Wood Frame Envelopes - Building Technology, 1999, Canada Mortgage and Housing Corporation. All rights reserved

Description

Wood Frame Envelopes - Building Technology, © 1999, Canada Mortgage and Housing Corporation. All rights reserved.CMHC information: Tel: 1 800 668-2642 Fax: 613 748-4069 Outside Canada: 613 748-2003 Web site: www.cmhc-schl.gc.caTable of Contents1 / Introduction Purpose of the Guide 1-1 History 1-1 Notice to Designers 1-2 2 / Wood in Construction Characteristics of Wood 2-1 Wood Frame Construction 2-3 Evolution of the Building Envelope 2-4 3 / Heat Transfer Heat Flow 3-1 Thermal Insulation 3-1 Thermal Bridging 3-2 Optimizing Thermal Performance 3-4 4 / Moisture Transfer Sources of Moisture 4-1 Moisture Movement 4-1 5 / Moisture Control Moisture in Construction 5-1 Moisture Deflection 5-1 Drainage 5-12 Drying 5-13 Durability 5-13 6 / dimensional Change How Dimensional Change Occurs 6-1 Managing Dimensional Change 6-4 Compatibility with Other Materials 6-5 7 / Details Wall Assembly A–Basic Stud Wall with Polyethylene Air Barrier and Vapour Retarder 7-3 Wall Assembly B–Exterior Insultation System with Airtight Drywall Approach (ADA) 7-10 Wall Assembly C–Exterior Airtight Sheathing Element (EASE) 7-17 Wall Assembly A, B and C (Below Grade) 7-23 Window Openings 7-26 Cantilevered Floors 7-32 Balconies 7-38 Wheelchair Accessibility 7-48 Party Walls and Fire Walls 7-52 8 / Specifications Section 06100–Rough Carpentry 8-2 Section 06192–Prefabricated Wood Trusses 8-6 Section 07200–Insulation 8-9 Section 07212–Subgrade Insulation 8-13 Section 07900–Sealants, Gaskets and Air Barrier Membranes 8-14 Section 09250–Gypsum Wallboard 8-18 9 / Quality Control Responsibilities 9-1 Quality Control and Quality Assurance 9-2 Inspection 9-3 Steps for Quality Assurance 9-3 Site Inspection Checklist 9-4 Airtightness 9-6 10 / Maintenance and Repair General Inspection 10-2 Repair 10-3 References References R-1 Acknowledgement R-3 Appendix A–CAD usage Overview A-1 Conventions Used A-2 list of tables Table 2.1: Shrinkage of Green Wood 2-3 Table 3.1: Thermal Resistance 3-2 Table 5.1: Air Permeability Rates of Selected Building Materials 5-3 Table 5.2: Water Vapour Permeance of Common Materials 5-5 Table 7.1: Characteristics of Sample Wall Assemblies 7-2 Table 10.1: Estimated Life Expectancy of Wood Frame Construction Components 10-1 Table 10.2: Building Inspection Checklist 10-4 list of FIGURES Figure 2.1: Cellular structure of wood 2-2 Figure 2.2: Wood shrinkage and moisture content 2-4 Figure 2.3: Directional wood shrinkage 2-4 Figure 2.4: Grade stamps 2-5 Figure 2.5: Fibre saturation and wood cell structure 2-5 Figure 2.6: Components of a wood frame structure 2-6 Figure 3.1: Thermal bridging 3-3 Figure 3.2: Super insulation systems 3-4 Figure 4.1: Air leakage and vapour diffusion 4-2 Figure 4.2: Penetration of wind-driven rain 4-4 Figure 4.3: Rain and the effects of gravity 4-5 Figure 4.4: Air pressure difference driving moisture through the wall 4-6 Figure 4.5: Capillary action 4-6 Figure 4-6: Air pressures caused by wind 4-7 Figure 4.7: Stack effect and air leakage 4-8 Figure 4.8: Mechanical exhaust creates a negative pressure, drawing air in through the building envelope 4-8 Figure 5.1: Airtight Drywall Approach (ADA) 5-7 Figure 5.2: External Airtight Sheathing Element (EASE) Approach 5-8 Figure 5.3: Pressure-equalizing rainscreen reduces moisture entry (Airtight Drywall Approach) 5-10 Figure 5.4: How to obtain a pressure-equalized wall cavity 5-11 Figure 5.5: Corner compartmentalization between brick cladding and siding 5-12 Figure 5.6: Fungal growth in wood 5-14 Figure 5.7: Speeding up the drying process for framing lumber 5-15 Figure 6.1: Wood shrinkage and moisture content 6-1 Figure 6.2: Shrinkage changes in wood products 6-2 Figure 6.3: Equilibrium moisture content (per cent), relative humidity and temperature 6-3 Figure 6.4: Truss uplift 6-5 Figure 6.5: Floating corners 6-5 Figure 6.6: Steel column within wood framing 6-6 Figure 6.7: Separation of masonry party wall and exterior wood framed wall 6-7 Figure 6.8: Balconies on steel columns 6-8 Figure 6.9: Wood frame with brick veneer and cap flashing 6-9 list of DETAILS (All details are vertical sections except where noted) Detail 1: Brick Veneer Wall at Foundation 7-5 Detail 2: Brick Veneer Wall at Header 7-6 Detail 3: Brick Veneer Wall at Roof 7-7 Detail 4: Corner, Horizontal Section 7-8 Detail 5: Interior Partition, Horizontal Section 7-9 Detail 6: Section at Stair Stringer 7-12 Detail 7: Wood Siding Wall at Foundation 7-13 Detail 8: Wood Siding Wall at Floor 7-14 Detail 9: Wood Siding Wall at Roof 7-15 Detail 10: Corner, Horizontal Section 7-16 Detail 11: Stucco Clad Wall at Foundation 7-19 Detail 12: Stucco Clad Wall at Floor 7-20 Detail 13: Stucco Clad Wall at Roof 7-21 Detail 14: Corner, Horizontal Section 7-22 Detail 15: Foundation Wall at Slab 7-24 Detail 16: Foundation Wall at Slab 7-25 Detail 17: Window Opening, A 7-27 Detail 18: Window Opening, B 7-29 Detail 19: Window Opening, C 7-31 Detail 20: Cantilevered Floor, A 7-33 Detail 21: Cantilevered Floor, B 7-35 Detail 22: Cantilevered Floor, C 7-37 Detail 23: Column-Supported Balcony with Brick Veneer 7-39 Detail 24: Column-Supported Balcony with Siding Veneer 7-41 Detail 25: Attached Balcony with Stucco Cladding 7-43 Detail 26: Balcony Over Heated Space, A 7-45 Detail 27: Balcony Over Heated Space, B 7-47 Detail 28: Wheelchair-Accessible Balcony 7-49 Detail 29: Wheelchair-Accessible Entrance Door 7-51 Detail 30: Party Wall, Horizontal Section 7-53 Detail 31: Fire Wall, Horizontal Section 7-55 Detail 32: Fire Wall 7-56