It might not wear a flowing cape or spiffy tights, but the flash and batt method of home insulation is a real superhero. Its power combines two common insulation materials and transforms them into something that neither could be on its own: highly effective and budget-friendly. That's a genuine foe to the arch-nemesis of heat loss and air leaks when you're insulating an attic or any part of your home.
Who are These Heroes?
Flash-and-batt insulation uses a two-pronged, hybrid approach. One is expanding foam insulation, and the other is the familiar batt or blanket insulation that you're probably more familiar with. It's the stuff that comes in a roll.
The foam might be closed-cell that's sprayed as a film throughout the cavity, or it might be a single-component polyurethane foam like the gap filler that you would use around the house. As for the batts or blankets, those can be whichever material you prefer. Fiberglass is a longstanding favorite because it's economical. But it's also itchy, as anyone who has ever handled it can confirm, and some contain formaldehyde as a binder.
Eco-friendly batts and blankets are also available. Many homeowners choose that route. Some are made from fiberglass but use a natural binder that won't off-gas. Other types are made from recycled materials such as denim.
How Are They Installed?
The first part of the system is an application of foam insulation inside the wall cavity. If you opt for closed-cell spray foam, insulation supplier, A Warehouse Full, explains that it goes on as a thin, 1 or 2-inch layer throughout the entire space including the studs. If you choose the gap filler method, expanding polyurethane foam is applied along the seams inside the cavity only. Those seams would otherwise be potential air leaks, but the foam seals them tight.
Foam expands as it cures, reaching at least double its original size. That, plus the fact that it's waterproof, explains why it seals so well. Once the cure is complete, batt or blanket insulation fills out the remainder of the wall cavity. Green Building Adviser calls batts the money-saving layer.
A spray foam layer can cost a bit more than sealing just the seams, but it creates a uniform barrier inside the whole wall cavity. It also costs less than using foam alone. Polyurethane foam along the seams isn't a second-rate superhero, though, because it excels at filling every gap where air would sneak in.
Why Flash and Batt Works
Although not ideal for every home, the flash-and-batt system takes what's most effective about both materials and uses them to their best advantage. In a traditional installation, spray foam would fill the whole wall cavity, block air leaks and moisture, plus give you a hefty R-value. The cost of foam means that's a pricey job.
Traditional batt insulation does a fine job on its own, although foam does boast a higher R-value. But air and moisture can still work their way through the fibers. It's just not as effective as foam because it can't seal the wall cavity without an air/vapor barrier to help out. A typical air barrier has no R-value because it's a thin film. The same applies to vapor barriers.
With flash and batt, you get a wall cavity with a built-in air barrier plus insulation before the rest of the materials go in, or you get serious air leak control if you just use gap filler. Then with batts on top, you've got a one-two punch that's sealed and warm.
Real heroes to households just like yours, foam insulation and the fluffy stuff both work hard to reduce thermal transfer. That's what happens when heat from inside escapes or heat from outside makes its way in. And it's also what the R-value of any insulation indicates. R-value equals thermal resistance. But installed together, the products make a system that's downright amazing.
Luckily, you don't need a bat signal to bring the flash-and-batt superheroes to your home. We at Clean Crawls are experts in attic cleaning and insulation, and we can make your home more energy efficient and comfortable. Contact us today and request a quote.