I am in the LA area and we have an industural building that has a 24'
high celing that has exposed wood rafters and roof joists. The rafters
are made with 2'x6' and the gap between the rafters isroughly 2' x 8'
I recently ordered kraft faced R19 batts and FSKF-10 radiant barrier
(http://www.jkinsulation.com/materials1/view_all.nhtml ). The idea is to
install the batts between the rafters with the kraft side facing down
and then nail the radiant barrier foil on the underside of the rafters
to cover the batts. The foil will then act as the vapor barrier.
Someone then told me that by having both the foil and the kraft paper
batts, I will be creating 2 layers of vapor barriers and this is not a
good idea due to the possibility of condensation between the barriers.
Should I use unfaced batts instead so that I only have 1 vapor barrier
(ie the foil)?
There is actually no cost difference to me. Either going with faced or
unfaced batts is OK with me.
By the way, I do have HVAC in the warehouse, which is operated only
when the warehouse has people in it.
Please advice... thanks!
The A/C adds a whole new dimension to the problem. If the A/C running a
vapor barrier on the warm (top) side is required or moisture will be forced
into the insulation by the force of the differance in vapor pressure from
the outside to the inside. This is not a maybe, it is a certainty. The roof
construction needs to be considered prior to making a decision.
You are correct, and in the LA area .. Well I don't know that area well
enough to say if A/C would be a problem with the VB towards the inside.
Your comments point out how complex these decisions may be and how important
LOCAL assistance may be.
My guess was that LA (I have only been there a few times) would still
normally have the VB towards the living space, but that could be wrong. If
it were Florida, then I would certainly say it belongs away from the living
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