Post on 22-Feb-2022
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
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
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
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
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