Completely sealing off the attic and turning it into conditioned space is not that uncommon.
Turning it into a “conditioned livable space” is different than sealing the attic, if that is what you mean. I see it often in cape cods, but I still like to see air flow between the decking & the insulation. If you don’t vent the attic space you will cook the shingles and trap moisture.
But sealing the attic it is not by any means a standard practice. At least in Ohio. I’ve been inspecting for 7 years and have yet to see a “sealed or conditioned” attic space.
Why would anyone want to condition the attic unless you were going to use it as a livable space? It would be a huge waste of $$.
You need to understand building science a little more. Check this out.
Solution: Air Sealing
Although the solution is rather simple to state, it is quite difficult to achieve in practise. Great care must be taken to seal the ceiling air barrier (often the polyethylene vapor barrier is used as an air barrier or the drywall; see Photograph 4](http://www.nachi.org/forum/?full_view=1#P04)). Table 1](http://www.nachi.org/forum/?full_view=1#T01) provides a list of air leakage locations and means to ensure they are sealed.
Caulking can be used around small openings and gaps, but expanding polyurethane or acrylic foam should be used around openings more than about 1” (see Photograph 5](http://www.nachi.org/forum/?full_view=1#P05)). For large openings, drywall can be used as the air barrier with taped or caulked joints used to complete the seal. Great care and attention to detail is essentially the only solution to air leakage, although expensive answers such as spraying the entire ceiling with expanding foam (NOT dense-pack cellulose, or blown in batts) can provide the required airtightness quite easily.
***Photograph 4: ***Polyethylene sheet sealed as air barrier around bathroom fan housing
And this, great article.
This is not an attic. It’s an roughed in - unfinished bathroom.
Great article. I stand corrected.
Here is another good article I found on this subject.
Thanks Kevin, that is a good article.