The thermal performance of the building envelope is mainly required for guaranteeing a comfortableand hygienic interior climate. A roof is a part of the building envelope which provides protection from thethermal damage of the sun. To improve this protection ability, we can consider using a ventilated roof,which has a ventilation layer known as a cavity, beneath the roof cover panel.The objective of this study is to evaluate the influence of such factors as the slope of the roof, size orshape of the openings (i.e.
This paper is concerned with natural air flows between major construction cavities in New Zealand houses. A two tracer technique was developed to measure infiltration rates in the subfloor (crawl space), the living space and roof space, together with air flow rates connecting these zones. Five experimental houses were chosen to represent expected extremes in air flow resistance between subfloor and roof space.
The model of moisture concentrations in a building cavity containing hygroscopic material presented in earlier works is extended to allow for evaporating surfaces within the cavity (eg soil, water tanks) and fluctuating external climatic conditions. Linearized coupled differential equations are solved for three cases - 1. Steady state 2. Step function 3. Periodic climate driving forces. The third case gives formulae predicting the cavity moisture contents at any time of day or year, and shows that the steady state approximation is adequate for all but the tightest cavities.
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