Encapsulating attics with spray foam and conditioning them has become a popular alternative to the traditional unconditioned attic. There are obvious benefits: a much cooler attic, lower energy costs, and keeping out animals and bugs. However, the negative effects were largely unknown until the last few years. In the next two minutes, we’ll dig into the other consequences of having a foamencapsulated attic.
Traditional attic ventilation serves a crucial purpose, especially in Texas. Attics get hot—really hot—and asphalt products become unstable at high temperatures. Ventilation helps remove hot air from the attic to keep shingles healthy and lasting as long as intended. Attic ventilation is also a requirement by asphalt shingle manufacturers to maintain the warranty on the product. Another important element of attic ventilation is that it removes moisture from the attic. In the winter, when your attic is cooler, the hot pipes running through it create condensation. If this condensation has nowhere to go, it builds up on the roof deck and rafters, which can cause wood rot. This can lead to nails coming loose, shingles sliding off, and even structural damage.
Foam encapsulation was another way to achieve a cooler attic and is more effective than ventilation in that regard. If the priority is keeping the attic cool, HVAC waste down, and shingles healthy, foamed attics seemed like a winning idea… but the science proved otherwise and led to disastrous consequences. The highly efficient foam allows conductive heat to build up within the shingle, whereas attic ventilation previously allowed the heat to flow away from the underside of the shingle through convection and vent out the rooftop. In other words, it kept the attic cool, but not the shingles.
This created a problem for asphalt shingle manufacturers, and they quickly added warranty exclusions for shingles installed over foam-encapsulated attics. Now, to properly encapsulate the attic, there needs to be a gap of ventilated space between the spray foam and the bottom of the roof deck, which adds significant cost to the project. This cost will likely offset any savings expected from the spray foam. On most non-asphalt roof coverings, foam encapsulation is not an issue. However, if you have asphalt shingles, you’ll want to check with your shingle manufacturer before installing spray foam, as there’s a high likelihood you’ll void your warranty.
This might be a bummer for anyone looking to add square footage to their home, but there are other solutions and ways to make spray foam work if you are set on the product. If you need advice on your project or have concerns about your roof, you know where to find us.
Take care!