An investigation into the use of a supply air window as a heat reclaim device

Abstract

An 'airflow' window can be considered both as a passive solar and as a heat reclaim device. 'Supply air' airflow windows are of renewed interest given the increased volume of air needed for background ventilation in houses as stipulated in the 1995 amendment to the Building Regulations. This study was carried out using the test cells at BRE Scotlab; it sought to establish the effect of climatic conditions on the operation of a Scandinavian 'double' window that was converted for use as a supply air window. A clear correlation was established between intensity of incident solar energy and the temperature gradient within the window. It was also evident that the window acted at night as a heat reclaim device. During the period of the test, the problem of reverse flow was encountered (similar to that found in 'passive stack vent' systems), and the influence of wind speed was investigated. Comparison was made between test cell measurements of the U-value of the standard (unventilated) triple glazed window and those derived from the program FRAME. By reference to recent work on ventilated photovoltaic glazing systems it was possible to derive a simulation method for predicting the temperature rise within the window.