Thermal behaviour of vented roofs

Abstract

Purpose

The purpose of this paper is to present the results of an experimental study aimed at analysing the effect of the roof tile air permeability on the thermal performances of ventilation ducts in the roof. The main reason underlying this study is the fact that the theoretical reference assumed for the manufacture and sizing of ventilation ducts (the accepted theory on roof ventilation) is clearly limited when applied to ducts which are not perfectly airtight (Hens) and results in an oversizing of the ventilation ducts.

Design/methodology/approach

A section of roof is built, covered with different tiles and environmental and meteorological data collected. The data are analysed statistically.

Findings

The results show that the permeability of the layer of tiles determines heat losses which are in addition to those connected with the stack effect in a perfectly airtight duct with the same features. The results also confirm the correlation which has already been demonstrated between the geometric ratio of the length of the duct divided by its height and the amount of heat dissipated by the roof (Sandberg and Moshfeg).

Originality/value

This study analyses the performance of the roofs only during the summer season. The research is therefore continuing with a long‐term (one year) analysis of the roofs characterised by a high level of roof tile permeability so as to understand the consequences that the presence of a ventilation duct in systems with air permeable roofing may have on the thermal efficiency of the roof.

Citation

D'Orazio, M., Di Perna, C. and Stazi, F. (2009), "Thermal behaviour of vented roofs", Structural Survey, Vol. 27 No. 5, pp. 411-422. https://doi.org/10.1108/02630800911002657