LBNL Report Number
Infiltration has traditionally been assumed to affect the energy load of a building by an amount equal to the product of the infiltration flow rate and the sensible enthalpy difference between inside and outside. Results from detailed computational fluid dynamics simulations of five wall geometries over a range of infiltration rates show that heat transfer between the infiltrating air and walls can be substantial, reducing the impact of infiltration. Factors affecting the heat recovery are leakage path length, infiltration flow rate, and wall construction. The classical method for determination of the infiltration energy load was found to over-predict the amount by as much as 95 percent and by at least 10 percent. However, the air flow paths typical of building envelopes give over-predictions at the low end of this range.