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Home > Archive > Construction forum > December 2005 > vapor barrier question with kraft faced batts and radiant barrier foil
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vapor barrier question with kraft faced batts and radiant barrier foil
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| dchou4u@hotmail.com 2005-12-04, 2:21 am |
| 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'
in area.
I recently ordered kraft faced R19 batts and FSKF-10 radiant barrier
insulation foils
(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!
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| Joseph Meehan 2005-12-04, 8:21 am |
| dchou4u@hotmail.com wrote:
>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'
> in area.
>
> I recently ordered kraft faced R19 batts and FSKF-10 radiant barrier
> insulation foils
> (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)?
I would use un-faced.
>
> 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!
--
Joseph Meehan
Dia duit
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| Art Yokell 2005-12-04, 12:21 pm |
| 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.
"Joseph Meehan" <sligojoe_Spamno@hotmail.com> wrote in message
news:HqAkf.9354$lh.2278@tornado.ohiordc.rr.com...
> dchou4u@hotmail.com wrote:
>
> I would use un-faced.
>
> --
> Joseph Meehan
>
> Dia duit
>
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| Joseph Meehan 2005-12-04, 1:21 pm |
| Art Yokell wrote:
> The A/C adds a whole new dimension to the problem. If the A/C running a
> vapor barrier on the warm (top) side is required or
> moisture will be forced into the insulation by the force of the
> differance in vapor pressure from the outside to the inside. This is
> not a maybe, it is a certainty. The roof construction needs to be
> considered prior to making a decision. "Joseph Meehan"
You are correct, and in the LA area .. Well I don't know that area well
enough to say if A/C would be a problem with the VB towards the inside.
Your comments point out how complex these decisions may be and how important
LOCAL assistance may be.
My guess was that LA (I have only been there a few times) would still
normally have the VB towards the living space, but that could be wrong. If
it were Florida, then I would certainly say it belongs away from the living
area.
[color=darkred]
> <sligojoe_Spamno@hotmail.com> wrote in message
> news:HqAkf.9354$lh.2278@tornado.ohiordc.rr.com...
--
Joseph Meehan
Dia duit
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