As you can see, the temperature difference is only a few degrees. The graph in Fig. 12 below shows how the temperature difference between the two types of homes varied throughout the day. The largest temperature difference was about 9°F, which occurred around noon. The average temperature difference through the day was about 2°F.
Shingle Temperature And Durability
The paper covers a lot of ground, so here’s a short list of some of the other research results on insulated rooflines, temperature, and durability.
- Shingle color and geographic location affect shingle temperature more than attic ventilation (p. 9).
- We don’t know enough about the role of ultraviolet radiation (UV) in shingle durability.
- Homes with insulated rooflines have slightly higher shingle temperatures than roof decks with radiant barriers (7°F vs. 5°F).
- One study showed that shingle life is reduced by less than a year on homes in Miami with no attic ventilation. Another study showed a 2-year reduction.
Here’s a bit of anecdotal evidence for you. Southface has a building constructed with structural insulated panels (SIPs) that they built in 1996. The asphalt shingles have been on the insulated roofline for 17 years now. They also have a detached garage with a vented attic. The last time I was there, I saw no difference in appearance or performance of the two roofs.
To end, let me ask you ask you a question: Do you know anyone who has ever collected on a shingle warranty? The answer is probably no. Even if it’s yes, however, shingle warranties are structured so that you’re not going to collect much if you do make a claim unless you have catastrophic failure in the first couple of years. An insulated roofline should have minimal effect, and almost certainly will not result in catastrophic failure if done properly.
Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.