[16469] Low Energy Building Design

Critique 3

Adam Boney, Fraser Cassels, Marc Breslin and Nick Burns

Our Design

1st Floor

Building Fabric

West Facade Southern Facade

Thermal Envelope around building :

Excludes garage and front porch as these spaces will be rarely occupied so don’t require to be heated.

This will also minimize draughts and help reduce thermal bridging

Building Fabric

Section similar to the design of our wall consists of:• Timber cladding, k – 0.18 W/m K, 14mm•Battens 40 x 40•Isolair L sarking board, 0.047 W/m K, 22mm•Double timber stud work 288 mm with cellulose insulation, 0.035 W/m K, 280 mm•Racking board, 12mm•Service void 30 mm•Plasterboard, 0.16 W/m K, 12mm

Outer Inner

Calculations for U value :R = thickness/ thermal conductivityU Value = 1 / ∑ R

Ro = 0.014/ 0.18 = 0.077 Ri = 0.012/ 0.16 = 0.075R1 = 0.022/ 0.047 = 0.49 R2 = 0.280/ 0.035 = 8R3 = (0.030 + 0.040)/ 0.025 = 2.8

Rtot = 11.442 U value = 1 / 11.442 = 0.09 W / m2 K

Typical Wall :

Building fabricRoof Design :

Similar floor:

Section is constructed from :•Slates, 2 W/m K, 5mm•Battens 40 x 40•Isolair L sarking board, 0.047 W/ m K , 60 mm•Pavatherm insulation board , 0.038 W/ m K, 80 mm•Osb 12mm• 175 mm Rafters with sheep’s wool insulation , 0.038 W/m K•OSB 12 mm•Service void 30 mm•Platerboard , 0.016 W/ m K, 12mm

U Value of 0.10 W / m2 KSection constructed from :•Flooring finish•Fermacell 2 x 12mm•Pavatherm, 0.038 W/ m K, 50mm•Vapour barrier•220mm Floor joists with 200mm sheep’s wool insulation 0.038 W/ m K•Vapour barrier•200 mm air barrier

U value of 0.07 W / m2 K

Building fabricWindows:

•Ecopassiv windows are triple glazed

• Whole window U value – 0.75 W /

m2 K

•Warm edge spacers

•Polyurethane frame insulation

•Argon fill 44mm

Doors:

•Frostkorken doors which are triple

glazed

•Door whole U value of 0.72 W / m2 K

• Incorporates cork frame insulation to

reduce thermal bridging

•High performance seals and extruders

fitted to prevent draughts

Demand - HeatingFabric heat loss

= Area x U-value x Temperature Difference

= 8751 kWh/yr

Ventilation heat loss= mass flow rate x Cp x Temperature Difference

=3759.5 kWh/yr

Demand - HeatingGains:

Passive: = 5840 kWh/yr Total Gains = 8761.25

Solar : = 2921.25 kWh/yr

Difference = Gains – Loss

= -366.06kWh/yr

Demands – Hot water Outside Air Temperature 10 JCTemperature of hot water 45 JC

Hot water demand = 163 litres/day Assume usage = 5 hours

m = 0.009 kg/s Cp = 4187 Q = m * Cp * ∆t * ŋ

∆t = 35 °C Q =3229.146 kWh/yr ŋ = 0.75

Demand – Weekday Energy

Demand – Weekend Energy

Demand – Appliances

Total Energy DemandTotal Energy Needed = Appliances + Hot water + Heating

= 4646.7983 + 3229.146 + 366.06

= 8242.004 kWh/yr required

Power calculation formula:Worked example-

P=ρAV³xCp

http://www.raeng.org.uk

Turbine options:

Total demand data:Total demand=

Appliance demand + hot water demand +Heating demand

= 8242.004 kWh/yr

Turbine selection:Having calculated the potential total annual

demand for building we can select a suitable size of turbine to meet this demand.

We have opted for : - 10kW Westwind Turbine. - Producing ~12500kwh/yr. - 6.2m diameter blade. (taken from

http://www.westwindturbines.co.uk)

Turbine selection:The selected turbine satisfies the annual

demand however there is the possibility that it may not meet a particular monthly demand.

We have opted for a turbine with a higher output than required.

Should this occur we will look to recover the power loss via a - PV system.

- Power storage system.

Power storage from turbine:There is a potential to store power generated

from the chosen turbine.Variety of ways to store power- 1. Battery storage 2. Compressed air storage 3. Hydrogen Storage

These three types will be investigated and the most suitable selected.

Water – from last time

Above ground storage tank

Rainwater harvesting systems

WaterUsing correct numbers for water usage from Code for

Sustainable Homes, taking:

Water required = 60L/day/person = 109,500 L/year

Water yield = 152.29m2 x 1,220mm x 0.75 x 85% = 118,444 L/year So rainwater should yield enough to meet water demands

Water – grey water recyclingWaste water from bathtub, shower and wash-basin will be filtered and put back into use

This will require a secondary filtering process for grey water

Water – black water disposalSewage will be disposed of using a reed bed

system

Water passing through the reed bed is cleaned by micro-organisms

Whats nextsMVHR completionStorage systemsSavingsCost