May 29th, 2014
In our last article, we discussed how moisture can lead to mold and mildew. It was also pointed out that heating and cooling higher relative humidity spaces costs more than doing the same to drier spaces. Many people use their air conditioning systems to live more comfortably during hot, humid summer days, and, therefore do not concern themselves with higher relative humidity in their homes. But what they don’t realize is that they are paying an energy penalty to cool that humid air compared to cooling drier air.
We mentioned last time that as much as 50% of the air in a crawlspace can migrate into the living space above. How? Most existing homes have been built with vents in the roof ridges, the gable ends and the soffits. This allows air within the home to escape the confines of the building structure. As air warms, it rises, so air within a home has a tendency to rise and then escape the venting in the upper levels of the home. This naturally draws air from all lower areas of a home, including the crawlspace.
Now when a house has open foundation vents, can’t you understand how each of them will actually provide an entry point for the replacement air that the house requires? And when that air is hot humid summer air, it enters the crawlspace, relative humidity rises, condensation can occur and mold and mildew “smile” with the new increased supply of moisture. This added moisture works its way upstairs and costs the homeowner more money to cool the air. So, what does a homeowner do?
Building experts have been telling us for years to add more vents to provide for cross ventilation as a solution to this crawlspace moisture. Turns out there was no scientific basis for such an idea. Prove it yourself. Go in your crawlspace, light a match by a vent, and see for yourself what happens. The solution lies with covering the dirt floor with a heavy duty vapor barrier, sealed to the walls and piers to block moisture from the ground, closing all vents permanently, air sealing any other opening to the crawlspace, and conditioning (dehumidifying)the air. In effect, transforming the crawlspace into a dry clean area of the house. Now, who cares if 50% of the air in the crawlspace migrates upstairs? And the air that needs to be cooled upstairs is far drier and less expensive to cool. Did I just create extra storage space? You bet!
Next time we’ll talk about how you can save even more money by conditioning your crawlspace.