Project contact is Pierre Blanchet at Université Laval (Canada)
Summary
The work of Lessard et al. (2017) demonstrated that the building envelope was an important system in the building in terms of environmental impact, but only took into account the external components of the building envelope. This project will perform a life cycle analysis of the main building envelopes for a typical building under commercial construction. By relying on our design partners, the main systems and associated materials will be analyzed in a cradle-to-grave approach. It is desirable to identify hot spots and to indicate avenues for product development in order to reduce the envelope's environmental footprint. Among the scenarios to be considered: light framework, CLT, curtain walls and all their possible variants, but also commonly used non-biobased systems. The comparison between the systems studied will be based on an equivalent energy efficiency performance.
This report provides an overview of major changes occurred in the recent decade to design and construction of the building envelope of wood and wood-hybrid construction. It also covers some new or unique considerations required to improve building envelope performance, due to evolutions of structural systems, architectural design, energy efficiency requirements, or use of new materials. It primarily aims to help practicioners better understand wood-based building envelope systems to improve design and construction practices. The information provided should also be useful to the wood industry to better understand the demands for wood products in the market place. Gaps in research are identified and summarized at the end of this report.
Guide for Designing Energy-Efficient Building Enclosures for Wood-Frame Multi-Unit Residential Buildings in Marine to Cold Climate Zones in North America
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 guide was developed by FPInnovations and its partners to assist in the design and construction of durable and energy-efficient wood-frame buildings in Alberta. The Province adopted the National Energy Code for Buildings 2011, as of November 1, 2016, in order to comply with the energy-efficiency requirements for large buildings (Part 3). It is now also possible, with new building regulations, to build wood structures with a maximum of six storeys or 18 m height in Alberta. This guide aims to provide solutions for the building envelope (enclosure) of Part 3 wood buildings, particularly five- and six-storey wood-frame buildings, to meet the prescriptive thermal requirements of the new energy code. A range of wood-based exterior wall and roof assemblies are covered, based on light wood frame or mass timber, and various thermal insulation materials are discussed. Effective R-values are calculated based on typical thermal insulation values of commonly used materials. This document also covers key considerations for building envelope design to maintain long-term durability in Alberta’s varied climate.
A residential building with cross-laminated timber structure in Granada (Spain) was analyzed using the life cycle assessment methodology, life cycle energy analysis and sensitivity analysis to changes in efficiency of operating energy, materials database, transport distances and different scenarios for C&DW. The environmental impacts of the materials and construction production and embedded energy were relatively significant. The global warming impact category was very low due to the CO2 sequestration of wooden materials. Sensitivity analysis revealed that the most significant reduction in environmental impact was achieved through improvements in energy efficiency, high uncertainty in the impacts of the environmental product declaration, the low effect of long-distance transport on the overall impact and the feasibility of the objective of recovery of the Waste Framework Directive by 2020 (above 70%).
Air leaks have a considerable impact on the energy load and durability of buildings, particularly in cold climates. In wood construction using cross-laminated timber (CLT), air leaks are most likely to be concentrated at the joints between panels and other elements. This study used simulations of heat, air, and moisture transfers through a gap between two CLT panels causing air leakage in winter conditions under a cold climate. A real leakage occurrence was sized to validate the simulations. The aim of this work was to assess the impact on the energy loads and the durability of an air leak, as either infiltration or exfiltration, for different gap widths and relative humidity levels. The results showed that infiltrations had a greater impact on the energy load than exfiltrations but did not pose a threat to the durability, as opposed to exfiltrations. Gap sizes in CLT may vary, but the effect on the energy load was sensitive to the leakage path in the rest of the wall. As expected, a combination of winter exfiltration and a high level of interior relative humidity was particularly detrimental.
Set plans and requirements for monitoring vertical movement, energy efficiency, acoustics, and moisture management in demonstration buildings, and collaborate with the University of Ottawa for measuring structural characteristics of the demonstration buildings
This paper aims to discuss timber-wood lightweight concrete composites for application in wall components for buildings. The aim is to develop a multi-layer wall system composed of wood lightweight concrete, connected timber sections to gain and use advantages of each used material – lightweight, structural, thermal storage and insulation, ecological and economic benefits – to name the most important ones. The development of timber-wood lightweight concrete composites systems will lead to a new generation of polyvalent multi-material building components. By using renewable resources, waste products of the forest industry, and manufactured wood products, this technology provides statically and energy-efficient components for low-energy constructions. Such products support rapid-assembly construction methods, which use prefabricated dry elements to increase the efficiency of the construction. Wood-based alternatives to conventional concrete or masonry construction also open opportunities to reduce the carbon emissions.
The Italian building heritage is aged and inadequate to the high-performance levels required nowadays in terms of energy efficiency and seismic response. Innovative techniques are generating a strong interest, especially in terms of multi-level approaches and solution optimizations. Among these, Nested Buildings, an integrated intervention approach which preserves the external existing structure and provides a new structural system inside, aim at improving both energy and structural performances. The research presented hereinafter focuses on the strengthening of unreinforced masonry (URM) buildings with cross-laminated timber (CLT) panels, thanks to their lightweight, high stiffness, and good hygrothermal characteristics. The improvement of the hygrothermal performance was investigated through a 2D-model analyzed in the dynamic regime, which showed a general decreasing in the overall thermal transmittance for the retrofitted configurations. Then, to evaluate the seismic behavior of the coupled system, a parametric linear static analysis was implemented for both in-plane and out-of-plane directions, considering various masonry types and connector spacings. Results showed the efficiency of the intervention to improve the in-plane response of walls, thus validating possible applications to existing URM buildings, where local overturning mechanisms are prevented by either sufficient construction details or specific solutions. View Full-Text
Passive House Performance in Cold Climates: a Review of the Envelope Performance and Energy Consumption of a Certified Research and Testing Facility in Canada
The University of Northern British Columbia’s Wood Innovation Research Lab (WIRL) is the first industrial facility tested and certified to the International Passive House standard in Canada. Constructed using a glulam post and beam system and unique high-performance standing truss wall assembly, the building serves as a research and testing facility for University faculty and students. Temperature and humidity sensors were installed in the north and south wall façade during construction to measure the building’s hygrothermal performance. In addition, energy consumption meters were installed to measure the annual energy and heating demand of the building. Both the hygrothermal performance and energy use data are of interest due to the unique envelope design, the building’s location in a cold climate and the intended use of the building. Energy consumption results are compared to those calculated in the Passive House Planning Package (PHPP) model completed for the building. Initial findings after an eighteen-month data collection period found that the exterior walls did not experience 100% relative humidity during the data collection period but that high readings of relative humidity (>80%) did occur. The measured annual heating and energy demand of the WIRL exceeded the predicted consumption values calculated in the PHPP model due to occupant behavior, mechanical system operation inefficiencies and discrepancies that exist between modeled vs actual climate conditions.
