Attic Insulation - keeping rafters exposed.

6 Replies

We have a 100 y/o single family buy&hold in Missouri and would like to turn the attic into usable space. ideally we could keep the rafters exposed in keeping with the character of the home, so the standard 6 inch fiberglass would not work.

Is there a DIY compact type of insulation that would work? 

Short answer, no. You would need to tear off the roof and install rigid insulation on top of the roof and install a new roof. Even with the rafters covered up, 6" of insulation isn't enough. You should have at least R30 in the ceiling/attic and unless you're doing expensive spray foam you can only get R23 out of a 2x6 bay. You should still put 1" of rigid over that/under the sheetrock as to not turn the new space into an oven.

Originally posted by @Arlan Potter :

100 year old house probably has 2x4 ceiling joists and rafters.

 And they're probably rough sawn and somewhere between 20-28" OC, leaving spray foam as really the only good option, which still wouldn't be enough. There are so many reasons why this won't work that the list is endless really, I was just trying to address the one they asked about. We both know the only way to really do this is to essentially put a second (third?) floor addition on the house, which is probably on a field stone foundation, making that impossible also. 

@Melinda Miller Hi Melinda. I don’t think that you are going to find a “compact” insulation. Insulation derives it’s R-Value from the thickness of the insulation. There are some insulation brands/types that can make insulation more dense (i.e R30C) but in general you need to have a certain thickness in your framinign cavity for you to get the proper thickness. Most likely you would have to scan onto the rafters with additional framing and add insulation. Have you considered covering it up with some type of decorative boards? You may be able to keep the feel of an upstairs area in doing so. Just a thought and hope this helps.

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