

High, DSF Opt

Lessons on DSFs from the previous slides

• The insulation level is far more important than adding a second skin for the heating load

• The building operating strategy (opening windows when appropriate, and appropriate use of day and night-time ventilation) is far more important than adding a DSF for the cooling load

• If there is already a sensible operating strategy, adding a second facade can increase the cooling load

• However, the second facade may be necessary to permit a sensible operating strategy in the first place (by protecting against wind, noise, dust and intruders (human or animal) with open windows)

• Based on simulations for a 5-story office building in Belgium, the combination of modestly higher insulation levels and modestly better glazing with addition of a second facade and the use of the natural ventilation that it permits reduces heating energy use by ~50% and cooling energy use by ~80%

Low-energy Cooling Techniques

• Natural (passive) ventilation• Hybrid (passive-mechanical) ventilation• Mechanical ventilation at night (combined with

thermal mass and external insulation)• Evaporative cooling• Earth-pipe cooling

Natural driving forces for air flow:

• Wind forcing

• Temperature differences (which create pressure differences)

Wind forcing:

• Cross ventilation

• Wing walls

• Wind catchers

• Wind cowls

Cross-ventilation

Source: Givoni (1998), Passive and Low Energy Cooling of Buildings, von Nostrand Reinhold, New York

Wing walls:

Source: Givoni (1998), Passive and Low Energy Cooling of Buildings, von Nostrand Reinhold, New York

Winds catchers in Iran and Doha

Source: Koch-Nielsen (2002), Stay Cool: A Design Guide for the Built Environment in Hot Climates, James and James, London

Wind catcher at Sir Sanfred Fleming College, Peterborough, Canada

Source: Loghman Azar, Line Architects, Toronto

Airflow at Sir Sanfred Fleming College, Peterborough, Canada

Source: Loghman Azar, Line Architects, Toronto

Wind cowl

Source: www.arup.com

Thermally-driven ventilation

• Atria

• Solar chimneys

• Cool towers

Figure 4.30 Solar chimneys on the Building Research Establishment (BRE) building in Garston, UK

Source: Copyright by Dennis Gilbert, View Pictures (London)

Figure 4.31 Torrent Centre, Ahmedabad, India

Exhaust

ExhaustExhaust

Micrionizers

Exhaust

Offices Laboratories

Source: George Baird (2001, The Architectural Expression of Environmental Control Systems, Spon Press, London)

Figure 4.32 Torrent Centre, Ahmedabad, India

Source: George Baird (2001, The Architectural Expression of Environmental Control Systems, Spon Press, London)

Evaporative Cooling

• Direct – water evaporates into the airstream being cooled, increasing its relative humidity

• Indirect – water evaporates into a secondary airstream (such as exhaust air heading to the outside) but cools the primary airstream (which enters the building) through a heat exchanger without adding moisture to the primary airstream

Figure 4.33: Combined direct-indirect evaporative cooler

Falling film sof water

Dry O utside A ir

Recircu lation of a portionof the pre-cooled outside a ir,m ixed w ith exhaust a ir

Figure 4.34: Indirect+direct evaporative cooling

20 25 30 35 40

100%RH 60%RH80%RH

Indirect evaporativecooling of primaryairstream

Original TwbDirect evaporative

Final Twb

Direct evaporativecooling of primaryairstream

cooling of

secondary

airstream

Figure 4.35: Rooftop (left) and window-mounted (right) direct evaporative coolers from Adobe Air

Source: www.adobeair.com

Earth-pipe cooling

• Ventilation air is first drawn through underground pipes so as to be cooled by the ground

• COP (cooling over fan energy) of 7-50 obtained (depending on ground and air temperatures)

• Airflow can also be driven with solar chimneys

Figure 4.36: Jaer School, Norway – combining solar chimneys and earth-pipe cooling

Source: Schild and Blom (2002, Pilot Study Report: Jaer School, NesoddenMunicipality, Norway, International Energy Agency, Energy Conservation in Buildings and Community Systems, Annex 35, hybvent.civil.auc.dk)

Atria and stair wells can also serve as solar chimneys, driving a natural

ventilation if so-designed

Figure 4.37 Panasonic building in Tokyo – hybrid mechanical/passive ventilation

Source: Nikken Sekkei, Japan

Mechanical cooling equipment

• Air conditioners – directly cool the air, and the condenser is cooled with outside air

• Electric chillers (normally just called “chillers”) – produce cold water, which is circulated through the building, with small chillers having an air-cooled condenser and large chillers having a condenser cooled with water from a cooling tower

• Absorption chillers – use heat to drive a thermodynamic cycle that produces chilled water, with the condenser invariably cooled with water from a cooling tower

The efficiency of air conditioners and chillers is represented by the coefficient of performance (COP), the ratio of cooling provided to energy used by the unit

• Wall-mounted air conditioners, COP = 2.5-3.5 except in Japan, where COP=3.5-6.5

• Electric chillers, COP = 4.0-7.5 (larger units have a higher COP)

• Absorption chillers, COP = 0.6-1.2

Note: for electric chillers, we should multiply the COP times the efficiency in generating electricity to get the COP in terms of primary energy. So, if COP=3.0 and the powerplant efficiency is 0.33, the COP in terms of primary energy is only 1.0 – that is, one unit of primary energy gives one unit of cooling

Absorption chillers:

• Use heat rather than electricity as the energy input to produce cooling

• The COP (cooling provided over heat energy input) is small (0.6-1.2)

• Can use waste heat from cogeneration, but there is a penalty in terms of reduced electricity production

• It is normally better to maximize electricity production and use the extra electricity so-produced in an electric chiller, and throw away the waste heat, rather than to use the waste heat (with reduced electricity output) in an absorption chiller

Figure 4.38: Schematic diagram comparing a vapour-compression chiller (top) and an absorption chiller (bottom)

C om pressor

C ondenserEvaporator

Expansion Valve

H eatA bsorbed

H eatR eleased

Electricity Input

C ondenserEvaporator

Expansion Valve

H eatA bsorbed

H eatR eleased

Water Vapour Water

VapourPum p

H eat R eleased H eat Input

LiquidWater

C oncentrated LiB r

A bsorber G enerator

Figure 4.40 COP of an absorption chiller vs the temperature of the heat used to drive the chiller

60 80 100 120 140 160 180 200 220 240

Heat-source Temperature (oC)

Supply chilled-water temperature: 7.2oC

Supply cooling-water temperature: 29.4 oC

Single-effect

Double-effect

Triple-effect

Source: Lee and Sherif (2001, ASHRAE Transactions 107, 1, 629–637)

Recall: Fig 3.13 – the greater the temperature at which steam is withdrawn from a steam turbine for other purposes, the greater

the loss in electricity production

80 100 120 140 160 180 200 220 240

Steam Temperature (oC)

Source: Bolland and Undrum (1999, Greenhouse Gas Control Technologies, 125-130, Elsevier Science, New York)

Options:• Take 1 unit of heat from a steam turbine at 80ºC – use it in a

single-effect absorption chiller with a COP of 0.7 – will get 0.7 units of cooling

• However, we had to give up 0.11 units of electricity production, which could have been used in an electric chiller with a COP of 5-7.5 and produced 0.55-0.83 units of cooling

• Thus, it is better to maximize electricity production, throw away the remaining waste heat, and use the extra electricity in the best available electric chiller

• As the larger electric chiller COPs pertain to the larger chillers, there may be situations where the COP of the chiller that can actually be used is at the small end of the range given above, in which case the absorption chiller appears to be a better choice

• However, both electric and absorption chillers require additional electricity for pumps and fans, and this auxiliary electricity requirement is greater for absorption chillers – so this shifts the balance in favour of electric chillers

Desiccant cooling systems

• Use a solid or liquid desiccant to remove moisture from the outdoor air supplied to a building

• Then use evaporative cooling to cool the air without making the final relative humidity too large

• Use heat (ideally, from solar thermal panels) to regenerate the desiccant

• In effect, extends evaporative cooling to the hot-humid regions of the world where it otherwise cannot be used because the air is already too humid

Key difference between desiccant and electric (or absorption) chillers:

• In electric or absorption chillers, humidity is reduced by overcooling the air (forcing some water vapour to condense out), then reheating the air

• In a desiccant system, we go directly to the desired final T-humidity combination

• Apart from tending to save energy, avoiding over chilling and reheating is healthier – there are no wet surfaces where moulds and fungi can grow

Impact of desiccant systems on primary energy use

• If the desiccant is regenerated using heat from a boiler – primary energy use can increase or decrease slightly compared to over chilling with large electric chillers and reheating (the COP of desiccant systems today is only about 0.8-1.0, compared 5-7.5 for electric chillers)

• If the desiccant is regenerated using waste heat from micro-turbine cogeneration, there may or may not be a net savings in primary energy use, depending on the overall (electric + thermal) efficiency of cogeneration and the efficiency of the powerplant that would otherwise supply electricity to an electric chiller

• If the desiccant is regenerated using solar heat, then there is a large energy savings (up to 90%)

Figure 4.41 Idealized solid-desiccant cooling system

Desiccant wheel. Rotation rate: 2 rpm if passive (is dried only by the unheated outgoing air)

60 rpm if active (outgoing air is heated before passing through)

Source: Danny Harvey, photo taken at GreenBuild 2011 in Toronto

Figure 4.42 Desiccant Chiller Performance

Source: IEA (1999, District Cooling, Balancing the Production and Demand in CHP, Netherlands Agency for Energy and Environment, Sittard)

Summary so far on chillers• Major kinds: electric (vapour-compression), absorption and

desiccant• The COP of an electric chiller in terms of primary energy is

equal to the chiller COP x efficiency in generating electricity ~ 5.0-7.5 x 0.35-0.6 = 1.8-4.5

• Absorption or desiccant chiller COP is based on the heat input and is much smaller than the COP of an electric chillier, namely, ~ 0.6-1.2

• If using waste heat from cogeneration with a steam turbine to drive an absorption or desiccant chiller, some electricity production is sacrificed

• The direct or sacrificed electricity requirement along with the electricity required to operate auxiliary equipment needs to be considered in comparing electric and heat-driven chillers

Cooling Towers

• These are usually found on the roof of big buildings• Water is cooled evaporatively and then used to cool

the condenser of the chiller• As evaporation produces temperatures cooler than

the air temperature (approaching the wetbulb temperature, rather than the drybulb temperature), a condenser that is cooled with water from the cooling tower rather than with air will be cooler.

• This in turn means a smaller temperature lift (from the evaporator to the condenser temperatures) (see Figure 4.25), and so a larger COP for the chiller.

Figure 4.43: Schematic diagram of a cooling tower

Source: ASHRAE (2001, 2001 ASHRAE Handbook, Fundamentals, SI Edition, American Society of Heating, Refrigeration and Air-Conditioning Engineers, Atlanta)

Cooling Tower on Top of Medical Sciences BuildingWater is cooled through partial evaporation, to below the air temperature, then goes to the condenser of the “chiller” to remove heat, with the result that the chiller does not need

to work as hard (and does not require as much energy) as it would if it had to make the condenser hot enough to dump

heat directly to the hot outside air

Source: Photo by Danny Harvey

Fans on a Cooling TowerFans are used to force a greater flow of air next to the evaporating water, thereby forcing faster evaporation and greater cooling. Electricity energy for fans and pumps can be 15%

or more of the electricity needed to operate the chiller itself. With absorption chillers, which can use waste heat for the cooling itself, even more electrical energy is needed to operate

the cooling tower fans and pumps (and larger cooling towers are needed), thereby significantly reducing the overall benefit of using waste heat. As well, if the heat that drives

an absorption chiller is taken from a steam turbine that generates electricity, there is a penalty in terms of reduced electricity production.

Source: Photo by Danny Harvey

The amount of heat that must be removed by a cooling tower is equal to the heat that needs to be removed from the building plus the energy input to the chiller (for absorption chillers, this is additional heat, while for electric chillers the energy input is electricity that is ultimately dissipated as heat)

From the definition of chiller COP as the ratio of heat removed to energy input, it follows that the total amount of heat that needs to be removed by the cooling tower per unit of building heat that needs to be removed is equal to 1 + 1/COP

Because absorption chillers have a low COP (0.6-1.2 vs 5.0-7.5), they require much larger cooling towers – which means much more electricity for the cooling tower fans and pumps (this is a large part of the auxiliary electricity requirement mentioned earlier)

For an electric chiller, the auxiliary electricity requirement might be 15% of the chiller electricity requirement. If we switch to an absorption chiller, the auxiliary electricity requirement might be 30% of the original electricity requirement

Using the cooling tower as an evaporative cooler

• The cooling tower can often produce water at a temperature of 16-18ºC or colder

• For displacement-ventilation/chilled ceiling HVAC systems (described later), this is plenty cold enough for cooling purposes

• Thus, the cooling tower water can bypass the chiller condensers (and the chillers can be turned off) and be used directly for cooling the building

• The cooling tower thus becomes another type of evaporative cooling system

Figure 4.44a Cooling tower during normal operation. There is a cooling water loop between the cooling tower and the condenser of the chiller, and a chilled water loop from the evaporator through the

building and back to the evaporator

Cooling Tower

Figure 4.44b Cooling tower as an evaporative cooler with direct connection of the cooling water loop and the chilled water loop

Cooling Tower

Correct Sizing of Cooling Equipment

• The amount of cooling required in a building is usually vastly over-estimated, due to the use of simple but inaccurate estimation techniques with a desire to “play it safe”

• As a result, the air conditioning equipment installed in buildings is usually way too big, causing it to operate at a small fraction of its peak capacity

• This in turn increases the energy requirements by up to 20% or so compared to properly sized equipment (and increases first costs)

Off-peak air conditioning

• Cool down water in a large storage tank at night, when electricity rates are often lower, and use the chilled water for cooling purposes during the day when it is needed

• The amount of coldness stored depends on: volume of water x temperature drop

• If the water is cooled twice as much, only half the volume would be needed to store the same amount of coldness

• If ice is made, even less volume is required

Energy implications of off-peak chilling:

• The colder the stored water, the lower the required evaporator temperature, reducing the COP of the chiller (and hence increasing its energy use)

• To make ice, the evaporator T has to be at around -10ºC, whereas in a system with chilled ceiling cooling and

displacement ventilation (which requires chilled water and air cooled only to about 18-20ºC), the evaporator could be at around 10ºC – so there would be a substantial energy penalty with an evaporator cold enough to make ice

• On the other hand, the condenser would be a little cooler at night (which would improve the chiller COP), fossil fuel powerplants are more efficient at night (up to 40% less primary energy is required to make one kWh of electricity at night), and transmission losses are up to 5% less at night than during the day

Solution (if you really want to reduce the need for running cooling equipment during the day):

Store coldness in something that freezes at a temperature warmer than 0ºC

Eutectic salts (which have been used for this purpose) fit the bill – they have a freezing point in the 8-10ºC range and a latent heat of freezing about half that of water (which is not bad – they store about half the coldness of water when they freeze)

Heating Ventilation Air Conditioning (HVAC) systems

HVAC Energy-Efficiency Principles

• Circulate only the amount of air needed for ventilation, and only when needed, while circulating hot or cold water for most of the heating and cooling (recall: energy required to move air or water varies with flow rate cubed, and ~ 25-100 times less energy is required to deliver heat via water than via air)

• In other words, separate the heating/cooling and ventilation functions

• Separate cooling from dehumidification functions using solid or liquid desiccants, with the desiccant regenerated using either waste heat from cogeneration (entailing ~ 0 sacrificed electricity because temperatures of only 50-65ºC are needed) or using solar thermal energy

• Distribute heat at the coolest possible temperature and coldness at the warmest possible temperature – in both cases by using large radiators (such as radiant ceiling or floors)

• Allow the temperature maintained by the HVAC system to vary seasonally (allowing temperatures of up to 28-30ºC on the hottest days)

HVAC systems in residential buildings

• If super-insulated, heat from the airflow at the rates required for ventilation only is often sufficient (with perhaps supplemental radiant heating of floors or towel racks in bathrooms)

• Otherwise, use radiant floor heating or large wall radiators (water at 30ºC will be plenty warm enough in super-insulated buildings)

• Mechanical ventilation with heat recovery via a heat exchanger when windows need to be closed

• Variable-speed drives on ventilation fans

Large wall-mounted radiator in a daycare centre in Frankfurt – an inexpensive alternative to radiant floor heating

Heat Exchangers

• Transfer heat from a warm air or water flow to a cold air or water flow

• Do so by maximizing the surface area between the two fluid flows

• This can be done either with one tube inside another, or through a series of plates

Figure 4.45a Counterflow flat plate heat exchanger

Source: Bower (1995, Understanding Ventilation: How to design, select, and install residential ventilation systems, Healthy House Institute, Bloomington, Indiana)

Figure 4.45b Crossflow flat plate heat exchanger

Source: Bower (1995, Understanding Ventilation: How to design, select, and install residential ventilation systems, Healthy House Institute, Bloomington, Indiana)

Figure 4.46 Residential heat exchanger (as part of amechanical (fan-driven) ventilation system)

Apartment heat exchanger (top)and heating or cooling coil (bottom)

Heating or cooling coil (depending onif hot or cold water is sent through it)

Heat exchanger

Damper

The performance of a heat exchanger is measured by its “effectiveness”, which is defined as

(Tsupply-Tincoming)/(Toutgoing-Tincoming)

Heat exchangers for commercial buildings have an effectiveness of 60-80%, meaning that 60-80% of the temperature difference and hence heat content difference between the incoming and outgoing air can be added to the incoming air rather than sent outside.

Residential heat exchangers have an effectiveness as high as 95%

However, adding a heat exchanger increases the fan energy required to move air (since it adds resistance to air motion) – so it should be bypassed when there is little difference in the temperature of inside and outside air

• Do not cool the air, they only make the air feel cooler

• They in fact add heat to the air• Thus, they should be turned off when not in use• They only save energy if people set the

thermostat on the air conditioner to a higher temperature (or dispense with the AC altogether)

• Most are incredibly inefficient (only 4-12% of electrical power input ends up moving air)

Figure 4.47 An aerodynamic ceiling fan (36% efficiency at high speed vs 12% for typical fans, where efficiency = power

imparted to air flow divided by electrical power)

Source: Florida Solar Energy Center

Recent conventional HVAC heating systems

• The fans operate at a fixed speed, tending to circulate a fixed quantity of air all the time

• The air is either overcooled centrally, then reheated electrically by the required amount just before entering a room, or

• The air flow is throttled to prevent overcooling (but usually some rooms end up too warm and others too cold)

New HVAC systems

• Will use variable speed fans – with the airflow rate varying according to a fixed schedule. Savings of 50-60% in overall HVAC energy use have been achieved from this alone

• As the airflow is still much more than required for ventilation purposes, 80% or so of the air will be recirculated on each circuit and blended with 20% outside air,

• This saves energy compared to venting 100% of the air to the outside and completely replacing it with fresh air that needs to be cooled and dehumidified or heated and humidified

However, we can still do much better

• If heating and cooling are largely provided through radiant floor or ceiling panels, then the airflow can be reduced to just that needed for ventilation (fresh-air purposes)

• Having reduced the airflow to that level, it can be entirely vented to the outside and replaced with 100% fresh air on each circuit (this is called a Dedicated outdoor air supply, or DOAS, system) without wasting energy

• This gives better indoor air quality and saves energy- reduced fan energy use- heat picked up from lights at the ceilings is directly vented to the outside rather than having to be removed by the chillers before 80% of the air is sent through the building again

We can also do much better in the way that the ventilation enters in and passes through a room.

The ventilation air typically enters a room from some outlet in the ceiling or in a wall and mixes turbulently with the room air, relying on dilution to remove air contaminants. This requires greater air flow (and recall, required fan power increases with air flow rate almost to the third power) but is not very effective in providing good air quality. A better alternative is outlined next/

Two essential elements of highly-efficient HVAC systems in commercial buildings

• Displacement ventilation

• Chilled ceiling cooling

Chilled ceiling cooling

• Our perception of temperature depends roughly 50:50 on the air temperature and on the radiant temperature (the temperature of the surroundings, which are a source of infrared radiation on our bodies)

• A nice sensation of coolness is achieved if the ceiling is cooled to 16-20ºC by circulating water at this temperature through panels attached to the ceiling

• The result is a much higher chiller COP than conventional cooling systems (which use water at 6-8ºC) and warmer permitted air temperature

Figure 4.48 Chilled Ceiling cooling panels

Source: www.advancedbuildings.org

Energy Savings• Compared to an all-air cooling system, simulations

indicate that chilled ceiling cooling save about 5-40% cooling energy use, with the smallest relative savings in hot-humid climates and the largest relative savings in hot-dry climates.

• This does not include savings from direct use of the cooling tower (as noted earlier, because the ceiling panels need water cooled down to only 16-20ºC, and the cooling tower almost always produces water at this temperature, the cooling tower water can be directly used in a chilled ceiling cooling system most of the time)

Displacement ventilation

• Ventilation air is introduced from vents in the floor at a temperature slightly below the desired room temperature

• The air is heated from internal heat sources and rises in a laminar manner, displacing the pre-existing air, and exiting through vents in the ceiling

• 40-60% less airflow is required than in a conventional ventilation system (which we assume to be already reduced to the flow required for air quality purposes only)

Figure 4.49 Displacement ventilation floor diffuser

Because the airflow has been reduced to that needed for ventilation purposes only (with most of the cooling done with chilled ceilings), 100% of the (much reduced) airflow must be vented to the outside and replaced with fresh outside air on each circuit. As previously noted, this forms a dedicated outdoor air supply (DOAS) system. It is healthier because air is not recirculated from one part of the building to another, and saves energy because internal heat that is transferred to the air is directly vented to the outside, rather than passing through the chiller when the air is recirculated

Energy savings

• The overall impact of energy use of displacement ventilation/chilled ceiling system compared to mixed ventilation/chilled ceiling or a VAV all-air cooling system depends on many competing factors, and if the system is not fully optimized (through computer simulation tests), there can be little net savings

• If overcooling and subsequent reheating for dehumidification are avoided, then cooling+ventilation energy use can be reduced by 30-60%

Demand-Controlled Ventilation

A further efficiency measure is to vary the airflow based on human occupancy (as determined by CO2 sensors). This gives a demand-controlled ventilation (DCV) system (this is now required by the California building code for high-density buildings). DCV alone can save 20-30% of total HVAC energy use.

To summarize, the most energy-efficient building will have

• Optimal orientation and form• A high performance envelope • Capacity to use passive ventilation and cooling whenever

outdoor conditions permit• Demand-controlled, displacement ventilation that, of

necessity, will be a DOAS system• Chilled ceiling cooling• Desiccant dehumidification using either waste heat from

cogeneration (ideally supplied by a district heating system) or using solar thermal energy

• Heat exchangers to transfer heat or coldness from the outgoing to the incoming air

• High efficiency equipment, correctly sized and commissioned

Supplemental figures, EnergyBase building, Vienna

Adjustable external shading

Windows on south facade are slightly overhanging

Source: Ursula Schneider, Pos Architekten, Vienna

Exhaust air is overheated by passing through a sort of solarium, then passes through a heat exchanger to heat the incoming fresh air to a greater extent than would be possible with a

conventional heat exchanger system. And unlike systems for passive solar preheating of ventilation air, we still get the benefit of heat recovery on the

exhaust air at night

Air temperatures during flow through solarium and heat exchanger

Source: Ursula Schneider, Pos Architekten, Vienna

Storage tank for solar hot water – used

in a desiccant cooling system

Solar-desiccant cooling unit

Recap: Fig. 4.41(top)

E F G H

E vaporativeC ooler

H eatE xchanger

D esiccantW heel

H eatInpu t

DOMESTIC HOT WATER

Figure 4.50 Breakdown of DHW energy use in the US

Showers35%

Standby and Distribution

Losses31%

Clothes Washer11%

Dishwasher 7%

Bath16%

Reducing DHW Energy Use

• More efficient production and supply

• Reduced demand

• Heat recovery after use

More efficient DHW supply• Efficient, condensing boilers are normally not available as stand-

alone heaters for DHW (typical efficiency ~ 65%)• For single-family housing – use a combined space and hot and

water heating system (90-95% efficiency)• Reduce storage and distribution losses through a wall-hung boiler

– this is a small, tankless, modulating and condensing boiler that can be located in a closet close to the DHW load

• In multi-unit housing – use a separate, small boiler for DHW in the summer (otherwise, the boiler used for space heating and DHW in the winter will be running at ~ 10% of peak load on average during the summer, and hence very inefficiently)

Recirculation-loop systems in hotels, office buildings, schools

• Hot water is continuously circulated through a pipe loop that returns to the boiler

• Branches provide water to faucets• The result is that hot water is instantly available (so

water is not wasted running the tap until warm water is received)

• Insulating the pipes well allows ‘priming’ the pipes with hot water only once every hour for 5 minutes

• This combined with replacing one central boiler with separate boilers in different zones resulted in a 91% savings in total energy use for hot water (including pump energy use) in a school in Tennessee

More efficient use of DHW

• Low-flow showerheads and faucets• Cold-water clothes washing• Personal behaviour:

- showers instead of baths (this is an issue _especially in Japan) - shorter showers, water not running all the time

- water-efficient hand washing of dishes instead of _using a dishwasher

• The fractional savings is diluted by the fact that, in most systems, a large part of the energy used to heat water is used to overcome standby losses

Recovery of heat from wastewater

• Applicable only when there are simultaneous hot and cold water flows

• Thus, applicable to showering but not to using a bathtub

• 45-65% of the available heat can be recovered from that portion of the hot water use related to simultaneous flows

Figure 4.51 Heat exchanger for wastewater

60% coolerWaste water to sewer

IncomingCold water

Model F-601Falling filmheat exchanger

Preheated or coldWater to fixtures & water heater

HotDrain water from showers & sinks

Source: Left: Vasile (1997, CADDET Energy Efficiency Newsletter December, 15–17) , Right: Danny Harvey, NSEA 2004 Conference exhibits

Finally – solar energy can provide 50-80% of DHW requirements in most countries (this is C-free energy supply, not energy efficiency,

and so is discussed in Volume 2)

REDUCING LIGHTING ENERGY USE

• Daylighting• Efficient lighting systems (including controls and

sensors)• Efficient lighting devices (ballasts, lamps and

luminaires)

Daylighting

• Simple passive daylighting – window size, orientation, shape, building floor plan

• Complex passive daylighting – devices to collect and reflect daylight deep into a building

• Complex active daylighting – devices to actively track the sun so to collect more daylight

• All kinds of daylighting require photosensors and dimmable electric lighting

• Efficient design of electric lighting systems• Efficient lighting fixtures (ballasts, lamps,)

Major types of lamps• Incandescent – requires heating a tungsten filament to

2100-2800ºC• Halogen – like an incandescent lamp, but has some

halogen gas and a quartz rather than a glass envelope, permitting higher temperatures (with more of the emitted radiation in the visible part of the spectrum)

• Fluorescent, compact fluorescent lamp (CFL) – an electric arc travels between electrodes, vapourizing mercury and producing UV radiation that in turn is absorbed by phosphors lining the inner tube, which in turn emit light of various colours as they drop down in energy level

• Light emitting diode (LED) – like a photovoltaic cell but running in reverse

Technical notes:• Energy is transmitted from the sun in the form of

electromagnetic (EM) radiation• Light is simply EM radiation of the wavelengths that we can

see• When EM is absorbed (whether visible or not), it warms the

object that is absorbing the radiation. Thus, the light emitted from a lamp (as well as daylight) has a heating effect (and the distinction sometimes made between “heat” and “light” from the sun is artificial)

• To maximize the amount of light from a lamp while minimizing the amount of heat that it also produces, the lamp should emit only at wavelengths that we see and not at other wavelengths.

Reminder: Figure 4.3 Blackbody Radiation

0.1 1.0 10.0 100.0

W/m2 /

/m2 /u

Wavelength (um)

BlackbodyRadiation:

Solar Radiation ExtraterrestrialSurface (1.5 atm)

RelativeSensitivityof Human

Emission from incandescent lamps (T = 2100-2800ºC)

0.1 1.0 10.0

10000s o

Wavelength (um)

BlackbodyRadiation:

2100oC

2800oC

Solar Radiation ExtraterrestrialSurface (1.5 atm)

RelativeSensi-tivity of HumanEye

The “efficiency” of a lamp is measured in terms of its efficacy, which is the ratio of lumens of

light to watts of power

• A lumen is the electromagnetic radiation output (W) weighted by the sensitivity of the human eye (times a factor of 683)

• Efficacies range from:

10-17 for incandescent lamps

50-70 for compact fluorescent lamps

105 for T5 fluorescent tubes

50-60 now and 200 projected for LEDs

105-130 for natural sunlight

Figure 4.52 Daylighting Roof Configurations

Source: Hastings (1994, Passive Solar Commercial and Institutional Buildings: A Sourcebook of Examples and Design Insights, John Wiley, Chichester)

Figure 4.53a Interior Light Shelf

Figure 4.53b Interior light shelves

Source: IEA (2000 , Daylighting in Buildings, Lawrence Berkeley National Laboratory)

Figure 4.54a Fixed exterior and interior light shelves

In c re as e d u n i fo rm i ty o f d a y l ig h t le v e l

S h a d in g fro m h ig h s u m m er s u n

Figure 4.54b Adjustable light Shelf

V ie w g la z in gT ilte dg la z in g

P a th o f ro lle r

R o lle r

P ro te c tiv eg la z in g

R o lle r

Figure 4.55 Sun-tracking light pipe

Prism Light Guide

Pipe Solar Input Housing

TrackingReflector

HeliostatDrive

ConvergingReflector

Diffuser

Reflector

End Mirror

Prism Light Guide

Figure 4.56 Light Pipe

Source: International Association of Lighting Designers

Figure 4.57 Passive Light Pipe

(a) (b)Source: Zhang and Muneer (2002, Lighting Research and Technology 34, 149–169)

Active Light Tracking Skylight

Figure 4.58 Laser-cut Panels

Source: IEA (2000, Daylighting in Buildings, Lawrence Berkeley National Laboratory)

Passive Daylighting (light louver)

View from inside

View from outside

Source: Danny Harvey, photo taken at GreenBuild2011 in Toronto

Source: Donald Yen, BCIT

Daylighting effects

Source: Donald Yen, BCIT

Figure 4.59 Residential Lighting

Source: Banwell (2004, Lighting Resources Technology 36, 147–164)

Appliances and Consumer Electronics

Figure 4.60 Residential per capita electricity use in 2005 (bars) and average growth rate (squares) from 1995 to 2005

OECD North America

OECD Europe OECD Pacific Non-OECD

Figure 4.61a US non-space or water heating residential electricity use in 2001

Refrigerators & Freezers

Air conditioning19.9%

Lighting10.9%

Clothes dryers7.2%

Other11.7%

Stereo system, 0.6%

Water bed, 0.6%

Coffee maker, 0.7%

Pool/hot tub/spa, 0.8%

Pool filter/pump, 1.1%

Ceiling fan, 1.0%

Clothers washer, 1.1%

Computers, 2.5%

Dishwasher, 3.2%

TV and related, 5.3%

Ovens, 4.6%

Furnace fan, 4.2%

Electric range, 3.5%

Figure 4.61b EU-27 non-space or water heating residential electricity use in 2007

Refrigerators and freezers21.0%

Lighting14.5%

Electric ovens10.4%

Clothes washers8.6%

Standby7.5%

Air conditioners6.1%

Other7.3%

Set top boxes 1.7%

TVs 9.3%

External power supplies 2.6%

Dishwashers 3.7%

Ventilation 3.7%

Computers 3.7%

Figure 4.61c Indian residential electricity Use in 2007

Fans34%

Lighting28%

Refrigerators13%

Air conditioners7%

Evaporative coolers

Other10%

Figure 4.62a. Annual electricity use by refrigerator/freezer units available in North America

2.5 4.5 6.5 8.5 10.5 12.5 14.5 16.5 18.5 20.5 22.5 24.5 26.5 28.5 30.5 32.5

Volume (ft3)

Figure 4.62b Annual electricity use by freezers available in North America

3.5 5.5 7.5 9.5 11.5 13.5 15.5 17.5 19.5 21.5 23.5 25.5

Volume (ft3)

Upright

Figure 4.63 Annual electricity use by ovens available in North America (standard test conditions)

< 80 litres

80 -100 l

100 -120 l

120-140 l

< 80 l 80-100 l

100-120 l

< 60 litres

60 -80 l

80 -100 l

100 -120 l

Self Cleaning Ranges Non-Self Cleaning Ranges Single Oven

Figure 4.64 Annual energy use by stoves, dishwashers, clothes washers and clothes dryers available in North America

Built-In Mobile Compact Top- Front-

Loading Loading

Clothes Washers

Cook-tops

ClothesDriers

Dishwashers

Figure 4.65 Energy use by new refrigerators sold in the US

1940 1950 1960 1970 1980 1990 2000

Energy Use

Adjusted Volume

2001 US Standard

1980 CaliforniaStandard

1993 US Standard

1978 CaliforniaStandard

1987 California Standard

Source: Rosenfeld (1999, Annual Review of Energy and the Environment 24, 33–82)

Figure 4.66 Average energy use by the refrigerator stock in different countries

1973 1980 1990 1998

Australia

Canada

Denmark

Finland

France

Germany

Netherlands

NorwaySweden

Further opportunities for energy savings in refrigerator/freezer units

• Use of vacuum insulation panels• Separate chilling of the fridge and freezer

compartments (at present, the fridge is cooled indirectly by cooling down to the temperature required by the freezer, which means a greater-than-necessary temperature lift and lower COP)

• Variable speed compressor• 200 kWh/year for a standard size unit is a

reasonable target• Get rid of the beer fridge!

Clothes washers

• Vertical axis (top opening) – lots of water required• Horizontal axis (side opening) – uses less water, has

higher spin speed, so the clothes come out dryer• Energy use should take into account direct energy

use, hot water requirements, detergent embodied energy (horizontal axis machines require less detergent) and the energy required to dry the clothes after washing (greater electricity used to spin the clothes is more than compensated by reduced clothes dryer energy use)

Figure 4.67 Energy used to wash 200 3.2kg loads per year, with heating of 1/3 of the water used by 50 K

US pre-2000

US 2007 EU Worst Category

EU Best Category

Chinese impellor

Chinese drum

Water heating

Note: the impact of 100% hot-water vs 100% cold-water washing is 3 times greater than shown in the

preceding figure

Clothes Dryers

• Vented (almost all there is in North America)• Condensing (common in Europe)• Heat pump (becoming common in some

European countries)

Table 4.16 Comparison of embodied energy and lifetime (over 13 years) operating energy of different clothes dryers and comparison of annualized purchase cost (neglecting interest) and operating costs. The given savings is for the new heat pump model compared to the vented model. Source: Gensch (2009)

Alternatives

• Clothes line outside (perhaps the simplest and cheapest form of solar energy!)

• Air drying indoors in winter (common practice in most European countries)- as evaporation of water cools the surrounding air, the heat for drying the clothes comes from the building space-heating system, but the air is also humidified

Dishwashers

• An energy-intensive way of washing dishes compared to water-efficient washing by hand

• Air-drying option minimizes electricity use

Televisions and related equipment

• Energy use depends on- technology- size- hours of use- standby energy use (when turned off)- auxiliaries (set-top boxes, DVD players and _DVRs)

• Annual energy use by auxiliaries alone can equal the total average per capita residential electricity use for all purposes in the non-OECD group of countries (300 kWh/yr)!

Figure 4.68a Power draw by TVs when turned on

0 2000 4000 6000 8000 10000

Screen Area (square cm)

Plasma

Source: Digital CEnergy (2007, www.energyrating.gov.au/library/pubs/200710-tv-meps-labelling.pdf)

Figure 4.68b Power draw by TVs when turned off

0 2000 4000 6000 8000 10000

Screen Size (Square cm)

Plasma

Source: Digital CEnergy (2007, www.energyrating.gov.au/library/pubs/200710-tv-meps-labelling.pdf)

Figure 4.69 Number of TVs per household

1990 1992 1994 1996 1998 2000 2002 2004 2006

Australia

Canada

Europe (EU25)

Brazil

Mexico

China (urban)

China (rural)

India (urban)

India (rural)

Source: IEA (2009, Gadgets and Gigawatts: Policies for Energy Efficiency Electronics, International Energy Agency, Paris)

Figure 4.70 Household TV viewing

0 1 2 3 4 5 6 7 8 9

United States

Turkey

Belgium

Portugal

Australia**

South Korea***

Canada*

Britain**

Denmark

Finland

Austria

New Zealand

Ireland**

Switzerland

Sweden

Average Daily Household TV Viewing (hours)

Source: OECD (2007, OECD Communications Outlook 2007, OECD, Paris, www.economist.com/research/articlesBySubject/displaystory.cfm?subjectid=7933596&story_id=9527126)

Figure 4.71 Power draw by set top boxes

No Disc Disc No Disc Disc No Disc Disc

Cable Satellite Aerial

The big opportunities for reducing TV energy use are

• Improved technology – 40-50% savings possible• Limitations on size (in effect, by setting upper

limits to the allowed electricity use)• Reductions in standby energy use by TVs and

set-top boxes• Improving the quality of public space, making

more recreational facilities available (or making them free) to encourage alternative forms of entertainment and a healthier lifestyle

Figure 4.72 Computer monitor energy use

12 14 16 18 20 22

Monitor Size (inches)

LCD Monitors

CRT TVs or Monitors

500 750 1000 1250 1500

Monitor Area (cm2)

Huge additional savings in energy use by computers and monitors are possible

• Better chips in CPUs (we are nowhere near the quantum-mechanical limits)

• LEDs eventually in LCD monitors• Better power management (and education to

enable power management options)• More efficient internal AC-DC transformers

(typical efficiencies are 60-70% in PCs vs 70-80% for external transformers for laptops)

Figure 4.73 Energy use by office equipment in US commercial buildings

Monitors and displays

PCs and workstations

Server computers13%

Photocopiers11%

Printers 6%

UPSs6%

Other11%

Computer networks

Source: Roth et al (2002, Energy Consumption by Office and Telecommunications Equipment in Commercial Buildings. Volume 1: Energy Consumption Baseline, Arthur D. Little Inc., Cambridge, MA, www.eren.doe.gov/buildings/documents/pdfs/office_telecom_vol1_final.pdf)

Information Technology (IT) Centres

• Account for about 1% of worldwide electricity use• Energy is used by the computers themselves• Energy is lost from the UPS (uninterruptible power

supplies)• Energy is used by the HVAC system (there are

large cooling requirements)

Reducing IT Centre Energy Use

• Decreasing energy requirements for computation and data storage lead to direct savings in computer energy use, and indirect savings through reduced production of waste heat that needs to be removed by the HVAC system

• Better sizing of UPS units reduces energy loss due to low part-load operation (typically, 2 units each capable of handling the entire peak load will be used; 3 units each capable of handling 2/3 of peak would reduce total electricity use by 5%)

Reducing IT Centre HVAC Energy Use

• Conventional techniques to reduce HVAC energy use (variable-speed fans, displacement ventilation, chilled ceilings)

• Better sizing of all equipment• Separately enclosing the “cold” and “hot” aisles (heat

from computers is ejected into the hot aisles)• 50% reduction in HVAC energy use is possible, with a

further 10-20% through better sizing of UPS units• Migration over time of data centres to cold-climate

regions

Embodied Energy vsOperating Energy

• Embodied energy is the energy required to make the materials used in the building, and the energy used during the construction process. Include both original construction and ongoing maintenance and repair

• Operating energy refers to the recurring, annual energy use for operating the building – heating, cooling, lighting, and so on

Embodied energy and non-energy GHG emissions

• Concrete vs wood vs steel construction• Advanced windows• Embodied energy in insulation• Blowing agents used for foam insulation • Demolish and rebuild vs retrofit

Figure 4.74 Building Embodied Energy

German, 1984 code

Passive House Norwegian, 1987 code

Low energy

Operating Energy

Recurring Embodied Energy

Initial Embodied Energy

Concrete

• Much higher embodied energy and CO2 emissions than wood

• However, it provides thermal mass – which can be used to greatly reduce air conditioning requirements if combined with night ventilation and external insulation

• Most analyses of wood vs concrete do not take this into account

• It also absorbs sound, making multi-unit residential buildings (with their large energy savings potential) more acceptable

Advanced windows

• Extra layers of glass, low-e coatings, and argon between the layers of glass can all be justified from an energy point of view in regions with cold winters – the savings in heating energy is many times (1000s of times in the case of low-e coatings) the extra energy needed to add these features

• A lot of energy is required to separate krypton from air, so windows with krypton between the layers of glass can only be strongly justified if the krypton makes the windows good enough that perimeter radiators (which have lots of aluminum in them) can be eliminated (if they could not otherwise be eliminated)

Insulation

• Each extra cm of added thickness of insulation has a diminishing benefit (see Fig. 4.9), but the energy required to make the insulation increases in direct proportion to the thickness of insulation

• Thus, at some point (as the thickness of insulation is increased) the savings in heating energy due to extra insulation (over its 50-100 year lifespan) will be less than the extra energy required to make the insulation, and this point will come sooner the milder the winters

Insulation (continued)

• Fibreglass and foam insulation require a lot of energy to make (fibreglass is melted sand, foam insulation is made from petroleum), so this is an important consideration for these kinds of insulation

• Cellulose is just recycled newsprint, so the embodied energy is essentially zero. However, newsprint and other biomass materials have energy value as a fuel for heating or cogeneration, so this energy value should be included in doing the accounting

The savings in heating energy with successive equal sized increments is smaller with each successive increment, so

the energy benefit-energy cost ratio decreases

0 10 20 30 40 50 60

R-Value

Walls at R12 (RSI 2.1, U=0.47 W/m2/K)

Walls at R20 (RSI 3.52,U=0.28 W/m2/K)

Roof at R32 (RSI 5.6,U=0.18 W/m2/K)

Walls (R40, RSI 7.0)Roof (R60, RSI 10.6)Advanced House:

RSI-Value

0 2 4 6 8 10

Figure 4.75a. Time required for energy savings due to insulation to offset the energy used to produce the insulation, starting with RSI=0.5 for a climate with

4000 HDD (heating degree days) per year

4 5 6 7 8 9 10

Final RSI Value

Solid polystyrene foam

Spray -on polyurethane foam

Cellulose &mineral fibre

Fibre glass and flax

Solid polyurethane foam

Figure 4.75b. Time required for energy savings due to an extra RSI 1.0 of insulation to offset the energy used to produce the extra insulation for a

climate with 4000 HDD per year

4 5 6 7 8 9 10

Final RSI Value

Solid polystyrene foam

Spray -on polyurethane foam

Cellulose &mineral fibre

Fibre glass and flax

Solid polyurethane foam

Figure 4.76a. Time required for savings in GHG emissions due to insulation to offset the emissions associated with producing and using

the insulation, starting with RSI=0.5 for a climate with 4000 HDD per year

4 5 6 7 8 9 10

Final RSI Value

HFC-365mfc

HCFC-141b

n-pentane

Figure 4.76b. Time required for savings in GHG emissions due to an extra RSI of 1.0 of insulation to offset the emissions associated with producing

and using the extra insulation for a climate with 4000 HDD per year

4 5 6 7 8 9 10

Final RSI Value

HFC-365mfc

HCFC-141b

n-pentane

The latest (2012) foam insulation products available use (or could be using) a new generation of blowing agents (including

some made in part from soy oil) that have substantially less GWP than those illustrated

in the previous slides

Applications of Foam Insulation

• Structural Insulation Panels

• External Framing and Insulation Systems (EIFSs)

• Solid Insulation Forms

• Spray-on Foam Insulation

Various Insulation Levels with Structural Insulation Panels (SIPs), consisting of solid foam insulation, oriented strand board (OSB) for strength on one or both sides, or some

other finish on one side

Different thicknesses (R-values)Illustrated here (divide by 5.678 toget RSI value)

Different facings on the insulationare illustrated here

Source: Danny Harvey, Green Build 2011 exhibits, Toronto

Example of EIFS (External Insulation Finishing System)

Behind the insulationis an undulating plateto permit drainage of any water that getsInto the system and behind the insulation. Thus,there is an air gap that is open at the bottom only. If there are any openings at the top,air will flow behind the insulation, short circuiting theinsulation and rendering it next to useless. Other systems (whichI prefer) have a gap between a separate rain barrier and theinsulation on the outside of the insulation.

Expanded polystyrenefoam insulation

Almost any finish isAvailable to go overthe insulation, includingthose looking like bricks

Solid insulation forms – concrete is poured into the gap. The white is solid foam insulation that serves as the forms

for the concrete, and remains after the concrete sets

Source: Danny Harvey, 2004 Construct Canada exhibits, Toronto

Use of spray-on foam in difficult-to-reach, irregular spaces during a renovation

Before After (not quite finished, wraps around a chimney)

Source: Danny Harvey, Toronto, 2010

Before (left) and after (right). Note the hollow column (which formerly held acounter-weight) to the left of the triple-glazed window in the before photo – a horrendous thermal bridge! A gap (not visible) between the door joist and outside wall is also filled with foam insulation.

Before After

Solid-foam insulation example

Low-Embodied Energy Insulation

• Cellulose (recycled newsprint, can be blown in)

• Hemp

• Wood-fibre products

• Recycled blue jeans

Hemp Insulation

Source: Danny Harvey, 2009 Passive House Conference exhibits, Frankfurt

Passive House Levels of insulation on display at the 2009 Passive House Conference in Frankfurt

Full thickness ofinsulation under theentire roof area(including edges)

Wood fibre insulation

Cellulose insulation

Rain barrierwith a gap behind it

Source: Danny Harvey, 2009 Passive House Conference exhibits, Frankfurt

Insulation made from recycled blue jeans

Demolition and replacement of existing buildings

• What matters from an energy point of view is how much energy would be required to make the materials that would go into the building that would replace the existing building, not how much energy was used in the past to make the materials in the existing building

• If the replacement building is designed to be highly energy efficient, the energy required to make a new building will usually be paid back through reduced annual operating energy use in only a few years

• Thus, from an energy point of view, demolishing old, energy-guzzling buildings and replacing them with new, efficient buildings is generally highly favourable

Demolition (continued)

• However, the energy savings through renovation can often be almost as large as in replacing an energy-guzzling building with a new building

• For example, with regard to heating, we might go from 100 units to 20 units through renovation, and from 100 units to 10 units with replacement. The renovated building requires twice as much heating energy as the new building, but the savings is 80/90 = ~ 90% as large

• There are of course other considerations in the choice of renovation vs replacement, such as preserving the architectural heritage and reducing the generation of waste materials

EXEMPLARY BUILDINGS FROM AROUND THE WORLD

Residential Buildings

The German Passive Standard:

• A heating load of no more than 15 kWh/m2/yr, irrespective of the climate, and

• A total on-site energy consumption of no more than 42 kWh/m2/yr

• For cooling-dominated climates, the standard is a cooling load of no more than 15 kWh/m2/yr

Current average residential heating energy use:

• 60-100 kWh/m2/yr for new residential buildings in Switzerland and Germany

• 220 kWh/m2/yr average of existing buildings in Germany

• 250-750 kWh/m2/yr for existing buildings in central and eastern Europe

• 150 kWh/m2/yr average of all existing (single-family and multi-unit) residential buildings in Canada

Comparison of PH standard with German standards for heating energy use in residential buildings

Source: Figure by Danny Harvey, data compiled from various sources

2 /yr)

-- pre 1982 -- ---- 1982 --- ---- 1995 ---- ---- 2002 ----

Saskatchewan House, 1977 – inspiration for the first Passive House in 1991

Source: The Encyclopedia of Saskatchewan, http://esask.uregina.ca/entry/energy-efficient_houses.html

The first Passive House, Darmstadt, Germany, 1991

Source: Steinmüller (2008), Reducing Energy by a Factor of 10 – Promoting Energy Efficient Housing in the Western World, http://www.bsmc.de/BSMC-Factor10-WesternWorld.pdf

The first Passive House community, Weisbaden Lummerlund, 1997

Source: Steinmüller (2008), Reducing Energy by a Factor of 10 – Promoting Energy Efficient Housing in the Western World, http://www.bsmc.de/BSMC-Factor10-WesternWorld.pdf

Growth of Passive Houses in Germany, 1991-2003

Source: Steinmüller (2008, Fig. 3-7), Reducing Energy by a Factor of 10 – Promoting Energy Efficient Housing in the Western World, http://www.bsmc.de/BSMC-Factor10-WesternWorld.pdf

Number of dwelling units meeting the Passive House standard in Austria

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

New during current year

Finished at start of year

Figure 4.78 Progressive decrease in cost with learning.Extra costs are about 5% of the construction cost in Europe,

and about 10% of the construction cost in Canada.

Source: Feist (2007, Conference Proceedings, 11th International Passive House Conference 2007, Bregenz, Passive House Institute, Darmstadt, Germany, 383-392)

t(€/

s 1991 Prototype: experimental house,4 dwellings in Kranichstein usinghandicraft batch production

PH in Groß-Umstadt:Reduced costs bysimplification

Settlement in Wiesbaden:Serially produced windows & structural elements

Settlements in Wuppertal,Stuttgart, Hanover

Row houses in Darmstadt, 80 €/m2

Profitability with contemporary

interest rates & energy prices

Occurrence of buildings meeting the Passive House Standard:

• Several thousand houses have now been built to and certified (based on measurements after construction) to have achieved the PH standard in Germany, Austria and many other countries in Europe

• The standard has also been successfully achieved in schools, daycare centres, nursing homes, gymnasia and a savings bank

The PH standard is now the legally required building standard in many cities

and towns in Germany and Austria

• City of Frankfurt: since 2007, all municipal buildings must meet the standard

• City of Wels, Austria: same thing since 2008• Vorarlberg, Austria: Passive Standard is mandatory

for all new social housing• Freiberg, Germany: all municipal buildings must

meet close to the PH standard• City of Hanover: since 2005, all new daycare

centres to meet the Passive House standard (resolution only – legal status not clear)

Modern Examples of Passive House Buildings

The Biotop office building in Austria, with a combined heating+cooling energy demand of 19.4 kWh/m2/yr.

Two views of the new wing of the Aarhus Municipal building, Denmark, which is intended to meet the Passive Building standard.

Source: www.buildup.eu/cases/12312

Best Ontario Building (to my knowledge):

EnerModal Engineering headquarters building, Waterloo, Ontario.

Measured heating+DHW: 23 kWh/m2/yrMeasured total onsite energy: 70 kWm/m2/yrCost premium: 10%, payback time: 20 years

Estimated fuel energy use (largely for heating) in Canadian multi-unit residential buildings

/m2 /y

PassiveHouse Standard

Climate Comparisons, Heating Season

Thermal energy requirements for U of T campus buildings without chemical laboratories or large DHW requirements

l of C

Studie

Centre

l of M

Educat

rgeSt (C

ithHal

ltyClu

/m2 /y

Passive Building Standardfor spaceheating

Thermal energy requirement for U of T student residences

College

Univer

SDWRes

NewCol

Passive BuildingStandardfor spaceheating load

To achieve the Passive House standard on the heating side requires

• High levels of insulation (U-values of 0.10-0.15 W/m2/K, R35-R60)

• High performance windows (usually TG, double low-e, argon-filled)

• Meticulous attention to avoidance of thermal bridges

• Meticulous attention to air-tightness• Mechanical ventilation with heat recovery• Attention to building form (achieving the

standard is much easier in multi-unit than single family housing)

Passive House level of insulation on display at the 2009 Passive House Conference in Frankfurt

Insulation stripshere reduce thethermal bridge around the window frame

Insulationlayers

Cross section of the frame of window (imported from Germany) used in a renovation project in Toronto

Outside Inside

Insulated spacer,low psi-value

Insulation attachedto both parts ofwindow frame, reducing the frame U-value From this line

and below would be excludedin Canadian applications

Two ways of installing a window- which one is a poor way?(answer is on the next slide)

Insulation

Bricks

Answer:

The installation on the left is poor, because there is no insulation below the window frame, so heat can flow from inside to outside underneath the frame. The installation psi-value would be large, as there is a large thermal bridge.

The window should be aligned with the insulation, as in the figure on the right.

A Zero Net Energy project in 2010 – correction of the errors in this design (windows not centred over the insulation, thereby creating a huge thermal bridge) throughout the project would have allowed elimination of several $1000 in PV panels while still giving net zero energy, at much less cost

Source: Malcolm Isaacs, Canadian Passive House Institute

Passive House Projects in Toronto

South façade, showing large window areas and double-wall construction. After external sheathing and drywall have been installed, cellulose insulation will be blown in from the top, filling all the gaps and irregularities.

Source: Danny Harvey, 2012, Toronto

Basement wall and floordetails – note thermal-bridge free insulation ofwalls and concrete floor Slab. The heavy black arrows delimit the edgesOf the insulation layers

Thermal-bridge free basement corner and walls (there is a gap between the wood and the concrete wall, which will be filled with

insulation – as well as the area between the wood joists)

Passive House – north side (left) and south side (right) – and typical pre-existing house (lower left)

Complicated roof structures

• Are more expensive to build

• Create a large surface-to-volume ratio, which will leads to greater heat loss for a given house volume and roof and wall U-values

• Add lots of potential and actual thermal bridges, which are other sources of heat loss

Potential thermal bridges

Source: Danny Harvey, Toronto

This slide shows that buildings with a simpler shape cost a lot less to build than buildings with more complex shapes. The simpler shape also makes it easier to

achieve the Passive House standard. So, if in striving to meet the Passive Standard we adopt a simpler building shape, the net result can be that building

to the Passive House standard can cost no more than regular construction.

(The shape factor is just the surface: volume ratio (m2/m3))

Source: Smutny et al. (2011)

Recall: buildings with a simpler shape save energy by

• Reducing the surface area for a given building volume

• Reducing the number of thermal bridges• Making it easier to make the building air tight (by

having fewer joints that need to be sealed)

Thermally-separated

balconies in Frankfurt

Supplemental figures: High school example: Grandschule in Riedberg,

Frankfurt

South facade

Triple-glazing throughout, maximized passive solar heat gain

Retractable external shading

Passive ventilation and night-time cooling; mechanical system shut off from ~ early May to end of September

Heating required during the winter for only a couple of hours Monday mornings, using two small biomass-pellet

boilers

Global Survey – Impact of Modest Improvements

Figure 4.77: Simulated energy use of residential buildings with and without modest improvements to the thermal envelope and to

the heating and cooling equipment

New York Ref

New York Low

New Delhi Ref

New Delhi Low

Beijing Ref

Beijing Low

Madrid Ref

Madrid Low

OtherLightingCoolingHeating

High Performance NewCommercial Buildings

To achieve ultra-low-energy office buildings requires

• Attention to building form, glazing fraction, thermal mass (all four facades will not be identical!)

• Attention to insulation levels and glazing properties

• Provision for passive ventilation (even on 50-story office towers), daylighting, heat recovery

• Almost mandatory use of demand-controlled displacement ventilation with radiant slab heating and cooling

• Lots of attention to control systems

In complex buildings, the usual largely linear design process needs to be

replaced with the Integrated Design Process (IDP), in which

• The building is treated as a system• Architects, engineers of various sorts, and

specialists get together at the very beginning of the design process

• Multiple options for achieving deep energy savings are considered, then tested with building computer simulation specialists in order to find the optimal solution

Figure 4.79a Conventional design process when client will not occupy the building

Building design process

Level 1:

Client Architect Engineers

Government

Contractors

Source: Hien et al (2000, Building and Environment 35, 709-736, http://www.sciencedirect.com/science/journal/03601323)

Figure 4.79b Conventional design process when the client will occupy the building

Building design process

Level 2:

Government

Contractors

Figure 4.79c Integrated Design Process

Government

Contractors

Simulation team

Dynamic integration in design process

Design Team

Level 3:

Source: Montanya et al (ASHRAE Journal, July 2009, p30-40)

Core team assembled at the beginning of a project

Source: Pope and Tardiff (2011, ASHRAE Transactions 117, pp433-440)

Participants in the integrated design process

Integrated Design Process: Principles

• Consider building orientation, form, shape, thermal mass and glazing fraction

• Specify a high-performance thermal envelope• Maximize passive heating, cooling, ventilation

and day-lighting• Install efficient systems to meet remaining loads• Ensure that individual energy-using devices are

as efficient as possible and properly sized• Ensure that systems and devices are properly

commissioned

Sample Work Load in the IDP

Ta b le 4 . 2 0 C o m p ariso n o f co m p o n en t co s ts fo r a b u ild in g w ith a co n v en tio n a l VAV m ech an ica l sy s tem an d co n v en tio n a l (d o u b le -g lazed , lo w -e ) w in d o w s w ith th o se fo r a b u ild in g w ith rad ian t s lab h ea tin g an d co o lin g an d h ig h -p e rfo rm an ce (tr ip le -g lazed , lo w -e , a rg o n - f il led ) w in d o w s, a ssu m in g a 5 0 % g laz in g a rea /w a ll a rea ra tio . C o s ts a re in 2 0 0 1 C an ad ian d o lla rs fo r th e Van co u v e r m ark e t in 2 0 0 1 , a re g iv en p e r m 2 o f f lo o r a rea , an d a re b ased o n fu lly co s ted an d b u ilt ex am p le s o v e r a 3 -y ea r p e r io d . S o u rce : G eo ff M cD o n e ll (O m ic ro n C o n su ltin g , Van co u v e r) , p e rso n a l co m m u n icatio n , D ecem b er 2 0 0 4 , an d M cD o n e ll (2 0 0 3 ).

B uild in g C o m p o n en t

C o n v en tio n a l B u ild in g

H ig h - p e rfo rm an ce B u ild in g

G laz in g

$ 1 4 0 /m 2

$ 1 9 0 /m 2

M ech an ica l S y s tem

$ 2 2 0 /m 2

$ 1 4 0 /m 2

E lec trica l S y s tem

$ 1 6 0 /m 2

$ 1 5 0 /m 2

Ten an t f in ish in g s

$ 1 0 0 /m 2

$ 7 0 /m 2

F lo o r -to -f lo o r h e ig h t

4 .0 m

3 .5 m

To ta l

$ 6 2 0 /m 2

$ 5 5 0 /m 2

E n e rg y U se

1 8 0 k W h /m 2/y r

1 0 0 k W h /m 2 /y r

Ta b le 4 . 2 2 E n erg y sav in g s re la tiv e to A S H R A E 9 0 .1 -1 9 9 9 a n d c o s t p re m iu m fo r b u ild in g s m ee tin g v ario u s le v e ls o f th e L E E D s tan d a rd in th e U S A . S o u rce : K ats e t a l. (2 0 0 3 ).

% E n erg y S av in g s , B a sed o n L E E D L ev e l

S am p le S iz e G ro ss E n erg y U se N e t E n erg y U se

C o s t P rem iu m

C ertified 8 1 8 2 8 0 .6 6 % S ilv er 1 8 3 0 3 0 2 .11 % G o ld 6 3 7 4 8 1 .8 2 %

Ta b le 4 .2 3 E co n o m ics o f th e n e w O reg o n H ea lth an d S c ie n ce U n iv ers ity b u ild in g . S o u rce : In te rfac e E n g in eer in g (2 0 0 5 ) . Item To ta l p ro je c t c o s t $ 1 4 5 .4 m illio n E n erg y e ff ic ien cy fea tu res $ 9 7 5 ,0 0 0 P V sy s tem $ 5 0 0 ,0 0 0 S o la r th e rm al sy s tem $ 3 8 6 ,0 0 0 C o m m iss io n in g $ 1 5 0 ,0 0 0 To ta l $ 2 ,0 11 ,0 0 0 S av in g s in m ec h an ica l sy s tem s $ 3 ,5 0 0 ,0 0 0 V alu e o f sav ed sp ac e $ 2 ,0 0 0 ,0 0 0 N e t c o st -$ 3 ,4 8 9 ,0 0 0 E stim a te d a n n u a l o p e ra tin g c o s t sav in g s $ 6 0 0 ,0 0 0

Figure 4.80 Simulated energy use of commercial buildings with and without modest improvements to the thermal envelope and to

the heating and cooling equipment

New York Ref

New York Low

New Delhi Ref

New Delhi Low

Beijing Ref

Beijing Low

Madrid Ref

Madrid Low

Lighting

Cooling

Heating

Figure 4.81 Simulated energy use for an office building in Malaysia

0 50 100 150 200 250 300

Reference

Add daylighitng

Add Insulation

Add EE lighting

Add EE equipment

Add energy management

Increase room temp 1 K

Reduce leakage

Energy Intensity (kWh/m2/yr)

Figure 4.82 Simulated energy use for an office building in Beijing

0 50 100 150 200

Reference

Add window shading

Add advanced glazing

Add more insulation

Add natural ventilation

Energy Intensity (kWh/m2/yr)

Rating of architects & design teams:

• Can’t deliver 25% savings: totally incompetent, fire them all

• Can deliver 50% savings: competent and knowledgeable team

• Can deliver 75% or greater savings at little or no additional construction cost: truly outstanding

CASE STUDIES

• Designs that permit natural ventilation

• Earth-pipe cooling

• Evaporative cooling

• Advanced daylighting

Examples of Designs that Permit Natural Ventilation

Deutches Post Headquarters

• 45 stories high with double skin façade to permit natural ventilation

• Big savings in air conditioning and ventilation energy use

• Heating load is large compared to the Passive House standard, but small compared to typical buildings in spite of a largely all-glass facade

Wind Catchers in Israel

Source: MED-ENEC (Energy Efficiency in the Construction Sector in the Mediterranean) website,www.med-enec.com, under pilot projects, Israel

Wagner KfW Bank

Airflow

Declining energy use during the 1st few years as the systems are adjusted

Evaporative Cooling Case Study

Conventional Evaporative Cooling Equipment

Source: Torcellini et al (2006). Note: They indicate a final temperature of 54 F (12 C) which, based onthe psychrometric chart, requires a starting relative humidity of 5% in order to end up at 12 C with26 C as the temperature after the indirect evaporative cooling step. A 16 C final temperature requires an initial relative humidity of 20%, which is still very dry for desert regions but is more reasonable

26°C 16°C

Recall: Figure 4.34, Indirect+direct evaporative cooling

20 25 30 35 40

100%RH 60%RH80%RH

Indirect evaporativecooling of primaryairstream

Original TwbDirect evaporative

Final Twb

Direct evaporativecooling of primaryairstream

cooling of

secondary

airstream

Cooltower in the Zion Visitor Center, Utah

Source: Torcellini et al (2006)

Case study buildings from the German Research for Energy-Optimized Construction (EnOB)

program. Web site: www.enob.info/en

Energon Passive Office, Ulm, 21.7 kWh/m2/yr measured heating + DHW demand, 67 kWh/m2/yr total onsite demand (a typical German office building is around 280 kWh/m2/yr and a typical Canadian office

building is around 350 kWh/m2/yr total energy demand)

Intakes forgroundconditioningof ventilationair

Lamparter Passive Office (17.9 kWh/m2/yr measured heating + DHW energy use, 125 kWh/m2/yr primary energy use)

Earth-pipeintakes

Overbach Science College, calculated energy intensities: 16 kWh/m2/yr heating, 68 kWh/m2/yr primary energy

Wagner Passive Office with hot water storage of summer solar heat for use in the winter, 23.1 kWh/m2/yr measured heating+DHW energy use

and 66 kWh/m2/yr primary energy use

Hot water tank

Clerestory windows for daylighting

Solar thermal collectors

Hot water tanks, earth-pipe for ventilation air,

solar thermal collectors

SurTec Factory and Offices, 29 kWh/m2/yr measured heating+DHW,

169 kWh/m2/yr primary energy

Underfloor heating pipes

Centre for Interactive Research in Sustainability (CIRS) building, UBC, Vancouver – Net Energy Positive

Daylighting Examples

Light shelves, Cambria Office, Pennsylvania

Source: Torcellini, P., S. Pless, M. Deru, B. Griffith, N. Long, and R. Judkoff, 2006: Lessons Learned from Case Studies of Six High-Performance Buildings, National Renewable Energy Laboratory, Technical Report NREL/TP-550-37542.

Recall: Figure 4.52 Daylighting Roof Configurations

Clerestory, Oberlin College, Ohio

Clerestory

Clerestory Window, Cambria Office

Clerestory

Daylight central chamber, Barnim Service and Administration Centre, Brandenburg, Germany

Source: EnOB website (www.enob.info/en), new buildings case studies

Existing Buildings

• The term “retrofit” refers to the deliberate upgrading of the building envelope or systems some time after the building has been built

• The term “renovation” refers to the renewal of building components in response to deterioration over time, and may or may not be accompanied by an improvement in the performance levels

• The ideal will be to perform a significant retrofit when routine renovations are required anyway, as this will greatly reduce the cost of the energy efficiency upgrade

Retrofits of existing buildings

• Insulation• Windows • Air sealing• Mechanical systems• Lighting• Solar measures

Renovations to the Passive House Standard (15 kWh/m2/yr heating load)

• Dozens carried out in old (1950s, 1960s) multi-unit residential buildings in Europe, resulting in 80-90% reduction in heating energy use

• Two examples will be shown here:-BASF buildings in Ludwigshafen, Germany- apartment block in Dunaújváros, Hungary

Figure 4.83 BASF retrofit, before and after

Source: Wolfgang Greifenhagen, BASF

Figure 4.84 BASF retrofit (a) installation of external insulation, (b) installation of plaster with micro-encapsulated phase change materials

Source: Wolfgang Greifenhagen, BASF

Figure 4.85 Renovation to the Passive House Standard in Dunaújváros, Hungary. Before:

Source: Andreas Hermelink, Centre for Environmental Systems Research, Kassel, Germany

After:

Source: Andreas Hermelink, Centre for Environmental Systems Research, Kassel, Germany

Net result:

• 90% reduction in heating energy use – this saves natural gas that can be used to generate electricity at 60% efficiency (or even higher effective efficiency in cogeneration), thereby serving as an alternative to new nuclear power plants

• Problems of summer overheating were greatly reduced

• A grungy, deteriorating building was turned into something attractive and with another 50 years at least of use

In Toronto and some other North American cities

• There are opportunities for similarly large reductions through retrofitted old 1960s and 1970s apartment towers

• Single-family houses will be harder and more expensive, but are doable

• But what will we do with all the glass condominiums and office towers being built now?

Table 4.34 Current and projected energy use (kWh/m2/yr) after various upgrades of a typical pre-1970 high-rise apartment building in Toronto.

DHW=domestic hot water, IRR=internal rate of return, HRV=heat recovery ventilator.

N a tu r a l G a s M e a su re H ea t in g D H W

E lec -tr ic ity

P r im a ry E n e rg y

C o st ($ /m 2 )

P a y b a ck (y e a rs)

IR R (% /y r )

C u rren t b u ild in g 2 0 3 3 6 7 1 4 4 3 R o o f in su la tio n 1 8 4 3 6 7 0 4 2 0 1 3 11 .4 11 .3 C la d d in g u p g r a d e 1 6 7 3 6 6 9 3 9 8 4 4 1 8 .1 3 .4 W in d o w u p g r a d e 1 2 2 3 6 6 4 3 3 6 7 3 1 3 .5 9 .2 B a lco n y e n c lo su re 1 2 2 3 6 6 8 3 4 5 1 2 1 2 1 4 .3 A ll o f th e a b o v e 4 7 3 6 6 4 2 5 2 1 9 9 1 8 .6 5 .6 B o ile r u p g r a d e 11 8 3 6 7 0 3 4 7 2 3 5 .5 2 3 H R V 1 3 6 3 6 6 8 3 6 2 1 7 7 .8 2 5 .8 W a ter c o n se rv a t io n 2 0 3 2 5 7 0 4 3 0 5 3 .4 3 5 .1 P a r k a d e lig h tin g 2 0 3 3 6 7 0 4 4 0 0 4 .4 2 8 A ll o f th e a b o v e 9 .4 2 5 5 9 1 8 5 2 5 7 1 6 .9 6 .7 A b o v e w ith 5 0 % less te n a n t e le ctr ic ity 2 4 .1 2 5 2 9 1 2 8

Karlsruhe High rise, before and after renovation (measured energy requirement for heating+DHW dropped

from 115 kWh/m2/yr to 61 kWh/m2/yr)

Source: http://www.enob.info/en/refurbishment/

Figure 4.86 Prefabricated replacement roof for a residential building in Zurich, Switzerland

Source: Zimmermann (2004, ECBCS News October 2004, 11–14, www.ecbcs.org)

Figure 4.87 VIP Dormer Retrofit

Source: Binz and Steinke (2005, 7th International Vacuum Insulation Symposium, EMPA, Duebendorf, Switzerland, 28–29 September, p43–48,www.empa/ch/VIP-Symposium )

Examples of installation ofexternal insulation in retrofit projects as part of

the EnOB (Energy Optimized Building) program in Germany

Construction of pre-fabricated window-wall units in a factory – allows for quality assurance

Installation of external pre-fabricated unit over the pre-existing wall (Hofheim pilot project)

External vacuum-insulationpanels are shown here

Before and after photos of the previous project (each of the three buildings was insulated to a different

standard, so as to provide a basis for comparingcosts and benefits)

Compilations of Case Studies of Energy Savings that Have Been

Achieved (or are expected) through Comprehensive Retrofits of

Existing Buildings

From the Retrofit For the Future database in the UK: Comparison of projected energy intensity after a retrofit vs measured energy intensity before (ongoing

monitoring to verify or refute the projected savings is occurring). About half the buildings are expected to achieve a factor of 2-4 reduction in energy use, and

half are expected to achieve a factor of 4-10 reduction. This is what we need for “sustainability”!

0 500 1000 1500 2000

Initial Primary Energy Intensity (KWh/m2/yr)

Factor of 10reduction

NoSavings

Comparison of before and after heating+DHW for buildings retrofitted in Germany under the EnOB Program

Studen

Second

ary sc

Printin

High-ri

Double-

Sports

r) Before renovation

After renovation

Solar Retrofits

• Double-skin facades (protects deteriorating original facade from further deterioration)

• Enclosure of balconies (so that they no longer serve as radiator fins)

• Transpired solar collectors

Figure 4.88 Telus Retrofit, Vancouver

Source: Terri Meyer-Boake, School of Architecture, University of Waterloo, Canada

Figure 4.89 Solar renovation in Zurich

Source: Zimmermann (2004, ECBCS News October 2004, 11–14, www.ecbcs.org)

Figure 4.90 Transpired solar collector (“Solarwall”) on an apartment building in Windsor, Canada

Source: www.solarwall.com

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