Crawl Spaces #1: Crawl Space Vents: Do they work?

Blog entry by CyFree posted 09-03-2010 07:12 PM 25207 reads 0 times favorited 1 comment Add to Favorites Watch
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moldy crawl space

After many years in denial, trying to go on with your life without thinking too much about it, one day you decide to finally do something about that wet, moldy, scary crawlspace under your house.

Maybe because you’re tired or hearing the buckled floors creaking under your feet, or you might have had enough of the drafts during the winter causing your heating bill to soar.

It might be because you can no longer living with chronic flu-like symptoms, triggered by the mold in the crawl space or because you swore that you would never again go through the process of crawling on filth to remove a wild critter (dead or alive) from under your house.

When you start to shop around for ways to deal with the problem, you are very likely to find two mainstream “solutions” being offered.

1 – Adding more vents to the crawl space
2 – “Improving” the air flow within the crawl space, by installing fans on the vents.
The “logic” behind this concept is that air is know to dry things therefore the more air you allow in, the more the chances that the crawl space will dry. It is only common sense, right?

Truth is that, if these fans are being used to bring air from the outside, into your crawl space, I have a serious piece of advice: Don’t do it.

Crawl spaces are like no other structure in the house. Because of that, the air already coming from the outside, combined with evaporating ground moisture, is actually the reason why your crawl space is wet right now.
Puzzled? Allow me to explain.

Crawl Spaces are Different!

crawl space vents fallacy Crawl spaces have a pretty steady temperature year round (around 68 degrees) and, during summer, they are naturally cooler than the outside: usually 10 to 20 degrees. So, let’s say we have a nice day outside, with 77 degrees and an average 80% relative humidity. Your crawl space temperature is 20 degrees cooler. When that air from outside comes in, it will cool down too.

When that happens, the relative humidity in the air will increase about 2.2% for each degree the air is cooled.

That added to that 80% that was already in the outside air will result in 98.8% RH. Can you guess what happens then?

That moisture will cause condensation to form all over and your crawl space will get more wet, causing your floor joists to grow mold and rot.

The best, and U.S. Department of Energy recommended way to treat a crawl space is to encapsulate it. That means, line the whole space with a vapor barrier, seal it to keep ground moisture and outside air from getting in, then run a dehumidifier or a crawl space conditioner to keep it dry and conditioned year round.

This procedure. will solve crawl space moisture problems once and for all and protect your floor joists and hardwood from rot and buckling. It will also make your whole house an average of 18% more energy efficient, by cutting energy losses which can be as high as 50% if you have ducts running through the crawl space.
It will make your home easier to cool and heat, and will eliminating problems such as cold floors and clod drafts from the crawl space during winter.

There are tons of scientific studies on the matter, conducted by reputable independent organizations, to prove that, when it comes to crawl spaces, common sense is sometimes just a collective misconception.
If you live in Tennesee, there are two dealer who are Basement Systems Certified crawl space moisture control professionals and can help you with your crawl space moisture problem:

Master Dry Basement and Crawl Space Systems provides crawl space encapsulation services in Knoxville

Basement Redeemers offers solutions for moldy crawl spaces in the greater Memphis area.

-- "All truth goes through 3 stages: First it is ridiculed. Then it is violently opposed. Then it is accepeted as self evident." - Schoppenhauer

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1 comment so far

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2 posts in 4422 days

posted 02-11-2011 10:09 PM


that was very informative, but i found http://crawlspaceinfo.com to have more information regarding my questions

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