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.

Basics of Mold Testing

Once you have had your home tested by a professional, how do you determine if the results are accurate? Hopefully, you have hired an ethical professional who has the proper training and expertise to perform the testing; just in case, as a homeowner, you should have a little understanding on how to interpret the sample results.

While there are several different types of samples used in the industry - and just as many sampling devices - two kinds of samples are the most common. These are the non-viable air sample and the surface sample.

Non-Viable Air Samples
The non-viable air sample is collected by pulling a known amount of air over a sticky slide. Contents of the air are deposited on the slide. This includes mold spores, insect parts, fibers, and anything else in the air. Some labs report on the other contents of the slide, while some only report on the mold. Several things can be inferred from the additional contents, but to keep this simple, we will concentrate on the mold spores.

The spore counts will be listed in the number of spores of a category, spores per cubic meter of a category, total spores, and total spores per cubic meter. The number of spores is the actual number of spores on the slide, while the spores per cubic meter is derived from a formula based on the amount of air pulled over the slide.

Both findings are important along with the location of the samples. An outdoor control sample should always be taken, and an air sample should never be taken in an unoccupied zone such as an attic or crawlspace. The sample taken from the investigated area is to be compared to the control sample.

There is a lot to interpreting non-viable spore samples, and a homeowner cannot be expected to understand all the aspects of the testing. A lot comes from experience and dealing with a large number of samples. I always recommend that you remember the following and don’t be afraid to ask questions or even another opinion:

1. In most situations, spore counts in the home should be similar to or below the outdoor control;
   
   
2. The type of mold spores in each sample should be similar;
   
   
3. Variations in the samples can occur, but this doesn't necessarily mean there is an abnormality in the home - you must look at the amount and type of spore in the variation;
   
   
4. Just because spore levels in the home are higher than outside does not mean there is a problem - levels must be considered significantly higher to cause alarm;
   
   
5. Actual counts of spores should also be considered - one spore in the sample can read as 13 spores per cubic meter or more, depending on the amount of air passed over the slide when the sample was taken. One spore may not indicate a problem!
   

Surface Samples
I have found surface samples to be one of the most misused samples out there. A surface sample can be used to determine the type of mold present, or if there are a large number of spores on a surface due to cross contamination. However, many people have been using surface samples to indicate abnormal fungal growth. This should not be the case if mold is visible.

A surface sample can be taken using a swab, tape lift, or stick slide. All are proper methods of sampling; the only difference is how you record the area sampled. The area sampled is only in question when quantitative results are desired; in most cases, the samples are qualitative and only used to determine what type of mold is present.

How results are reported vary by lab, but most use a scale, such as "occasional, few, moderate, numerous." Wording and categories may change between labs, but in this case, "occasional" and "few" would be viewed as normal, while "moderate" and "numerous" would be viewed as abnormal. The scale is typically listed at the bottom of the results.

Here are some items to remember when reviewing surface samples:

1. Surface samples do not indicate how much growth is present on a surface, just in the sampled area;
   
   
2. For the most part, surface samples are only for mold identification;
   
   
3. All surfaces may contain some amount of spores, even if everything is normal;
   
   
4. Generally, surface samples should not be used to determine abnormal conditions or remediation protocol.

The final item of this list is the most important, and should be further explained. The best example that can be given is as follows:

There are two walls in the home, Wall A and Wall B. Wall A has one square inch of mold on it that is very dense, and Wall B is fully covered (80 square feet for an 8x 10 wall), but it is not very dense. Two samples are taken from each wall. The results from Wall A come back with "Numerous" spore levels for one genius of mold, where Wall B comes back with "Moderate" and "Few" spore levels for several genera of mold. According to the samples, Wall A has a problem, while Wall B does not. Someone could determine based on the samples that Wall A needs remediation more than Wall B. In actuality, Wall A has had all the mold removed by the sample, while Wall B has a significant problem. The variation comes from the density and area sampled.

This just gives a rudimentary example of why surface samples cannot be used to determine the need for remediation. I see this happening the most in crawlspaces, with recommendations being made over the density of the growth - not the actual coverage area.

With surface samples, only take them for what they can actually tell you. Again, as a homeowner, don’t be afraid to ask questions or get a second opinion!



Install weather stripping.

This may seem like a simple item, but many people forget about it. Check around your windows and doors and see if they are leaking, or if you can see daylight. If so, install weather stripping to seal this up! There are various types, and each one has it use. Ask someone at your local hardware store which one works for your situation or you can research your options online. Also, while door socks can help, many people will remove them in the summer. Just because you are not uncomfortable in the summer with the draft under the door, it's still there and costing you money! If you do this, also remember to pick up a door sweep while you are at the store getting your other weather stripping supplies.

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.

Have You Ever Seen a Home With Lungs? (Why Your House Doesn’t Have to Breathe)

Every day, I am presented with the argument that a home can not be sealed tight because it must breathe. A long time ago, a friend and colleague of mine answered this comment by asking,“Have you ever seen a house with lungs?” Of course, the answer to this is no, but many people still believe that their house must get fresh air to breathe.

What you must remember is that it is not the house that needs fresh air, but the occupants of the home. Also, you have to realize that everything we put in a house doesn’t need to be there, so we need to get it out. You may ask, “Isn’t this basically the same thing as the house breathing?” The answer to this is yes and no. Currently, many builders believe that fresh air needs to enter the home, but don't really care how or where. This can be a real energy buster for you if your home gets too leaky! What you want to do is control how much and where the fresh air enters - and let’s not forget about getting rid of the stale air.

You do this by creating a tight home that has few uncontrolled air leaks or air changes. Air changes are the number of times the air in your home is exchanged with fresh air over a given period of time. Typically, this is figured over an hour. Often times, air exchange rates are amplified for measurement purposes. This is done with a blower door that decreases the pressure in a home, and is usually measured at 50 Pascals. Most new homes that I see range between 5 and 8 air changes per hour at 50 Pascals (ACH50). However, there are the exceptions in which they have leakage below and above this range. I like to see homes around 3 ACH50, with controlled ventilation. The most efficient homes that I see are in this range and will typically have ERV’s or other means of air changing. (An ERV is an additional piece of equipment for your HVAC that can exchange and condition air.)

Once the home is tight, you need to get air in and air out. Building codes may state how much air you need to bring in and out of a home, so check there first! They may also limit the amount that can be brought in by natural means, such as leakage or passive ventilation. Once you have checked with someone who knows about the codes, you will want to get someone who is knowledgeable about exchange rates and how to achieve them. This is done by various means, and each has its own pros and cons. You may see the use of any of the following types or a combination of them:

1. Passive ventilation
This is ventilation that operates on natural forces and is most commonly seen in crawlspaces and attics; however, you may see it on exterior of walls as well. This is used to lower temperatures and humidity levels in these areas.

2. Spot ventilation
This is used to remove contaminants/stale air from a central location. An example of this is bathroom exhaust. Spot ventilation is very important to remove unwanted moisture in bathrooms and kitchens, but it can produce a negative pressure on the home. Just make sure you don’t go overboard on the size of the fan.

3. General Ventilation
This is simply the ventilation of the entire living space using fans. It may be broken down into sub categories or considered supply only or dilution ventilation, depending on the source. Dilution ventilation is achieved by only pumping in air to dilute stale air, and it can create a positive pressure on the home. The exhausting of air is not controlled. It can be achieved via a standalone unit or through the HVAC.

4. Exhaust Only Ventilation
Exhaust can be sub category of general ventilation, and it is achieved through exhausting of air only. This may seem like spot ventilation, but it is for the whole house and not just a certain location. It can be achieved through an exhaust fan in a central location, the HVAC unit, or through a bathroom fan that is designated to permanently stay on. This can cause a negative pressure on the home, because the intake of air is not controlled. A negative pressure can cause back drafting.

5. Balanced Ventilation
This is also called supply and exhaust ventilation. The air taken in will typically equal the air exhausted. This is often achieved with piece of equipment, such as an ERV or HRV. It keeps a balanced pressure in the home, and both sides of the air exchange are controlled and possibly conditioned to help lower heating and cooling loads.

There are several systems and variations on the ventilation types mentioned above. If you are building a home or just working to better your current one, talk to your contractor or someone knowledgeable about ventilation to work out a system that best fits your home, needs, and budget.

Install Energy Star Appliances

Since we are taking the time to talk about ventilation this week, I thought I would just mention Energy Star appliances. Many people will probably say that they already know about this, yet wouldn't understand its connection with ventilation. Many people don't realize that there are appliances and fixtures approved by Energy Star other than the typical dishwasher and refrigerators!

In respect to the topic on ventilation, there are Energy Star ventilation fans. When looking at a system that may be using one of these fans to provide ventilation, it is a good idea to have one that will save you energy.

So next time you’re looking for a new appliance or fixture, check to see if there is one that is Energy Star approved, because you just may be surprised by what you find!