Insulating a floor: vapor barrier?
OK,
I have searched the archives and I found nothing particularly relevant to my situation.
The facts:
1. Location: Boulder, Colorado- dry climate.
2. House: single story ranch with 2×8 floor joists over crawlspace; gas furnace in crawlspace. Floor uninsulated. Crawlspace vents in place (about 6 in 1040 ft^2)
3. Radon test: 5.0 (barely above EPA limit, but I’d rather not ignore it).
My main question is how should I insulate the floor?
I realize some would suggest conditioning the crawlspace- putting down plastic and rigid foam along the perimeter and blocking off the vents (except in the summer.)
I have narrowed it down to FG batts with or without a vapor barrier underneath them.
Despite the dry climate will this still cause condensation in the joist bays collecting on the vb?
Replies
when you say " the floor" I think you mean the floor of the house and not the dirt floor.Right?
Dirt poly will cut your free vapor alot. foam on the walls will cut your cold creep thru the fondation and keep the radiant heat from the earth in the crawl space which will help your floor issue.
as for the floor (joist) I would use the red wrapped FG which is not a VB but helps alot with the free floating fibers when working overhead. Don't forget the steel wires that you can snap between the joist to support the FG from sagging. As for a dedicated VB in the floor FG I see two different camps that others may chime in on.
1-- don't use a VB and let the FG breathe( I douht you get much thru a floor and the dirt poly will keep the free vapor to a min.
2-- VB the top side of the FG to keep the VB on the warm side of the insulation envelope.
Hope this helps MIke
no... insulate the walls of the crawlspace with foam....treat the crawlspace as part of the conditioned space.. your floors will be warmer..
IF.. you didn't have your furnace down there.. then you could think about insulating the floor..
make sure you allow make up air for the furnace
Mike Smith Rhode Island : Design / Build / Repair / Restore
What about the vents?
Should I just seal the dirt with 6mil poly and close the vents and call that good enough for radon mitigation?
if so, what is a good adhesive to use for sealing poly to concrete?
if so, what is a good adhesive to use for sealing poly to poly?
thanks
if you have a radon problem.. you need a mitigation system.. which is different than just venting your crawl space..
also . latest thinking is to seal the crawl space.. so you block the vents.. however.. some codes still require venting of crawl spaces.. but it is not because of radon..
you may have to have closeable vents... (like basement windows).. just keep them closed..
radon mitigation involves trapping the air from the ground, and blowing it outside.. you need pipes, a ducted blower, and an air passage to do this.. sometimes you form the air passage by putting perf pipe in a layer of crushed stoneMike Smith Rhode Island : Design / Build / Repair / Restore