Improper Operation of a Crawlspace

Over the last few weeks, I’ve focused on the sealed crawlspace and what goes into one. This week, I will review why you shouldn’t leave a crawlspace open and what is not a proper solution to a vented crawlspace. The reasons for sealing a crawlspace have already been discussed in the previous post; however, here's a review of what a vented crawlspace will typically have:

1. Higher moisture content in the wood
2. Increased fungal growth
3. Higher relative humidity
4. Overall less energy efficient for the home
5. The need for more pest control
6. Lower indoor air quality in the home

Since most homeowners know about these issues, some are looking for alternatives to the sealed crawlspace. While there are possibly individual solutions to each one of these problems, none of them solve the problem like a sealed crawlspace.

There is one solution - the foundation fan - that I have seen used  time and time again in an attempt to control moisture. However, it not only fails to eliminate the problem, but will actually increase the issues in the crawlspace. There are several variations to this product, ranging from simple humidity-controlled fans that install in the vents to larger, more powerful fans that are run on timers. Most individuals will sell these fans on the premise that the crawlspace needs more ventilation to “dry” the space. This is the concept on which the foundation vent was based: By providing ventilation under a home, you are able to keep it dry. Here in the South, this is not the case, especially since we began installing plumbing and HVAC in the crawlspace. By exposing the crawlspace to the exterior air and having surfaces in the space with lower temperatures, you are just providing an optimum situation for condensation.

Condensation occurs when the temperature of the surface is below the dew point of the air. This is the same thing as dew in the morning. When we have surfaces such as plumbing pipes and ducts that will consistently be below the dew point of the outdoor air, we will get condensation of these surfaces. This condensation can wet the other surfaces and cause even greater problems.

Wood surfaces can also be affected, and since fungal growth can occur with a humidity over 60%, you increase the risk of providing an environment conducive to growth when introducing the outdoor air. This brings up another aspect of introducing outdoor air, because as you lower the temperature, the relative humidity rises. We can all assume that the crawlspace will typically be cooler than the outdoor air in the summer time, so as the outdoor air comes into the crawlspace, you will actually increase the air's relative humidity.

Originally, the idea of a foundation vent fan was to increase the ventilation of the crawlspace; however, all it does is actually increase the moisture content of the space by pulling in more exterior air. Therefore, the fan actually increases the relative humidity and the potential for condensation. Many will argue that the air will help remove the condensation, but as you lower the temperature and raise the humidity, you will actually decrease the amount of moisture the air can even hold. Adding more moisture to it will only increase the dew point temperature. There are several cases I've seen in which a vent fan has been installed to combat a small amount of fungal growth, and actually ended up causing the floor structure to rot!

So, if someone tells you that a sealed crawlspace is a bad idea, and that you should instead install a foundation fan, take the time to consider the negatives.

Reduce your air leakage.

If you have a leaky home, think of it as spilling money through the cracks. Most of your loss is through the ceiling, so start looking there first. Seal all ceiling penetrations you can; these include recessed lights, attic stairs, and even standard lights. Next, look to your walls and floors. Last should be your outlets, as they only account for about 2% of the leakage in your home.

Need help finding the leaks? As a homeowner, you can feel for drafts, use a candle, or have a professional set up a blower door.

How Do I Prevent Mold?

This is a very common question among homeowners. Concerns for fungal growth or mold often arise when an unfamiliar odor is noticed or a small leak occurs, and at that time one starts to investigate how to prevent the growth from occurring! I am often asked if there is a special treatment or construction product that can be used to prevent fungal growth in the home. While there are products on the market that are resistant or retard growth, there are even simpler solutions to prevention.

Before even looking at how to prevent fungal growth, what must first be understood is whether mold is ubiquitous to the environment. No matter what we do, we cannot keep mold spores from being in the air! It is the nature of our world and part of the air we breathe. With the understanding that these spores are everywhere, we can look at how to stop them from growing. In order for fungal growth to occur, there are four items that need to be present; removal of any of the four will prevent growth:

1. Mold Spores
Common sense would prompt the thought that for if spores are everywhere, then why even discuss this? Of course, spores are one of the four items that are required for growth, and there is little that can be done to prevent them from being in the air. What should be understood is that if you have some growth in the home, remove it - you don’t want to increase the number of spores that are there. I have had several individuals ask if they could just leave the mold growth if they removed one of the other three items required for growth; the answer is no. If you leave the growth, you have left spores on the surface; if you reintroduce optimum conditions for growth, you have just created a bigger problem because there are more spores present than under normal conditions. The bottom line is that you can do little to prevent the number of spores in the home; however, if you have growth, no matter how little, remove it before you just create a bigger problem if the conditions that are conducive to growth become favorable.

2. Temperature
This is the one item that is hard to control, and in all actuality, you really can’t. Though there are some species of mold that like to grow outside of our comfortable temperature range for living, many grow in the same temperature range that we like to inhabit, so there is not much that we can do. I am often asked if someone can cool or heat a home to help with the growth. There is some possibility to this, but often the range that inhibits (or prohibits) growth is out of our comfort range, so this is difficult to do.

3. Nutrition Source
Like all living organisms, fungus needs something to "eat" to grow. This comes down to organic material, which is often drywall paper and wood in our homes. Things that are not organic and will not support fungal growth for the most part are bricks, stones, and fiberglass. These objects do not have nutritional value for the fungal growth, and for the most part will not support it. However, dust and dirt collected on these items can have nutritional value, so there can be an exception to this rule. If we build our homes primarily out of material that supports growth, how do we eliminate this item? For the most part, we can’t, but this is where all the new materials on the market can help, such as fungal-resistant wall board and the variety of products that have Microban as a component. We can limit the nutritional value in the products we use, but again, this is something that comes along with the construction of the home, so it is less of a preventative measure in older homes.

4. Moisture
This is the most preventable of the four items in preventing fungal growth from ever occurring. Stop the moisture in the home! If you have a water leak, correct it and dry out the area. If you have water intrusion through your basement wall, stop it. Plain and simple, keep your home dry. Most homeowners understand this and do well with stopping the large water intrusions. Some of us could do a little better at doing maintenance inspections to find leaks, but again, for the most part, active leaks are typically corrected. Sometimes catastrophic damage occurs from a water line breaking or when piece of equipment malfunctions, such as a dishwasher. This cannot always be prevented, but there are items on the market that can help reduce the likelihood of the damage being significant, as well as good practices with preventive maintenance.

The one moisture source that most homeowners overlook is humidity. We all know how high humidity affects us, especially in the south, but mold likes a relative humidity above 60%. If your air conditioner is not properly operating and removing the moisture from the air in the summertime, or even in some cases putting more moisture into the air, you can have a mold problem without ever having water damage. The solution to this is to monitor your relative humidity and make sure the air conditioner is functioning properly.


Install a Radiant Barrier

A radiant barrier in your attic does not add to the insulation value of the attic, but it does help manage radiant heat. Radiant heat is the warmth we feel when standing in the sunlight. In the summertime, we want to keep this out, and in the wintertime we want to keep it in. Depending on the installation of the barrier, you can achieve both of these functions and reduce the heating and cooling cost of the home.

Can I Test My Home For Mold Myself? Do Self Test Kits Work?

Mold is a very common concern when dealing with indoor air quality. Many homeowners will believe that an odor or the reason they are feeling sick is due to mold without ever seeing the growth. The truth of the matter is that I find mold in only about 30% of the "unknown odor" cases I investigate! Often, the odor is coming from other sources, or it eventually goes away and the source is never discovered. The percentages are even smaller when it comes to a sickness in the home. Often times, these are truly resulting from work stress, lighting, or other factors in the home.

While it is not as common as it used to be, I still come across scenarios in which the concern has been increased due to the use of a home test kit. These test kits typically consist of two petri dishes that are set out for a period of time. One is used as a control outside, and one is the sample of concern. These tests work off the idea that spores will settle out of the air over a period of time and grow on the auger in the dish.

So you may ask, "Why doesn't this test work? If there is mold in the dish, doesn’t that mean I have a problem?" Here are some answers for you:

1. Mold is ubiquitous to the environment
Mold is everywhere! Contrary to what many homeowners may believe, there are many spores in your home. These spores are brought in through the air exchanges in the home, on your clothes, the HVAC system, and anything else that has air in or around it. Just because there is mold in the dish does not mean that there is a problem in the home. A control of the outside is needed for comparison. In a normal environment, the indoor sample and the outdoor sample should have a similar composition; spore levels in the indoor sample should be equal to or less than the outdoor one, and any variations from inside should be small or of a type that is not considered a water damage mold. Self-test kits did get one thing right by providing the exterior control, but there are other flaws.

2. A known volume of air must be passed over the samples.
Using petri dishes as a collection media is not a problem, as it is used in viable testing (living specimens are able to grow). However, the issue with the self-test kits is that there is no known volume. You know the time, as the homeowner will write down the hours the dishes were left out, but how much air passed over the dishes? Were fans on in the room, was an HVAC duct blowing on the dish, was there a lot of movement in the room, was the wind blowing outside? All these are factors that will impact the amount of air moving over the dish and the spores it may be exposed to. Some could argue that these are settled dishes and movement of air will lessen the amount of spores; however, this is still an issue with the accuracy of the dishes, as we don’t know the volume of air sampled and therefore do not know if you can accurately compare the interior and exterior sample.

3. Non-viable vs. Viable
This test is only looking for viable or living spores. What about the non-viable ones, or total counts? When looking at the indoor air quality of the home, all spores are of a concern because even non-viable spores can have health effects. While this is a minor concern with the self-test kits, it is still a concern, because looking at only viable samplings can misconstrue findings. Typically non-viable samples are taken first to determine if there is a problem, and then viable are used if further investigation is needed for specific species of mold.

4. Result interpretation
The home test kits are usually interpreted at the lab. While this is not necessarily a bad thing, I have often seen any variation in levels labeled as abnormal. When someone is interpreting results from a lab, they have not seen the home and cannot make assessments based on conditions in the home. I will say that their assessment may not be incorrect; I just caution that there may be other influences in the home that are causing a variation and are not attributed to actual growth. I will often review samples taken by other individuals and make comments on them, but I always caution that in order to make an accurate assessment you have to be at the home at the time of the sampling. I have intentionally taken samples as less than optimum locations in the past to see how sample results vary. A specific one that comes to mind is one I took near a bowl of rotting fruit. The fruit had visible growth on it, and the results showed elevations as compared to the outdoors. Had someone read these in a lab and had not been present in the home, they may have said there was an abnormality - when in actuality, someone just needed to get rid of some fruit!

Install Low Flow Fixtures

This saves in several different ways, depending on your situation: By installing low flow faucets and toilets, you can save money on your water bill, you can save power by not running your pump as often, and you can save by not using as much hot water.