Analytical Calculation of Pressure Distribution on a Residential Roof 1999-01-2650

Using a panel method, the flow over various residential roof designs was analyzed and an estimate of the pressure distribution across the roof was determined. This pressure distribution was analyzed to determine the potential for flow reversal through the ventilating system of a gas-fired appliance. It was found that, for several roof configurations and wind speeds, relatively low pressures could exist on the roof of a residence. In addition, some appliance venting configurations, combined with the local pressure distribution, will impose pressures on the appliance inlet and exhaust that can result in a reversal of the normal flow direction. If the flow is reversed and the appliance is installed in a closed area like an airtight closet, hot exhaust gasses will be allowed to enter areas not designed for high temperatures and a fire can result.