May 21, 2012

Crawlspace Humidity

Really High Humidity!!!! 
Crawl space humidity can spell trouble for your home. The ideal humidity - for any part of your home - is below 55%. This prevents mold and mildew from growing, and also minimizes the risk of pest invasion, structural damage from wood rot and a dust mite infestation. 

The top photo shows a crawl space with 87.9% humidity. In this case the homeowner had wood rot, mold growth, ruined crawlspace insulation, high indoor humidity - which led to high electric bills - and one giant headache from dealing with all of these things!


Crawl Space Mold
I wouldn't want to go in there...
So you can see why high crawlspace humidity is a complete pain.

Now you're probably wondering what causes it. The answer is: an unsealed crawl space causes high humidity and other crawl space problems.

Here's how it works: A dirt floor soaks up moisture from the ground to release it into the air when it warms up (evaporation). Open vents and loose crawl space doors allow outside air to enter your crawl space. As the warmer outside air enters your crawl space and combines with the cooler it, it forms humidity. 


Stack Effect
Now add in the stack effect (illustrated by the bottom photo) and those problems will only grow. As air warms up - as it does naturally - it rises and takes any airborne particles with it. Mold spores, humidity, rodent droppings and anything light enough to travel with the air hitches a ride into the main areas of your home. The air will eventually exit your home through the chimney or attic eaves. And the cycle continues. 

So now, thanks to the stack effect, you not only have a nasty crawl space but you also have mold in your home, health problems and a higher electric bill. Yikes!

What do you do now?! 

The best way to eliminate crawlspace humidity is to seal up - or encapsulate - your crawl space. Crawl space encapsulation completely separates your crawl space from the outside elements. This involves installing a thick vapor barrier over the floor and walls, covering the vents and doors with airtight covers and installing a dehumidifier. 

A crawl space repair professional should be consulted before taking on an encapsulation project. There are several termite control codes and other safety codes (depending on your area) that need to be taken into account.

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