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Building Enclosure Fundamentals and Best Practices for Wood-Frame Buildings

COLIN SHANE M.ENG., P.ENG. ASSOCIATE, SENIOR PROJECT MANAGER

RDH BUILDING SCIENCES INC.

Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.

SEPTEMBER 16, 2015

“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.

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. 2014

Copyright Materials

Course Description

!  Through a combination of building science fundamentals and current research, this presentation will explore design considerations associated with wood-frame building enclosures. Discussion will focus on best practices for designing durable, energy-efficient enclosures for mid-rise buildings using traditional light wood-frame construction. Differences in enclosure design associated with taller wood-frame buildings using mass timber products will also be reviewed.

Learning Objectives

!  Review building science fundamentals and building enclosure design considerations for light wood-frame buildings.

!  Discuss best practices for light wood-frame building enclosure design, detailing, and construction techniques

!  Explore the thermal benefits of utilizing wood-frame construction. !  Compare the differences in building enclosure design criteria and

systematic approaches between light wood-frame structures and tall, mass timber-frame structures.

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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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 wood-

frame assemblies to meet current

and upcoming energy codes

! CLT Handbook

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!  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!

Building Enclosure Design Fundamentals

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Trends in Building Enclosure Design

!  Trend towards more energy efficiently building enclosures

!  Air barriers now required in 2012 IECC and 2013 CEC

!  Continuous insulation becoming more common

!  Seeing more new building materials, enclosure assemblies and

construction techniques

!  More insulation = 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, for vapor, air

and moisture control

!  Need to fully understand the science and interaction of design parameters

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What do we know?

Building Enclosure

Control Air

Control Vapor

Control heat

Control Rain

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Building Enclosure Control Layers

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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!  3 Conditions for Rain Penetration:

1.  A source of water 2.  A water entry path 3.  A driving force

!  4 Ways to Control it:

1.  Deflection 2.  Drainage 3.  Drying 4.  Durability

Rain Penetration Control

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How do Walls get Wet and Dry?

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Water Penetration Control Strategies

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Rainscreen Cladding

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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! Code requirement

! Moisture !  Air holds moisture that can be

transported and deposited

within assemblies.

! Energy !  Unintentional airflow through

the building enclosure can

account for as much as 50% of

the space heat loss/gain in

buildings.

Air Penetration Control – Why?

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Air Barrier Systems

! Air Barrier Systems Must: !  Be continuous, airtight, durable

!  Resist structural loads

!  Bridge joints across inter-story

and drift joints

!  Not negatively affect drying

ability

! Traditional loose sheet applied house-wrap products are challenging to make air-tight on larger buildings

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Types of Air Barrier Systems

Sealed Gypsum Sheathing – Sealant Filler at Joints

Loose Sheet Applied Membrane – Taped Joints & Strapping

Liquid Applied – Silicone sealants and silicone membrane at Joints

Sealed Plywood Sheathing –Sealant & Membrane at Joints

Sealed Sheathing – Membrane at Joints

Self-Adhered vapor permeable membrane

Plywood sheathing with taped joints (good tape)

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Airtightness Does Not Happen By Accident

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How to Tell the Membrane is Not the Air Barrier

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Definitely Not An Air Barrier… But What Is?

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Definitely Not An Air Barrier… But What Is?

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Importance of Testing Air Barrier Systems

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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Conductive Heat Loss Control

!  Insulation between studs is most common heat control strategy

! Need to consider effective R-values

! Continuous insulation on exterior becoming more common

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Wood Framing Factor Impact on Effective R-values

Fram

ing @

16

” o.c

.

Fram

ing @

24

”o/c

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Insulation Placement

!  Consider effective thermal resistance

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Cladding Attachment Through Exterior Insulation

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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

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Thermally Improved Performance

Continuous metal Z-girts

Fiberglass Clips & Hat-Tracks

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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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!

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Wood-Frame Assemblies – ‘Perfect’ Wall

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Wood-Frame Assemblies – ‘Perfect’ Roof

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Wood-Frame Assemblies – ‘Perfect’ Roof

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Wall-to-Roof Detail

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Wall-to-Roof Detail

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Details – 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

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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Cross Laminated Timber – Ronald McDonald House

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CLT – Construction Moisture

!  Keep it dry during construction – as best as possible

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

CLT – Air Barrier Considerations

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CLT – Unique Details for Consideration

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CLT Panel Details Requiring Attention

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

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CLT – Wall Assemblies

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Roof Assembly

R-40+ Conventional Roof Assembly – 2 ply SBS, 4” Stonewool, 4” Polyiso, Protection board, Tapered EPS (0-8”), Torch applied Air/Vapor Barrier(Temporary Roof), ¾” Plywood, Ventilated Space (To Indoors), CLT Roof Panel Structure (Intermittent)

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! Get the architect to take the final photos

CLT Considerations

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Basics

Water

Air

Heat

BACKGROUND

Walls

Low-slope Roofs

Steep-slope Roofs

BEST PRACTICES

CLT

Deep Energy Retrofit

CASE STUDIES

Roadmap

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!  Moisture damage at walls and windows

!  Concealed barrier stucco

cladding

!  Vented low-slope roof

assembly

!  Energy efficient

rehabilitation of wall, window, and roof

assemblies

Deep Energy Retrofit

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5-Storey Wood-frame w/ Exterior Insulation

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New Exterior Wall Assembly

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New Sloped Roof / Overhang Assembly

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New Low-Slope Roof Assembly

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Completed Building Enclosure

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Summary

!  Control moisture, air, and heat

!  Best practices: !  Rainscreen cladding !  Keep structure warm and dry:

control layers on exterior

!  ‘Less than perfect’ practices: !  Analyze and understand

hygothermal behaviour

!  Provide continuity of control layers

within and between assemblies and

details

This concludes The American Institute of Architects Continuing Education Systems Course

Joe Piñon – jpinon@rdh.com Colin Shane – cshane@rdh.com Brian Hubbs – bhubbs@rdh.com www.rdh.com

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!  rdh.com

Discussion + Questions

Colin Shane – cshane@rdh.com

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!  Tallest wood structure in North America

!  Cross Laminated Timber

panel construction

!  Next project will be 18

storeys

Wood Innovation Design Center

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Wood Innovation Design Center

Design & Architectural Renders: Michael Green Architecture (MGA)