Computer fire modelling is one of the most important high-tech tools in fire safety engineering and fire science. The movement towards objective-based building codes means that these models will be essential tools for performance-based fire-safety design of wood structures. Accordingly for more than a decade, fire researchers at Forintek have been striving to develop heat-transfer models (HT models) for wood-frame assemblies exposed to fire. Then, in 2001 Forintek elected to outsource all future development of these models. This project provides funding, direction and oversight for the outside development of these design tools.
Because both the Canadian government and the wood industry had identified construction of wood-frame buildings in Japan as a market priority, and the fire performance of exterior wood-frame walls with exterior foam-plastic insulation and ceramic-siding rain screens, a popular Japanese housing design, as one of their biggest hurdles in capturing a larger share of that market, in 2002-2003, efforts were focused on development of a model to predict heat transfer through that specific type of assembly.
Using WALL2D, Forintek’s HT model for wood-frame walls with gypsum board on both sides as the foundation, Nortak Software Ltd. was contracted to complete Forintek’s development of a model to predict heat transfer through wood-frame exterior walls subjected on the exterior face to ISO 834 fire exposures.
While Forintek researchers knew that the Japan Testing Center for Construction Materials (JTCCM) in Tokyo had carried out fire tests on exterior wood-frame walls with expanded-polystyrene (EPS) exterior insulation and ceramic-siding rain screens, little was known about the outcome of those tests, the pass/fail criteria used in assessing such assemblies, and the problems, if any, that were encountered in carrying out the tests. Also, in ISO 834 tests, the fire gases within test furnaces are under a small positive pressure. The ability, if any, of those furnace pressures to drive hot fire gases through the ventilation/drainage holes in the rain screen and directly into the cavities behind the ceramic siding, and the direction of that gas flow within the cavities were completely unknown. Of greater significance and equal uncertainty was the effect that those conditions might have on the EPS insulation backing upon the cavities. Also, there was a dearth of information in Canada about design and construction practices followed in Japan for these types of walls. Another concern for Forintek was our ability to obtain test data for validation of the HT model once it had been developed. Finally, overriding all other concerns was the willingness of Japanese testing organizations, regulatory officials, manufacturers of building materials, and builders to accept the use of models to predict the fire performance of these types of assemblies. Therefore, Forintek contracted the service of Dr. Hisahiro Takeda to travel to the JTCCM to gather intelligence answering each of these concerns.
Development of Foritnek’s HT model for exterior walls with exterior EPS insulation and ceramic-siding rains screens will be completed by September 2003. Forintek will then aid Canadian government and industry officials in exporting Canadian housing technology and Canadian building products to Japan by working with officials at NRCan CANMET in selecting optimum designs for exterior wall assemblies to be used in construction of energy efficient houses in Japan. At the same time, Forintek will work with other industry and governmental officials to promote and market Canadian housing technology and Canadian building products in China, Taiwan and Korea by using the model to demonstrate the fire resistance of exterior wood-frame walls. Finally, Forintek will attempt to work with researchers at the JTCCM to market the model in Japan.