Originally Posted by deerhunter
My house is two stories. I just noticed that there is insulation at the ceiling of the first floor. But there is a gap between that insulation and the up stairs floor. I researched a little bit it seems that it's considered unnecessary to add insulation between floors, because it's like insulating interior walls. But the issue is that the space between first and second floor isn't really air tight, there is one part that's not sealed and opens to the attic (the second floor is in the attic). And even though I can seal this part, there is also the path for the ducts for the first floor AC and heating, which can be hard to seal. What's the common practice in this situation?
Insulation between floors is usually installed to reduce the transmission of sound. Interior walls are sometimes insulated for this reason, also.
When I built my house, I framed the bathroom walls with off-set studs and wove batt insulation in and out to reduce bathroom noise.
It seemed to have been effective!