Do we need vaporbarrier under new floor?

Irishgirl · Sat Apr 06, 2013 2:35 pm

We have taken up all the particleboard and are installing osb on our SW.

We have decided to put in a radiant floor heating system knowing we will lose a little bit of height in our rooms we feel it will be worth it.

SO, now there will be no heating under the new subfloor.

We will be adding more insulation under new subfloor, but wonder if we should also now be putting down a vaporbarrier "before" we put down new subfloor?

THanks
Judy

Greg S · Sat Apr 06, 2013 4:40 pm

You do need to put down a vapour barrier.
Did you move your water lines to inside your home. When the home was built the main water lines are run along the primary heating duct to prevent freezing in winter. If you are changing to in floor heating no heat will go down to insure the water lines do not freeze. Or are you in a zone where freezing is not an issue.

Irishgirl · Sat Apr 06, 2013 5:53 pm

We are in the Northeast, so the water lines were removed and we'll be reinstalled inside.

What do you suggest for a vapor barrier? Same stuff that you use on the walls under the sheetrock?

Thanks for the quick response!

Greg · Sat Apr 06, 2013 8:46 pm

The underbelly will act as a vapor barrier, but I would also insulate the skirting.

Greg

jpingram5 · Sat Apr 06, 2013 9:08 pm

Not to go off topic but could you shine some light on us with the radiant heating part perhaps in separate thread? Just interested in seeing how you are going about doing it. I do not think I heard of anyone using radiant floor heat in a mobile home before, assuming this is a hydronic system.

Greg S · Sun Apr 07, 2013 9:06 am

If Greg is correct in that the underbelly is a vapour barrier, and I have no reason not to believe him, then installing a vapour barrier under the floor would not be a good Idea. It would create a enclosed space that could not breath.
However a vapour barrier on the cold side of the insulation serves no purpose in that it would not prevent moist air from entering the insulation and reducing it's efficiency in the winter.
If you had a vapour barrier under the floor the underbelly would need to be able to breath much like house wrap..