Quote:
Originally Posted by Shaneajanderson
I'm not buying a new house soon, nor looking to redo my roof, but I'm just curious. If you insulate and finish an attic does it need to be vented still? How does this work if that space is supposed to be heated and/or cooled? It just seems like intentionally letting outside air leak into a controlled environment in substantial quantities would be wasteful?
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You don’t want to ventilate your heated or cooled air to the outside.
I can’t speak for elsewhere but in Vermont there are some disadvantages to finishing an attic. It’s what you’d called a “hot roof”, because no matter how well you insulate it, if there’s no vented space between insulation and roof, the roof will be warmer than the air around it and in winter you’ll get ice dams, increased risk of water damage and generally just far lower roof lifespan.
I’m being facetious when I say this, but if you want to finish an attic and turn it into living space, ideally you’d rip the roof off and build a new vented attic on top of your attic so your roof can be cold.
In summer, having a vented space between shingles/sheathing and insulation greatly improves thermal performance of the structure.
Think of your roof as just being a tarp or shield to keep rain and snow off.