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Crawl Spaces and Health Issues
| | Wednesday, January 14, 2004 @ 08:00 AM EST
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Contributed by: Jeff Haynes
Jeff Haynes Properties
Read more archived articles about Construction and Building
There can be a correlation between health issues and your crawl space.
Does this mean that I favor slab foundations over the conventional crawl space, simply put the answer is No.
I love crawl spaces for obvious reasons but depending where you live, they can be a problem if not inspected.
I can easily right a page of things that should be fixed in most crawl spaces I do home inspections on. As a matter of fact the crawl
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space is one of the last areas I do inspect when doing a home inspection…….they are usually wet, musty and moldy.
The typical things that I find is that the crawl is used for storage of building materials such as extra lumber, boxes, flammable materials etc. All of these present problems in and of themselves. Many older homes have no insulation between the floors and those that do have insulation it is common to find in installed improperly.
A house does breath, so what is often in your crawl space air will eventually make it into the house. I found this out first hand this summer when we had about 4 – 5 field mice that got inside the house and made a nice little home in my ductwork. Of course I didn’t know this until my eyes started watering frequently and I was sneezing quite a bit while working in my home office. The smell was faint but after a few days of feeling miserable I knew it was something in my ductwork or in the crawl.
I managed to kill what mice I could (against my wife’s objections…she is an animal lover) and was able to figure out which duct work had to be replaced because some mice had died in my ductwork.
The majority of the smell went away........however after several days / weeks of rain I was getting a musty smell coming through my office as well as my downstairs bathroom. I went back under the crawl space to see if more mice had come to pay their respects to Mickey and Minnie, but I was unable to find anything. I checked the new ductwork which was taped fairly tight. After another week of feeling miserable I went back under the crawl space and finally found the problem. A couple register / damper boots were never completely sealed around the subfloor where they had been cut out. Even though my floor had plenty of insulation under it and I did have plastic in about 75% of the crawl, my house was sucking crawl space air into my house.
This is what is called the stack effect. Think of it as a chimney, you open the damper of the chimney and air will be drawn from inside the house to the outside. If you have a wood burning fireplace than you know the easiest way to get a fire going is to open up a door or window near the fireplace to get the chimney to draw the air up.
With a house it works on the same principle but like this; as warm air in your house rises it is replaced with air that is sucked from the lowest part of the house. This is where your crawl space comes into play.
Now in my case my house is predominantly glue down hardwood flooring as well as tile. My subfloor consist of ¾’ OSB and of course I have R-19 installed in the crawl space. My crawl space is dry however with the large amount of rain we had this summer along with the vents required by code, I was experience high levels of humidity in the crawl. Ideally 30 – 50% humidity is all you want….anything above or below that can become a problem. As I stated earlier, I had a couple of duct boots that were not tighly sealed which allowed the damp air in the crawl space to enter my office and bathroom. Even though I had insulation around those areas, because of “stacking” I was breathing the damp air that was in my crawl space.
Once I sealed the boots then the problem was solved. Imagine the effects there would be if I did have a mold and mildew issue. You can now understand the importance of keeping your crawl space dry and maintaining a proper grade for your foundation.
There are methods including but not limited to completely sealing your inside your crawl space as well as controlling the air inside the crawl space via means of a hvac system for the crawl itself.
In most cases it’s just a matter of properly installing gutters and grading.
In most states where you have a crawl space there are requirements to put foundation vents in same. Even though by code I install these vents I am strongly opposed to the useless contraptions. I lived up north for 20 years (nothing I am proud of), but I will say that the north knows how to build a basement…..and trust me there are no foundation vents in them, unlike down here in the south. I apply the same principle to crawl spaces.
Other problems I find is that even in dry crawl spaces where the furnace is under the crawl it is common to find moisture sitting on the plastic.
Typically the moisture comes from condensation that has formed on the ductwork.
Again most of this moisture can be accounted from high humidity levels due to the foundation vents as well as moisture getting in from the foundation walls and at times high water tables.
I suspect with time (and lawsuits) the insurance commission will change the building codes to get rid of the useless vents, but until then ………next time you’re under your crawl space look around to see what you may be breathing.
If you suspect you have radon gas in your crawl space, simply putting plastic in the crawl will not necessarily take care of the problem, contact a professional for further evaluation and remediation.
NC_Yank
Note: NC_Yank is a licensed building contractor and home inspector in the state from which he derives his name and while he had no say so in his birth place, he was smart enough to move south of the Mason Dixon line once he had the means.
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