Inusulation Question:
I am wondering about the effectiveness and pros and cons of applying rigid foam board insulation (1/2″ to 1″) over the inside face of wall studs (stud bays already insulated with batts or blowin-in). It seems like a good way to create a thermal break between the interior space and the wood framing, as well as a good way to cut down on air infiltration. Interior finish such as drywall would be applied over the rigid insulation, and of course screwed into the wall studs.
Has anyone had any experience with such an assembly? Other than creating a deeper wall and the necessity for extension jambs at doors ad windows, are there other reasons to think twice?
Thanks.
Todd
Replies
I did it to my kitchen on my first house. 2X4 wall construction. It was a way of increasing the R value on a DIY budget and without extensive rebuild of the structure.
Two things I ran into and how I solved it were.
The cabinets had to be screwed through the extra thickness. I put a strapping at the height I needed to screw directly into wood.
The other thing are the wall plugs and switch boxes. I used screw extenders for the plugs and switches where I couldn't use the retro fit boxes with the ears that can be screwed to the dry wall.
If at first you don't succeed...try again! After that quit! No sense being a dam fool about it! W.C.Fields
yes i frequently use this procedure, i am a firm believer in insulation. what i usually do is put the foam and then instal plywood rips to attach the drywall to. this allows you get an even plane for the back side of the drywall and gives you ample opportunity to make sure with long screws in the ply strips that you have gotten a good bite in the studs. also i use 5 ply because it has less of a tendancy to split or spall. i always use this procedure an cathedral ceilings. yes it is an incredible pain in the butt, but the well insulated house pays you back over and over again
For all you "This Old House" fans...As I recall from reading Norm Abrahms' book on building his own dream house, he put rigid insulation on the inside of the studs. Few people do it this way, but it makes great sense in cold climates. I imagime it's much beter than the foam on the outside that all the vinyl siding guys use.
Al Mollitor, Sharon MA
Did it myself also for the same reasons (on my walls and ceilings). Its interesting to see in cooler weather when frost condenses over night, I can see the lines of my neighbors ceiling rafters on their shingles (where the frost forms) but not mine. One caveat, use 5/8" drywall if you are going to use polyisocyanurate insulation boards.
Jon
Do it as often as I can. That is the way foam panel baord is intended to be installed. You get extra insulation, varporbar all in one.
Adding the furring to the inside for sheetrock attachment is prime. It is much easier to hit with sr screws
Excellence is its own reward!
Having recently added 1" Dow board to the exterior of a Habitat house, we were in contact with the manufacturer about the use of housewrap. The manufacturer stated that the Dow board is a moisture/weather barrier and there was no further need for a housewrap. Now with this said, IF the kraft paper is left on the insulation then you have created an area that will trap moisture. I have not tried this so I have no long term experience but I feel there is enough evidence to eliminate or slash the kraft paper before installing the foam board.