TECHNICAL FEATURE these builders.† This also means for builders in CZ 3 who prefer 2 × 4 wall construction without exterior insulated sheathing, the high R-value windows trade-off allows the builder to continue with their desired wall confi guration without the need for +5 continuous insulation. These trade-offs would also allow some fl exibility to reduce the amount of exterior insulation below the +10 requirement for builders who prefer 2 × 4 wall construction in CZ 4 through CZ 8. These trade-offs would be allowable under the UA trade-off approach (e.g., prescriptive path) or through either of the performance compliance paths. Benefi t-Cost Trade-Offs The trade-off options characterized for this study were selected based on their potential impact on both the marginal benefi ts and marginal costs of code-compliant home construction. Note that once a home is constructed, insulating envelope and window retrofi ts are rarely made; thus, one could argue that any trade-off made away from enhanced envelope insulating measures at the time of construction is likely an opportunity lost over the life of building. This analysis does not consider the long-term impacts of window and wall insulating tradeoffs over the lifetime of the home, and the authors would advocate for the use of both enhanced opaque envelope insulation and highperformance windows whenever possible. Although many trade-off analyses focus exclusively on energy †Continuous insulation has been a requirement for wood-framed walls in Climate Zone 6 through Climate Zone 8 since the 2012 IECC. However, the 2021 IECC has an envelope backstop linked to the 2009 IECC. Thus, the insulation of wood-framed walls can be reduced down to R-20 or U-0.057 in Climate Zone 5 through Climate Zone 6 and R-21 in Climate Zone 7 through Climate Zone 8. M A R C H 2 0 2 2 ashrae.org ASHRAE JOURNAL 59 cost saving benefi ts in comparison to material fi rst costs, there are other benefi ts and costs that should be considered. Non-Energy Benefi ts In addition to saving energy, the thermal components of a home's envelope affect occupant health andhttp://www.airflowbalancing.com http://www.ashrae.org