It sounds like a good Idea “Spray foam is a good moisture barrier with a low perm rating”, False. Closed cell spray foam has a perm rating of 2.6 at a thickness of 1″. In order to get to a perm rating of less than 1, the spray foam will need to be a minimum of 3.5″ thick. This type of insulation has a fairly high R-value at 6.0 per inch. This means that you will need to buy an R-21 worth of spray foam in order to get a perm rating under 1.0. This product is priced by the square foot per inch of thickness. The other major issues with spray foam are; if it is sprayed on your floor joists or rim (band) joist you will not be able to inspect or repair your flooring system, it is widely known that spray foam can trap moisture and invites wood boring insects, and the building code requires an inspection gap of 3″ on the foundation wall for termites. Spray foam may be a good alternative for the parts of your home that are above grade, but it is not a superior product for a crawl space regardless of the salesman’s insistence that it
Read more →This design is referred to by many different names; encapsulated crawl space, closed crawl space, conditioned crawl space. All of these names refer to essentially the same thing but may have a different process. The vents are permanently closed. The crawl space is completely sealed off from any moisture infiltration by using a heavy duty vapor barrier like DrySpace™. In a conditioned crawl space the foundation walls need to be insulated with a rigid foam to keep any cold air from entering the crawl space from this area. Then the DrySpace™ vapor barrier is draped down the foundation walls and the entire floor is covered. All the seams are lapped by at least 8” and taped with a Waterproof Seam Tape and the supports are wrapped and sealed. The vapor barrier is sealed to the foundation wall with either a polyurethane caulk, butyl caulk or Foundation Seal Tape™ to keep the moisture from escaping from under the barrier. The next step is using Foundation Pins™ to permanently fasten the DrySpace™ to the foundation. R-19 insulation is installed in the rim joist cavity to keep the outside air outside. Once this has been completed you can successfully condition the crawl space air. Conditioning the air is controlling the
Read more →The concrete floor In this design a concrete pad called a “mud pad” is poured on the crawl space floor. This is essentially a concrete vapor barrier meant to help control moisture in the crawl space. This is done several ways; with and with out a vapor barrier. The traditional mud pad is a poured concrete pad over a roughly graded dirt floor. There is little prep work done to flatten the area so the concrete thickness can range from 2” to 6” thick. The final grade of the concrete will appear flat. A good contractor will install a vapor barrier on the floor prior to pouring the mud pad. This is done because the concrete itself is not a good moisture barrier. Water and moisture will pass through a concrete slab that does not have a vapor barrier with little trouble. The reason this is important is because if a vapor barrier was not used then closing the vents will cause other issues unless a dehumidifier is used. But if a barrier was used, then you will have more options on how to best control the humidity. Closing the vents is the key to fixing the cold crawl space
Read more →There are three major environment situations that call for insulation in a crawl space. The first is your standard dirt floor (may have some plastic laid on the floor) crawl with open vents which is referred to as an open crawl space. This environment is similar in temperature to the outside air in the winter which causes the homes floors to be cold and rooms farthest from the furnace to be drafty. Frozen water lines are common in this situation as is an odor in the warmer months. Most often these crawl spaces will have a lot of bugs and maybe even a rodent problem. This is the most common environment for a crawl space. Here you will find R-19 insulation (usually) in the floor joist cavities. This is required by code in most areas because of the open foundation vents and the problems they cause with energy loss. When I say open vents, I am referring to any permanent foundation vent whether it mechanically opens and closes or not. On a side note, closing a mechanical vent does very little to keep the cold air out. It would be similar to a window in your home with metal louvers instead of
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Although it may seam more difficult to close your foundation vent with a concrete block it is actually not that hard and far more cost effective. The franchise companies sell their “vent covers” for around $25 each. To close your vent with a cement block will cost you about $3. Vent covers will not keep out the winter temperatures or keep the mice out (I have see them chew through metal). Cement block are easily accessible at you local home improvement center as well as the mortar or cement caulk
Read more →Homes built on a crawl space needs ventilation! Right? Right! Notice I did not say “Needs vents”, that’s because a crawl space does not need the foundation vents (that go outdoors) if, and I quote: IRC 2006, Section 408.3 Unvented crawl space Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where: Exposed earth is covered with a continuous vapor retarder. One of the following is provided: Continuously operated mechanical exhaust ventilation at a rate equal to 1.0 cfm (0.47 L/s) for each 50 ft² (4.7 m²) of crawlspace floor area, including an air pathway to the common area, and perimeter walls insulated in accordance with Section N1102.2.8. Conditioned air supply sized to deliver at a rate equal to 1.0 cfm (0.47 L/s) for each 50 ft² (4.7 m²) of under-floor area including a return air pathway to the common area, and perimeter walls insulated in accordance with Section N1102.2.8. Plenum complying with Section M1601.4 if under-floor space is used as a plenum. Source- http://resourcecenter.pnl.gov/cocoon/morf/ResourceCenter/article//131 So, the answer to the question “Can I really seal them up?” is, YES you can seal them up and you should seal them up once you
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