Energy-Saving Assemblies

in Commercial Structures

Matthew Brown, CGP, APADisclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the

Softwood Lumber Board.

“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516.

Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

__________________________________

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

Course Description

While it’s fairly well known that wood products sequester carbon and tend to

require less energy to manufacture than other building materials, their

performance related to operational energy efficiency is sometimes overlooked.

From a thermal perspective, wood-frame building enclosures are inherently

more efficient than steel-frame, concrete, or masonry construction—because of

the insulating qualities of the wood structural elements, including studs, columns,

beams and floors, and because wood stud walls are easy to insulate. Using real-

world project examples, this presentation will examine options for utilizing wood-

frame assemblies to achieve compliance with the International Energy

Conservation Code.

Learning Outcomes

Identify and understand IECC pathways for

compliance.

Develop a general understanding of wood frame

construction in choosing pathways for compliance.

Recognize the energy advantages of utilizing wood

construction materials.

Understand the means and methods for utilizing

wood construction through demonstration of real-

life compliance scenarios.

History of Energy Codes

A Brief History of Commercial Codes

U-Factor

Total Building

Performance

(software)

R-Value

R-values

C402.1.3

Performance

Alternative

C407

U-factor

C402.1.4

ASHRAE

90.1

ASHRAE

90.1-2013

IECC

OR

Prescriptive

Four Options to Commercial Energy Code Compliance

2015 IECC Climate Zones

Prescriptive –R-Value Method C402.1.3

Climate Zone 4 5 6

All Other Group R All Other Group R All Other Group R

Mass R-9.5ci R-11.4ci R-11.4ci R-13.3ci R-13.3ci R-15.2ci

Metal Building R-13+13ci R-13+13ci R-13+13ci R-13+13ci R-13+13ci R-13+13ci

Metal Framed R-13+7.5ci R-13+7.5ci R-13+7.5ci R-13+7.5ci R-13+7.5ci R-13+7.5ci

Wood Framed R-13+3.8ci

or R-20

R-13+3.8ci

or R-20

R-13+3.8ci or

R-20

R-13+7.5ci

or R-

20+3.8ci

R-

13+7.5.8ci

or R-20+3.8

R-13+7.5ci

or R-

20+3.8ci

Above Grade Walls

Prescriptive –U-Factor Method C402.1.4

Above Grade Walls

Climate Zone 4 5 6

All Other Group R All Other Group R All Other Group R

Mass U-0.104 U-0.090 U-0.090 U-0.080 U-0.080 U-0.071

Metal Building U-0.052 U-0.052 U-0.052 U-0.052 U-0.052 U-0.052

Metal Framed U-0.064 U-0.064 U-0.064 U-0.064 U-0.064 U-0.057

Wood Framed U-0.064 U-0.064 U-0.064 U-0.064 U-0.051 U-0.051

U-Factor Trade-off Approach

Allows limited flexibility

in the building envelope

design.

R-value for R-value

Trade.

Does not credit high

efficiency equipment, air

sealing and duct sealing.

Total Building Performance

Allows greatest flexibility in code.

Credits tight infiltration, ducts and HVAC equipment.

Software usage depends on occupancy type.

Energy Efficiency Analysis of Three Construction Material Types

Multifamily Building Design: Multifamily Group R

3 story on slab

28,500 sq. ft.

27 units, 57 bedrooms

256,500 cu. ft. conditioned air

Philadelphia

Wood and Steel Framed WallsComparison - Composition

R-13 Cavity

Insulation

1-1/2” R-7.5

Continuous

Insulation

Water resistant

barrier or tape

joint

Mesh

Drainage

5-1/2” Steel

header

1/2” Drywall

5-1/2” Studs and

plates

R19 Compressed or

R18 cavity insulation

Wood structural

panel sheathing

Water resistant

barrier

Exterior Cladding

v

Exterior

3-1/2” Steel studs

Wood and Masonry Framed WallsComparison - Composition

5-1/2” Steel

header

R19 Compressed or

R18 cavity insulation

Wood structural

panel sheathing

Water resistant

barrier

Exterior Cladding

Exterior

1/2” Drywall

5-1/2” Studs and

plates

Thermal Characteristics of Wood & Steel

Steel Wall Construction

Exterior Insulation

Wood Wall Construction

Interior GypsumExterior Cladding

Thermal Bridging

Thermal Characteristics of Wood & Masonry

Masonry Wall Construction

Exterior Insulation

Wood Wall Construction

Interior GypsumExterior Cladding

Thermal Bridging

Above Grade Wall Analysis

Wall Assemblies1 Total Energy (MMBTU) Wall – Energy Cost2

CZ 4- Wood R-20 Wall 95.40 $1030.14

CZ 4-Steel R-13 + 7.5 c.i. 94.20 $1019.70

CZ 4-Block +11.4 c.i. 90.00 $980.33

1. Continuous Insulation (c.i.)

2. Monthly total energy usage and cost for Above Grade Wall assemblies only.

Above Grade Wall Analysis

Assembly1 Total Energy (MMBTU) ABG wall – Energy Cost2

CZ 5 - Wood R-21 - no c.i 92.2 $594.00

CZ 5 - Wood R-20 + 3.8 c.i. 98.6 $632.00

CZ 5 - Steel R-13 + 7.5 c.i. 94.1 $605.00

CZ 5 - Masonry + R-13.3 c.i. 108.7 $709.00

CZ 6-Wood R-21Wall- no c.i 112.7 $827.86

CZ 6-Wood R-20+3.8 c.i. 110.40 $825.82

CZ 6-Steel R-13 +7.5 c.i. 125.10 $923.43

CZ 6-Block + R-15.2 c.i. 141.00 $1034.70

1. Continuous Insulation (c.i)

2. Monthly total energy usage and cost for Above Grade Wall assemblies only.

Results

Code requires steel and masonry to have continuous

insulation while wood does not in order to meet

assembly U-factor levels.

Studies have shown that wood buildings can cost

significantly less to construct while providing the

same or better energy performance.

A common misconception is that continuous

insulation makes masonry and streel walls more

energy efficient than wood walls without continuous

insulation.

The effects of thermal bridging in wood walls is often

overstated.

Commercial Roof Insulation Requirements

Roof/Ceiling Assemblies –R-Values

Climate Zone 4 5 6

All Other Group R All Other Group R All Other Group R

Insulation Above deck R-30ci R-30ci R-30ci R-30ci R-30ci R-30ci

Wood Framed R-38 R-38 R-38 R-49 R-49 R-49

Table C402.2 – Opaque Thermal Envelope Requirements.

Roof/Ceiling Assemblies –U-Factor

Climate Zone 4 5 6

All Other Group R All Other Group R All Other Group R

Insulation Above

deck

U-0.032 U-0.032 U-0.032 U-0.032 U-0.032 U-0.032

Wood Framed U-0.027 U-0.027 U-0.027 U-0.021 U-0.021 U-0.021

Table C402.3 – Opaque Thermal Envelope Requirements.

Energy Efficiency Analysis of Roof/Ceiling Assemblies

Building Design: Multifamily Group R

3 story on slab

28,500 sq. ft.

27 units, 57 bedrooms

256,500 cu. ft. conditioned air

Philadelphia

Insulation Entirely above the Roof Deck

Foam board insulation -considered continuous

Insulation (c.i.)

Varies in thickness

R-values range from R-5 to R-6 per inch

Wood Attic

Install insulation between

framing members

Roof/Ceiling Analysis

Roof Assemblies Total Energy

(MMBTU)

Energy Cost2

CZ 4- R-30 Above Deck 30.70 $225.45

CZ 4- R-38 Wood Attic 21.50 $158.27

1. Continuous Insulation (c.i.)

2. Monthly total energy usage and cost for Roof/Ceiling assemblies only.

Roof/Ceiling Analysis

Assembly1 Total Energy (MMBTU) ABG wall – Energy Cost2

CZ 5-R-30 Above Deck 39.00 $282.98

CZ 5-R-49 Wood Attic 21.50 $156.65

CZ 6 - R-30 Above Deck 43.1 $317.42

CZ 6- Wood Attic R-49 26.8 $196.56

1. Continuous Insulation (c.i)

2. Monthly total energy usage and cost for Roof/Ceiling assemblies only.

Raised Heel Trusses

Insulation:

Energy-heel truss

Full-height insulation extends

over top plates

Continuous wood wall sheathing

overlaps onto truss heel

Raised Heel Roof/Ceiling Analysis

Roof Assemblies Total Energy

(MMBTU)

Energy Cost2

CZ 4 - Above deck R-30 c.i.1 53.3 $338.00

CZ 4 - Wood attic R-38 31.5 $203.00

CZ 4 - Wood attic raised heel3 R-30 30.3 $195.00

Note: Raised Heel Trusses with R-30 insulated yield a 3.2% energy savings on average.

1. Continuous Insulation (c.i.)

2. Monthly total energy usage and cost for Roof/Ceiling assemblies only.

3. Raised Heel Truss

Raised Heel Roof/Ceiling Analysis

Assembly Total Energy

(MMBTU)

Above Grade wall –

Energy Cost2

CZ 5- Above Deck R-30 c.i 30.10 $205.36

CZ 5- Wood Attic R-49 26.8 $196.56

CZ 5 Wood Attic Raised Heel3 R-38 25.1 $184.09

CZ 6- Above Deck R-35 c.i 45.5 $333.27

CZ 6- Wood Attic R-49 34.6 $253.87

CZ 6-Wood Attic Raised Heel3 R-38 33.22 $243.74

Note: Raised Heel Trusses with R-38 insulated yielded a 4% on average

savings in energy.

1. Continuous Insulation (c.i)

2. Monthly total energy usage and cost for Roof/Ceiling assemblies only.

3. Raised Heel Truss

Results

Wood attic assemblies are more energy efficient than

insulation above deck assemblies.

Studies have shown that wood roof assemblies can

cost significantly less to construct.

In many cases the energy cost of the wood attic was

half that of the metal framed buildings with

continuous insulation roofs.

Wood raised heel trusses require less insulation

while providing better energy performance.

Performance Code Compliance

Simulated Performance Alternative

Performance Based Code Compliance

R-13+ 3.8 c.i. Exterior walls

(U-0.062)

R-38 Attic insulation

U-.32 Windows

R-10 Footing insulation -

24 inches deep.

IECC Reference Building: Proposed Design:

R-19 Exterior walls, no c.i.

(U-0.064)

R-30 Attic insulation with

raised heel trusses

U-.32 Windows

R-10 Footing insulation -

36 inches deep.

Whole Building Energy Performance

Climate Zone Above Grade Walls1 Attic/Roof Footings Energy Cost2

CZ 4 Wood R-19 - no c.i. R-30 Raised Heel3 R-10, 36 inches vertical $4,178.00

CZ 4 Wood R-13 + 3.8 c.i. R-38 Attic R-10, 24 inches vertical $4,204.00

CZ 4 Steel R-13 + 7.5 c.i. R-20 c.i.1 R-10, 24 inches vertical $4,658.00

CZ 4 Masonry + R-13.3 c.i. R-38 Attic R-10, 24 inches vertical $4,912.00

1. Continuous Insulation (c.i.)

2. Yearly energy cost for heating and cooling used to determine 2015 IECC compliance.

3. Raised Heel Truss

Performance Based Compliance

The proposed design

not only meets the 2015

IECC requirements, the

design exceeds them.

By 2.4%

Energy Efficiency Analysis of Three Construction Material Types

Building 2: Elementary School

1 story on slab

50,000 sq. ft.

500,200 cu. ft. conditioned air

Climate Zones 5 and 6

This evaluation was conducted by Nexant Energy Consultants, Boulder, Colorado.

Elementary School Analysis

Wall Assemblies Roof Assemblies Attics Annual Energy Cost

CZ 4 - Wood R-20 R-38 $31,525

CZ 4 - Steel R-13 + 7.5 c.i.1 R-38 $31,269

CZ 4 - Masonry 11.4 c.i.1 R-38 $31,242

1. Continuous Insulation (c.i.)

Attic Roof Assemblies

Wood Attic on Masonry Walls

Wood Attic on Wood Walls

Wood Attic on Steel walls

Elementary School Analysis

Wall Assemblies

Roof Assemblies

Insulation Above Deck1 Annual Energy Cost

CZ 5 - Wood R-20 R-30 c.i $32,675

CZ 5 - Steel R-13 + 7.5 c.i.1 R-30 c.i $32,401

CZ 5 - Masonry 11.4 c.i.1 R-30 c.i $32,373

1. Continuous Insulation (c.i.)

Nexant Analysis Results

Similar to the multifamily analysis code required

assemblies with continuous insulation are not as

energy efficient as wood framed assemblies without

the use of continuous insulation.

Wood framed attics with ceiling insulation are more

energy efficient than assemblies with continuous

insulation over the structural roof systems.

Air leakage Control

According to the US

Department of Energy

as much as 30

percent of a buildings

energy usage can be

from air leakage.

Utility penetrations.

Drop ceilings/utility chases adjacent to the thermal boundary.

Common walls between dwelling units.

Multifamily Building Air Leakage

Key Areas for Air leakage:

Utility Penetration Air Sealing

Drop Ceiling Utility Chase Air Sealing

Common Wall Air Sealing

Air Leakage Testing

Air leakage testing

ensures the air barriers

and air sealing are

functioning.

Energy codes allow

greater trade-offs for

less air leakage.

Principals of Air Sealing

Air is lazy and will take the least path of resistance, start

with the biggest penetrations and gaps and work down to

the smaller ones.

Where air moves so does heat and moisture.

There is not a “one size fits all” solution, balancing

product price, functionality and use is important.

Air sealing is often the most cost effective energy

improvement made to buildings.

On Your Next Project

Code required wood framed assemblies are more cost

effective than other assemblies.

Wood assemblies are more energy efficient that masonry

and steel assemblies.

Both of these points mean lower building costs and

operational energy costs for the client for years to come.

Learning Outcomes

Identify and understand IECC pathways for

compliance.

Develop a general understanding of wood frame

construction in choosing a pathways for compliance.

Recognize the energy advantages of utilizing wood

framed construction materials.

Understand the means and methods for utilizing

wood construction through demonstration of real-life

compliance scenarios.

Questions

Matthew Brown, CGP.

EMAIL:

Matthew.Brown@apawood.org

PHONE:

(219)-369-6711