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Contractor says no vapor barrier on walls so house will breath - sound right?

Contractor says no vapor barrier on walls so house will breath - sound right?


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Old 09-12-11, 09:07 AM
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Contractor says no vapor barrier on walls so house will breath - sound right?

I'm building a new addition to my house in the Seattle area. I'm about to get insulation installed. My general contractor and my insulation subcontractor both say that a vapor barrier is NOT necessary on the new walls but only in the ceiling.

So, the plan is to install unfaced insulation fiberglass batts in the walls with no vapor barrier and unfaced batts in the ceiling with a 6 mil vapor barrier over it. The general says we don't want a vapor barrier on the walls in order to let the house "breathe".

Does this sound right?
 
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Old 09-12-11, 09:23 AM
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Sounds like BS to me...never heard of such a thing.

Your house does need to have air exchange...but not through the walls. That's just asking for issues.

I dunno if there are any special circumstances where you DON'T want a VB...maybe so, for an old house or something, but this will be built to modern standards. I would think it's even REQUIRED by your local codes office. This work is permitted and licensed isn't it, it will be inspected right?
 
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Old 09-12-11, 10:08 AM
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I know building specs and needs differ in various locations but in the S.E. a vapor barrier is required on the walls but optional for the ceilings. I'd call your building dept and ask them what the requirement is for your location.
 
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Old 09-12-11, 10:23 AM
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I've read a lot about this topic but it's still confusing to me. I think there is complete agreement about using insulation for thermal benefit. The benefit is immediate and noticeable. Vapor movement though is a hard topic to understand and you can't see any immediate benefit to using a vapor barrier or not. It can take a long time to realize it wasn't done correctly and the design needs to be different depending on local climate.

I've read the Building Science paper on Understand Vapor Barriers:
BSD-106: Understanding Vapor Barriers — Building Science Information

It takes a few readings to digest that document but I think using an appropriate primer and paint on the inside of the drywall will suffice for me given that we live in a marine type environment here in Seattle.

This project does have all permits and will be inspected so we will see what the inspector says.
 

Last edited by fromhollywood; 09-12-11 at 11:07 AM.
 

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