No vapor barrier, wood sheeting or house wrap in MN. Is this normal?
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HU-687509180
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house wrap in the basement
Comments (4)lewis, if you re-read my original post you will see the system I'm asking about (which is not the Building Sciences way, but which I saw on the DIY show) has the housewrap against the foundation wall surface, on the outside of the insulated stud wall. I guess the idea was that the house wrap is not a vapor barrier, so the only vapor barrier is on the warm side of insulated stud wall, and also as house wrap is a good air infiltration barrier, it would also provide a contact barrier between the wood studs and the concrete. Any ways, as I said before, I'm going with the Building Sciences system. However, i have decided to also incorporate the house wrap. Here's what I've done on the one wall already. I applied continuous house wrap on the wall and extended it well up to the top of the rim joist to the underside of the subfloor and sealed the edges with acoustic sealant. I installed 2" thick foam 8' x 4' boards horizontally on top of the house wrap, also taking it up into the rim joist (double thickness here) and sealing the edges with spray foam. Laps between the sheets were sealed with spray foam and Tuck Tape. The stud wall was installed against the foam boards, the sill plate sitting on foam isolation srips. I'll be installing the insulation batts and the wiring next, followed by the drywall and alkyd paint. No vapour barrier. For the cost of the house wrap, which I bought in bulk, I think it's a double protection against air filtration, along with the foam board barrier. I don't believe there is any conflict here with good practice. Ted...See MoreAm not getting the vapor barrier thing, at all?
Comments (20)"He (GC) says that any water wicking through will have no chance to dry out if it becomes trapped by the vapor barrier, and you increase the chances of mold growing between the vapor barrier and cement board. This makes sense to me!' How can mold and mildew form and thrive between poly sheeting and cement board? Mold and mildew need food to survive. That food it cellulose. Cellulose is wood or wood-derived products like paper. Paper facing on kraft-faced insulation, paper facing on drywall, etc. Moisture trapped between a 6-mil poly vapor barrier/drainage plane and the cement backer board has no cellulose in sight, so the green stuff can't thrive. The moisture will eventually dry out back into the bathroom, just as Bill described. No poly vapor barrier? Then when the moisture gets behind the cement board and wets the the kraft paper facing of the insualtion, or the framing, then you get the funky green stuff. Moisture, spores, and food equals the dreaded green funk. It's tough to get your head wrapped around these concepts, but trust me, the way Bill and others have said is correct. Your GC is wrong. He may have good intentions, but he's just uneducated. Building Science is a continually evolving process. Changes to the building code normally lag bulding science by as much as a decade. Sometimes even longer. Too many builders don't learn about or apply changes made to the code until several years after the code has been changed. Many "rotted wall" stories are from having vapor barriers behind greenboard. Trapped water and the paper facing food source on greenboard leads to the dreaded green funk, soon followed by the wetting and rotting of the gypsum core of the greenboard. But who here has been tiling over greenboard? Only the guys who like greenboard because it's cheaper than cement board and easier to cut and hang than cement board. Greenboard was allowed by code as a tile backer in wet areas until January of '06. Yet I've NEVER used it as a tile backer. Doing what's allowed by code isn't always the right way to build. Remember, code is the MINIMUM building standard. In some areas of construction the minimum is good enough. In other areas it's far below. That's why the code evolves. Mongo...See MoreVapor Barrier: Placement & Recommendation Questions
Comments (19)A vapor barrier protects the warmth and integrity of your home. Below was pasted from the internet. The friend is incorrect in his statement. New homes are very tight due to better barriers and very good sealing windows, but eliminating barriers causes bigger issues. Very tight homes you can leave a window cracked at times. Some newer heating/cooling systems have exchange systems built to pull in fresh air. I personally use poly sheeting as a vapor barrier because it is far superior to faced insulation. Regarding ceilings, check your local building codes, this may vary. But as mentioned below, attics can naturally ventilate as compared with a closed in wall. Through a process called convection, warm air will always move toward colder air, meaning that during the winter the air inside your home is always trying to escape the house and move toward the cold air outside. Warm air also expands, and therefore has the capacity to hold more moisture than cold air -- moisture that is picked up naturally from inside your house. As the air cools, it contracts and loses some of its capacity, so the moisture is given off to cooler surrounding surfaces. The result of all this is that warm, moisture-laden air is constantly on the move from inside to outside. As it leaves the warm interior of the house and enters the walls, attic, and crawl space, it cools off and gives up its moisture, which in turn can saturate the insulation and framing. The more moisture there is in the air and the more differential there is between the inside and outside temperatures, the worse the problem can become -- in the more extreme cases, the insulation is rendered virtually useless and severe rot can take place in structural members. It is the purpose of the vapor barrier to prevent that movement or penetration of moisture from one area to another. Placed between the inside of the house and the insulation, the vapor barrier acts as a physical shield to repel the moisture and keep it from entering enclosed cavities where it can do serious damage. Vapor barriers can be created from a variety of materials. The only requirement is that the material be resistant to moisture, which is indicated by its vapor permeance value, called a "perm" rating. To be an effective vapor barrier, a material needs to have a perm rating of 1.0 or lower. Common vapor barriers used with insulation include plastic sheeting, foil sheeting, and kraft paper that has been treated to achieve the proper perm rating. Vapor Barriers in the Home One of the most important vapor barriers in the home is the one between the wall insulation and the interior side of exterior walls. Because wall cavities are sealed and have no means of allowing accumulated moisture to escape, an effective moisture barrier is crucial in preventing warm, wet air from entering the walls. For wall insulation, foil- or kraft paper-faced insulation is typically used. The insulation is installed between the studs with the vapor barrier facing in toward the house -- the one thing to remember about vapor barriers is that they are always installed between the insulation and heated portion of the house. The "wings" along the edges of the insulation are stapled to the studs to hold the insulation in place -- stapling to the face of the studs instead of the sides creates a more effective vapor barrier. Another alternative for walls -- which is also commonly used in the enclosed cavities of vaulted ceilings where the pressure of warm air trying to escape is even greater -- is to place unfaced insulation into the cavities between framing members and then cover the insulation on the inside with plastic sheeting. The sheeting is stapled to the face of the studs or joists, and overlapped at all seams to prevent moisture penetration. In today's construction, separate vapor barriers are typically not used between the home's interior and a ventilated attic. Most attics are insulated with blown fiberglass, which is relatively porous in comparison to the denser batt insulation used in the walls. The attic also has a continuous flow of air through it that is created by the roof and soffit vents, so moisture from inside the house passes through the insulation and is removed from the attic by the air currents. In areas of high humidity where moisture in the attic could still be a problem, a vapor barrier paint can be applied over the inside ceilings. Another area that typically does not have a vapor barrier is the floor. Most of today's homes are now constructed with subfloors of interlocking tongue-and-groove plywood or other sheet materials -- waterproof resins are used in the making of the sheets, so the subfloor itself becomes an effective vapor barrier that protects the insulation below it. A vapor barrier is used, however over the ground under the house. Typically a layer of 6-mil plastic (1 mil = 1/1000 of an inch) that is laid directly on the dirt floor of the crawl space, the moisture barrier prevents ground moisture from entering the enclosed crawl space and wetting the insulation or the framing....See MoreBathroom Wall Insulation & Vapor Barriers
Comments (11)First, the tuck tape. Look for "sheathing tape". It's usually sold in the box stores, sometimes it's red colored. You could use Tyvek tape as well. The vapor barrier is a bit tougher to diagnose. Your exterior foam, "expanded polystyrene" is usually quite leaky with regards to moisture transmission and is not a strong vapor retarder. "Extruded polystyrene" is a much tighter product, and it could indeed be a vapor barrier, probably a Class II barrier. If the exterior foam is indeed continuous on the walls and well detailed, then it might be best to omit the interior poly and just use the Roxul. Your walls may take in some vapor over time, but the vapor should also transmiss back into the bathroom during drying cycles. The biggest problems occur when you have two barriers and one or both are poorly detailed. Over time moisture gets in but has difficulty getting out. Thus the "sandwich" that you referenced. The "imperfect" in your system is the exterior foam. I'm a proponent of foam, but only if it is the right type and the proper thickness. With your exterior foam probably being a Class II on the exterior side of your wall, your best bet is probably to omit the interior poly and simply use other methods on the interior walls. You can use something like Hydroban in your shower (if the shower is on an exterior wall), it's a waterproof barrier but does allow vapor to transmiss through it. For the remainder of your walls, simply use two coats of latex paint over your interior drywall. Latex paint is classified as a Class III vapor retarder. As such, it'll slow moisture vapor transmission that wants to get into your wall, but if any does, it'll allow your wall cavities to dry out during a drying cycle. It's an imperfect solution for an imperfect situation. I'd be completely confident in my reply were your exterior foam thicker than it is and if I knew it was well-detailed. My concern is the interior side of the foam reaching dew point temperatures in winter and any moisture vapor within the framing cavity condensing on the interior surface of the foam, between the foam and the sheathing. That may not be a problem. But it is a consideration, especially since I tend to go towards the conservative side with an "over the internet diagnosis" such as this one. I'd certainly do more research if you can, you might get better information than what I'm offering. You are addressing moisture generation within the bathroom. That's good. Other stuff: 1) I do sometimes insulate interior walls, Roxul is good for that. 2) A simple yet effective sound deadener behind your washer and dryer is nothing more than a second layer of drywall over the first. 5/8" is better than 1/2" due to the added mass. Beyond that you can go fancier: 2a) sandwich a 1/2" sheet of homasote between the two layers of drywall. 2b) Use RC clips and metal channel between the studs and the drywall. 2c) Use green glue between the two layers of drywall. 2d) If you do research you'll probably see references to mass loaded vinyl, but I usually use that only when doing fully integrated sound deadening room "systems". I think you'd do better (and save money) with just using drywall....See MoreSpringtime Builders
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