Canadian Wood Council G063

Meeting New Energy Code Requirements with Wood

Frame Construction

Rob Jonkman, P.Eng., Manager Structrural Engineering and

WoodWorks software, CWC

Dr. Jieying Wang, Senior Research Scientist, Durability and

Building Enclosure Group, FPInnovations October 29, 2013

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.

FPInnovations recently completed a “Guide for Designing Energy‐Efficiency Building Enclosures for

Wood‐Frame Multi‐Unit Residential Buildings in Marine to Cold Climate Zones in North America”. This

guide serves two major objectives: to assist architects, engineers, designers and builders in improving

the thermal performance of building enclosures of wood multi-unit residential buildings and to advance

design practices, construction practices, and material use based on best knowledge, in order to ensure

the durable performance of wood-frame building enclosures that are insulated to higher levels than

traditional wood-frame construction. The Canadian Wood Council has developed an Online interactive

above-grade wall assembly catalogue for architects, designers, engineers, consultants and contractors

to use to quickly determine suitable wall assemblies for each climate zone in Canada with confidence.

While the focus is complying with 2010 National Building Code (NBC) December 2012 amendments for

houses and 2011 National Energy Code for Buildings (NECB) for larger buildings, the wall assemblies

will be a handy reference to comply to any building code that enables the designer to choose an

effective R value. Durability, ease of construction, and affordability of the wall construction are all

considered, providing an overall assessment of the wall assembly.

Course Description

Learning Objectives

1. Information to assist architects, engineers, designers and builders in improving the

thermal performance of building enclosures of wood multi-unit residential buildings.

2. Information to advance design practices, construction practices, and material use

based on best knowledge, in order to ensure the durable performance of wood-frame

building enclosures that are insulated to higher levels than traditional wood-frame

construction.

3. Information on an Online interactive above-grade wall assembly catalogue for

architects, designers, engineers, consultants and contractors to use to quickly determine

suitable wall assemblies for each climate zone in Canada.

4. Information on tools available to calculate Durability, ease of construction, and

affordability of the wall construction.

At the end of the this course, participants will be able to:

www.fpinnovations.ca

Meeting New Energy Code Requirements with Wood Frame Construction

Part 1: Jieying Wang

What Is FPInnovations?

A private non-profit research institute

Supports competitiveness of the Canadian forest sector

Science & technology based solutions

– Forest management

– Pulp and paper

– Wood products, buildings…

– …

Supporting Members from Coast to Coast

FPInnovations Vancouver Research Centre

WFORC Hinton, AB

FPInnovations Research Centres

CWFC Research Centres

FPInnovations Pte. Claire Research Centre

FPInnovations Québec City Research

Centre

FPInnovations Field Staff

Wood-Based Building Solutions

Wood Building Systems

Light Frame

Post & Beam

CLT

Energy-related Context

Buildings account for 50% energy consumption

and 40% CO2 emissions in N. America

New building codes to improve energy efficiency

Construction industry needs to meet code

Wood industry wants to meet evolving demands

9

National Energy Code for Buildings (NECB)

published in November 2011

– The Province of BC has adopted it (in parallel with

ASHRAE 90.1-2010)

– Be effective in December, 2013

10

National Energy Code Changes

NRC 2011; Building and Safety Standards Branch 2013

Climate Zone and HDD(°C) Wood-frame, above-grade wall Wood-frame roof, flat or sloped:

[R-value (RSI)] [R-value (RSI)]

Zone 4: <3000 HDD 18.0 (3.17)

25.0 (4.41)

Zone 5: 3000 to 3999 HDD 20.4 (3.60)

31.0 (5.46)

Zone 6: 4000 to 4999 HDD 23.0 (4.05)

31.0 (5.46)

Zone 7a: 5000 to 5999 HDD 27.0 (4.76)

35.0 (6.17)

Zone 7b: 6000 to 6999 HDD 27.0 (4.76)

35.0 (6.17)

Zone 8: >7000 HDD 31.0 (5.46)

40.0 (7.04)

Document durability and energy performance

– Old/New energy efficient houses/buildings

Assist academia in field testing

– Testing highly insulated framed walls and CLT walls

• Using test huts (Waterloo, Edmonton)

• Particularly research under NSERC NEWBuildS

Help develop durable and energy efficient solutions

– Buildings, houses, and log homes etc.

Assist in improving performance prediction

– Wood property data and modelling validation

Wood products development

Related Research at FPInnovations

Building Energy Design Guide Published

FPInnovations published a building energy design

guide in March 2013

– In collaboration with RDH, HPO, and CWC

– Available on website for free

12 http://www.fpinnovations.ca/ResearchProgram/AdvancedBuildingSys

tem/designing-energy-efficient-building-enclosures.pdf

Assist in meeting new energy codes for buildings

Advance good design/construction practices

Help improve energy performance

Ensure long-term durability performance

Assist in design of larger/taller wood buildings

13

Objectives

Climate Zones

Marine to Very Cold Climate Zones

– Part of Canada (including most BC) and the U.S.

– DOE/ASHRAE Climate Zones 5 through 7 and parts of

Zone 4

14

Platform framing

Mass timber—e.g. CLT

Post-and-beam framing

Wood-frame infill in concrete structure

15

Four Types of Enclosure Systems

Dominant construction type for low-rise buildings

– Mostly up to 4-storey in N. America

– Up to 6-storey in BC, Quebec, and Oregon etc.

– Inherently energy efficient

• Higher thermal resistance

• Lower thermal bridging

• “Free” cavity for insulation

How to meet higher energy requirements?

16

Platform Frame Construction

Cavity fill insulation with higher R-values

Deeper wall/roof cavity for more insulation

– 2 by 8, 2 by 10, engineered joists, built-up trusses…

17

Platform Frame: Solutions

Double-stud walls (sometimes

staggered stud walls)

– Typically using 2 by 4s filled with sprayed

cellulose insulation

– Effective R from 20 to 40 (a gap

between)

– Practices started in 1970s for

houses/small buildings

– Rainscreen wall improves durability

18

Platform Frame: Solutions

Page 4-14, Table 4.2., effective R values for double-stud walls

Double-stud walls

FPInnovations survey confirm airtight and durable in

Prairies

– Six homes built or retrofitted for energy efficiency from 1979-1992

in Saskatoon

– All had double stud rainscreened walls

– All had poly as air barrier

– Still performing well for energy efficiency and durability

– Paper published in Journal of Building Physics

19

Platform Frame: Solutions

H. Orr, J. Wang, D. Fetsch, R. Dumont. 2012

Split-insulation wall

– Exterior insulation + cavity insulation

• Such as rigid foam, mineral wool

– Exterior insulation keeps sheathing

warmer

• Confirmed by the Coquitlam field testing

• The thicker, the warmer (outboard/Inboard

thermal resistance ratio)

• Permeable exterior insulation/membrane

allows drying towards exterior

• Interior poly be removed when exterior has

low vapour permeance

20

Platform Frame: Solutions

P4-7: Table 4.1.1-4.1.4, effective R values for split-insulated walls

Mass timber—e.g. CLT: Solutions

Exterior insulation keeps wood warm

and dry

– Wood provides about R-1.2/in.

– Permeable exterior insulation allows

drying towards exterior

– No need for interior poly or exterior low-

permeance membrane

• Confirmed by the Waterloo field testing

• Thick panel has low vapour/water permeance

• Wood is a good moisture buffer

21 P4-20: Table 4.3.1-4.3.3, effective R values for CLT walls

Wood-Frame Infill Walls

For wood post-and-beam or concrete structure

22

23

Wood-Frame Infill Walls

Easier to meet thermal insulation requirements

Easier to attach cladding and windows etc.

Courtesy of Fougere Architecture Inc.

Other Information Covered in Guide

Roofs and below-grade walls

Interface detailing including windows etc.

24

How to Ensure Durability Performance?

“Leaky condo crisis” in Vancouver

– A lesson not to be forgotten

Other guidelines on design for durability

– Best Practice Guide for Wood-Frame Envelopes /in

the Coastal Climate of BC (CMHC, 1999)

– Building Enclosure Design Guide – Wood Frame

Multi-Unit Residential Buildings (HPO, 2011)

25

26 Building Science Corporation 2001

Rain usually the Largest Water Source

Traditional durability measures still relevant

– Pitched roofs and generous overhangs

4 “D”s effectively protect assemblies from moisture

– Rain deflection, drainage, drying and durable materials

Rainscreen concept important

Interface detailing

27

Moisture Management Design Principles

Deflection – Overhangs, divert water

Drainage – Remove bulk water

Drying – Allow wood to dry

Durability – Durable materials

Hazleden, D.G., Morris, P.I. 1999

Moisture Management

Protect Walls from Rain: 4 Ds

150mm

Concrete

Sill gasket Spunbonded olefin Pressure Treated sill Floor framing and plywood subfloor

Interior gypsum wallboard Vapour barrier (Poly)

Sealant

Spunbonded polyolefin wrap Wall framing Plywood or O.S.B. sheathing Metal flashing Building paper

Framing and insulation

Pressure Treated strapping + screen Horizontal cedar siding

Drainage and Drying through Cavity

Two drainage planes

– Cladding

– Sheathing membrane

Air space

– Capillary break

– Pressure moderation

– Ventilation (drying)

Construction Moisture Management

Wood may absorb moisture depending on:

Climate (and season)

– Rain, melting snow…

Wood species and products

Use of water repellant, coating, membrane, tarp…

Use of dunnage (supports under packages)

…

Time of on-site exposure

– Prefabrication reduces this time

Construction Moisture Management

On-site protection needed in most climates

Simple protection measures can make a difference

– Temporary shelters etc.

Consider season for construction?

Design assembly to allow drying

Left photo courtesy: Vaxjo University

Additional durability concerns about highly

insulated assemblies, in cold climate in particular: – Increased potential for condensation on sheathing

• Reduced heat loss from living space

• Lower sheathing temperature

• When there is a large amount of air leakage from living space

– Reduced drying capacity • With a larger amount of insulation etc.

• Particularly when low-permeance materials used

32

Additional Considerations for High Insulation

Assess drying rates of wood roofs in lab

– After severe wetting of wood panels

– Under 3 ambient drying conditions

Over 10 roof assemblies

– Plywood, OSB, CLT, LVL

– With the wet surface covered with blue skin/felt+shingles

– With/without spray foam on the dry side

– With/without temperature gradient

33

Results from Roof Drying Test

Results from Roof Drying Test

34 Drying condition: Shed, no sun or rain, started in Feb-March 2013

Drying may take a long time after severe wetting

Low-permeance materials retard drying

– Blueskin and felt+shingles both retard direct drying from

the wet surface

• Felt+shingles only slightly better than blueskin

– Closed-cell foam retards drying through the drier surface

Key implications:

– Never close assembly when wood is wet

• Space heating can be used to accelerate drying

– Consider potential consequences when low-permeance

materials are used in assemblies

35

Results from Roof Drying Test

36

Durability Summary for High Insulation

Construction moisture management critical

– Never close assemblies when wood MC is high

Rainscreen assemblies become more important

– Even in drier climates

Air leakage must be minimized

Exterior insulation

– Can overall make wood sheathing warmer

– Permeable exterior insulation allows drying to exterior

– Interior poly removed when low-permeance exterior

insulation is used

37

For More Details on

Durability by Design

Durability by Nature

Durability by Treatment

Check out the durability website

WWW.DURABLE-WOOD.COM

Questions?

jieying.wang@fpinnovations.ca

This concludes The American

Institute of Architects Continuing

Education Systems Course

Canadian Wood

Council

Wood WORKS!

BC

www.cwc.ca

www.wood-

works.org