Advances in modelling heat transfer through wood framed walls in fire

Described in this paper are advances made in modelling heat transfer through wood framed walls in fire. Previously unpublished experimental results are also given. This type of modelling is used for the determination of the performance of fire safety systems, such as wood framed wall barriers, in accordance with new performance-based building regulations being introduced around the world. Advances include a discrete modelling method for radiative heat transfer in cavities with re-entrant corners and gaps formed by the shrinkage of stud cross-sections. It has been shown that the formation of the gaps can prevent temperatures rising in the fire side of studs by as much as 100-200degreesC. A simple means of modelling heat transfer by the movement of moisture and vapour, involving the modification of conductivity values has been developed. Sloughing of gypsum board sheets has been satisfactorily modelled assuming that a sheet sloughs when the temperature on the surface opposite the fire reaches the melting point of glass fibres in the gypsum board; that is, approximately 700 C. Recommendations on thermal properties obtained independently by other researchers are presented. Overall, the advances improve temperature predictions and broaden the range of walls that can be modelled including staggered stud walls as well as ordinary cavity walls. Copyright (C) 2002 John Wiley Sons, Ltd.