Why you need a crawl space dehumidifier

You have a dehumidifier in your home to control the amount of moisture in the air.  It might not seem like you need to worry about the other sections of the house, but for the safety of your family and the well being of the foundation of the home, a crawl space dehumidifier is an important addition.  You can make things easier on yourself by hiring a reputable contractor to help you take care of the project.  Naturally, you aren’t going to be willing to shell out the funds until you understand exactly what a dehumidifier under your house can actually do for you.

Almost every crawl space in the world has one common denominator.  They all are at least partly constructed from wood.  Wood is prone to water damage.  Since the wood is touching the ground, you can bet your crawl space will be exposed to water and moisture quite a bit.  If water damage is allowed to occur, you are facing problems with your foundation, the possibility of mold, and horrible odors in your home.

Crawl Space Dehumidifier

Take a look at some of the advantages to having a crawl space dehumidifierprofessionally installed in your home.  The first thing you can look forward to is increased property value.  Any improvement you made to make your home last longer and require fewer repairs is a good thing.  You can also expect the value to increase because you don’t have any wood damage in your home.  These dehumidifiers also limit the amount of oxygen in the space for the mold and fungi to live on.  These organisms require temperatures of 40 to 100 degrees Fahrenheit to survive as well.  Crawl space dehumidifiers help with that as well as eliminating the moisture source they need as well.

If you want to do what is best for your home, look into the various crawl space dehumidifier options on the market, find a good contractor, and take care of this problem once and for all.

Why do I have mold in my crawl space

Home inspectors have become very picky about mold in vented crawl spaces. If mold is discovered on floor joists or sub floors in the crawl space, you will definitely see it in the final report. The reason is simple – LIABILITY. Considering the abundance of publicity surrounding the perils of “toxic mold”, the last thing any home inspector wants is a law suit. Fair enough. However, once mold is identified, what is the appropriate response?

Here is an actual excerpt from a home inspector’s report:

Mold growth is visible on many of the floor joists and sub floor in the crawl space. The level of mold growth is low to moderate. The presence of certain mold and mold spores can result in mild to severe health effects in humans and pets and can deteriorate the structure of the dwelling. Health effects include, but are not limited to: sinus congestion, blurry vision, sore throat, dry cough, aches and pains, skin irritation, bleeding of the lungs, headaches, memory loss and fever.

This type of wording can create friction between the buyer and the seller of the property. Considering all the nasty health effects described above, is a moderate exposure acceptable? Even if I were willing to expose myself to this risk, is it appropriate to expose my children even to moderate levels of mold?

The home inspector is doing the prudent thing by stating the known health effects of mold exposure and trying to establish a relative description of the magnitude. In effect, the inspector is passing the decisions about risk on to someone else: either the buyer of the property or another professional with more experience in assessing health exposure. The report goes on as follows:

As a practical matter, there are several things that can be done to minimize mold growth: (1) Keep the crawl space well ventilated (2) Divert downspouts away from the foundation wall and keep gutters clean.

Is this an effective plan for avoiding mold in the crawl space? While getting storm water away from the foundation and keeping the gutters clean are certainly good things to do, they are not likely to prevent mold from growing in the typical crawl space. The reason this is true relates to two of the biggest myths in building construction:

Myth # 1. Standing water is the main cause of mold in the crawl space. Myth # 2. Mold can be prevented by keeping a crawl space well ventilated.

Why Do I Have Mold in My Crawl Space?

Let’s see why these statements are not true.

While different mold species need varying amounts of moisture, let’s stick to the basics: mold cannot grow without moisture. For mold to grow on floor joists and sub floors, water vapor must condense out of the air and onto the surface of the wood.

Where does this water come from? The prevailing wisdom is that this moisture comes from the ground, but reflecting on some basic science principles will show why this is not usually the case.

Take a look at the chart below prepared by the non-profit Advanced Energy Corporation. You will see that the relative humidity in a vented crawl space is almost totally a function of the relative humidity of the outside air.

When the outside humidity is high, the humidity in the crawl space will also be high. In absolute terms, the amount of moisture entering the crawl space from the outside is many, many times the amount of moisture evaporating from the ground surface. (Note: The blue line in the graph represents the relative humidity in a closed crawl space assembly which is what we promote at DocAir.)

To understand the origins of mold growth in a crawl space you must become familiar with the term dew point. For water vapor to condense onto a surface, the temperature of that surface must be below the dew point of the surrounding air. At the dew point, the air is 100% saturated and can no longer hold any more moisture. When the temperature of the air reaches its dew point, water vapor changes from a gas to a liquid: the process of condensation. The colder the surface, the more condensation will form. That is why there is usually more mold.

Why Do I Have Mold in My Crawl Space?

on underneath bathrooms and kitchens. These floors are not insulated as well as carpeted floors, and can become very cool in the summertime. Moisture forms on the cool surface in the crawl space, and mold proliferates. We may also see damage to hardwood floors when the wood absorbs condensation and expands outward. This swelling creates tremendous compressive forces, and when the wood reaches a limit, it will buckle or cup.

What Can Be Done?

So is mold in the crawl space a problem? The answer depends on your expectations.

In any discussion of mold exposure, it is important to note that there is a wide spectrum between unsafe and pristine. There is also large variability in human sensitivities to mold spores and fungal particulates depending on sex, age, genetic makeup, and overall health. With these considerations in mind, the environmental condition of most homes with vented crawl spaces should not be considered unsafe. However, air quality can definitely be improved by keeping crawl spaces dry throughout the year.

Although standards are beginning to change, building codes have traditionally required crawlspaces to be ventilated. The intent is not to prevent moisture from entering the crawlspace (which is really what happens during the summer months) but to allow excess moisture under the building to evaporate. It is assumed that this moisture is coming up from the ground. If the outside air is sufficiently dry and the amount of moisture is not too great, this process is adequate. Unfortunately, during the summer months, the outside air is usually too humid, and vents in the foundation transport moisture from the outside to the inside rather than the other way around.

Condensation in the crawlspace can best be prevented by sealing it off both from the ground and from the outside using a continuous liner such as the one shown below.

Why Do I Have Mold in My Crawl Space?

As a final measure to ensure a dry, energy efficient crawl space, we recommend the installation of an electronically controlled dehumidifier in the crawl space that will maintain the relative humidity below 60% throughout the year.

Summary

It is predictable that vented crawl space will have some mold growth on wood floor joists and sub floors exposed to the ambient air. DocAir installs closed crawl space assemblies for both new and existing homes. A closed crawl space delivers major benefits in terms of air quality, energy efficiency, and structural sustainability. However, we always emphasize that there are millions of vented crawl spaces in existence throughout the southeastern United States. The decision to install a closed crawl space assembly should be governed by the sensitivities, preferences, and budgets of the home owner.

Moisture Problems in Crawl Spaces

In the mid- atlantic region there are thousands of crawl spaces that have moisture problems, insects, wood rot and sweating duct work.
Most all crawl spaces are vented and have the same problems. Until recently, the building codes did not recognize conditioned crawl spaces.
We now have the option of building foundations without crawl space vents and adding dehumidifiers to control temperature and humidity levels.
The conditioned crawl space concept has been around for years; however, with the advancement in technology we have been able to convert old or build new spaces for much less money then just 10 years ago. The attached photo shows what an Aprilaire dehumidifier looks like when installed in a crawl space (this was an attic knee wall crawl space).
If you have moisture issues under your house or in some cases improperly vented attics, you want to have it corrected as soon as possible.

Crawl Space and Moisture Problems

Every day that I wake up and head out to inspect someone’s home that has a crawlspace, I could probably fill out some of my inspection forms ahead of time. It is an unfortunate fact that most crawlspaces have moisture problems. As we all know, there are plenty of horror stories out there about crawlspaces and moisture problems so why don’t we talk about the cause and cure of these problems.

 

There are two different types of crawlspace setups, vented and non-vented.

 

Vented:  There are vents that provide adequate cross ventilation, the sub floor of the home is insulated along with the pipes in the crawlspace to prevent freezing, there is a vapor barrier on the ground and the vents get closed in the winter time. A small heater or heat tape is used to help keep the pipes from freezing in addition to the insulation on the pipes.

 

Non-vented:   The crawlspace foundation walls are insulated, the sub-floor is not.  The vents are blocked off with insulation all year long, a vapor barrier is in place on the crawlspace ground and the air is conditioned with a dehumidifier.  A small heater and pipe insulation are still recommended.

 

Causes & Cures:

 

1.)     No rain gutters.  Although controversial, we all need gutters to keep the rainwater away from our homes. The average roof sheds 1,000 gallons of water during 1 inch of rain. This water will fall along the foundation and find the crawlspace very quickly. The best rain gutter covers are solid and cover the gutter opening, allowing water to come in by curling under the cap via gravity. Mesh and screen covers just get clogged up or collapse.

 

2.)     Downspouts terminate along foundation.  The downspouts need to shed water away from the home at least 6 feet or more or to underground pipes that lead away from the home.

 

3.)     Terrain slopes toward foundation.  Make sure that the landscaping does not do this.  All surface water should be directed away from the home. A swale may be necessary if your home is built on a slope. The foundation can have significant structural damage caused by water along the foundation that freezes in the winter collapsing the foundation inward.

 

4.)     Inadequate ventilation.  Don’t forget to open those vents that you closed for the winter. A crawlspace needs a minimum of 1 square foot of ventilation for every 150 square feet of crawlspace floor area and should be within 3 feet of the corners allowing for cross ventilation. Low decks, other types of construction above or against vents along with shrubs can block the vents making them useless. Your home needs to breathe.

 

5.)     Insulation installed upside down.  Depending on how you have your crawlspace set up, either vented or non-vented, you may have insulation in the flooring. The paper side of the fiberglass insulation should always face the heated living space and sit against the sub flooring.  When it faces downward towards the earth, it has a tendency to trap moisture between the sub floor and the paper hiding moisture damage. If your crawlspace is set up properly as a non vented crawlspace, no insulation is necessary in your floor.

 

6.)     Damaged or loose vapor barrier.  You should have a 6 mil thick poly vapor barrier on the ground of your crawlspace, overlapped and sealed around columns and the walls. This will help to keep the ground moisture vapors from rising up into your framing. Most homeowners will add gravel on the top for protection.

 

7.)     No or non functioning sump pump.  If you have a sump pump installed, make sure it is at the lowest point in the crawlspace and all areas easily drain to it. The pump should be inspected regularly and function automatically. If you get standing water in your crawlspace even with items 1 through 6 in place, you need a sump pump. Nothing can take the place of a properly installed perimeter foundation drainage system by the builder but a sump pump is the next best thing. The pump should be in a plastic cylinder in the ground and eject water outside, away from the building and not into the septic or sewer system.

 

8.)     A non vented crawlspace with no dehumidifier.  If you are going to set up your crawlspace as non-vented, you must condition the air with a dehumidifier and have the water collected and piped to the sump pump or install a condensate pump. If you don’t pipe it to drain automatically, you will be emptying the collection device daily. Buy a quality dehumidifier with an adjustable, automatic setting so it does not run all of the time.

 

Please remember that a crawlspace is an integral part of your home and should be kept neat, clean and easily accessible. Inspect it often looking for signs of moisture or mildew and consult the local code official for any repairs. Remember the old saying “An ounce of prevention is worth a pound of cure”.

 

From experience, my personal preference is the non-vented crawlspace. Talk with your home improvement specialist or builder to see what is best for your situation. All systems should be professionally installed and inspected by local code enforcement.

Greening Your Crawl Space

Remodeling in a green fashion is a way to leave a smaller carbon footprint on the planet and to create a healthier and a safer environment. The condition of the basement or crawl space affects the rest of the home. By making some adaptations to these spaces, you can reduce the homeowner’s footprint and help them to become more financially savvy.

Basements and crawl spaces tend to be the dampest areas in a residence. The stack effect causes the moist air to rise from the lower levels to the top of the home, and to exit through the attic or the roof. This could cost residents money and even make them ill. As moist air travels upward from the basement or crawl space, it carries with it the mold spores commonly found in the lowest level or in the crawl space. Although it is difficult to predict how mold will affect different individuals in various locations, it can lead to common health problems, including difficulty breathing, eye, throat, nose or skin irritation, sinus or nasal congestion, or upper respiratory infections. Because of these potential issues, it is best to rid the residence of mold.

Keep in mind that the mold and rot that originate from moisture are nature’s maid services. When an animal or a plant dies outdoors and remains on the ground, then mold eventually consumes the remaining organic material. Inside a moldy basement, the same process can occur. Mold and moisture can accumulate, and then insects feed on the mold and on the wood. Worse, rodents may then enter the home to eat the insects. This is the front line in the war against moisture. Guidelines to stop the escalation include keeping the relative humidity of the basement or crawl space below 60 percent to prevent mold growth, and avoiding the rotting of any lumber by keeping its moisture content below 16 percent. This way, you can avoid having to repair or to replace the wood in these areas of the home.

To maintain low levels of moisture in the air and in any lumber, stop any water from entering, or standing, in the basement or crawl space. This will empty the home of a key element that mold needs to grow. The methods to achieve this are different in basements and in crawl spaces. Here are some means of eliminating water intrusion.

Waterproofing

Crawl spaces: Use a different strategy for crawl spaces. Isolate the home from the earth to drastically lower the humidity level and, in turn, eliminate mold growth. To accomplish this, install a vapor barrier system in the crawl space. This should completely stop moisture penetration. Blocking off the vents in the crawl space is also necessary. Vent covers prevent cold air from rushing in during the winter and hot air from entering during the summer. Cover the vents and use a vapor barrier to use less energy and fewer resources, and to reduce heating and cooling costs. Note that some crawl spaces do require a drainage system underneath a liner to provide a dry, healthy crawl space.

          

Dehumidification

Once the basement or crawl space is waterproofed, the next step is dehumidification. Separate models are designed to tackle basements or crawl spaces. These units dry the air, and some drain the water out of the attached hose, rather than needing to be emptied by hand. Energy-efficient models can remove more water than typical dehumidifiers could, and achieve this with the same amount of energy that a standard unit would use. As discussed above, the stack effect causes the air in the basement or crawl space to move upward, through the rest of the house. By using a dehumidifier, the air will be dryer and safer throughout the entire residence.

Finishing

Crawl space: After installing a vapor barrier system, the crawl space will be finished. The thickness of the liner not only keeps humidity low, but also allows the space to be used as storage. Some barriers are also strong enough to allow other professional contractors, such as plumbers or electricians, to work in the crawl space without damaging or tearing the liner.

          

To successfully keep the basement or crawl space dry and environmentally friendly, waterproof, dehumidify and finish the crawl space or basement. These steps will help homeowners to green their residences, decrease their carbon footprints, and, overall, make the environment healthier.

How to Choose a Crawl Space Dehumidifier

If you happen to live in a humid part of the United States, then you are very familiar with how damp and wet certain parts of your home gets. The basement is one obvious location but if your house has a crawl space, then it might be time to but a crawl space dehumidifier.

So are probably asking yourself, “What the heck is a space dehumidifier?” Well that is a very good question. As you can tell by any Google search, there are thousands of different types of dehumidifiers on the market. Well there are some that are specialized to work in different parts of your home. Your space is no different.

Think about your crawl space for a second. Mine is actually located underneath our stairs so space is very limited. Also, since it is an enclosed area, the moisture is probably the most intense then any other portion of your home. Well a crawl space dehumidifier is designed just for this. It s sized to fit most areas. It is also more powerful then your normal dehumidifiers.

It is important to get rid of the humidity in your crawl space. The biggest reason is the damage that it can cause your foundation. One of concretes worst enemy is moisture.

Of time, it will rot away, causing a lot of damage. Another reason is that humidity is just a breeding ground for dust mites and other diseases baring insects. Just think of what could be growing in crawl space.

Just think what it will do to books and even pictures if you are storing them down there. Not a pretty sight.

Crawl Spaces….The issues under your home

I run across many homes that have crawl spaces instead of a basements, either under the whole house or under additions built on after the original house was built. This was done for a number of reasons, most usually cost or how high the water table is. Some are built with a concrete floor but most are just bare dirt and/or gravel. Although this is a less expensive way to go, it can cause bigger problems down the road if not done correctly.

The original rule of thumb for the crawl space dealt with ventilation. It did not matter what the base of the crawl space was as long as the ventilation was correct. This was later changed. Now the experts recommend no ventilation. They recommend the owner create an environment where someone could live in the crawl space. Obviously the experts do not think someone would live in the crawl space, but if the air quality, temperature, and humidity are no different than the living space, there should not be a mold issue.

A concrete pad will help control the moisture in the crawl space. Dirt or gravel, however, will not stop moisture from evaporating into the crawl space, which can cause a mold issue on the subfloor or possibly in the living space. In this situation, a plastic membrane should be installed. This should be attached to the walls of the crawl space and sealed at any seams, including any supports in the center of the crawl space. A thicker plastic (such as 6mil) should be used to help avoid tears when someone needs to use the crawl space. In certain situations, the height of the crawl space will make it impossible to work without taking up the flooring above it.

Once the flooring of the crawl space is set, a dehumidifier should be installed. This may be difficult if there is no drain to empty into, so a condensate pump may need to be installed to pump into a drain or piping. If there is a full basement attached, an opening connecting the crawl space to the basement will allow the dehumidifier to operate in the basement while dehumidifying the crawl space.

Conditioning the air in a crawl space will reduce the potential for mold, and it will also make your living space seem warmer in the winter months due to less humidity in the air rising up from the crawl space. If your crawl space is very wet, these changes are highly recommended. If you are getting mold on items in your living space, this could be the biggest culprit. A trained professional will be able to help you determine what would need to be done.

Don’t Overlook Your Crawl Space

Every house is unique and foundation-type is one distinct difference between them.  A home typically has a crawl space, basement or a concrete slab foundation.  In this three part article series author Joe Provey explains how foundation-type should be taken into consideration when upgrading a home’s energy efficiency. Joe’s first article explains how a home with a crawl space foundation can increase their energy efficiency.
Save energy with the bonus of controlling excess humidity and improving home air quality!

Like it or not, your crawl space and living space are joined at the hip. Holes for wiring and pipes, plumbing chases, leaky heating ducts, gaps in subflooring, ensure that your living space and your crawl space communicate freely! It is no surprise that the U.S. Department of Energy recommends you insulate your crawl space. Insulation in the floor joists is typically inadequate to offer much of a barrier. To make matters worse, the laws of physics actually cause the air in your crawl space to be pulled up into your living areas. As warm air rises in the upper levels of your home, it creates a draw on the lower areas. As much as 40 percent of the air in your crawl space eventually mixes with the air inside your home.

This creates a whole series of problems, ranging from energy loss to breathing unhealthy air. In summer, cool air is lost to the crawl space. In addition, excess humidity from the crawl space causes your air conditioner to work harder and use more electricity than it should. In winter, cold air entering through the crawl space makes your floors cold and first level rooms drafty. Heating bills climb. Winter and summer, you’re apt to be breathing unhealthy air laden with allergens and soil gases.

There are five steps you can take to turn a crawl space into a clean, healthy, energy-efficient part of your home. Here they are roughly in the order you should tackle them:

1. Seal and insulate rim joists
The first framing member attached to a foundation is called the sill plate. It lays flat atop the home’s foundation wall and is fastened to it with J-bolts or by some other mechanical means. Because the top of the foundation is often uneven, there may be gaps under the plate. In new construction, a gasket helps to solve this problem, but in older homes it is a major cause of air leakage. The second framing member is the rim joist. It rests on edge upon the sill plate and provides a way to secure floor joists. Subflooring is installed over the rim and floor joists. Air leakage may occur at the joints between the sill plate and rim joist as well as between the rim joist and subfloor. In addition, the R value of the rim joist (its ability to stop conductive heat loss) is only 1.88 – about the R value of a single pane window with a storm window in place.

To stop energy loss from the framing assembly that rests upon your foundation wall, seal all joints with a bead of closed-cell foam insulation. Then install rigid foam board insulation against the rim joists wherever possible. For example, cut the board insulation to snuggly fit between the floor joists and between the sill plate and subfloor. Then press it against the rim joists. If the fit is loose, fill the gaps with spray foam insulation.

2. Seal ducts that run through crawl space

Heating and cooling ducts often reside in the crawl space. Typically fabricated from sheet metal, they’re used to distribute warm or cool air to the rooms of your home. Unfortunately, ducts typically leak a large percent of the air they carry. This means your HVAC equipment must work overtime and that your energy bills are higher than they need to be.

To stop energy loss from ducts, seal all metal-to-metal joints and holes with mastic sealant or with metal tape. Do not use duct tape because it will eventually fail. Seal joints between the subfloor and ducts with spray foam insulation. If you do not plan on insulating the walls of your crawl space, consider insulating the ducts with duct wrap. Duct wrap is fiberglass product with a foil vapor barrier to the outside. Be sure to seal all seams with aluminum duct tape. Otherwise, air leaks will allow moist air to penetrate the wrap. In summer, that moisture is likely to condense on the cooler ducts and wet the fiberglass – and wet fiberglass is ineffective as an insulator.

3. Insulate walls

The above- and below-grade portions of your crawl space wall will lose heat in winter, so you will save energy and be more comfortable by installing wall insulation. Rigid foam boards can be adhered to or mechanically fastened to either block, stone or concrete walls. They are waterproof and will not support the growth of mold. The recommended R value depends upon where you live. Check with D.O.E. recommendations or with local building department officials for recommendations in your area.

4. Encapsulate

A continuous vapor barrier that covers both floor and walls adds another layer of insulation by sealing out air leaks. It will also help control moisture and stop soil gases from infiltrating your home. For a vapor barrier to be effective in the long term, it must be durable. If interested in taking on this project yourself I recommend this great guide that explains how to install a vapor barrier.

If your crawl space is susceptible to water infiltration, install drainage matting before installing any liner. It will allow water to drain toward either a drainage pit (no pump) or to a sump basin and sump pump for discharge. Here is a great resource explaining in detail what needs to be done to fix crawl space water leaks.

5. Dehumidify

If you’ve opted for encapsulation, install a dehumidifier in your crawl space to dry out framing and flooring that has long been exposed to excess humidity as well as to ensure against excess humidity on an ongoing basis. Lower humidity in your newly conditioned crawl space will translate to lower cooling costs and greater comfort in warm weather.

An investment in any or all of the above will make your home more energy efficient and improve the comfort level and health of family members. In addition, controlling moisture levels protects your home from structural damage due to rot, corrosion, termite infestation and can give your home extra storage space.

Interested in learning more about crawl spaces? This very informative crawl space learning center can educate you on this often overlooked part of a home.

Interested in learning how to make your basement more energy efficient? Check out Joe’s next article on the CleanEdison about Insulation your Basement.

Have any other tips to help make your crawl space more energy efficient? I would love to hear about them in the comments below!