Tampa Convention Center • Tampa, Florida

Roof and Wall Systems

Using Your Building’s Envelope to Minimize Heating and Cooling Loads

Kaushik Biswas, Ph.D.Oak Ridge National Laboratory

August 16, 2017

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Presentation summary

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• The building code• The market• Technology options

• Roofs• Insulation• Cool roofs• Thermal mass

• Wall types• Case Studies:

• Retrofit of masonry wall system• Resources

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Roof Systems

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ASHRAE Standard 90.1 has changed appreciably in recent years

4

0

5

10

15

20

25

30

35

1975 1980 1989 1999 2001 2004 2007 2010 2013

R-va

lue, h

r ft °

F/Bt

u

Data for Climate Zone 4 (Kansas City, MO) DOE Climate Zone

2013 Non-Res Roof

R-value

1 20

2 25

3 25

4 30

5 30

6 30

7 35

8 35

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Insulation used in low-slope roofing

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• Expanded Polystyrene (EPS)+ Low cost option.– Low softening temperature precludes its use under

dark colored membranes.• Extruded Polystyrene (XPS)

+ Excellent moisture resistance.– Softens similar to EPS.

• Polyisocyanurate (PIR)+ Fire resistance and higher R/inch.

• Fiberboard and Perlite+ Structural or thermal protection layer.– Low R-value.

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Insulations used in low-slope roofing

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8%

75%

5% 2%9%

New construction market share, percent

EPS & XPSPolyisocyanurateFiberboardPerliteOther

2014-15 NRCA Market Survey

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Low-slope waterproofing market

7

05

101520253035

BUR Mod Bit EPDM Metal Other SprayFoam

PVC TPO

Mark

et S

hare

, Per

cent

New construction low-slope roofing sales

• Cool roofs (PVC, TPO, and Spray Foam) represent 48% of market.• BUR, Mod Bit, and Metal (22%) can be any color based on

aggregate/paint.• Cool roofs are now about 60% of market.

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When do cool roofs save energy?

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• http://energy.gov/sites/prod/files/2013/10/f3/coolroofguide.pdf

• What climate zone?• What happens when they

get dirty?• How about more

insulation…..• Ballast…...

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Cool roof impact on an energy bill

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Impact of demand charges

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DOE cool roof calculator

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Estimates energy and peak demand savings for flat roofs with non-black surfaces

• http://web.ornl.gov/sci/roofs+walls/facts/CoolCalcPeak.htm• Input:

– Roof location (city and state); – Roof characteristics (R-value, solar reflectance, thermal emittance);– Equipment data (heating and cooling energy costs and efficiencies); and– Demand charge details (demand charge and duration).

• Output:– Cooling and heating energy savings– Demand savings

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Comparison between a cool and black membrane

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Location Energy Savings per square foot, $ or Percent

Cooling Heating Demand Total % Demand

Miami $0.083 -$0.002 $0.069 $0.150 46%

Atlanta $0.049 -$0.015 $0.067 $0.101 66%

Baltimore $0.040 -$0.018 $0.063 $0.085 74%

Fargo $0.017 -$0.015 $0.061 $0.064 95%

• Assumptions:– Roof R-value = 15 – Solar reflectance = 10% vs. 75%– Thermal emittance = 90%– Equipment (air conditioning for cooling; electric resistance for heating in

Miami, heat pump for heating in Atlanta, and gas for heating in Baltimore and Fargo)

– Demand charge = $20/kW

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Ballasted roof systems available since the early 1970’s

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Temperature profiles of “cool” roofs

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0 2 4 6 8 10 12 14 16 18 20 22 24Hours into 4/22/2007

0 2 4 6 8 10 12 14 16 18 20 22 24Hours into 4/22/2007

0 2 4 6 8 10 12 14 16 18 20 22 240 2 4 6 8 10 12 14 16 18 20 22 24 Heat

Flu

x thr

ough

Insu

latio

n [B

tu/(h

·ft²)]

0 2 4 6 8 10 12 14 16 18 20 22 24

Mem

bran

e Tem

pera

ture

(°F)

0 2 4 6 8 10 12 14 16 18 20 22 2430

70

90

110

150

170

-8

8

12

20

0

Under 21 lb/ft² Coated Paver Under 16 lb/ft² Coated PaverBare White TPO

Bare Black EPDM Under 10 lb/ft² Stone

Under 17 lb/ft² Stone

Under 24 lb/ft² Stone

Under Uncoated Paver

4

130

50 -4

16

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Wall Systems

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IECC 2015 wall R-value requirements

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• Some buildings can also contain R20 cavity insulation with lower levels of continuous insulation (C.I.)

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Adoption of IECC

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• IECC adopted statewide or at a local level in 46 states.– Others (CA, IN, MN & OK): State-code (CA) or ASHRAE 90.1 with

amendments.

IECC adoption by vintage

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Exterior commercial wall material distribution

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Total number of buildings: 5,557,000Source: Energy Information Administration (EIA): Commercial Building Energy Consumption Survey (CBECS 2012)

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Commercial building renovations

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• Renovation in pre-2008 buildings, per CBECS 2012:– Any type of renovation – 2,094,000 (out of 5,254,000 buildings)– Exterior wall replacement – 194,000 (9.3% of all renovations)– Interior wall reconfiguration – 889,000 (42.5% of all renovations)– Insulation upgrade – 382,000 (18.2% of all renovations)

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Wood- and metal-framed walls

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Cavity + Exterior continuous insulation (C.I.)

Prefabricated wall panels with open-cell spray foam insulation (fibrous batt insulation also used)

Exterior spray-applied closed-cell foam insulation on stud wall assemblies

• Primary applications – Office buildings, schools, retail buildings (pre-1980), restaurants, apartment buildings, etc.

• Utilize both cavity and exterior continuous insulation (C.I.)

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Mass walls

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Insulated concrete form (ICF)

Polystyrene foam

Concrete fill

• Primary applications – Large office buildings, retail buildings, supermarkets, large hotels, hospitals, etc.

Concrete masonry unit wall with exterior C.I. (spray-

applied or rigid foam insulation)

Mass wall with exterior C.I. (mineral fiber)

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Precast concrete walls

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Insulated precast concrete basement walls; challenging to form & pour foundation walls during winter in cold climates.

ORNL’s MAXLAB

Precast panels: 3-inch exterior concrete wythe, 2 inch of insulation (center) and 4-inch interior structural wythe.

New ORNL and Industry R&D: Lighter, lower-cost panels; 3D printed forms; advanced composites for reinforcement.

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Metal buildings

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Interior spray-applied foam insulation

Fiberglass insulation for interior application

Interior reflective insulation

• Primary applications – warehouses, aircraft hangars, etc.

• Typically contain insulation compressed between metal members.

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Insulated metal panel and curtain wall

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Prefabricated insulated metal panels (IMP)(Serve as cladding and interior finish)

Curtain wall insulation(Typically used in high-rise buildings)

IMP with rock wool insulation sandwiched between metal sheets

(foam insulation is also used)

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Case study: interior retrofit of a masonry wall

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• Target market: Masonry walls on pre-1980 buildings in climate zones 4 (mixed climate, needing heating and cooling) and 5 (cold climate, heating-dominated).

• Goal: Exceed ASHRAE 90.1-2010 requirements with a payback of 10-15 years with façade retention and moisture durability.

Solution category No. Retrofit strategyRetain existing wall 1 2” polyisocyanurate (PIR) foam board over

existing drywallRemove existing fiberglass insulation

2 6” open-cell spray polyurethane foam (SPF) within extended stud cavity

3 4.5” closed-cell SPF within stud cavity

Remove existingfiberglass insulation and steel studs

4 2.5” continuous cellulose + 3.5” cellulose

5 1.5” continuous closed-cell SPF + 2” closed-cell SPF

6 2” continuous closed-cell SFP + 3.5” cellulose

7 1.5” continuous closed-cell SPF + 3.5” cellulose

8 2.5” foam board w/ separate air barrier layer

9 2.5” foam board w/ taped seams

Baseline: Typical pre-1980s commercial construction around

Philadelphia, PA.

ORNL’s Flexible Research Platform

Build

ing

inte

rior

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Interior retrofit of a masonry wall

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Final ranking* Retrofit strategy Cost

($/ft2) R-value Conden-sation

A 2” PIR foam board over existing drywall 4.35 25.5 No

6” open-cell SPF within extended stud cavity 8.75 19.2 No

4.5” closed-cell SPF within stud cavity 8.65 15.2 No

2.5” continuous cellulose + 3.5” cellulose 9.75 22.1 Yes

C 1.5” continuous closed-cell SPF + 2” closed-cell SPF 9.40 22.1 No

2” continuous closed-cell SFP + 3.5” cellulose 10.10 25.0 No

1.5” continuous closed-cell SPF + 3.5” cellulose 9.00 22.0 No

B 2.5” foam board w/ separate air barrier layer 8.05 20.8 No

2.5” foam board w/ taped seams 6.55 20.8 No

* Additional evaluation criteria: Air tightness, indoor air quality and lack-of-disruptiveness.

PoorLowModerateHigh

Effectiveness Indicator

Exterior

Existing insulation and studs removed

Existing insulation and studs removed

Exterior

• Only option with payback <15 years.

• Assuming existing insulation performing as expected.

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Resources

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• National Roofing Contractors Association Roofing Manual, www.nrca.net, the ‘bible” on how to construct commercial roofs.

• Single Ply Roofing Industry, www.spri.org, technical information pertaining to single ply roof systems.

• Asphalt Roofing Manufacturers Association, www.asphaltroofing.org, technical information pertaining to asphaltic roof systems.

• Polyisocyanurate Insulation Manufacturers Association, www.polyiso.org, technical information pertaining to polyisocyanurate foam.

• Annual Book of ASTM Standards Volume 04.04, Roofing and Waterproofing Standards and Specifications, www.astm.org.

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Tools

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• Roof Savings Calculator, http://rsc.ornl.gov, calculation tool that estimates roof design energy performance.

• Cool roof peak demand calculator, http://web.ornl.gov/sci/roofs+walls/facts/CoolCalcPeak.htm, estimates energy savings and peak demand reduction for roofing systems.

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Questions and answers

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Kaushik Biswas, Ph.D.

biswask@ornl.gov

Visit our website: www.ornl.gov/buildings

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