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Wall Insulation...What is the consensus on the direction of faced wall batting?
Posted on 3/19/19 at 2:35 pm
Posted on 3/19/19 at 2:35 pm
What is the consensus on the direction of faced wall batting. Should the vapor barrier be on the outside or the inside of the house? Does it matter?
I've ready many opinions and studies that state the vapor barrier should face the most humid environment. In the south, the exterior is more humid than the interior. In the north, the opposite is true. So, it seems the vapor barrier should be against the outside wall in Louisiana. However, that is not what I typically see in new construction in the south. I also found that ~25% of the opinions and articles that I read say it doesn't matter either way.
I've ready many opinions and studies that state the vapor barrier should face the most humid environment. In the south, the exterior is more humid than the interior. In the north, the opposite is true. So, it seems the vapor barrier should be against the outside wall in Louisiana. However, that is not what I typically see in new construction in the south. I also found that ~25% of the opinions and articles that I read say it doesn't matter either way.
This post was edited on 3/19/19 at 3:59 pm
4
Posted on 3/19/19 at 3:11 pm to ThermoDynamicTiger
I believe there is an extensive article from LSU out there on the subject. Research attic insulation in the south to find it. My understanding is that the vapor barrier faces the interior of the home, same as with attic insulation. This is all I have ever seen, and I've never seen or heard of anybody doing different in the South.
Posted on 3/19/19 at 3:20 pm to Jester
Posted on 3/19/19 at 3:26 pm to ThermoDynamicTiger
The best choice is never use fiberglass batts to begin with. There are just much better choices out there for little cost increase. Go with a blown insulation like cellulose or fiberglass to insure good insulation around pipes, wires, etc. The blown provides more benefits than just better R value. You get more consistent coverage naturally and you get lower air leakage (and better sound dampening) with blown.
This post was edited on 3/19/19 at 3:27 pm
Posted on 3/19/19 at 3:48 pm to Jester
The DNR article states the following: "During the winter in south Louisiana the air is usually drier on the outside and more humid on the inside because of interior generated moisture from cooking, bathing and doing laundry. Because this situation is even worse in areas north of Louisiana with drier air and longer winters, the insulation companies suggest putting the vapor barrier on the warm side - which is the inside for this winter situation. The better solution for south Louisiana is to keep interior generated moisture to a minimum during the winter. This can be done by venting the areas of high moisture, like kitchens and bathrooms, to the exterior with an exhaust fan. Clothes driers should also be vented to the outside.
During the summer, in south Louisiana, the outside air is laden with moisture while the air-conditioned space inside is much drier. This would suggest that the vapor barrier should be placed on the outside during the warmer time of the year. Never place a vapor barrier on both sides. This could trap moisture and cause decay. Current research suggests that if a vapor barrier is used, it should be placed on the inside of the wall for locations above Baton Rouge, and on the exterior for locations below Baton Rouge."
So, it sounds like baton rouge can go either way.
During the summer, in south Louisiana, the outside air is laden with moisture while the air-conditioned space inside is much drier. This would suggest that the vapor barrier should be placed on the outside during the warmer time of the year. Never place a vapor barrier on both sides. This could trap moisture and cause decay. Current research suggests that if a vapor barrier is used, it should be placed on the inside of the wall for locations above Baton Rouge, and on the exterior for locations below Baton Rouge."
So, it sounds like baton rouge can go either way.
Posted on 3/19/19 at 4:09 pm to ThermoDynamicTiger
quote:
So, it sounds like baton rouge can go either way.
More like, vapor barriers can cause a problem either way in Baton Rouge.
Posted on 3/19/19 at 9:52 pm to ThermoDynamicTiger
Neither. You're not supposed to use faced-batting in warm humid climates like ours. Go look at the articles on buildingscience.com. The test case is Houston but that's pretty much the same climate we have.
Unfaced batts are impossible to find and if you order them they're expensive. Just buy the faced batts and tear the facing off. There's no other difference.
This is what I did.
When I renovated my own home - Unfaced fiberglass batts, 1/2" OSB, Tyvek vapor barrier(taped seams), 1/4" PT furring strips for drainage plane(screen mesh at bottom to prevent insect access), fiber cement lap siding, Miratec corner boards and gable.
Over 10 years later and still kicking arse.
Unfaced batts are impossible to find and if you order them they're expensive. Just buy the faced batts and tear the facing off. There's no other difference.
This is what I did.
When I renovated my own home - Unfaced fiberglass batts, 1/2" OSB, Tyvek vapor barrier(taped seams), 1/4" PT furring strips for drainage plane(screen mesh at bottom to prevent insect access), fiber cement lap siding, Miratec corner boards and gable.
Over 10 years later and still kicking arse.
This post was edited on 3/19/19 at 9:58 pm
Posted on 3/19/19 at 10:07 pm to nola000
quote:
Unfaced batts are impossible to find and if you order them they're expensive. Just buy the faced batts and tear the facing off. There's no other difference.
Every Home Depot has unfaced batts from 3.5” to 12” thick, 16’ or 24” wide and rolls or bundles. All the supply houses have it and it is cheaper than faced and a hell of a lot easier and quicker than peeling the kraft paper off.
And as cheap as it is I suggest using it in all interior walls as well as sound batts.
Posted on 3/20/19 at 2:10 am to ThermoDynamicTiger
If you can afford a little extra go with JM spider insulation. To do an entire house around 400ft2 it’s about 3k more, you’ll save that back in electricity cost in 2 years. I’d also recommend flash and batt or just entirely closed cell but $$$. Batt alone is very poor.
Posted on 3/20/19 at 7:09 am to Martini
If I had it to do over, I would use rockwool insulation throughout the house. Something like the Roxul/Rockwool ComfortBatt.
Posted on 3/20/19 at 7:31 am to convertedtiger
quote:
If I had it to do over, I would use rockwool insulation throughout the house. Something like the Roxul/Rockwool ComfortBatt.
Home Depot, INEX and Acoustical Specialties carry rockwool.
Posted on 3/20/19 at 7:48 am to Martini
quote:
Home Depot
It is special order and expensive as hell. You have to order pallet quantities in the BR area from HD.
Posted on 3/20/19 at 8:22 am to Martini
quote:
Every Home Depot has unfaced batts from 3.5” to 12” thick, 16’ or 24” wide and rolls or bundles
Good to know.
That must be new. Last time I looked everything they had was Kraft paper faced. I tried all the local building suppliers as well.
quote:
hell of a lot easier and quicker than peeling the kraft paper off.
Absolutely. Peeling the paper is a fricking pain but at the time, it was far preferable to the cost difference of unfaced batts.
quote:
And as cheap as it is I suggest using it in all interior walls as well as sound batts.
This sounds good in theory but from what I understand it can create some issues with HVAC maybe if you were using a multi-unit mini split with an air handler in each room or had returns in every location you had registers, it would work. It's also a pain in the arse to fish lines for cable or electrical inside of insulated walls, especially ones with fiberglass batting and impossible with foam. It's why I don't use spray foam and will never use spray foam insulation. Blown cellulose has the potential to be the best if they've ever addressed the settling issue. We've renovated tons of houses in New Orleans and in every one with blown cellulose there was a one to two foot gap at the top of every wall cavity from the cellulose settling. From what I understand they've addressed it by blowing it in moist and dense now instead of dry and loose.
A good option for sound barrier is to use QuietRock. 2 - 1/4" sheets of gypsum bored glued together with a 1/8 inch thick layer of goo.
This post was edited on 3/20/19 at 8:28 am
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