Supply air windows provide fresh air in buildings whilst minimising heat loss. Fresh air is drawn into the window at the bottom, and having been pre-heated by heat exchange and by solar radiation, it enters the room at the top of the window. A PASSYS test cell was used to evaluate a model for the prediction of supply window performance, and to optimise window design. The window consisted of a sealed double glazed unit with a 12 mm gap and a single outer pane of 4 mm float glass. The gap between the outer pane and the sealed unit was varied between 10 and 30 mm, and low emissivity ( low-E ) coatings were applied to different glass surfaces. The windows were fitted in the south-facing wall of the test cell, and temperatures were measured using an array of thermocouples. The effective thermal transmittance ( Ue-value ) and ventilation preheating decreased with increasing levels of ventilation. The window Ue-value was halved when the low-E coating was applied to the outer surface of the double glazed unit. Modelling of the window using thermal and mass flow network software ( ESP-r ) gave good agreement with the experimental data. 11 refs.
Primary author(s): McEvoy M E; Southall R G;Baker P H
Source: Energy Build.
Vol.35, No.10, 2003, p.1009-1020