QC-06-056 (RP-1169) - Infiltration Heat Recovery, Part I—Field Studies in an Instrumented Test Building ✓ Most Recent

The flow of air through the porous media that is used asbuilding insulation has the potential to recover energynormally lost through the building envelope via conduction. Inessence, the walls of the building can be used as a crude heatexchanger, the effectiveness of which depends on the flowdirection, flow rate, and material thermal properties. In theory,the largest effects will be seen in the situation where the air flowis counter to the conduction loss and is distributed uniformlyover the entire envelope surface. In theory, this form of distributedheat exchanger, at the appropriate flow rate, should becapable of recovering all of the energy that crosses the innergypsum board boundary.

To examine the potential for energy recovery, anASHRAE-supported research project was undertaken in twoparallel studies: laboratory work with carefully constructedwall sections and field studies with a well-instrumented testbuilding. The study dealt only with sensible heat transferthrough the building envelope during heating conditions. Noattempt was made to gauge the effects of moisture or to applythe results to a cooling situation.

This paper presents the results of the field studies andshows that the energy recovery potential is strongly dependenton the fraction of the building envelope that participates in theexchange process, and that given the unknowns, number ofcracks or holes, crack geometry, and location, the traditionalmethods used to calculate component U-factors are adequate.No allowance for air infiltration, other than the traditionalmethods of calculating the energy impact, are needed.