To determine the effect of an evergreen windbreak on residential heat losses attributable to air infiltration, 8-m tall pine trees were arranged as an experimental windbreak to shelter a townhouse for 9 weeks. Air infiltration was measured continuously with SF6 as a tracer to compare air infiltration rates before and after the windbreak. For ASHRAE design wind and temperature conditions, air infiltration was reduced by 42%. As air infiltration accounts for about one-third of the total winter heat loss in these houses, a space heating reduction of about 14% is predicted under these conditions with the wind perpendicular to the windbreak. A dimensionless parameter was derived to distinguish between wind- and temperature-produced air infiltration and to determine the effect of wind direction on air infiltration:
M=V2/g*l*beta*deltaT
The parameter is the ratio of wind inertia to buoyancy effects: where V is wind speed, g the gravitational constant; lower-case “l”, a characteristic length; beta, the coefficient of the thermal expansion of air; and deltaT, the indoor-outdoor temperature difference.
Citation: Symposium, ASHRAE Transactions, Volume 85, Part 2, Detroit, MI
Product Details
- Published:
- 1979
- Number of Pages:
- 17
- File Size:
- 1 file , 1000 KB
- Product Code(s):
- D-DE-79-01-2
