Ok,
I asked in a previous post about placing 1/2″ rigid foam insulation on the outside of my house (on top of the osb) to prevent thermal bridging. The main response was, use SIPS. Well, SIPS are about $4,000 more than the building envelope I have designed in my head, and I know, in the long run they’ll pay for themselves, however, inital cost is EVERYTHING to me. So, considering that,
Would you recommend placing 1/2″ ridgid foam over the osb to prevent thermal bridges? With house wrap over it?
Also, planning on r-21 FG with 6 mil poly in walls
R-38 and another layer of R – 15 in ceiling with 6 mil poly over that to get me R- 53.
Would you consider this to be ample insulation to create an energy efficient house?
Thanks for any input…
upnorthframer
Replies
UpNorth, are you in northern Manitoba or northerm Florida? (Fill in your profile.)
Unless this is Florida, I hope you're not planning to put the poly ON TOP OF the ceiling insulation.
Sorry, i'm building in Northern Wisconsin. Hot humid summers, cold (-25 sometimes) winters.
Humid is relative. Not nearly as humid as Florida or the Gulf Coast, eg. Vapor barrier definitely goes on the inside in conventional construction.How far from a large (multiple square mile) body of water, and what direction if close?
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Aside from the poly on top of the insulation in the attic, it looks like a double vb at the walls too.
Foam board (blue board) outside the wall will act as an exterior vb if taped, and the poly inside, means trouble down the road.
Dave
There's always a bit of an argument over this. The hazard you describe appears to be more theoretical than real. In any event, it's not the "double" vapor barrier but rather the vapor barrier on the wrong side of the dew point line that's the problem. You can have as many VBs as you like so long as they all fall in areas where the dew point won't be reached.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Edited 2/27/2007 6:53 am by DanH
do a search on Mooney wall... substitutes labor for materialMike Smith Rhode Island : Design / Build / Repair / Restore