Measured energy penalties from crawl space ventilation.

While there is no convincing technical basis for current code requirements for crawl space ventilation, most codes still require operable vents and the practice is well established among builders and architects . While the evidence against venting is compelling to many if not most in the research community builders and code officials apparently want to see hard evidence. In this research project I measured weekly energy consumption for space heating for a 1150 square foot home in a climate with 5900 heating degree days. The house was built to meet the 1992 Model Energy Code and the perimeter of the crawl space was insulated with R-10 foamboard. The supply ducts of the gas-fired, forced air system are located in the crawl space and were carefully sealed and pressure tested. Utilizing a "flip flop" research design , with the crawl space vents open one year and closed the next , I measured the "energy penalty" resulting from leaving crawl space vents open during the winter. This measured penalty or, conversely, the savings from closing and insulating the vents was 21 % (12 MMBtu/yr) in year two of the research. Savings were 32 % (19 MMBtu/yr) in the most recent winter, in which the crawl space access cover was insulated and made airtight in addition to closing and insulating the vents.