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Enclosure Design for Mass Timber Buildings
COLIN SHANE M.ENG., P.ENG., P.E.
PRINCIPAL, SENIOR PROJECT MANAGER
RDH BUILDING SCIENCE INC.
Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board.
NOVEMBER 16, 2017
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
Copyright Materials
“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.
Course Description
• Larger and taller mass timber buildings are becoming common in North America. These buildings typically utilize cross-laminated timber or nail-laminated timber panels, glulam beams and columns, and new engineered timber components to meet the structural and fire requirements associated with greater heights. With these larger wood structures and heavier timber components comes the need for efficient building enclosure assemblies that can be installed quickly on tight sites and are in many cases new and unique to the industry. Prefabricated building enclosure elements are now also commonly used. This presentation shares guidance on building enclosure design and detailing best practices for mass timber buildings. It includes case studies and lessons learned from the design, construction, and monitoring of enclosures for recently completed projects.
Learning Objectives
à Review building enclosure design principles for mass timber
buildings.
à Discuss common details used for mass timber wall and roof
enclosure assemblies.
à Highlight the potential for increased construction efficiency through
the use of prefabricated enclosure assemblies.
à Referencing case studies and details from recently completed
mass timber projects, demonstrate lessons learned and best
practices associated with enclosure assemblies.
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à Building enclosure design + mass timberà What’s the same? What’s different?
à Lessons learnedà Case Study – Wood Innovation Design Centerà Case Study – Brock Commons
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Building Enclosure Design
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Taller Wood Building Structures
à Fast
à Sensitive to moisture
à Greater movement (shrinkage& drift)
à Fire code challenges
à Mixed steel, concrete& wood materials
à Is not the same as light wood-frame and also different fromhigh-rise steel or concrete structures
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Tall Wood Building Enclosures
à Need for Speed
à Erect and seal fast
à Protect wood structure
à Accommodating of inclement weather
à Ensure Durability
à Robust materials –high-rise appropriate
à Tolerant of movement
à Thermally efficient
à Non-combustible
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The Building Enclosure
Image Credit: MGA - Wood Innovation
Design CentreStructure
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Building Enclosure Design Fundamentals
à Primary function of the Building Enclosure/Façade: Separate the exterior & interior environments
à Protects mass timber during construction & in-service
à Both functional and aesthetic
à Controls heat, air, and moisture
à Designed to accommodate building movement, structural loads, initial & seasonal wood movement
à Key passive design element for an sustainable, energy efficient building
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What is Unique about Mass Timber Buildings?
à Greater use of engineered heavier timber components (panels, beams, columns)
à Alternate structural systems (post/beam, engineered panels, infill components)
à Unique & new connections, interfaces & details
à Longer & heightened exposure of large wood components to rain and weathering during construction
à Is not the same as light mid-rise wood-frame, but is also different from high-rise steel or concrete structures
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Tall Versus Shorter Mass Timber Buildings
à Tall Wood Structuresà More repetitive, more exposed, difficult
access, need for more speed – ideal for prefabricated facades
à Less focus on roof and more on walls for weather protection
à Low to Mid-rise Wood Structuresà Easier access to walls from ground à Greater focus on roof for weather
protection than wallsà Prefabrication of façade also possible
though less economies of scale
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Rain Control – Taller Buildings
à Increased height = increased rain deposition at upper floors and cumulative run-down at lower levels
à Water shedding features become more critical – continuity, drip edges, flashings etc.
à Need for more robust water penetration control strategy – good practice: drained & ventilated rainscreen
à Increased exposure to moisture during construction (severity & length of time)
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Site Protection & Sequencing
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Wall Design for Taller Wood Buildings
à Key Considerations:
Durability, Airtightness &
Thermal Efficiency
à Strategies:
à Non-combustible rainscreen
claddings
à Exterior or split-insulated with
thermally efficient cladding
attachments through exterior
insulation
à Non-combustible & moisture
tolerant cavity insulation
Screws through insulation over split insulated wall
Clip & rail cladding attachment system through exterior insulation
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Wall Design for Taller Wood Buildings
Curtainwall systems w/ modified anchors for wood framing
à Strategies (continued)
à Pre-fabricated components
where possible
à Robust air-tight, water resistant
& vapour permeable wall
membrane (AB/WRB)
à Membrane compatibility with
glazing, roofing, and other
assembly materials
à Simple integration with glazing
systems & other penetrations
à Details, details, details!
SIPs & other Pre-fabricated wall panels
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Roof Design for Larger Wood Buildings
Conventional roof with tapered insulation over wood joists
Protected membrane roof over vented & tapered structure over CLT
à Key Considerations: Keep dry,
allow to dry, robustness of
assemblies, sloping strategy
à Strategies:
à Protect wood roof from getting wet
during construction
à Design assembly with redundancy
for in-service drying
à Slope structure where possible
à Insulation on top - conventional or
protected membrane assemblies
à Question the need for heavy timber
panels up here?
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Lessons Learned
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Potential Challenges with Mass Timber Buildings
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Lessons Learned - Roofs
à CLT/ NLT roofs get really wet when rained on and are very hard to dry out in-service and need expansion gaps
à Careful with selection of temporary waterproofingmembranes – assume it will be exposed roofing for a while. Need for water-tight laps/details
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Lessons Learned - Roofs
à Protect large wood roofs from rain – but not too late
à Mechanical drying of wetted roofs is slow & causes costly construction delays
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Lessons Learned - Roofs
à Design for the inevitable to keep roofing and project on schedule
à Design roof assemblies for redundancy and in-service drying where possible
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Industry Lessons – Protection
5 ply CLT – ½ Untreated & ½ Treated with water repellant
End grain is very absorptive
Splits, checks & joints that allow water past top layer can be problematic
Erect & roof as fast as possible to protect from rain to avoid delays
Water repellants can help reduce uptake into wood
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Industry Lessons - Long Term Exposure
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Case Study 1Wood Innovation and Design 6 Stories, 98’ Feet
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Taller Wood Building Precedents
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à 6 ‘tall’ storeys (equivalent to 8 storey, 98’ tall)
à CLT shear walls, glulam columns with glulam beams and staggered CLT floor & roof structure
à Thermal performance design targets (effective R-values)
à R-40 roof
à R-25 walls
à R-5 wood curtainwall glazing
à Pre-fabricated design for infill walls and wood curtain wall
Wood Innovation Design Center
Michael Green Architecture (MGA) –Contractor: PCL Construction
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WIDC – Structure & Enclosure Systems
Design & Architectural Renders: Michael Green Architecture (MGA)
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Wood Veneer Curtainwall/Windows
à Aluminum veneer curtainwall
framing over LVL mullions
à Installed as individual window
units, ground bearing
à Stick built/site glazed with triple
glazed IGUs, argon filled, dual
low-e coatings
(U-0.15)
à R-5 (U-0.20) overall thermal
performance
(vs. ~R-3.5 for aluminum system)
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Wood Veneer Curtainwall/Windows
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Infill Wall Assembly Design
à Designed for prefab light-frame wall assemblies between curtainwall units
à Target R-25 effective R-value
à Structurally Insulated Panels (SIPs) proved cost effective, fast & easy to install
à WRB/AB membrane on exterior surface (applied in factory) ties nicely into curtainwall assembly
à Sealed joints (interior & exterior & filled)
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Curtainwall to SIPs Interface
Aluminum CurtainwallVeneer Framing
Silicone Applied Liquid AB/WRB
Interior Air Seal at Joints
Silicone Transition Strip AB/WRB attached with silicone to curtainwall and wall membrane
LVL Framing Backup
SIPs
Charred fire-treated cedar cladding attached to plywood backup & cleat system over drained & ventilated rainscreen cavity
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Liquid Applied AB/WRB over SIPS
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Wood Movement & Wall Detailing
Plywood over end grain
Larger movement joint at curtainwall & SIPs panel head
Continuous Columns
Horizontal wood kept relatively dry during construction to minimize swelling
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Curtainwall & Wall Movement Joints
Flexible joint material at head & jamb
Slip structural connection
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SIPs & Curtainwall Movement Joints
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Charred Fire-Treated Cedar Cladding Panels
John Boys, Nicola Log-works
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Charred Fire-Treated Cedar Cladding Panels
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Conventional 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)
Construction Photos by PCL/MGA/RDH
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Wood Innovation Design Center
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Wood Innovation Design Center
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WIDC – Building Enclosure Summary
à Durable and energy efficient
à High performance materials and
systems
à Small panel pre-fabrication
à Required full exterior access
during construction
à Scaffolding, exterior sealants
à Appropriate for suburban site
and modest height
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Case Study 2UBC Brock Commons 18 Storeys – 175 Feet
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UBC Brock Commons– Façade Challenge
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Initial Concerns & Questions from Project Team
à Vancouver = Temperate rainforest
à How to protect mass timber from rain during construction in any season
à Giant tarps?
à Temporary roof lifted by crane?
à Waterproof the floors?
à Enclose as fast a possible?
à Enclosure must keep up with pace of structure
à How long can mass timber floors get wet for? Best way to protect it?
à How to enclose & seal the walls quickly and not be slowed by inclement weather?
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UBC Brock Commons - Façade Design Criteria
Fast installation – 1 floor/day & water tight to
protect structure Thermally
Efficient, >R-16
effective walls
Inexpensive, <$50/sqftinstalled & finished
Installed without access to exterior –no sealing or
finishing
Pre-installed cladding & windows
Durable & High-
performance
Resistant to water & able to install in
rain
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Precedents for Prefabrication of Tall Wood
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Precedents for Prefabrication of Tall Wood
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Precedents for Prefabrication of Tall Wood
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UBC Brock Commons- What Wasn’t Feasible
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Unitized Curtain wall OptionProblem: Cost, Schedule, Energy
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Window-Wall OptionProblem: Schedule, Energy
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Small Panel Prefabrication Wall – PrecedentsProblem: Schedule
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Tall Wood Prefabrication Option – Large Panel with Pre-installed Windows
Tall Wood Concept Panel
Tall Wood Concept Panel
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Prefabricated Panel Competition Mock-ups
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UBC Brock Commons - The 4 Panel Contenders!
Pre-Cast Concrete Sandwich Panels Steel Stud Framed Panels
Wood Stud framed or CLT Panels Aluminum Window-wall
Not thermally efficient enough for project nor met the design intent, but
kept as contingency and costed
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Laboratory Mockup & Physical Testing
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Centura – Factory Floor Prefabrication
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Site Installation – at Pace with Structure – 1 floors/day
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Field Testing and Commissioning
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Future Facades?
This concludes The American Institute of Architects Continuing Education Systems Course
Colin Shane – [email protected]
