Extract

ABSTRACT: The importance of sub-floor ventilation as long been appreciated to prevent the
deterioration of the timber structure of suspended floors. In mid-1999 the Building Code introduced
amendment 5 to include uniform ventilation requirements of sub-floor spaces of Class 1 and 10
buildings based on climatic conditions. This amendment was based on work by Cole (1997) at CSIRO.
Here ventilation areas are calculated based on a scientific method, given certain wind and humidity
conditions, so that the underfloor humidity does not exceed a critical value that was assumed will lead
to the deterioration of timber. The vent requirements vary according to three humidity zones defined to
cover Australia. Recent concerns to improve the thermal resistance (R-value) of the building fabric
have lead to a critical examination of ventilation requirements. This paper will present a re-evaluation
of the Cole work and applying a “first principles” ventilation model to investigate the performance of
sub-floor conditions to prevent deterioration of timber and possible health hazards due to mould
growth. The implications for the present BCA requirements are discussed.

PDF

Download