Article #146 - Does REScheck Take Air Infiltration into Consideration?
REScheck does not take air infiltration into consideration. REScheck implements Chapter 5 of the MEC and IECC which does not have any infiltration requirements -- the code''s component performance approach (Chapter 5) specifies maximum Uo-factor requirements for walls, ceilings, floors, crawl space walls, and basement walls and minimum R-value requirements for slab perimeter insulation. Section 502.2.2 of the IECC state that the Uo-factor or U-factor of a given assembly may be increased or the U-factor of a given assembly may be decreased if the total heat gain or loss of the entire building does not exceed the total resulting from conformance to these requirements.
The Uo-factor is the overall conductive thermal transmission coefficient of an envelope component or of the envelope of the entire residential structure. The coefficient excludes, for example, the effects of mechanical ventilation and natural air infiltration.
The U-factor measures how well a product prevents heat from escaping. The rate of heat loss is indicated in terms of the U-factor of a window assembly. U-factor ratings generally fall between 0.20 and 1.20.
REScheck requirements are based solely on U-factor x Area (UA, the heat loss/gain rate) calculations for each building assembly to determine the whole-building UA of the user''s building design. The whole-building UA from a building conforming to the code requirements (the code building) is compared against the UA from the user''s building design (the proposed building).
At present there is no support for the performance approach in REScheck due to inconsistent requirements in the IECC between the trade-off approach and the performance approach.