Effect of cavity depth on smoke spreading of double-skin façade

Glazing has been very popular among the construction industry in the Far East. Possible reasons are that it offers the desired views, favorable environmental design and good appearance. Numerous glass configurations with full-height curtain wall were designed. However, there are concerns on increasing the cooling load in tropical areas. Double-skin façade (DSF) is one of the architectural glass features to reduce the solar heat gain. This design might give fire problems and many such projects failed to comply with the fire safety codes. Engineering approach similar to performance-based fire codes practicing in some countries was applied to demonstrate the design is safe. Fire hazard assessment should be supported by in-depth investigations. Experiments with physical scale models were carried out to investigate the fire hazard of this new architectural feature. A facility developed in a remote area of Northeast China was selected for the full-scale burning tests on part of the DSF feature. The cavity depth was identified as the key factor. The effects of the cavity depth on fire spreading will be discussed in this paper. Data from four sets of tests performed with glass sheets were extracted to clarify this point. Surface temperature and heat flux received on the test panels were measured and analyzed. Cracking patterns found on the glass panels and collapse, if any, were also recorded. Smoke movement patterns inside the air cavity between the two layers of glass were observed and compared with the measured surface temperature of the inner and outer glass panels.