The 2015 edition of the National Building Code of Canada (NBCC) includes significant changes to the acoustic requirements for residential constructions. The 2015 edition defines the acoustic requirements in terms of the Apparent Sound Transmission Class (ASTC) rating which includes contributions from flanking transmission and therefore is a better descriptor of how well the sound insulation of a building will actually protect the inhabitants of the building from unwanted noise than the STC rating which was used in earlier editions of the NBCC. The 2015 NBCC requires an ASTC rating = 47 for constructions between dwelling units.
The ASTC rating that a construction will achieve depends on the design of the building elements including the gypsum board, the framing and the thermal insulation as well as the design of the junctions between the building elements. Changes to the building elements or the junctions will change the ASTC rating.
Fifty five examples of the calculation of the ASTC rating for typical mid-rise wood constructions (single and triple staggered wood stud walls and floors constructed of I-joists) with 15.9 mm (5/8”) SilentFX® QuickCut gypsum board, 15.9 mm CertainTeed Type X gypsum board and CertainTeed Sustainable fiberglass insulation are presented. All of the constructions shown in the examples have an ASTC rating which is greater than 47.
In addition to the examples for mid-rise wood framing, an example using 15.9 mm SilentFX® QuickCut gypsum board as a lining on a cross laminated timber (CLT) construction is also presented.
Sustainable Northwest (SNW) and Hacienda Community Development Group (HCDC), both based in Oregon, have proposed a plan to demonstrate pathways for building affordable housing with regionally sourced mass timber. In response to the region’s housing shortage, the partners’ proposal demonstrates the use of mass timber products while supporting efforts to educate stakeholders on wood product companies and forest restoration. The project outlines a plan to explore financing options, build one or more prototypes, and perform a structural material life cycle analysis.
The anticipated growth and urbanization of the global population over the next several decades will create a vast demand for the construction of new housing, commercial buildings and accompanying infrastructure. The production of cement, steel and other building materials associated with this wave of construction will become a major source of greenhouse gas emissions. Might it be possible to transform this potential threat to the global climate system into a powerful means to mitigate climate change? To answer this provocative question, we explore the potential of mid-rise urban buildings designed with engineered timber to provide long-term storage of carbon and to avoid the carbon-intensive production of mineral-based construction materials.
Provincial code changes have been made to allow construction of light wood-frame buildings up to 6 storeys in order to satisfy the urban housing demand in western Canadian cities. It started in 2009 when the BC Building Code was amended to increase the height limit for wood-frame structures from four to six. Recently, provinces of Quebec, Ontario and Alberta followed suit. While wood-frame construction is limited to six storeys, some innovative wood-hybrid systems can go to greater heights. In this report, a feasibility study of timber-based hybrid buildings is described as carried out by The University of British Columbia (UBC) in collaboration with FPInnovations. This project, funded through BC Forestry Innovation Investment's (FII) Wood First Program, had an objective to develop design guidelines for a new steel-timber hybrid structural system that can be used as part of the next generation "steel-timber hybrid structures" that is limited in scope to 20 storey office or residential buildings. ...
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.
This short report summarizes a life cycle assessment (LCA) study comparing a cross-laminated timber mid-rise building to the same building in concrete1. For more detail, refer to the original report which was the product of a rigorous, comparative LCA research project that complied with the international LCA standard ISO 14040:2006. In that study an apartment building in Quebec City, Canada was analyzed using two different building systems in order to understand the environmental footprint of each relative to the other. A LCA model was developed for a real, 4060 m2, 4-storey, cross-laminated timber (CLT) apartment building. The same building was then designed using reinforced concrete slabs and columns with light gauge steel stud walls. That design was intended as a building system that CLT would likely be compared with in the midrise construction market where CLT is likely to compete.
This report presents an overview into cross laminated timber (CLT) as a construction material and how it compares to traditional methods of construction. CLT is also examined in the context of a move to off-site manufacturing (OSM) and a greater emphasis on sustainability in the construction sector. In this context it is found to perform well with mass timber products such as CLT being the only carbon negative building materials capable of building mid and high-rise buildings.
The barriers and opportunities for CLT are explored looking at literature, industry reports and case studies. The main barriers to wider use of CLT still come from uncertainties around the material. Although they have been proven to not be a problem, worries over issues such as how it performs during fires and the lifetime of buildings persist. A lack of standardisation may be the primary cause for this as a range of products and specifications across different manufactures and countries creates confusion and means that each building needs to be individually specified. The opportunities identified for CLT include its carbon saving properties which could benefit governments wanting to reach their carbon reduction targets. In addition, the ability to use CLT on a wider range of sites such as unstable brownfield land and over service tunnels lends to its strength in aiding with urban densification.
In terms of costs, these are found to be comparable to those of traditional construction methods with high material costs being offset by reduced foundations and construction time. CLT buildings do, however, face a premium in insurance costs. Transport costs, resulting from a concentrated production base in central Europe, also add a considerable amount to the overall cost of the finished product. This in turn encourages domestic production in countries outside of Europe.
The possibilities for CLT in the UK residential construction market are investigated with a focus on mid-rise and high-rise flat construction as that is what the economics and material properties of CLT most lend itself to. Although CLT currently has a low market share of less than 0.1% of homes in this sector there is the potential for this to increase to 20-60% over time. The lower range of this estimate is not predicted to be reached before 2035 and this is also dependant on rising CLT production levels. The volume of timber that is needed to manufacture enough CLT to reach these increased construction volumes can be sourced sustainably from existing forests production in Europe and North America. In addition, the UK has enough excess timber harvesting capacity to provide for the entirety of CLT buildings in the UK, however, large scale domestic CLT production is required to make this a reality.