Building Enclosure Details and Assemblies for Wood-Frame Buildings

Transcription

1 Building Enclosure Details and Assemblies for Wood-Frame Buildings COLIN SHANE M.ENG., P.ENG. ASSOCIATE, SENIOR PROJECT MANAGER RDH BUILDING SCIENCES INC. NOVEMBER 19, 2015 Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.

2 The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/ CES), Provider #G516. 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.

3 Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited. RDH Building Sciences Inc. 2015

4 Course Description This presentation will provide an in-depth look at a variety of wood-frame building enclosure assemblies and details. Beginning with a review of building enclosure design fundamentals and considerations, it will then focus on best practices with references from technical guidelines and case studies. Finally, the critical detail interfaces between different enclosure assemblies (i.e., walls, roofs, balconies, windows, foundations) will be reviewed with a focus on continuity of critical barriers. A series of details and case studies will be presented for each.

5 Learning Objectives Review building enclosure design best practices for light woodframe buildings. Demonstrate effective methods of controlling heat, air, and moisture movement through wood-frame assemblies. Discuss common details used for light wood-frame wall and roof enclosure assemblies. Using case studies and details from past projects, demonstrate unique considerations and best practices associated with the interfaces between adjacent enclosure assemblies

6 Building Enclosure Design Fundamentals Separate indoors from outdoors, by controlling: Heat flow Air flow Vapor diffusion Water penetration Condensation Light and solar radiation Noise, fire, and smoke While at the same time: Transferring structural loads Being durable and maintainable Being economical & constructible Looking good! 7 of

7 Trends in Building Enclosure Design Trend towards more energy efficiently building enclosures Air barriers now required in 2012 IECC and 2013 CEC Washington and Seattle are ahead of the curve Higher R-value requirements - thicker walls More insulation / less air leakage = less heat flow to dry out moisture Marginal assemblies that worked in the past may no longer work Amount, type and placement of insulations matters 8 of

8 The Perfect Assembly Rain penetration control: rainscreen cladding over water barrier Air leakage control: robust air barrier system Heat control: continuous insulation layer Locate all barriers exterior of structure Keep structure warm and dry 50+ year old concept! 9 of

9 Wood-Frame Assemblies Pretty Good Wall 10 of

10 Wood-Frame Assemblies Perfect Roof 11 of

11 Wall-to-Roof Detail 12 of

12 Continuity of Control Layers In practice, need to evaluate and design assemblies and details that are not perfect Continuity of control layers within and between assemblies is critical Hygrothermal analysis? 13 of

13 Interfaces & Challenges Balconies & Roofs 14 of

14 Wood-frame Building Enclosure Design Guides 2011 Building Enclosure Design Guide Wood-frame Multi-Unit Residential Buildings Emphasis on best practices, moisture and new energy codes 2013 Guide for Designing Energy- Efficient Building Enclosures Focus on highly insulated woodframe assemblies to meet current and upcoming energy codes CLT Handbook 15 of

15 Continuous Insulation 16 of

16 Getting to Higher R-values - Walls Traditional 2x6 w/ R-22 batts = R-16 effective Exterior Insulation: R-20 to R-60+ effective Constraints: cladding attachment, wall thickness Good for wood/steel/concrete Deep/Double Stud: R-20 to R-40+ effective Constraints: wall thickness Good for wood, wasted for steel Split Insulation: R-20 to R-60+ effective Constraints: cladding attachment Good for wood, palatable for steel 17 of

17 Building Enclosure & Passive Design Building enclosure is key element in passive design Exterior insulation is only as good as the cladding attachment strategy What attachment system works best thermally? Need to also consider: Structural Air / water tightness Constructibility 18 of

18 Many Cladding Attachment Options & Counting 19 of

19 Cladding Attachment: Vertical Steel Z-Girts ~65-75%+ loss in R-value 20 of

20 Cladding Attachment: Horizontal Steel Z-Girts ~45-65%+ loss in R-value 21 of

21 Cladding Attachment: Clip & Rail, Stainless Steel 22 of

22 Cladding Attachment: Clip & Rail, Isolated Galvanized Isolate the metal, improve the performance ~10-25% loss in R-value (spacing dependant) 23 of

23 Cladding Attachment: Clip & Rail, Non-Conductive Remove the metal maximize the performance ~5-25% loss in R-value (spacing & fastener type dependant) 24 of

24 Cladding Attachment: Continuous Wood Framing ~15-30% loss in R-value 25 of

25 Cladding Attachment: Screws through Insulation Longer cladding Fasteners directly through rigid insulation (up to 2 for light claddings) Long screws through vertical strapping and rigid insulation creates truss short cladding fasteners into vertical strapping Rigid shear block type connection through insulation, short 26 cladding of fasteners into vertical strapping

26 Publications / Research Reports And many others! 27 of

27 Lab Examples and Testing ± 25 psf 28 of

28 Cladding Attachment: Screws Through Insulation 29 of

29 5-Storey Wood-frame w/ Exterior Insulation 30 of

30 Current Passive House Project Modular construction for a remote site in a cold climate Highly insulated walls with screws through 6 inches of exterior insulation 31 of

31 Exterior Insulation and Windows Need to provide a water shedding seal between exterior cladding and window With exterior insulation exterior cladding is often too far away Flashing or trim piece required to create continuity 32 of

32 Exterior Insulation and Windows 33 of

33 Balcony Designs 34 of

34 Wood-Framed Balcony Likely the most common framing method Questions: Where is the air barrier? Thermal barrier? Water barrier? Saddles? Do we vent? Guardrail attachment? 35 of

35 Cantilevered Balcony Control Layers Air barrier: Use the shortest path possible Prevent interior air from entering balcony soffit Vent soffit Thermal barrier: Remember perfect wall Water barrier: Over a sloped and drained balcony surface 36 of

36 Cantilevered Balcony - Saddles Can you spot them? 37 of

37 Cantilevered Balcony - Saddles 3-dimensional integration of assemblies Include a 3-dimensional detail 38 of

38 Cantilevered of Water Control Layer 39 of

39 Continuity of Air / Thermal Control Layers Air barrier and thermal barrier continuity often overlooked Difficult to reliably detail sheet membrane around penetrating joists Spray foam often used for air and thermal control 40 of

40 Continuity of Air / Thermal Control Layers 41 of

41 Pre-Finished Steel Balcony over Wood Balcony is a bolt-on architectural component, but not part of building enclosure Air, water, and thermal control layers continuous behind pre-finished balcony Simplifies detailing no saddles Continuous water, air, thermal layers 42 of

42 Pre-Finished Steel Balconies 43 of

43 Roof Designs 44 of

44 Roof Design for Larger Wood Buildings Key Considerations: Keep dry, allow to dry, robustness of assemblies, sloping strategy Strategies: Protect wood roof from getting wet during construction Insulation on top of air and vapor control layers - conventional or protected membrane assemblies Conventional roof with tapered insulation over wood joists Connect control layers at walls Be cautious of interior insulated approaches, with or without venting Protected membrane roof over vented & tapered structure over CLT 45 of

45 Roof to Wall Control Layers (EI) Air barrier: Use the shortest path possible Ideally below parapet framing Thermal barrier: Ideally to exterior of control layers Water barrier: Roof membrane to sheathing membrane 46 of

46 Roof to Wall Control Layers Air barrier: Use the shortest path possible Ideally below parapet framing Thermal barrier: Ideally to exterior of control layers Water barrier: Roof membrane to sheathing membrane 47 of

47 Interfaces & Challenges - Parapets 48 of

48 Air Barrier Details Pre-stripping AB membrane is often recommended at balconies and roof-wall transitions but often forgotten! 49 of

49 Air Barrier Details 50 of

50 Summary Control moisture, air, and heat Best practices: Rainscreen cladding Keep structure warm and dry: control layers on exterior Think about the details! Provide continuity of control layers within and between assemblies and details Easier said than done: modern large buildings often architecturally complicated Walls, roofs, balconies, and?

51 This concludes The American Institute of Architects Continuing Education Systems Course Joe Piñon Colin Shane Brian Hubbs

52 Discussion + Questions COLIN SHANE CSHANE@RDH.COM rdh.com