The Guide for Designing Energy-Efficient Building Enclosures for Wood-Frame Multi-Unit Residential Buildings in Marine to Cold Climate Zones in North America was developed by FPInnovations in collaboration with RDH Building Engineering Ltd., the Homeowner Protection Office, Branch of BC Housing, and the Canadian Wood Council.
The project is part of efforts within the Advanced Building Systems Program of FPInnovations to assemble and add to the knowledge base regarding Canadian wood products and building systems. The team of the Advanced Building Systems Program works with members and partners of FPInnovations to address critical technical issues that threaten existing markets for wood products or which limit expansion or access to such new markets. This guide was developed in response to the rapidly changing energy-efficiency requirements for buildings across Canada and the United States.
This guide serves two major objectives:
To assist architects, engineers, designers and builders in improving the thermal performance of building enclosures of wood multi-unit residential buildings (MURBs), in response to the increasingly stringent requirements for the energy efficiency of buildings in the marine to cold climate zones in North America (U.S. DOE/ASHRAE and NECB Climate Zones 5 through 7 and parts of Zone 4);
To advance MURB design practices, construction practices, and material use based on best knowledge, in order to ensure the durable performance of wood-frame building enclosures that are insulated to higher levels than traditional wood-frame construction.
The major requirements for thermal performance of building enclosures are summarized (up to February 2013), including those for the following codes and standards:
2011 National Energy Code of Canada for Buildings (2011 NECB);
2013 interim update of the 2010 National Building Code of Canada (2010 NBC, Section 9.36–Energy Efficiency);
2012 International Energy Conservation Code (2012 IECC);
American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1– Energy Standard for Buildings Except Low-Rise Residential Buildings (2004, 2007, and 2010 versions).
In addition to meeting the requirements of the various building codes and standards, a building may need to incorporate construction practices that reflect local preferences in material use, design and construction.
Regional climate differences will also affect design solutions.
This guide primarily addresses above-grade walls, below-grade walls and roofs of platform wood-frame construction. It also includes information regarding thermal performance of cross-laminated timber (CLT) assemblies as well as the use of non-bearing wood-frame exterior walls (infill walls) in wood post-and-beam and concrete structures.
Examples of thermal resistance calculations, building assemblies, critical interface detailing, and appropriate material selection are provided to help guide designers and builders meet the requirements of the various energy-efficiency codes and standards, achieve above-code performance, and ensure long-term durability. This guide builds on the fundamentals of building science and on information contained within the Building Enclosure Design Guide: Wood-Frame Multi-Unit Residential Buildings, published by the Homeowner Protection Office, Branch of BC Housing.
This guide is based on the best current knowledge and future updates are anticipated. The guide is not intended to be a substitute for professional advice that considers specific building parameters.
Wood-frame construction is the dominant building construction in low-rise buildings. The growth in the urban population and the need to meet sustainability objectives will mean having to allow taller buildings in areas that were traditionally low-rise construction. While the need for higher and environmentally sustainable building solutions increases, the Canadian codes responsible for the health and safety of buildings continued to limit wood building solutions to four storeys. Mid-rise (5- and 6-storey) wood-frame construction is a natural extension of low-rise wood-frame construction. In 2009, the BC Building Code (BCBC) was amended by the BC Building and Safety Standards Branch (formerly Policy Branch) to allow mid-rise wood-frame construction. The amendment brought the BC Building Code more closely in line with the U.S. states of California, Washington, and Oregon, where mid-rise wood construction is permitted. More than 100 mid-rise wood-frame construction projects in BC followed the BCBC amendment. Later, the provinces of Québec, Ontario, and Alberta took steps to permit mid-rise wood-frame construction, and finally the Canadian Commission on Building and Fire Codes (CCBFC) accepted code change proposals to allow 5- and 6-storey wood-frame construction in the 2015 edition of the National Building Code Canada (NBCC). NRC, CWC, and FPInnovations worked collaboratively on a project, funded by Natural Resources Canada and several provinces to provide additional technical information to support mid-rise wood-frame construction. This Handbook consists of ten multi-disciplinary chapters, which have been prepared to facilitate the design and construction of mid-rise wood-frame construction in Canada. Building on the information that formed the basis of Association of Professional Engineers and Geoscientists of British Columbia (APEGBC) Bulletin and the Régie du bâtiment du Québec (RBQ) guide, this Handbook covers broad design and construction topics and provides practical solutions by making use of the most recently developed technical and research information. The Handbook has been prepared to assist architects, engineers, code consultants, developers, building owners, and Authorities Having Jurisdiction (AHJ). It is designed to be used in conjunction with the upcoming 2015 edition of the NBCC and the 2014 Edition of the CSA Standard on Engineering Design in Wood. It also complements existing design aids such as the CWC Wood Design Manual.
Building tall in wood is not a new phenomenon. In fact, Canada has a history of constructing tall wood buildings out of heavy timber and brick elements, reaching up to nine storeys. In the early 20th century, with the increase in reinforced concrete and structural steel research and construction, and with growing concerns over fire and durability, the structural use of wood fell out of common use in tall buildings. This trend is beginning to reverse, however. In the last few decades, the world has seen a resurgence of mass timber products and systems that are paving the way for tall wood buildings. This triggered an initiative by Natural Resources Canada (NRCan) to support tall wood building demonstration projects to enhance Canada’s position as a global leader in wood building construction, by showcasing the application and performance of advanced wood technologies. The Technical Guide for the Design and Construction of Tall Wood Buildings in Canada has been prepared to assist architects, engineers, code consultants, developers, building owners, and Authorities Having Jurisdiction (AHJ) in understanding the unique issues to be addressed when developing and constructing tall wood buildings.