b'YOUR TOOLKIT FOR BUILDING EXCELLENCEFigure 1:construction. The COMcheck report also gives a convenient The International Energyscore showing the building envelopes performance as a Conservation Codepercentage better than (passing) or worse than (failing) is a model buildingthe code requirements. code published by the International CodeSome requirements of the energy code are considered Council and widelymandatory because they will always apply (i.e. cannot be adopted throughout thetraded off), even when the energy efficiency of the project United States. exceeds the code requirements. One mandatory example in the building envelope is resistance to air leakage (C402.5) because even the most robustly insulated building will not be energy efficient if the envelope allows unconditioned air to pass into and out of the building when the wind blows. Post-Frame buildings as a framing system do not have unique energy code requirements, but a few topics may frequently Figure 2:come up during project design and construction which may The extent of the building envelope in this example is represented by the orangedeserve mention: surfaces. The unheated storage area (far end) and the vented attic spaces are notR-values for wall and ceiling assemblies, with wider conditioned spaces and are excluded from the building envelope. framing cavities than in standard construction. Although using higher effective R-values in Post-Frame wall and ceiling cavities with common framing spacing of 6\' on center to 10\' on center (compared to 16" on center or 24" on center in standard wood frame construction) can be justified, the impact on code compliance software models is small and may not be worth specialized analysis. To determine appropriate U-values for walls and other assemblies in the UA / Component Performance Alternative calculation, designers should reference tables and methods within ASHRAE 90.1. In my experience it has been better to Designers for most projects tend to use the COMcheck tooluse a conservatively safe U-Value (slightly higher than to demonstrate how the IECC prescriptive requirementswhat I think could be used), rather than trying to be so of C402-C406 will be satisfied. But within this complianceprecise for the unique assembly framing and features path, three options exist for satisfying the building envelopethat the authority having jurisdiction (AHJ) may not requirements in a prescriptive way:understand (nor agree with) the analysis presented.1.R-value-based method (C402.1.3) U-values for large garage doors. Most garage door2.U-/C-/F-factor-based method (C402.1.4) manufacturers publish a nominal R-value for the door slab (R-12, R-15, etc.), but this cannot be converted 3.Component Performance Alternative (C402.1.5). directly into an effective U-value for the entire door. If the manufacturer does not provide an installed My experience indicates that the Component PerformanceU-value, the code prescribes conservative default Alternative method provides the most flexible and economicalU-values for these doors in Table C303.1.3(2). Using compliance path for my own project design work.I havethese default values in buildings with many garage found it very helpful to review the example for this methoddoors can make it difficult or impossible to meet the shown in the IECC Commentary (see Figure 3 on page 22)energy code envelope standards, so look for door to confirm that I understood the method properly beforemanufacturers with published ANSI/DASMA 105-2017 using it in my own designs. high-performance U-Values, the lower, the better! Using COMcheck to document compliance for the entire(Door and Access Systems Manufacturers Association building envelope allows a designer to enter all assemblies andInternational, 2017).components and their performance criteria into the software.Best ways to insulate foundations and building The resulting report produces a summary of the envelopeperimeter. A 2010 Frame Building News article and any requirements that must be satisfied during and after(Bohnhoff, 2010) discussed the importance of using continued on page: 22 FRAME BUILDER - VOL5 5 / 21'