Kraft-faced bats in attic or no?


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Old 12-24-13, 08:46 PM
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Kraft-faced bats in attic or no?

Many sources on the web seem to take it for granted that a vapor barrier/retarder should be used when insulating attic space. Then there's this:

Vapor retarders are not a standard recommendation for attics. Except for very cold regions and in isolated cases where there is high humidity in the house during the winter, attic vapor barriers arenít required provided the attic is sufficiently ventilated (as a rule of thumb, one square ft. of vent opening is needed for every 150 square ft. of ceiling).

Insulation - CertainTeed Learning Center

So...is using vapor barrier/retarder an out of date practice that is still pushed via conventional wisdom...or to put another way, does most current construction use unfaced batts for attic insulation?
 
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Old 12-24-13, 09:07 PM
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Most current new construction in our area uses blow in insulation (either cellulose or fiberglass) in the attics and the vapor retarder isn't even an issue because it is omitted on the ceilings. Batts are used primarily in walls. In cathedral ceilings, more are going with spray foam and no ventilation.

Can't comment on the right or wrong / pros and cons of these methods, it's just what's commonly being done.
 
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Old 12-25-13, 04:41 AM
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Make sure it's air sealed before doing anything.
Add baffles so the soffit do not get plugged up. You need air flow from the soffit to the roof vents.
Then use blown in.
Any box store will let you use the machine for free if you buy 10 bags of insulation.
Buy some dust mask and a pair of goggles, it's get pretty dusty.
It's going to take two people, one to feed the machine, one in the attic.
 
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Old 12-25-13, 06:19 AM
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It is not that vb and retarders are out of date, it is just that they have learned where and wherenot to use them. When I started in this business one of the first confusing points was vb on the warm side. Up north that would be on the inside and down south the outside. So I asked, what do the people in the middle do, put it in the middle?? There was no answer. Today we have learned that a 4x8 piece of drywall will pass about a pint of water in the form of moisture over an entire year. Not sure of the test conditions, but their point was, that's not a big deal and the drying cycles will take cars of it. Add to that, the paint will slow that process anyways. So in many cases the plastic VB or kraft facing can be omitted with confidence.

Now, WA can be on the coast with high humidity or half way up Mt Rainier. Your individual climate may come into play.

In general, as Joe stated, air sealing is the number one priority. Baffles and wind stops at the eaves are a must. As for batts, fiberglass I don't like as cold air just filters right down to the drywall. Roxul is much denser as is blown in cellulose. But attention to details is important, be neat.

Bud
 
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Old 12-26-13, 06:59 PM
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Thanks for the info guys, this helps clear things up.
 
 

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