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Torben

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Posts:21

03/12/2009 12:13 PM
I am planning on building a garage apartment with living space above the garage. The walls and roof would be SIPS. Does anyone have any sugestions or experience on how best to insulate/isolate the living space from the garage below? I would like to insulate below my floor trusses to maintain the area between and through the trusses for plumbing and HVAC (within building envelope). Since the insulation does not need to provide structural support I was thinking about a vapor barrier on the bottom side of the trusses, covered by one or two layers of XPS foam sheets. Does anyone have any suggestions? Thanks, Torben

Torben

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Posts:21

03/16/2009 6:05 PM
I should probably clarify the other option I was thinking about was affixing a SIP panel to the bottom side of the floor joists. My concern was if this would be as easy to seal as the XPS foam and of course the relative cost. I was hoping someone would have some experience or thoughts about this. I think this would be an issue anytime you have living space above a garage in a SIP home.

Nick735

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Posts:10

03/16/2009 10:13 PM
Torben- Im having a similar issue that I am running into building my own house; a 1800sqft cape with a 2 car garage underneath. For the walls I will be going with 8-1/4" eps sips w/ 1/2" eps sheeting to prevent thermal bridging. For the roof I am going with a hybrid of closed cell/ open cell foam or a hybrid of closed cell foam/ celulose. My goal is to economically achieve close to a r40 in the walls and an r60 in the roof. Since its just about impossible to find a garage door with a super tight seal (if anyone knows of one please let me know!) I think my biggest weak point will be my insulating barrier between the first floor and garage. My plan was to just use plain old fiberglass between the floor joists and 2" eps sheeting on the garage ceiling. From what I understand the biggest weak point with Fiberglass is the fact that air easily flows through it which is why you get convective loops in wall and roof applications, which in turn greatly reduces its effective r value. With the first floor you have a cold surface on the bottom and a warm surface on top, so you shouldnt get the same convective loops that you get with fiberglass in the wall and roof. To me this seems like a fairly cost effective way to do this, but will it be enough....? I dont know.... Id really like to get some feedback as well. Nick

GuyB

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Posts:21

03/17/2009 8:59 AM
On the garage door: How about building your own using 4" sip with a carriage door type veneer on the exterior. I have a dual bulb seal on my garage door which has eliminated almost all of the sealing issues. One bulb is installed conventionally on the exterior jamb. The other bulb is mounted to the sides of the door sections. Since there is only seal to seal contact, no wood or metal to seal contact, there is no wear. The seals remain pliable and seal well for going on 4 years now.

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