Sealed Attic vs Vented Attic
The most common type of attic is the vented attic, since most attics were, and are, built that way. When deciding how to insulate your attic, you can change this – but should you?
A vented attic is often the best option when you have a high-pitched roof – one with a high angle. This is because it is difficult to insulate the ceiling with such an angle. However, if you don’t have a high-pitched roof, an unvented, or sealed, attic is pretty much always the optimal choice.
This is because a sealed attic is a conditioned space, like the rest of the building, and you can use it for storage or even as a living space. A vented attic can’t be used for much of anything, since the temperature in a vented attic fluctuates a lot throughout a single day and it can become humid inside one.
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A vented attic also means more maintenance – you have to periodically check on the vents, moisture can build up, and if there are any mechanical components in your attic, such as HVAC ducts, you have to make sure those don’t get damaged by the unstable environment. Ice dams can build up in vented attics and cause major roof damage, while this is not a concern with a sealed attic.
There is a common misconception that sealed attics cause the roof to heat up and shingles to curl – while it is true that a sealed attic may warm your roof by a few degrees, it is not enough to cause any damage. Some roofing companies still hold this to be true, though, and may void your warranty if you seal your attic, so do check with your roofing company before you seal it.
It is worth noting, though, that a sealed attic is a bad idea if lower areas of the building are not sealed. This is because hot air can accumulate in the attic and turn it into an oven. If the building envelope is fully sealed, this is not an issue.
To sum it up, a sealed attic is almost always the better choice, but a vented attic can be better if you have a high-pitched roof, your air environment is unsealed on lower floors, or your roofing company doesn’t like sealed attics.