Crawl Spaces and Health Issues

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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 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.



    • Lufos24th January, 2004 Reply

      Dear Joel,

      I know, I know your time is limited. Besides learning the correct position to assume while crawling away under a house is a delicate balance and does require practice.

      I myself at this advanced age, can no longer participate in the extended crawl of the early morning looking for the ruptured waste line or listening to the trickle trickle of the failed water supply pipe.

      But on long winter evenings, snug in my den with the heater turned up, a decent Merlot at my side, I do think back to those long ago times when I so crawled. I miss those long dead cats, strange hairy spiders and the cockroach that safe in thisbelow grade structure has grown to a size that defeats the will of god.

      Dear Joel, there is nothing to be learned on such a crawl except the improvement in the pronouncement of various profanities that are best left unsaid.

      Stick to the written word and the manipulations of esoteric programs which will keep you productive in this the new information age. Leave the crawling to us Neanderthal types who have been left in the mire by the emergence of a new form of advanced Cro Magnon Programer.

      I am buried in the Mire of a CAD, how do you do layers on layers on an IBM oriented machine. I yearn for Apples. My mind is still trapped in the mire which resides underneath structures.

      I follow the path of Cronus and you the path of upcoming Zeus.


  • joel14th January, 2004

    Why are you opposed to the vents?? I thought the main purpose of the vents was to close them during winter, so the crawl space could retain some heat. And in the summer to ventilate the area so it wouldn't retain heat.

    I grew up in a ranch style house with a basement, and I think for the most part, this style house is probably the most efficient in heating and cooling (Besides an underground house).

    • NC_Yank14th January, 2004 Reply

      Hi Joel,

      I am opposed to vents, in particular in states where humidity levels are high, because they do nothing more than add moisture into a crawl space while not allowing the crawl space to dry out as is their original intent.

      A hundred years ago when homes were being built on brick / rock piers you didn’t have the mold and termite issue for the most part. The air would travel freely allowing the ground to dry out.

      Don’t get me wrong, I am not advocating we go back to that style of foundation however the principle is sound.

      What we are doing to day is closing up crawl spaces, putting plastic on the ground to try to keep the moisture out from rising water tables and attempting to vent any moisture with foundation vents.

      What is actually going on though is this; in the summer the cold air travels through duct work at which time it hits warm air which causes condensation to form. We have plastic sitting on the ground that now holds the moisture on top.

      This becomes a breeding ground for mildew, mold as well at presenting ideal conditions for termites and other wood destroying insects. It’s no wonder we have the problem that we have today.

      I have been in hundreds of crawl spaces and my findings are that most are smelly and damp with little air flow through same. Think about all the things you find in a crawl space preventing the free flow needed to dry out the crawl space……it is not happening.

      Myself as well as other inspectors have brought this to the attention of Raleigh but to no avail.

      It will not be until insurance companies have to pay out of pocket through lawsuits that they will resolve the problem.

      Eventually it will be resolved by getting rid of the foundation vents and sealing up the crawl spaces in a more controlled manner as I have outlined.

      • joel14th January, 2004 Reply

        Either way, I for one really appreciate this article. I don't have time to follow you around for a week learning all the nitty gritty about construction. But, I will always have time to read your articles. Keep them coming.

  • Lufos14th January, 2004

    Sometimes in pursuit of solutions it pays to go back in time and look at prior solutions. Then again the solutions may be present in some unlikely place. Like Korea.

    Most of my time in Korea I spent flying a really nice F-86. But alas one day I found myself sitting in the middle of nothing, still straped to the seat, and holding the stick. But the aircraft had suddenly disappeared. I dropped for a while, then unstrapped myself from the seat and discarded the control stick that I was still clutching. After a period of deep contemplation I opened my chute and shortly thereafter arrived at the ground.

    In any case I spent the next few days living in a very nice Korean house way out in the country. Now that house had the nicest system of heating and heat transfer I have ever seen in my entire life. Just a farmers house but go underneath and while primative it had all the answers. They had a coke oven burning in about the middle in a lined pit. From that pit were tubes dug in the soil emanating to all parts of the house. The grade levels starting at the oven climbed about 1/4 inch per foot. Just enough to let that old first law of thermodynamics work. Heat Rises. The entire house was confortable and believe me it was built with very tired wood and lots of spit. But that heating system really worked. At one time I had to hide undenneath the house for a while and I made a drawing of that heating system. Also at the same time I found out where they buried the KimChee waiting for it to age and ferment. As you know it is addictive so I had a rather pleasant time while the Chinese and North Koreans were bothering my hosts.

    I noticed that they did something which as an ex plumber I wish we would adopt in this country. They cleaned and raked under neath the house. No dead cats, well that figures cause they would have been served for dinner. I enjoyed my time and learned a lot. Love KimChee and the Koreans, I have the scars on my knees to prove it. I never fully adjusted to sleeping on the floor. So I occupied my time in more interesting occasions. I read books like Bob Allan! Yeah sure.

    I ate so much KimChee that my breath was pure garlic. It was so strong that a full Major General almost fainted while having a conversation with me. Now you know why it took so long to make a star.

    Reflective Lucius


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