Doug Rye, licensed architect and the popular host of the "Home Remedies" radio show
Solving the dirty sock smell in your home
House wrap and crawl space vapor barrier help prevent mold and mildew
One of the most often asked questions I get is, “Do I need a house wrap?” The answer is, for energy purposes on a Doug Rye house, no. But, there’s more to the story. For weatherproofing or moisture-proofing purposes, the answer is yes.
When you build your house to my specifications, which includes insulating your walls with cellulose or foam insulation, all air infiltration will be stopped at the walls. Therefore, a house wrap for this purpose would be of no benefit. However, Mother Nature can play havoc with a house, especially when it is under construction. As a house is being built, it rarely escapes rain, fog and high humidity. And even when it is finished, it often is pounded with high winds and rain. A house wrap, properly installed, will be of great benefit to the house by keeping it dry during construction and when completed.
One of the best-known brands is Tyvek, which is made by DuPont. According to the company’s Web site, it is made from very fine, high-density polyethylene fibers and “offers all the best characteristics of paper, film and fabric in one material.” Simply put, it is an extremely tough plastic-type material that is a moisture barrier. With a properly installed house wrap, your home is better protected from moisture, which is the key component of mold and mildew.
Do I recommend that you use a house wrap? Yes, I absolutely do.
Now let’s talk about one of the most important places to install a vapor barrier — the crawl space.
Mold in air conditioning ducts is not uncommon in homes with a crawl space. Mold results in musty smells, allergies, and sometimes-serious health problems. Proper HVAC duct construction and a crawl space vapor barrier installation help eliminate this mold growth problem.
When sealing a crawl space, I suggest using a 10 to 20-mil plastic or polyethylene vapor barrier. A 16-mil plastic vapor barrier should be heavy enough to resist punctures during installation.
A tip when installing vapor barriers in a crawlspace is to overlap each section one foot or so, then use a short piece of duct tape about every three feet along the seam to hold it together and prevent gaps. Turn the vapor barrier up the wall about eight inches and make sure there is contact between the barrier and the wall. You need to close the vents on the outside walls, too. If you leave them open, humid air from the outside enters the crawlspace.
Excess condensation leads to mold and mildew problems. When warmer humid air comes in contact with the colder surface of your ductwork, it causes condensation. Musty odors in your home are sometimes referred to as “dirty sock syndrome.” Any leakage in your ductwork causes moisture and odor to be brought into your house.
You should also insulate inside the stem wall of a crawl space with foam or cellulose; a heavy plastic or vinyl ground cover should be used as a moisture barrier and close all vents. If this method is used to insulate a crawl space, it is critical that the elevation of the ground in the crawl space be higher than the ground elevation outside the crawl space. It is also critical there are no standing water or moisture problems within the crawl space. Insulating the slab keeps its temperature similar to that of the conditioned space. Insulating and sealing the crawl space stops sharp contrasts in temperature and humidity. It’s similar to an insulated basement.
If the foundation is a concrete slab, insulate the perimeter of a slab using extruded 1" extruded polystyrene foam board. Place it between the outer edges of the slab and foundation. It should extend vertically 4-inches and 24-inches horizontally under the edge of the slab.
If you are searching for a solution for a basement vapor barrier, please call me at my office at 501-653-7931. Vapor barriers cannot be covered with a “blanket” answer. Several factors must be taken into consideration when considering a basement vapor barrier.
Doug Rye, the “Doctor of Energy Efficiency-the King of Caulk and Talk” can be heard on several different Illinois radio stations. Or you can go to his Web site at www.dougrye.com, e-mail him at firstname.lastname@example.org, or call 888-Doug-Rye or 501-653-7931. You can also sign up for a free newsletter and order his “how to” videotapes.
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