A vapor barrier is a high-density material (typically a plastic or foil sheet but sometimes a paint-like coating) used to prevent water vapor from moving from one area to another, where it can create problems with mold, rot, odors or bugs. Vapor barriers can be used in tandem with insulation in walls, in an attic, in a crawlspace or basement, under a concrete slab, over a concrete subfloor before installing wood or laminate flooring, or anywhere it's necessary to reduce the amount of water vapor that passes through. Most materials commonly referred to as vapor barriers are actually vapor diffusion retarders, because they limit the amount of water vapor passing through, but no material can block it completely.
Typical costs:
Vapor retarder paint costs about $20-$40 a gallon or $60-$90 for a five-gallon pail. For example, Sherwin Williams Master Touch Latex Vapor Barrier Primer[1] sells for about $80 for a five-gallon pail. Vapor barrier paint is usually white and used as an undercoat primer. It varies by brand, but generally one gallon will cover about 300-400 square feet; a five-gallon pail will cover 1,500-2,000 square feet. Vapor retarder paint is not as effective as a plastic or foil sheet and any damage to the painted surface reduces its ability to reduce the amount of moisture getting through.
Rolls of basic clear or black polyethylene plastic sheeting thick enough (usually single ply and at least 6-mil thick ) to be used as a vapor barrier --in walls, flooring, ceilings or under concrete slabs, start around 5 cents to 20 cents per square foot, or $75-$300 for 1,500 square feet. This basic plastic sheeting still allows some water and vapor to pass, and tends to tear easily. Thicker (8-mil to 23-mil), multi-ply vapor barriers (often designed for specific uses, such as under concrete slab or between new wood flooring and a concrete subfloor) can cost 25 cents to $1.50 a square foot, or $375-$2,250 for 1,500 square feet. In many cases these vapor barriers are installed as part of a larger project; if done by a contractor, the vapor barrier will be included in the overall cost. The Energy Efficiency Manual[2] gives an overview of vapor barriers and illustrates the installation of clear poly as a vapor barrier in the new construction of a large master bedroom.
Another common usage of a vapor barrier, especially in the Southeast and Northeast, is in the crawlspace under a home. This involves laying flat polyethylene plastic of at least 6-mil, on the crawlspace floor, with about 6 inches extending up the walls. All seams are sealed with special tape. Do-it-yourself materials for a 1,500-square-foot crawlspace start around $100-$400 for basic supplies, and go up for higher-quality materials designed specifically to be used as a vapor barrier. The U.S. Department of Energy[3] recommends using 6-mil polyethylene, overlapping all seams by at least 12 inches, taping all seams and sealing the poly 6 inches up the crawlspace walls, with an optional 2 inches of concrete poured over the poly. Hiring someone to install this in a 1,500-square-foot crawlspace could cost $1,000-$3,000 or more for labor and materials.
Crawlspace encapsulation uses a multi-layer 20-mil vapor barrier to completely cover the floor and and walls, while also sealing all crawl space vents and openings, and adding a dehumidifier or sump pump if needed. The total cost with installation is $3,000-$15,000 or more. See How Much Does Crawlspace Encapsulation Cost.
Readers' Digest provides illustrated how-to instructions for installing a 6-mil vapor barrier in a crawl space. Vapor barriers work best in primarily cold climates or primarily hot and muggy climates but not mixed climates where it's both extremely cold in winter and quite hot and humid in summer. The U.S. Department of Energy provides an overview of vapor barriers[4] .
Shopping for vapor barriers:
Rolls of basic 6-mil polyethylene sheeting are available at hardware and home improvement stores like Home Depot[5] , and from online sellers such as Amazon[6] . They also sell vapor barriers designed for specific purposes, such as under laminate flooring.
For thicker and higher-quality vapor barriers designed for other uses, check stores that sell concrete supplies to contractors. CrawlSpaceInfo.com[7] sells rolls of 8-mil, 12-mil and 20-mil DrySpace vapor barriers designed to be used in crawl spaces (and offers installation in some areas); BasementSystems.com[8] offers referrals to contractors authorized to install it seven-layer, 20-mil encapsulation systems (but does not sell the vapor barrier product direct to consumers).
Major manufacturers of vapor barriers include Carlisle[9] , ePro Waterproofing Systems[10] and Fortifiber[11] .
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Am Mike from N.C been doing weatherization work for about 5 years certified .so hey if u guys are needed in weatherization work done.please give me a call 9802573438,9109955063 can help u with improve the comfort level an lower energy cost,Covservation measures,provision of energy,
I had alot of moisture under my house and it was showing signs of mold,so i called cjs restoration and they did a great job. Got rid of the mold and cleaned the air and no more smellš Would definitely recommend!
I live in Fayetteville NC and I had a guy named James to do my work and he used 5mil and I had no problems or oder. You can call him if you want your barrier done (910)354-0598 he does Fayetteville NC and surrounding areas
Since installation in March (5 months ago), a terrible odor has emanated through the vent system and into the house. I've had the space tested for mold with negative results. But am considering removing the barrier as the stench (ammonia-like) is intolerable. The installed came back to put in a fan and extra drain pipes with no noticeable effect.
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