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“Fire-retardant treated wood” (FRTW), as defined by the National Building Code of Canada (NBC), is ‘…wood or a wood product that has had its surface-burning characteristics, such as flame spread, rate of fuel contribution and density of smoke developed, reduced by impregnation with fire-retardant chemicals.’ FRTW must be pressure impregnated with fire-retardant chemicals in accordance with the CAN/CSA-O80 Series of Standards, Wood Preservation and when fire-tested for its surface flammability, must have a flame spread rating not more than 25. Fire-retardant chemical treatments applied to FRTW retard the spread of flame and limit smoke production from wood in fire situations. FRTW products are harder to ignite than untreated wood products and preservative treated wood products. Fire-retardant treatments applied to FRTW enhances the fire performance of the products by reducing the amount of heat released during the initial stages of fire. The treatments also reduce the amount of flammable volatiles released during fire exposure. This results in a reduction in the rate of flame spread over the surface. When the flame source is removed, FRTW ceases to char. FRTW contains different chemicals than preservative treated wood. However, the same manufacturing process is used to apply the chemicals. FRTW must be kiln-dried after treatment to a moisture content of 19% for lumber and 15% for plywood. The fire-retardant treatments used in FRTW do not generally interfere with the adhesion of surface paints and coatings unless the FRTW has an increased moisture content. The finishing characteristics of specific products should be discussed with the manufacturer. Typical interior applications of FRTW include architectural millwork, paneling, roof assemblies/trusses, beams, interior load bearing and non-load bearing partitions. Exterior-type fire retardants use different chemical formulations from those used for interior applications, since they must pass an accelerated weathering test (ASTM D2898), which exposes FRTW to regular wetting and drying cycles to represent actual long-term outdoor conditions. Generally, exterior-type fire retardants are applied to shingles and shakes. FRTW can be crosscut to length (not ripped) and drilled for holes following treatment without reducing its effectiveness. End cuts in the field, whether exposed or butt jointed, do not require treatment, since any untreated areas are relatively small compared to the total surface area and the flame spread rating remains unaffected. Plywood can be both crosscut and ripped without concern, since the chemical treatment has penetrated throughout the individual layers/plys. FRTW is not excessively corrosive to metal fasteners and other hardware, even in areas of high relative humidity. In fact, testing has demonstrated that FRTW is no more corrosive than untreated wood.   Exterior use of FRTW Fire retardant coatings Fire-retardant-treated wood roof systems Flame-spread rating   For more information on FRTW, visit the manufacture’s websites: Arch Wood Protection, Lonza: www.wolmanizedwood.com Viance LLC: www.treatedwood.com

National Fire Code of Canada The National Building Code of Canada (NBC) and the National Fire Code of Canada (NFC), both published by the National Research Council of Canada (NRC) and developed by the Canadian Commission on Building and Fire Codes (CCBFC), are developed as companion documents. The NBC establishes minimum standards for the health and safety of the occupants of new buildings. It also applies to the alteration of existing buildings, including changes in occupancy. The NBC is not retroactive. That is, a building constructed in conformance with a particular edition of the NBC, which is in effect at the time of its construction, is not automatically required to conform to the subsequent edition of the NBC. That building would only be required to conform to an updated version of the NBC if it were to undergo a change in occupancy or alterations which invoke the application of the new NBC in effect at the time of the change in occupancy or major alteration. The NFC addresses fire safety during the operation of facilities and buildings. The requirements in the NFC, on the other hand, are intended to ensure the level of safety initially provided by the NBC is maintained. With this objective, the NFC regulates: the conduct of activities causing fire hazards the maintenance of fire safety equipment and egress facilities limitations on building content, including the storage and handling of hazardous products the establishment of fire safety plans The NFC is intended to be retroactive with respect to fire alarm, standpipe and sprinkler systems. In 1990, the NFC was revised to clarify that such systems “shall be provided in all buildings where required by and in conformance with the requirements of the National Building Code of Canada.” This ensures that buildings are adequately protected against the inherent risk at the same level as the NBC would require for a new building. It does not concern other fire protection features such as smoke control measures or firefighter’s elevators. The NFC also ensures that changes in building use do not increase the risk beyond the limits of the original fire protection systems. The NBC and the NFC are written to minimize the possibility of conflict in their respective contents. Both must be considered when constructing, renovating or maintaining buildings. They are complementary, in that the NFC takes over from the NBC once the building is in operation. In addition, older structures which do not conform to the most current level of fire safety can be made safer through the requirements of the NFC. The most recent significant changes in the NFC relate the construction of six-storey buildings using combustible construction. As a result, eight additional protection measures related to mid-rise combustible buildings have been added to address fire hazards during construction when fire protection features are not yet in place.

The provision of fire safety in a building is a complex matter; far more complex than the relative combustibility of the main structural materials used in a building. To develop safe code provisions, prevention, suppression, movement of occupants, mobility of occupants, building use, and fuel control are but a few of the factors that must be considered in addition to the combustibility of the structural components. Fire-loss experience shows that building contents play a large role in terms of fuel load and smoke generation potential in a fire. The passive fire protection provided by the fire-resistance ratings on the floor and wall assemblies in a building assures structural stability in a fire. However, the fire-resistance rating of the structural assemblies does not necessarily control the movement of smoke and heat, which can have a large impact on the level of safety and property damage resulting from fire. The National Building Code of Canada (NBC) categorizes wood buildings as ‘combustible construction’. Despite being termed combustible, common construction techniques can give wood frame construction fire-resistance ratings up to two hours. When designed and built to code requirements, wood buildings provide the same level of life safety and property protection required for comparably sized buildings defined under the NBC as ‘noncombustible construction’. Wood has been used for virtually all types of buildings, including; schools, warehouses, fire stations, apartment buildings, and research facilities. The NBC sets out guidelines for the use of wood in applications that extend well beyond the traditional residential and small building sector. The NBC allows wood construction of up to six storeys in height, and wood cladding for buildings designated to be of noncombustible construction. When meeting the area and height limits for the various NBC building categories, wood frame construction can meet the life safety requirements by making use of wood-frame assemblies (usually protected by gypsum wallboard) that are tested for fire-resistance ratings. The allowable height and area restrictions can be extended by using fire walls to break a large building area into smaller separate building areas. The recognized positive contribution to both life safety and property protection which comes from the use of automatic sprinkler systems can also be used to increase the permissible area of wood buildings. Sprinklers typically operate very early in a fire thereby quickly controlling the damaging effects. For this reason, the provision of automatic sprinkler protection within a building greatly improves the life safety and property protection prospects of all buildings including those constructed of noncombustible materials. The NBC permits the use of ‘heavy timber construction’ in buildings where combustible construction is required to have a 45-minute fire-resistance rating. This form of heavy timber construction is also permitted to be used in large noncombustible buildings in certain occupancies. To be acceptable, the components must comply with minimum dimension and installation requirements. Heavy timber construction is afforded this recognition because of its performance record under actual fire exposure and its acceptance as a fire-safe method of construction. In sprinklered buildings permitted to be of combustible construction, no fire-resistance rating is required for the roof assembly or its supports when constructed from heavy timber. In these cases, a heavy timber roof assembly and its supports would not have to conform to the minimum member dimensions stipulated in the NBC. Mass timber elements may also be used whenever combustible construction is permitted. In those instances, however, such mass timber elements need to be specifically designed to meet any required fire-resistance ratings.   NBC definitions: Combustible means that a material fails to meet the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.” Combustible construction means that type of construction that does not meet the requirements for noncombustible construction. Heavy timber construction means that type of combustible construction in which a degree of fire safety is attained by placing limitations on the sizes of wood structural members and on thickness and composition of wood floors and roofs and by the avoidance of concealed spaces under floors and roofs. Noncombustible construction means that type of construction in which a degree of fire safety is attained by the use of noncombustible materials for structural members and other building assemblies. Noncombustible means that a material meets the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials.”   For further information, refer to the following resources: National Building Code of Canada CAN/ULC-S114 Test for Determination of Non-Combustibility in Building Materials Wood Design Manual 2017

Flame spread is primarily a surface burning characteristic of materials, and a flame-spread rating is a way to compare how rapid flame spreads on the surface of one material compared to another. Flame-spread rating requirements are applied in the National Building Code of Canada (NBC) primarily to regulate interior finishes. Any material that forms part of the building interior and is directly exposed is considered to be an interior finish. This includes interior claddings, flooring, carpeting, doors, trim, windows, and lighting elements. If no cladding is installed on the interior side of an exterior wall of a building, then the interior surfaces of the wall assembly are considered to be the interior finish, for example, unfinished post and beam construction. Similarly, if no ceiling is installed beneath a floor or roof assembly, the unfinished exposed deck and structural members are considered to be the interior ceiling finish. The standard test method that the NBC references for the determination of flame spread ratings is CAN/ULC-S102, published by ULC Standards. Appendix D-3 of the NBC, Division B, provides information related to generic flame-spread ratings and smoke developed classifications of a variety of building materials. Information is only provided for generic materials for which extensive fire test data is available (refer to Table 1 below). For instance, lumber, regardless of species, and Douglas fir, poplar, and spruce plywood, of a thickness not less than those listed, are assigned a flame-spread rating of 150. In general, for wood products up to 25 mm (1 in) thick, the flame-spread rating decreases with increasing thickness. Values given in the Appendix D of the NBC are conservative because they are intended to cover a wide range of materials. Specific species and thicknesses may have values much lower than those listed in Appendix D. Specific ratings by wood species are given in Surface Flammability and Flame-spread Ratings fact-sheet, below. Information on proprietary and fire-retardant materials is available from third-party certification and listing organizations or from manufacturers. The values listed in Surface Flammability and Flame-spread Ratings fact-sheet apply to finished lumber; however, there has been no significant difference in flame-spread rating noted in rough sawn lumber of the same species. The American Wood Council has additional information in their Design for Code Acceptance publication, DCA 1 Flame Spread Performance of Wood Products for the U.S. Normally, the surface finish and the material to which it is applied both contribute to the overall flame-spread performance. Most surface coatings such as paint and wallpaper are usually less than 1 mm thick and will not contribute significantly to the overall rating. This is why the NBC assigns the same flame-spread and smoke developed rating to common materials such as plywood, lumber and gypsum wallboard whether they are unfinished or covered with paint, varnish or cellulosic wallpaper. There are also special fire-retardant paints and coatings that can substantially reduce the flame-spread rating of an interior surface. These coatings are particularly useful when rehabilitating an older building to reduce the flame-spread rating of finish materials to acceptable levels, especially for those areas requiring a flame-spread rating no greater than 25. In general, the NBC sets the maximum flame-spread rating for interior wall and ceiling finishes at 150, which can be met by most wood products. For example, 6 mm (1/4 in) Douglas Fir plywood may be unfinished, painted, varnished or covered with conventional cellulosic wallpaper. This has been found to be acceptable on the basis of actual fire experience. This means that in all areas where a flame-spread rating of 150 is permitted, the majority of wood products may be used as interior finishes without special requirements for fire-retardant treatments or coatings. In a room fire, the flooring is usually the last item to be ignited, since the coolest layer of air is near the floor. For this reason, the NBCC, like most other codes, does not regulate the flame-spread rating of flooring, with the exception of certain essential areas in high buildings: exits; corridors not within suites; elevator cars; and, service spaces. Traditional flooring materials such as hardwood flooring and carpets can be used almost everywhere in buildings of any type of construction. For further information, refer to the following resources: Wood Design Manual (Canadian Wood Council) Fire Safety Design in Buildings (Canadian Wood Council) National Building Code of Canada National Fire Code of Canada CSA O86, Engineering design in wood CAN/ULC-S102 Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies American Wood Council Table 1 : Assigned flame-spread ratings and smoke developed classifications Surface Flammability and Flame-spread Ratings

In the National Building Code of Canada (NBC) “fire-resistance rating” is defined in part as: “the time in minutes or hours that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria…” The fire-resistance rating is the time, in minutes or hours, that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria, or as determined by extension or interpretation of information derived therefrom as prescribed in the NBC. The test and acceptance criteria referred to in the NBC are contained in a standard fire test method, CAN/ULC-S101, published by ULC Standards. Horizontal assemblies such as floors, ceilings and roofs are tested for fire exposure from the underside only. This is because a fire in the compartment below presents the most severe threat. For this reason, the fire-resistance rating is required from the underside of the assembly only. The fire-resistance rating of the tested assembly will indicate, as part of design limitations, the restraint conditions of the test. When selecting a fire-resistance rating, it is important to ensure that the restraint conditions of the test are the same as the construction in the field. Wood-frame assemblies are normally tested with no end restraint to correspond with normal construction practice. Partitions or interior walls required to have a fire-resistance rating must be rated equally from each side, since a fire could develop on either side of the fire separation. They are normally designed symmetrically. If they are not symmetrical, the fire-resistance rating of the assembly is determined based on testing from the weakest side. For a loadbearing wall, the test requires the maximum load permitted by design standards be superimposed on the assembly. Most wood-stud wall assemblies are tested and listed as loadbearing. This allows them to be used in both loadbearing and non-loadbearing applications. Listings for loadbearing wood stud walls can be used for non-loadbearing cases since the same studs are used in both applications. Loading during the test is critical as it affects the capacity of the wall assembly to remain in place and serve its purpose in preventing fire spread. The strength loss in studs resulting from elevated temperatures or actual burning of structural elements causes deflection. This deflection affects the capacity of the protective wall membranes (gypsum board) to remain in place and contain the fire. The fire-resistance rating of loadbearing wall assemblies is typically lower than that of a similarly designed non-loadbearing assembly. Exterior walls only require rating for fire exposure from within a building. This is because fire exposure from the exterior of a building is not likely to be as severe as that from a fire in an interior room or compartment. Because this rating is required from the inside only, exterior wall assemblies do not have to be symmetrical. The NBC permits the authority having jurisdiction to accept results of fire tests performed according to other standards. Since test methods have changed little over the years, results based on earlier or more recent editions of the CAN/ULC-S101 standard are often comparable. The primary US fire-resistance standard, ASTM E119, is very similar to the CAN/ULC-S101 standard. Both use the same time-temperature curve and the same performance criteria. Fire-resistance ratings developed in accordance with ASTM E119 are usually acceptable to Canadian officials. Whether an authority having jurisdiction accepts the results of tests based on these standards depends primarily on the official’s familiarity with them. Testing laboratories and manufacturers also publish information on proprietary listings of assemblies which describe the materials used and assembly methods. A multitude of fire-resistance tests have been conducted over the last 70 years by North American laboratories. Results are available as design listings or reports through: APA Intertek QAI Laboratories PSF Corporation Underwriters’ Laboratories of Canada Underwriters’ Laboratories Incorporated In addition, manufacturers of construction products publish results of fire-resistance tests on assemblies incorporating their proprietary products (for example, the Gypsum Association’s GA-600 Fire Resistance Design Manual). The NBC contains generic fire-resistance rating information for wood assemblies and members. This includes fire and sound resistance tables describing various wall and floor assemblies of generic building materials that assign specific fire-resistance ratings to the assemblies. Over the last two decades a number of large research projects were conducted at the National Research Council of Canada (NRC) on light-frame wall and floor assemblies, looking at both fire resistance and sound transmission. As a result, the NBC has hundreds of different wall and floor assemblies with assigned fire-resistance ratings and sound transmission ratings. These results are published in the NBC Table A-9.10.3.1.A. Fire and Sound Resistance of Walls and NBC Table A-9.10.3.1.B Fire and Sound Resistance of Floors, Ceilings and Roofs. Not all assemblies described were actually tested. The fire-resistance ratings for some assembles were extrapolated from fire tests done on similar wall assemblies. The listings are useful because they offer off-the-shelf solutions to designers. They can, however, restrict innovation because designers use assemblies which have already been tested rather than pay to have new assemblies evaluated. Listed assemblies must be used with the same materials and installation methods as those tested. The previous section on fire-resistance ratings deals with the determination of fire-resistance ratings from standard tests. Alternative methods for determining fire-resistance ratings are permitted as well. The alternative methods of determining fire-resistance ratings are contained in the NBC, Division B, Appendix D, Fire Performance Ratings. These alternative calculation methods can replace expensive proprietary fire tests. In some cases, these allow less stringent installation and design requirements such as alternate fastener details for gypsum board and the allowance of openings in ceiling membranes for ventilation systems. Section D-2 in NBC, Division B, Appendix D includes methods of assigning fire-resistance ratings to: wood-framed walls, floors and roofs in Appendix D-2.3. (Component Additive Method); solid wood walls, floors and roofs in Appendix D-2.4.; and, glue-laminated timber beams

The National Building Code of Canada (NBC) defines fire safety under Objective OS1: “an objective of this code is to limit the probability that as a result of the design or construction of the building, a person in or adjacent to a building will be exposed to an unacceptable risk of injury due to fire.” In simpler terms, fire safety is the reduction of the potential for harm to life as a result of fire in buildings. Although the potential for being killed or injured in a fire cannot be completely eliminated, fire safety in a building can be achieved through proven building design features intended to minimize the risk of harm to people from fire to the greatest extent possible. Designing a building to ensure minimal risk or to meet a prescribed level of safety from fire is more complex than just the simple consideration of what building materials will be used in construction of the building, since all building materials are affected by fire. Many factors must be considered including the use of the building, the number of occupants, how easily they can exit the building in case of a fire and how a fire can be contained. Even materials that do not sustain fire do not guarantee the safety of a structure. Steel, for instance, quickly loses its strength when heated and its yield point decreases significantly as it absorbs heat, endangering the stability of the structure. An unprotected, conventional cold-formed steel joist floor system will fail in less than 10 minutes under standard laboratory fire exposure test methods, while an unprotected, conventional wood joist floor system can last up to 15 minutes. Reinforced concrete is also not immune to fire. Concrete will spall under elevated temperatures, exposing the steel reinforcement and weakening structural members. As a result, it is generally recognized that there is really no such thing as a fire-proof building. The NBC only regulates those elements which are part of the building construction. The building contents found in any building are typically not regulated by the NBC, but in some cases they are regulated by the National Fire Code of Canada (NFC). The occupancy classification of buildings or parts of buildings according to their intended use accounts for: the quantity and type of combustible contents likely to be present (potential fire load); the number of persons likely to be exposed to the threat of fire; the area of the building; and the height of the building. This occupancy classification is the starting point in determining which fire safety requirements apply to a particular building. The occupancy classification of a building within the NBC dictates: the type of building construction; the level of fire protection; and the degree of structural protection against fire spread between parts of a building that are used for different purposes. Fires can occur in any type of structure. The severity of a fire, however, is contingent on the ability of a construction to: confine the fire; limit a fire’s effects on the supporting structure; and control the spread of smoke and gases. To varying degrees, any type of construction can be designed as a system (combination of construction assemblies) to limit the effects of fire. This allows occupants sufficient time to escape the building and for firefighters to safely carry out their duties. Occupant safety also depends on other parameters such as detection, exit paths, and the use of automatic fire suppression systems such as sprinklers. These concepts form the basis of the NBC requirements. For further information, refer to the following resources: Wood Design Manual (Canadian Wood Council) Fire Safety Design in Buildings (Canadian Wood Council) National Building Code of Canada National Fire Code of Canada CSA O86, Engineering design in wood Fitzgerald, Robert W., Fundamentals of Fire Safe Building Design, Fire Protection Handbook, National Fire Protection Association, Quincy, MA, 1997. Watts, J.M. (Jr); Systems Approach to Fire-Safe Building Design, Fire Protection Handbook, National Fire Protection Association, Quincy, MA, 2008. Rowe, W.D.; Assessing the Risk of Fire Systemically ASTM STP 762, Fire Risk Assessment, American Society for Testing and Materials, West Conshohocken, PA, 1982.

Throughout history, protecting commercial structures from fire has been important. Fire poses risk in terms of safety to occupants, building integrity, business interruption and the economic health of a community. Consequently, reduction in the risk of fire for commercial buildings has been a significant goal for society, achieved through a better understanding of all the factors that contribute to fire risk. Designing and building structures in compliance with building and fire code requirements, and insurance industry guidelines, contributes to the reduction of fire losses. Wood has had a long history of use in commercial construction. Some of the reasons for this are: high strength-to-weight ratio, ease of use and constructability, known performance characteristics, resource abundance and renewability, economy in construction, and architectural aesthetics. Wood construction that makes use of good design and appropriate fire protection measures provides a level of fire safety that is comparable to other types of construction. This document discusses some of the basic factors that affect fire risk and property insurance rates, as well as some common misconceptions regarding what conditions make commercial buildings fire-safe.

The Mass Timber Demonstration Fire Test Program (MTDFTP) included two series of experiments: the pilot scale demonstration tests in summer 2021 in Richmond, BC [1] and the large scale fire tests in summer 2022 in Ottawa, ON. The series of large scale fire tests on a mass timber structure were conducted to study fire safety during construction, fire dynamics and performance in an open plan office space and residential suites, and influence of exposed mass timber on fire severity and duration. As part of its research to inform the advancement of safe and innovative solutions across Canada’s construction industry, the National Research Council of Canada (NRC) conducted the technical work and science-based large scale fire tests to support the MTDFTP. NRC was responsible for instrumenting the test structure, setting up fire scenarios and fuel loads, conducting the large scale fire tests, analyzing test data and documenting the results. This report documents the fire scenarios, fuel loads, experimental setups, instrumentation, measurements and procedure used in the large scale fire tests. The experimental data, results of data analysis, key findings and conclusions are provided in the report.  

The rate at which flame spreads on the exposed interior surfaces or a room or space can have an impact on the rate of fire growth within an area, especially if the materials of the exposed surfaces are highly flammable. Therefore, the National Building Code of Canada (NBC)¹ regulates the surface flammability of any material that forms part of the interior surface of walls, ceilings and, in some cases, floors, in buildings. Based on a standard fire-test method, the NBC uses a rating system to quantify surface flammability that allows comparison of one material to another, and the ratings within that system are called flame-spread ratings (FSR). For some buildings, the smoke generated by materials or products lining some areas of the building when they burn is also regulated by the NBC. Since it may take some additional time for occupants to exit the building, this applies to all unsprinklered high buildings and all elevators or Group B occupancies in high buildings. The FSR and SDC is also regulated for some materials used in ducts and plenums. The smoke produced from a material or product is measured and quantified through another rating system, based on a standard fire-test method — the smoke developed classification (SDC). For most wood products used as interior finishes, both of these properties — the FSR and the SDC — are to be determined in accordance with CAN/ULC-S102, “Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies.”² For flooring, CAN/ULC-S102.2 “Standard Method of Test for Surface Burning Characteristics of Flooring, Floor Coverings, and Miscellaneous Materials and Assemblies is to be used when a SDC or FSR is required.

Fire separations and fire-resistance ratings are often required together but they are not interchangeable terms, nor are they necessarily mutually inclusive. The National Building Code of Canada (NBC)1 provides the following definitions: A fire separation is defined as “a construction assembly that acts as a barrier against the spread of fire.” A fire-resistance rating is defined as “the time in minutes or hours that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria, or as determined by extension or interpretation of information derived therefrom as prescribed in [the NBC].” In many buildings, the structural members such as beams and columns, and structural or non-structural assemblies such as walls and floors, are required to exhibit some degree of resistance to fire in order to prevent the spread of fire and smoke, and/or to minimize the risk of collapse of the building in the event of a fire. However, fire separations are assemblies that may or may not be required to have a specific fire-resistance rating, while structural members such as beams and columns that require a fire resistance rating to maintain the structural stability of a building in the event of a fire are not fire separations because they do not “act as a barrier against the spread of fire.” Requirements for fire separations and fire-resistance ratings are just one aspect of the fire-safe design approach used by the Code to reduce risk to building occupants of injury, as well as to reduce risk of property loss. Together, they are key elements to the strategy of controlling fire spread called “compartmentation.”

The vulnerability of any building, regardless of the material used, in a fire situation is higher during the construction phase when compared to the susceptibility of the building after it has been completed and occupied. This is because the risks and hazards found on a construction site differ both in nature and potential impact from those in a completed building; and these risks are occurring at a time when the fire prevention elements that are designed to be part of the completed building are not yet in place. For these reasons, construction site fire safety includes some unique challenges. Developing an understanding of these hazards and their potential risks is the first step towards fire prevention and mitigation during the course of construction (CoC).

In a recent survey of building specifiers, the majority perceived wood to be the most environmentally friendly building material. Compared to other major building materials, this is due mainly to: the renewability of wood the low energy consumption required for production the low levels of pollutant emission during manufacture Lately, environmental considerations have acquired more importance in the specification of materials. Technical and economic aspects of building materials have always been primary considerations for specifiers. Increasingly, however, they are considering the environmental effects when selecting appropriate building materials for their designs. Architects, engineers and designers require accurate information to assess the true environmental consequences of the materials they specify. The environmental impacts of various building materials have been examined by a Canadian Research Alliance using the internationally accepted method called Life-Cycle Analysis (LCA). The Alliance consists of researchers from the wood, steel and concrete industries as well as university groups and consultants.