An experimental study dealing with the passive supply of combustion air for appliances located in cold climates was carried out over two heating seasons. During that period more than 8,000 hours of hourly air exchange rates data were gathered in two test buildings. Examines the performance of vents sized and located in accordance with the Uniform Mechanical Code. Examines the use of a mechanical system for the supply of combustion air. Passive combustion air supply systems sized according to codes can, on average supply sufficient outdoor air to meet the combustion and space-conditioning requirements. Air flows of nearly 300% of the design rates were observed under environmental extremes - low temperature and high wind speed. Flow rate reduction through a reduction in vent cross-sectional area was experimentally evaluated. There was a small reduction in average flow rate, but the extremes in flow remained comparable to the full-sized vents, indicating that the problems of oversupply of air during environmental extremes cannot be solved through a reduction in vent area without the danger of inadequate supply when conditions are mild. Mechanical supply of the combustion air using a fan was observed to always supply adequate amounts of air. Proper design of the fan system will ensure that the room is not pressurised by the system but that adequate air will be supplied. The use of a mechanical system for the supply of combustion air means that space-conditioning and combustion air must be necessarily separated.

KEYWORDS: year 1997, Combustion air, passive, ventilation, air change rate, buildings, performance, vents, mechanical ventilation, outdoor air, air flow rate, cold regions, experiment, housing, comparing, measuring