Guide for Designing Energy-Efficient Wood- Frame Building Enclosures

Transcription

1 Energy-Efficient Building Enclosure Design Guidelines for Wood-Frame Buildings Graham Finch, MASc, P.Eng Principal, Building Science Research Specialist RDH Building Engineering Ltd. Copyright Materials This presentation is protected by Canadian, US, and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited. RDH Building Engineering Ltd. October 29, 2013 Wood WORKS! Vancouver Program Education Credit Information Learning Objectives 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. 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. Evolution Wood-frame Building Enclosure Design Guides 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 RDH Building Engineering - rdhbe.com 1

2 Why a New Building Enclosure Guide? What Types of Buildings & Structures is the Guide For? 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 performance Little guidance on building durable and highly insulated enclosure assemblies and details Desire to build taller and taller more exposed woodframe buildings (4-6 stories and higher) Increased use of cross-laminated timber & other engineered wood products dictates alternate assemblies 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 Where is the Guide Applicable Overview: What is in the Guide North American Guide Marine, Cold and Very Cold Climate Zones Energy Code Climate Zones 4 through 7 Details 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 Chapter 1: Introduction Context of Guide Chapter 2: Building and Energy Codes across North America Canadian Building and Energy Codes US Building and Energy Codes Performance Rating Systems & Green Building Programs Differences between NECB & ASHRAE 90.1 Overview: What is in the Guide Overview: What is in the Guide Chapter 3: Moisture, Air and Thermal Control Building as a System Climate Zones Interior Climate, HVAC Interaction Critical Barrier Concept Control of Rainwater Penetration Control of Air Flow Controlling Condensation Construction Moisture Controlling Heat Flow and Insulation Whole Building Energy Efficiency Computer Simulation Considerations for Wood-frame Enclosures 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: Detailing 2D CAD (colored) and 3D build-sequences for various typical enclosure details Chapter 6: Further Reading & References RDH Building Engineering - rdhbe.com 2

3 Chapter 2: Building and Energy Codes Canadian Energy Codes NECB 2011 vs ASHRAE 90.1 Review of effective R-values & Consideration for Thermal Bridging Energy Use in Wood-frame MURBs Enclosure R-value Targets and Airtightness Requirements Canadian Building Codes 2010 NBC 2011 NECB ASHRAE 90.1 (2001 through 2010 versions) US Buildings Codes Performance Rating and Green Building Programs NECB 2011 Wood-frame, above-grade wall Climate Zone and HDD( C) Zone 4: <3000 HDD 18.0 (3.17) Zone 5: 3000 to 3999 HDD 20.4 (3.60) Zone 6: 4000 to 4999 HDD 23.0 (4.05) Zone 7a: 5000 to 5999 HDD 27.0 (4.76) Zone 7b: 6000 to 6999 HDD 27.0 (4.76) Zone 8: >7000 HDD 31.0 (5.46) Wood-frame roof, flat or sloped: 25.0 (4.41) 31.0 (5.46) 31.0 (5.46) 35.0 (6.17) 35.0 (6.17) 40.0 (7.04) Climate Wood-frame, above-grade wall Zone Effective Nominal Zone (A & B) (2.0) (2.3) Zone (A & B) (2.0) (2.3) Zone (A, B, & C) (2.0) (2.3) Zone ci (A, B, & C) (2.7) ( ci) Zone ci (A, B, & C) (3.5) ( ci) Zone ci (A & B) (3.5) ( ci) Zone ci (3.5) ( ci) Zone ci (4.9) ( ci) ci = continuous insulation, where denoted NECB has higher effective R-value requirements ASHRAE Wood-frame roof insulation entirely above deck Effective Nominal Wood-frame roof attic and other Effective 47.6 (8.4) Nominal 49.0 (8.6) ASHRAE vs NECB 2011 Effective Dec 20, 2014 US Energy Codes IECC vs ASHRAE 90.1 *7A/7B combined in ASHRAE 90.1 No Zone 4 in ASHRAE 90.1 NECB 2011 ASHRAE Residential Building Climate Zone Wall Above Grade: Min. R-value(IP) Roof Sloped or Flat: Min. R-value (IP) Window: Max. U-value (IP) A/7B 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) , 27.8, , 0.45, A/7B 14.1, 19.6, 23.8, 0.45, , 19.6, 15.6, 0.55, , 19.6, 15.6, 0.55, 0.35 Adoption of IECC and ASHRAE 90.1 varies by State Effective R-value tables provided Airtightness requirements covered Washington State and Seattle (<0.40 cfm/ft US Army Corps (<0.25 cfm/ft Performance Rating Programs & R-value Targets Chapter 3: Climate Considerations Consideration for above-code enclosure performance & green building programs Performance rating and energy modeling considerations Target high-performance building enclosure R-values by climate Zone Climate Zones Zones 1 to 3: hot, cooling dominated Zones 4 to 5: mixed, heating and cooling Zones 6 to 8: cold, heating dominated Wood-frame, above-grade wall Wood-frame roof insulation entirely above deck: Wood-frame roof attic and other: R-16 to R-22 (2.8 to 3.9) R-22 to R-28 (3.9 to 4.9) R-28 to R-40 (4.9 to 7.0) R-25 to R-30 (4.4 to 5.3) R-30 to R-40 (5.3 to 7.0) R-40 to R-50 (7.0 to 8.8) R-40 to R-50 (7.0 to 8.8) R-50 to R-60 (8.8 to 10.6) R-60 to R-80 (10.6 to 14.1) Exterior Climate Temperature & Humidity Rainfall Interior Climate HVAC systems Ventilation Architectural Form & Enclosure Design RDH Building Engineering - rdhbe.com 3

4 Chapter 3: Building Science Fundamentals Chapter 3: Air Flow Control Air Barrier Strategies Deflection, Drainage, Drying and Durability Wetting and Drying Mechanisms & Continuity Water Shedding Surface Water Resistive Barrier Air Barrier Thermal Insulation Rainwater Penetration control fundamentals Air Barrier Systems (Fundamentals, Materials, Performance, testing) Sealed Poly/Sheet Membranes Airtight drywall Sprayfoam Sealed-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: Condensation Control Managing Construction Moisture & Wood Shrinkage Relative Humidity control Maintaining high interior surface temperatures Reducing thermal bridging Use of better windows Controlling air movement (air barrier systems) Controlling vapour diffusion (vapour retarders) Keeping wood dry during transportation and construction and limiting built-in moisture Careful use of impermeable materials/membranes Controlling and accounting for wood-frame shrinkage Detailing for differential shrinkage Chapter 3: Heat Flow Control & Insulation Chapter 3: Effective R-values Control of Heat Flow Solar Control, Minimizing Conductive Losses, Minimizing Air Leakage Placement of Insulation within assemblies Wood framing factors Types of insulation, R-values and typical uses Thermal bridging and effective R-values All Energy Codes now consider effective R-values Nominal 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 RDH Building Engineering - rdhbe.com 4

5 Chapter 3: Wood Framing Factor Impact Insulation Placement and Assembly Design Considerations Framing factors for 16 o.c = 25% Taller wood-frame structures framing factors >30-40% depending on structural destign Interior Insulation Exterior Insulation Split Insulation Getting to Higher R-values Placement of Insulation Chapter 3: Insulation Placement Above Grade Walls Baseline 2x6 w/ R-22 batts = R-16 effective Exterior Insulation R-20 to R-40+ R effective Constraints: cladding attachment, wall thickness Deep/Double Stud R-20 to R-40+ R effective Constraints wall thickness Split Insulation R-20 to R-40+ R effective Constraints: cladding attachment Cladding Attachment through Exterior Insulation 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 RDH Building Engineering - rdhbe.com 5

6 Insulation Placement Below Grade Walls Insulation Placement - Roofs Chapter 3: Whole Building Energy Efficiency Chapter 4: Energy Efficient Walls Split Insulated Whole building energy efficiency considerations Impact of Wall, Window and Roof R-values on overall heatloss and energy consumption Example calculations of whole building R-values Thermal mass impacts of Heavy timber structures Hygrothermal and Thermal simulation guidance Wood framing Material selection & guidance Control Functions Effective R-value Tables 2x4 R-12 (2.1) R-14 (2.5) 2x6 R-19 (3.3) R-22 (3.9) Nominal studspace insulation None 10.7 (1.9) 11.5 (2.0) 15.5 (2.7) 16.6 (2.9) R-4 (1 inch) 15.0 (2.6) 15.8 (2.8) 19.8 (3.5) 21.0 R-8 (2 inches) 18.8 (3.3) 19.6 (3.4) 23.7 (4.2) 24.8 (4.4) Exterior insulation R-12 (3 inches) 22.5 (4.0) 23.2 (4.1) 27.3 (4.8) 28.5 (5.0) R-16 (4 inches) 26.2 (4.6) 27.0 (4.8) 31.0 (5.5) 32.2 (5.7) R-20 (5 inches) 29.7 (5.2) 30.5 (5.4) 34.5 (6.1) 35.7 (6.3) R-24 (6 inches) 33.2 (5.8) 34.0 (6.0) 39.2 (6.9) Exterior & Split Insulated Wood Assemblies Chapter 4: Energy Efficient Walls Double Stud/Deep Stud Wood-frame and Heavy Timber Building Wall R-value Targets R-19.6 ASHRAE 90.1 R-18.6 to R-20.4 NECB Can only get ~R-16 effective within a 2x6 framed wall Industry shift towards split and exterior insulated wood-frame walls Material selection & guidance Control Functions Effective R-value Tables Wood Nominal fill Gap width between stud walls framing insulation No gap 1-inch 2-inches 3-inches 4-inches 5-inches 6-inches /inch (RSI/cm)] Double- R-3.4/inch stud 2x4 (0.24/cm) (3.4) (4.0) (4.7) (5.3) (5.9) (7.1) R-4.0/inch (0.28/cm) (3.6) (4.4) (5.2) (5.9) (6.6) (7.3) (8.0) RDH Building Engineering - rdhbe.com 6

7 Double/Deep Stud Insulated Walls Chapter 4: Energy Efficient Walls Exterior Insulated 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 airtightness Inherently at a higher risk for damage if sheathing gets wet (rainwater, air leakage, vapor diffusion) due to more interior insulation Material selection & guidance Control Functions Effective R-value Tables Wood Exterior Exterior insulation thickness framing insulation 3 inches 4 inches 5 inches 6 inches 7 inches 8 inches /inch R-value (RSI/cm)] R-4/inch 3½-inch- (0.28/cm) thick CLT R-5/inch panels (0.34/cm) 17.2 (3.0) 19.8 (3.5) (4.3) 24.4 (4.3) 28.7 (5.1) 27.9 (4.9) 32.9 (5.8) 31.6 (5.6) 37.3 (6.6) 35.0 (6.2) 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 RDH Building Engineering - rdhbe.com 7

8 CLT Panel Details Requiring Attention - Parapets CLT Panel Details Requiring Attention - Corners Airflow path more convoluted lower leakage rates, but still a consideration Airflow increased by stack Roofing membrane applied, effect and pressures at parapet path becomes longer but corners doesn t go away even if clamped, sealed etc. Guidance for CLT Assembly Air Barriers CLT Assembly Air Barrier Considerations CLT panels air-tight as a material, but not as a system Recommend 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 Structural connections can interfere with air-barrier membrane installation/sequencing and sharp parts can damage materials (applied before or after) Infill Walls Post & Beam or Concrete Floor Slabs Chapter 4: Below Grade Walls Concrete frame with wood-frame infill Interior Insulated Exterior Insulated Post and Beam with wood-frame infill Control Functions Critical Barriers Effective R- values RDH Building Engineering - rdhbe.com 8

9 Chapter 4: Pitched-Roof, Vented Attic Assembly Chapter 4: Pitched-Roof, Exterior Insulated Assembly Materials & Control Functions Effective R-value Tables (accounting for insulation reductions at eaves) Materials & Control Functions Effective R-values Chapter 4: Low-Slope Conventional Roof Assembly Chapter 4: Low-Slope Inverted Roof Assembly Materials & Control Functions Effective R-values (Accounting for tapered insulation packages) Materials & Control Functions Effective R-values Chapter 5: Detailing Detailing Materials & Critical Barrier Discussion 2D CAD details (colored) provided for typical details for each wall assembly type (split insulated, double stud, exterior insulated) plus some for infill walls 3D sequence details provided for window interfacing (split insulated, double stud, exterior insulated) Thermal Continuity Air Barrier Continuity Water Shedding Surface and Water Resistive Barrier RDH Building Engineering - rdhbe.com 9

10 Detailing From Roof to Grade Detailing Colored 2D Details Details provided for each main wall assembly included Split insulated Double Stud CLT And roofs Sloped Low-slope Detailing Wall to Roof Interfaces Detailing Wall Penetrations Detailing 2D Window Details Detailing 3D Window Installation Sequences RDH Building Engineering - rdhbe.com 10

11 Chapter 6: Further Reading, References & Glossary Further reading Builder & Design Guides Building Science Resources Energy Codes and Standards Other Research Organizations Design Software References Glossary of Building Enclosure, Energy Efficiency and Wood terms Questions? Guide Available from FP Innovations: stem/designing-energy-efficient-building-enclosures.pdf Google: energy efficient building enclosure design guide Questions / Comments? This concludes the: American Institute of Architects Architectural Institute of British Columbia Engineering Institute of Canada Continuing Education Systems Program Energy-Efficient Building Enclosure Design Guidelines for Wood-Frame Buildings RDH Building Engineering - rdhbe.com 11