Energy-Efficient Building Enclosure Design Guidelines for Wood-Frame Buildings

Graham Finch, MASc, P.EngPrincipal, Building Science Research SpecialistRDH Building Engineering Ltd.

October 29, 2013 – Wood WORKS! Vancouver

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Program Education Credit Information

Canadian Wood Council, Wood WORKS! and the Wood Solutions Fair is a Registered Provider with The American Institute of Architects Continuing Education System; the Architectural Institute of British Columbia and the

Engineering Institute of Canada. Credit earned on completion of this program will be reported on behalf of members of each CES provider for those who complete a participation form at the registration counter. Certificates of Completion for non-AIA, AIBC or EIC members are available on request.

This program is registered with the 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.

Learning Objectives

1. Learn about the new wood-design resource for architects, builders, and engineers: the Guide for Designing Energy Efficiency Building Enclosures for Wood-Frame Multi-Unit Residential Buildings

2. Understand how upcoming building and energy code changes will impact typical wood-frame construction practices, and learn the best strategies to design, insulate, air-seal, and detail new wood frame wall and roof assemblies.

3. Learn about the building enclosure design considerations for heavy timber structures utilizing CLT and post-and-beam components.

4. Understand the importance of “critical barriers” in building enclosure detailing with examples of wall, roof and window details for highly insulated wood buildings.

Overview

Background

Overview of the new Guide for Designing Energy Efficient Building Enclosures for Wood-frame Buildings

Available as free download from FP Innovations

Original 1999/2011 Wood Frame Envelopes in the Coastal Climate of British Columbia - Best Practice Guide (CMHC)

Emphasis on moisture control on the west coast

2011 Building Enclosure Design Guide – Wood-frame Multi-Unit Residential Buildings (HPO)

Emphasis on best practices, moisture and new energy codes

2013 Guide (FP Innovations)Focus on highly insulated wood-frame assemblies to meet current and upcoming energy codes Passive design and green buildings

Evolution Wood-frame Building Enclosure Design Guides

Energy Codes across North America have incrementally raised the bar to the point where conventional wood-frame assemblies (i.e. 2x6 walls) no longer provide enough insulating value

Increased awareness of passive design strategies and green building programs dictate even higher enclosure performanceLittle guidance on building durable and highly insulated enclosure assemblies and details

Desire to build taller and taller more exposed wood-frame buildings (4-6 stories and higher)Increased use of cross-laminated timber & other engineered wood products dictates alternate assemblies

Why a New Building Enclosure Guide?

Multi-Unit Residential Buildings are the focus of the guide (and one of most challenging building types)Relevant for other building types as well utilizing platform framing, cross laminated timber, wood frame infill, & post and beam.Also applies to houses

What Types of Buildings & Structures is the Guide For?

North American GuideMarine, Cold and Very Cold Climate ZonesEnergy Code Climate Zones 4 through 7Details used as examples are west coast focused (i.e. rainscreen)

Guidance can also be applied to other climate zones (i.e. Far-North or Southern US) with engineering judgement & local experience

Where is the Guide Applicable

Chapter 1: Introduction

Context of Guide

Chapter 2: Building and Energy Codes across North America

Canadian Building and Energy Codes US Building and Energy CodesPerformance Rating Systems & Green Building ProgramsDifferences between NECB & ASHRAE 90.1

Overview: What is in the Guide

Chapter 3: Moisture, Air and Thermal ControlBuilding as a SystemClimate ZonesInterior Climate, HVAC InteractionCritical Barrier ConceptControl of Rainwater PenetrationControl of Air FlowControlling CondensationConstruction MoistureControlling Heat Flow and InsulationWhole Building Energy EfficiencyComputer Simulation Considerations for Wood-frame Enclosures

Overview: What is in the Guide

Chapter 4: Energy Efficient Wall and Roof Assemblies

Above Grade Wall Assemblies • Split Insulated, Double Stud/Deep Stud, Exterior

Insulated• Infill Walls for Concrete Frame

Below Grade Wall Assemblies• Interior and Exterior Insulated

Roof Assemblies• Steep Slope & Low Slope

Chapter 5: Detailing2D CAD (colored) and 3D build-sequences for various typical enclosure details

Chapter 6: Further Reading & References

Overview: What is in the Guide

Review of effective R-values & Consideration for Thermal BridgingEnergy Use in Wood-frame MURBsEnclosure R-value Targets and Airtightness Requirements

Canadian Building Codes• 2010 NBC• 2011 NECB• ASHRAE 90.1 (2001 through

2010 versions)

US Buildings CodesPerformance Rating and Green Building Programs

Chapter 2: Building and Energy Codes

Canadian Energy Codes –NECB 2011 vs ASHRAE 90.1

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)

NECB 2011

Climate Zone

Wood-frame, above-grade wall Wood-frame roof—insulation

entirely above deck Wood-frame roof—attic and other

Effective [R-value (RSI)]

Nominal [R-value (RSI)]

Effective [R-value (RSI)]

Nominal [R-value (RSI)]

Effective [R-value (RSI)]

Nominal [R-value (RSI)]

Zone 1 (A & B)

11.2 (2.0)

13.0 (2.3)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 2 (A & B)

11.2 (2.0)

13.0 (2.3)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 3 (A, B, & C)

11.2 (2.0)

13.0 (2.3)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 4 (A, B, & C)

15.6 (2.7)

13.0 + 3.8 ci (2.3 + 0.7 ci)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 5 (A, B, & C)

19.6 (3.5)

13.0 + 7.5 ci (2.3 + 1.3 ci)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 6 (A & B)

19.6 (3.5)

13.0 + 7.5 ci (2.3 + 1.3 ci)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 7 19.6 (3.5)

13.0 + 7.5 ci (2.3 + 1.3 ci)

20.8 (3.7)

20.0 ci (3.5 ci)

37.0 (6.5)

38.0 (6.7)

Zone 8 27.8 (4.9)

13.0 + 15.6 ci (2.3 + 2.7 ci)

20.8 (3.7)

20.0 ci (3.5 ci)

47.6 (8.4)

49.0 (8.6)

ci = continuous insulation, where denoted

ASHRAE 90.1 - 2010

NECB has higher effective R-value requirements

ASHRAE 90.1-2010 vs NECB 2011 – Effective Dec 20, 2014

Climate Zone

Wall – Above Grade: Min. R-value (IP)

Roof – Sloped or Flat: Min. R-value (IP)

Window: Max. U-value (IP)

8 31.0 40.0 0.287A/7B 27.0 35.0 0.396 23.0 31.0 0.395 20.4 31.0 0.394 18.6 25.0 0.42

NEC

B

2011

AS

HR

AE 9

0.1

-2010 –

R

esid

en

tial

Bu

ild

ing

Climate Zone

Wall (Mass, Wood, Steel): Min. R-value (IP)

Roof (Attic, Cathedral/Flat): Min. R-value (IP)

Window (Alum, PVC/fiberglass): Max. U-value (IP)

8 19.2, 27.8, 27.0 47.6, 20.8 0.45, 0.35

7A/7B 14.1, 19.6, 23.8 37.0, 20.8 0.45, 0.35

6 12.5, 19.6, 15.6 37.0, 20.8 0.55, 0.35

5 12.5, 19.6, 15.6 37.0, 20.8 0.55, 0.35

*7A/7B combined in ASHRAE 90.1No Zone 4 in ASHRAE 90.1

Adoption of IECC and ASHRAE 90.1 varies by StateEffective R-value tables providedAirtightness requirements covered

Washington State and Seattle (<0.40 cfm/ft2 @75Pa)US Army Corps (<0.25 cfm/ft2 @75Pa)

US Energy Codes – IECC vs ASHRAE 90.1

Consideration for “above-code” enclosure performance & green building programsPerformance rating and energy modeling considerationsTarget “high-performance” building enclosure R-values by climate Zone

Performance Rating Programs & R-value Targets

Climate Zones

Wood-frame, above-grade wall Wood-frame roof—insulation

entirely above deck: Wood-frame roof—attic and

other:

[R-value (RSI)] [R-value (RSI)] [R-value (RSI)] Zones 1 to 3: hot, cooling dominated

R-16 to R-22 (2.8 to 3.9)

R-25 to R-30 (4.4 to 5.3)

R-40 to R-50 (7.0 to 8.8)

Zones 4 to 5: mixed, heating and cooling

R-22 to R-28 (3.9 to 4.9)

R-30 to R-40 (5.3 to 7.0)

R-50 to R-60 (8.8 to 10.6)

Zones 6 to 8: cold, heating dominated

R-28 to R-40 (4.9 to 7.0)

R-40 to R-50 (7.0 to 8.8)

R-60 to R-80 (10.6 to 14.1)

Exterior ClimateTemperature & HumidityRainfall

Interior Climate HVAC systemsVentilation

Architectural Form & Enclosure Design

Chapter 3: Climate Considerations

Deflection, Drainage, Drying and DurabilityWetting and Drying MechanismsCritical Barriers & Continuity

Water Shedding SurfaceWater Resistive BarrierAir BarrierThermal Insulation

Rainwater Penetrationcontrol fundamentals

Chapter 3: Building Science Fundamentals

Air Barrier Systems (Fundamentals, Materials, Performance, testing)

Sealed Poly/Sheet MembranesAirtight drywallSprayfoamSealed-Sheathing Approaches• Unsupported sheet

membranes• Supported sheet

membranes with vertical strapping

• Sandwiched membranes behind exterior insulation

• Self-Adhered and liquid applied membranes

Other Approaches

Chapter 3: Air Flow Control – Air Barrier Strategies

Relative Humidity controlMaintaining high interior surface temperatures

Reducing thermal bridgingUse of better windows

Controlling air movement

(air barrier systems)Controlling vapour diffusion (vapour retarders)

Chapter 3: Condensation Control

Keeping wood dry during transportation and construction and limiting built-in moistureCareful use of impermeable materials/membranesControlling and accounting for wood-frame shrinkage

Detailing for differential shrinkage

Managing Construction Moisture & Wood Shrinkage

Control of Heat FlowSolar Control, Minimizing Conductive Losses, Minimizing Air LeakagePlacement of Insulation within assembliesWood framing factors Types of insulation, R-values and typical usesThermal bridging and effective R-values

Chapter 3: Heat Flow Control & Insulation

All Energy Codes now consider effective R-valuesNominal R-values = Rated R-values of insulation which do not include impacts of how they are installed

For example R-20 batt insulation or R-10 foam insulation

Effective R-values include impacts of insulation installation and thermal bridges

For example nominal R-20 batts within steel studs becoming ~R-9 effective, or in wood studs ~R-15 effective

Chapter 3: Effective R-values

Framing factors for studs @ 16” o.c = 25% Taller wood-frame structures framing factors >30-40% depending on structural destign

Chapter 3: Wood Framing Factor Impact

Insulation Placement and Assembly Design Considerations

Interior Insulation

Exterior Insulation

Split Insulation

Getting to Higher R-values – Placement of Insulation

Baseline 2x6 w/ R-22 batts = R-16 effective

Exterior Insulation – R-20 to R-40+ effective• Constraints: cladding attachment, wall

thickness

Deep/Double Stud– R-20 to R-40+ effective• Constraints

wall thickness

Split Insulation– R-20 to R-40+ effective• Constraints: cladding

attachment

Chapter 3: Insulation Placement – Above Grade Walls

2x6 stud wall Double-stud wall 2x4 (or 2x6) stud

wall CLT/mass timber 2x4 (or 2x6) stud wall

Interior-insulated wall assemblies Exterior-insulated wall assemblies Split-insulated wall

assembly

Cladding Attachment through Exterior Insulation

Longer cladding Fasteners directly through rigid insulation (up to 2” for light claddings)

Long screws through vertical strapping and rigid insulation creates truss (8”+) – short cladding fasteners into vertical strapping Rigid shear block type

connection through insulation, cladding to vertical strapping

Cladding Attachment through Exterior Insulation

Insulation Placement – Below Grade Walls

Interior-insulated wall Exterior-insulated wall Interior- and exterior-

insulated wall (ICF)

Insulation Placement - Roofs

Interior-insulated pitched roof Low-slope roof: conventionally

insulated Low-slope roof: inverted

Whole building energy efficiency considerationsImpact of Wall, Window and Roof R-values on overall heat-loss and energy consumptionExample calculations of whole building R-valuesThermal mass impacts ofHeavy timber structuresHygrothermal and Thermalsimulation guidance

Chapter 3: Whole Building Energy Efficiency

Material selection & guidanceControl FunctionsCritical BarriersEffective R-value Tables

Chapter 4: Energy Efficient Walls – Split Insulated

Wood framing

Nominal stud-space insulation [R-value (RSI)]

Exterior insulation

None [R-value

(RSI)]

R-4 (1 inch) [R-value

(RSI)]

R-8 (2 inches) [R-value

(RSI)]

R-12 (3 inches) [R-value

(RSI)]

R-16 (4 inches) [R-value

(RSI)]

R-20 (5 inches) [R-value

(RSI)]

R-24 (6 inches) [R-value

(RSI)] 2x4 R-12

(2.1) 10.7 (1.9)

15.0 (2.6)

18.8 (3.3)

22.5 (4.0)

26.2 (4.6)

29.7 (5.2)

33.2 (5.8)

R-14 (2.5)

11.5 (2.0)

15.8 (2.8)

19.6 (3.4)

23.2 (4.1)

27.0 (4.8)

30.5 (5.4)

34.0 (6.0)

2x6 R-19 (3.3)

15.5 (2.7)

19.8 (3.5)

23.7 (4.2)

27.3 (4.8)

31.0 (5.5)

34.5 (6.1)

38.0 (6.7)

R-22 (3.9)

16.6 (2.9)

21.0 (3.7)

24.8 (4.4)

28.5 (5.0)

32.2 (5.7)

35.7 (6.3)

39.2 (6.9)

Wood-frame and Heavy Timber Building Wall R-value Targets

R-19.6 ASHRAE 90.1R-18.6 to R-20.4 NECBCan only get ~R-16 effective within a 2x6 framed wall

Industry shift towards split and exterior insulated wood-frame walls

Exterior & Split Insulated Wood Assemblies

Material selection & guidanceControl FunctionsCritical BarriersEffective R-value Tables

Chapter 4: Energy Efficient Walls – Double Stud/Deep Stud

Wood framing

Nominal fill insulation [R-value/inch (RSI/cm)]

Gap width between stud walls No gap [R-value

(RSI)]

1-inch [R-value

(RSI)]

2-inches [R-value

(RSI)]

3-inches [R-value

(RSI)]

4-inches [R-value

(RSI)]

5-inches [R-value

(RSI)]

6-inches [R-value

(RSI)] Double-stud 2x4

R-3.4/inch (0.24/cm)

19.1 (3.4)

22.9 (4.0)

26.5 (4.7)

30.0 (5.3)

33.4 (5.9)

36.9 (6.5)

40.3 (7.1)

R-4.0/inch (0.28/cm)

20.5 (3.6)

25.1 (4.4)

29.4 (5.2)

33.4 (5.9)

37.4 (6.6)

41.5 (7.3)

45.4 (8.0)

Double 2x4/2x6 stud, single deep 2x10, 2x12, I-Joist etc.Common wood-frame wall assembly in many passive houses (and prefabricated highly insulated walls)Often add interior service wall – greater control over airtightnessInherently at a higher risk for damage if sheathing gets wet (rainwater, air leakage, vapor diffusion) – due to more interior insulation

Double/Deep Stud Insulated Walls

Material selection & guidanceControl FunctionsCritical BarriersEffective R-value Tables

Chapter 4: Energy Efficient Walls – Exterior Insulated

Wood framing

Exterior insulation [R-value/inch (RSI/cm)]

Exterior insulation thickness 3 inches R-value (RSI)]

4 inches [R-value

(RSI)]

5 inches [R-value

(RSI)]

6 inches [R-value

(RSI)]

7 inches [R-value

(RSI)]

8 inches [R-value

(RSI)]

3½-inch-thick CLT panels

R-4/inch (0.28/cm)

17.2 (3.0)

20.9 (3.7)

24.4 (4.3)

27.9 (4.9)

31.6 (5.6)

35.0 (6.2)

R-5/inch (0.34/cm)

19.8 (3.5)

24.4 (4.3)

28.7 (5.1)

32.9 (5.8)

37.3 (6.6)

41.5 (7.3)

Cross Laminated Timber Construction - Considerations

Cross Laminated Timber Construction – Wall Assemblies

CLT Panel Construction - Unique Details for Consideration

CLT Panel Details Requiring Attention – Panel Joints

Sealants, tapes, & membranes applied on either side can’t address this type of airflow path through the CLT lumber gaps

CLT Panel Details Requiring Attention - Parapets

Airflow increased by stack effect and pressures at parapet corners

Roofing membrane applied, path becomes longer – but doesn’t go away – even if clamped, sealed etc.

CLT Panel Details Requiring Attention - Corners

Airflow path more convoluted – lower leakage rates, but still a consideration

CLT panels air-tight as a material, but not as a systemRecommend use of self-adhered sheet product air barrier membranes or thick liquid applied membrane on exterior of panels (exterior air-barrier approach)Use of loose-applied sheets (House-wraps) not generally recommended – more difficult to make airtight, perforating attachment, billowing, flanking airflow behind membrane

Guidance for CLT Assembly Air Barriers

Structural connections can interfere with air-barrier membrane installation/sequencing and sharp parts can damage materials (applied before or after)

CLT Assembly Air Barrier Considerations

Infill Walls – Post & Beam or Concrete Floor Slabs

Post and Beam with wood-frame infill

Concrete frame with wood-frame infill

Interior Insulated

Chapter 4: Below Grade Walls

Exterior Insulated

Control FunctionsCritical BarriersEffective R-values

Chapter 4: Pitched-Roof, Vented Attic Assembly

Materials & Control FunctionsCritical BarriersEffective R-value Tables (accounting for insulation reductions at eaves)

Chapter 4: Pitched-Roof, Exterior Insulated Assembly

Materials & Control FunctionsCritical BarriersEffective R-values

Chapter 4: Low-Slope Conventional Roof Assembly

Materials & Control FunctionsCritical BarriersEffective R-values (Accounting for tapered insulation packages)

Materials & Control FunctionsCritical BarriersEffective R-values

Chapter 4: Low-Slope Inverted Roof Assembly

2D CAD details (colored) provided for typical details for each wall assembly type (split insulated, double stud, exterior insulated) plus some for infill walls3D sequence details provided for window interfacing (split insulated, double stud, exterior insulated)

Chapter 5: Detailing

Thermal ContinuityAir Barrier ContinuityWater Shedding Surface and Water Resistive Barrier

Detailing – Materials & Critical Barrier Discussion

Details provided for each main wall assembly included

Split insulatedDouble StudCLT

And roofsSlopedLow-slope

Detailing – From Roof to Grade

Detailing – Colored 2D Details

Detailing – Wall to Roof Interfaces

Detailing – Wall Penetrations

Detailing – 2D Window Details

Detailing – 3D Window Installation Sequences

Further reading Builder & Design GuidesBuilding Science ResourcesEnergy Codes and StandardsOther Research OrganizationsDesign Software

ReferencesGlossary of Building Enclosure, Energy Efficiency and Wood terms

Chapter 6: Further Reading, References & Glossary

Questions?

gfinch@rdhbe.com - 604-873-1181

Guide Available from FP Innovations: http://www.fpinnovations.ca/ResearchProgram/AdvancedBuildingSystem/designing-energy-efficient-building-enclosures.pdf

Google: energy efficient building enclosure design guide

Questions / Comments?

This concludes the:

American Institute of ArchitectsArchitectural Institute of British Columbia

Engineering Institute of Canada

Continuing Education Systems Program

Energy-Efficient Building Enclosure Design Guidelines for Wood-Frame Buildings