Thanks to the advancement and proliferation of a wider selection of home insulation products, builders can optimize a bevy of available options to achieve the best thermal results and also keep their costs in check. The “flash and batt” technique for wall stud cavities, for instance, combines more expensive but airtight closed-cell, expanding foam insulation and affordable fiberglass batts to create a thermally efficient and cost-effective envelope. Closed-cell offers an R-value per inch that’s almost double that of open-cell options and is easier to control for the “flash” phase. You also get the benefit of its air-sealing qualities without paying for a full-cavity application. The batts, meanwhile, are offered in a wide range of R-values to retard thermal transfer through the cavity—assuming they are installed properly (#2 in slideshow). An alternative is a “flash and BIB” concoction (#3 in slideshow), where a blown-in-blanket layer replaces the batts to better ensure complete cavity coverage—especially around intruding MEP runs.