8 votes

What are the pros and cons of adding a vapor barrier behind shower backer board?

I called USG,the maker of Durock cement board Next Gen, and they advised using no vapor barrier so that the wall cavity can breath and allow any moisture to evaporate. Their online instructions/...
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7 votes

Do I need a vapor barrier in an exterior basement wall if I use purple drywall?

Ask yourself this: "If I install a vapor barrier, where is the water that it stops going to collect?" If you put a polyethylene vapor barrier behind a drywall-covered stud framed wall, then ...
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  • 12.2k
4 votes

How to deal with upside-down insulation?

Nearly all of Virginia is considered to be in the "mixed-humid" zone. On an annual average, moisture migration is fairly evenly distributed (alternating toward the interior and toward the exterior). ...
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  • 1,316
4 votes

Can the vapor barrier between a dry floating concrete slab and linoleum flooring be foregone?

Insulated slabs usually have vapor barrier underneath. Since you did a test and found no moisture, there should be no problem installing vinyl flooring on it.
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  • 104k
3 votes
Accepted

Vapor and moisture barrier for "above ground" basement

You can put a vapor/moisture barrier up over rigid foam. A lot of new construction in the far north has this as a default. The idea is that you frame right outside of that. In that framing you are ...
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  • 46.2k
3 votes

Should I put vapor barrier only on exterior wall of a bathroom?

The TL;DR -- vapor barriers belong on the outside only You should only place a vapor barrier on the exterior side of the exterior wall, allowing the assembly to dry back to the inside if water does ...
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3 votes

Install plastic between drywall ceilings and rafters?

the plastic will trap moisture in your sheetrock and can cause black mold some areas require hazmat teams for black mold removal, Ran into this a few years ago and it was quite expensive for the home ...
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  • 95.5k
3 votes

Cost effective insulation for a 100 year old home?

I'd go with rock wool batt insulation in the stud bays. Rock wool has several advantages over fiberglass. Better sound deadening ability. Better fire resistance. R-value unaffected by moisture. ...
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3 votes
Accepted

A creative Eco-friendly Underlayment for a metal roof?

Red Rosin Paper (which is a bit old-school, but can still be found) would fill the bill, I believe. It's plant based. Seems to be getting sold for floors now, but was the thing people used before ...
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  • 132k
2 votes

What are the pros and cons of adding a vapor barrier behind shower backer board?

plastic behind cement board with waterproofing is essentially suspenders when you already have a belt. the waterproofing is also a vapor retarder so if the red guard or kerdi product is continuous, ...
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2 votes

What are the pros and cons of adding a vapor barrier behind shower backer board?

Follow manufacturer's instructions first and foremost. Also in places with hot humid climate vapor barrier on the inside wall causes more trouble than it fixes. https://www.jameshardiepros.com/...
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2 votes

How should I insulate the ceiling between floors in a ski cabin?

You are correct. The field of building science is gradually moving away from friendliness toward vapor barriers in exterior walls, and you certainly should not put one in an interior wall or floor. ...
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  • 12.2k
2 votes

Best way to air seal, vapor seal, and insulate exterior wall in old house?

Provided you don't have knob-and-tube wiring, this one is easy. Remove the vinyl siding, cut holes through the EPS foam and the sheathing at the top of each stud bay, and inject dense-packed cellulose ...
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  • 12.2k
2 votes

Can I use a 5 mil blue tarp as a moisture barrier over a dirt floor in a crawl space instead of poly sheeting?

Most blue tarps are usually some kind of coated fiber construction and first, I would question how vapor impermeable it really is, and second I think it would not be nearly as resilient and repairable ...
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  • 1,381
2 votes
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Vapor barrier problems

Ideally, you would have used rigid insulation against the concrete. This would have worked as both your insulation and a vapor retarder (but not barrier). These days, vapor barriers are frowned upon ...
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  • 23.8k
2 votes
Accepted

Should I add a vapor retarder to an interior cinderblock wall as part of my basement remodel?

Are you sure it was mold? It may have been mildew. In my experience, mildew can grow on nearly any surface as long as it stays moist...be it bare concrete or painted concrete. In this case, the ...
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  • 23.8k
2 votes

Vapor Barrier for Wine Cellar

Closed-cell foam insulation is a vapor barrier itself. If this closed-cell foam is continuous, then you shouldn't have any issues. If it is just in the cavities between wood studs, then the studs may ...
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  • 1,042
2 votes

How should I mend the plastic sheeting behind my drywall?

The standard now is to never do that again especially if you use air conditioning. Building science has determined this was a very bad idea because it traps moisture within the wall cavity. Here's a ...
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2 votes

How to deal with upside-down insulation?

Kraft paper is a vapor barrier (or more accurately a retarder), and in my opinion it's no more a fire hazard than the lumber it's stapled to and all the stuff you have in your home. Inspectors ...
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  • 104k
2 votes

Proper way to install subfloor in kitchen

We use to specify building paper between the underlayment and subfloor. About 10-15 years ago we stopped. Now, we worry about moisture (vapor) getting trapped between the underlayment and subfloor. ...
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  • 22.5k
2 votes

Insulating existing basement wall

Much depends on the dryness of your basement. For most basements, worthy of being made into finished living space, 3 mil. plastic sheeting between the framing and basement wall should be sufficient ...
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  • 1,316
2 votes
Accepted

How good of a vapor barrier is OSB in a dirt crawlspace?

Moisture barriers are not a water tight seal kind of thing. If you cover 75% of the dirt then you should reduce the mustiness by about that much. Anything will probably be an improvement and if is ...
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  • 19.3k
2 votes
Accepted

Is it necessary to replace plastic covering pink insulation in bedroom exterior wall?

You are fine. Vapor barrier holes of that size and bigger are typical in wall construction, in the form of switches, outlets, plumbing, etc. Let's keep calling it a vapor barrier. Makes geeky ...
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  • 1,954
2 votes

Should I use a vapor retarder in Missouri?

The US Dept of Energy also says 1/16" back drainage cavity for siding is appropriate even though capillary action occurs up to 1/4". Point being, the department of energy tends to lag significantly ...
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  • 31
2 votes
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How should I repair small tears in the kraft paper insulation caused while running a new water line?

You're right that your bathroom will have a lot of moisture in it, but if that much gets through to your insulation you're not ventilating enough. Make sure you run your bath fan regularly and for ...
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  • 104k
2 votes
Accepted

Vapor barrier behind electrical panel?

Since the garage is not within the conditioned envelope, then no The key to understanding a "vapor barrier" (really, an air barrier) is to understand that it is part of the system that separates "...
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2 votes
Accepted

How to insulate metal roof on shed and avoid condensation?

You need to prevent air from getting to the metal. If no air circulation there is no moisture will condense on the inside. Spray on insulation works well but is fairly expensive, Fiberglas works but ...
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  • 95.5k
2 votes

Should I put a moisture barrier between a single ply of pressure treated (PT) plywood and a second non-PT ply when constructing a shed?

Dont put moisture barrier between, it will just trap moisture and rot quicker. Moisture for shed should be under structure. But if it collects rain water on top you are just making humidity worse. Pt ...
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  • 337
2 votes

Cost effective insulation for a 100 year old home?

Vapor barrier goes on the WARM side of the insulation. So plastic up against the boards and insulation on top is a bad idea. If you've got the walls down to studs and sheathing, furring out the studs ...
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  • 132k

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