foam board inside walls????

[sleepie]

i have an attached garage --turning into a room--it already has 3.5 fiberglass in the walls--they are not sheetrocked yet---should i cover them with foam board first ---then sheet rock over ---anyone have any thoughts??? cost effectiveness --will it make the room warmer? and cooler in summer? thanks for any help..

 

[Willman]

anyone have any thoughts???

Foam board over studs is an excellent thermal break. Studs transfer heat out. Just need to extend your electrical boxes. I'd use the good foam for the best R for the inch.
Will

 

[Highbeam]

Is the fiberglass faced? That's your vapor barrier and by adding more insulation over it you will have youe vapor barrier in the middle of the insulation vs. the warm side where it is supposed to be. I'm pretty sure that the typical location for a foam layer is outside the studs before siding. If on the inside you'll need to add the sheetrock and how will you locate the studs? You'll need really long screws.

 

[sleepie]

was thinking of using the fan-fold 1/4" insulation they use under siding---i have 3.5 insulation in the walls now with paper facing the living space---i thought the foil-styro stuff would keep heat in in winter and hot out in summer---and a styrofoam cup is not much more than 1/4 inch thick---the stuff is cheap enough ---and not too much a hassel with the outlets---as i am using 1/2 sheetrock and not 3/4-------any more thoughts here,,,i schedualed to begin in october with this---thanks pat

 

[fossil]

Why not just pull out the 3.5 and install R-16 or R-19, sheetrock & be done with it? It'll be more effective than trying to build your own sandwich. Highbeam's point about the location of the vapor barrier in the wall is an important one, as well. Rick

 

[pete324rocket]

i have an attached garage --turning into a room--it already has 3.5 fiberglass in the walls--they are not sheetrocked yet---should i cover them with foam board first ---then sheet rock over ---anyone have any thoughts??? cost effectiveness --will it make the room warmer? and cooler in summer? thanks for any help..

The reply that mentioned the thermal break was good advice. It will interrupt the flow of heat thru to the outdoors via the wooden studs which have little r value. The white "bubble board" is probably the best deal for the money for this.