Crawlspace 101

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Purpose of a Crawlspace

Many customers want to know, very basically, what the purpose of a crawlspace is. In essence, a crawlspace, as its name implies, is a variation of basement in which one crawls around. It may be as small as a foot tall, and the surface is often bare earth. Traditionally, crawlspaces are built on homes lacking either a basement or that are not built on a slab. Many buildings, especially commercial buildings, have a crawlspace between some walls. The primary purpose of a crawl space is to promote air circulation through the home and also allow easy access to plumbing, electrical and other such maintenance, repair and installation needs. Crawlspaces offer an expedient and efficient way to access pipes, substructures and a variety of other areas that may be difficult or expensive to reach otherwise. Older homes in areas where basements are rare have high foundations with crawl spaces that allow cooling air to circulate throughout the home.

Though a crawlspace cannot be utilized as a living space, it can be used for storage of infrequently used items. One should be cautious in doing so, however, as moisture from the damp soil, along with humidity from crawl space vents and water seeping through permeable concrete, can and will create a breeding ground for mold and mildew to form on any organic surface, including cardboard boxes, wood floors and even some types of insulation. Overall, a crawlspace can serve a variety of purposes, not the least of which is the actual foundation of a home. And, as such, it should be treated like the rest of the home.

Why Vented Crawlspaces Are So Yesterday

It was once thought and actually mandated by the International Residential Code, that homes built on crawlspace foundations should be vented to the exterior. The original purpose of these vents was to bring in fresh air from the outside and circulate it with the air in the crawlspace, along with providing an escape for accumulated moisture. Initially, it seemed that venting solved the problems of crawlspace moisture and air circulation. Many homeowners, however, who still experience mold and decay, termite and other pest problems, along with increased condensation, misunderstand the problem and simply increase this ventilation.

Lots of older homes were built without central air conditioning and were cooled by putting fans in the windows. These days most people consider air conditioning to be a necessity. And, in most cases, ductwork is installed in the crawlspace where the ducts can most easily connect to the various living spaces within the home. These conditions have radically changed how homes “breathe.”
We now know that venting is not a great solution for keeping crawlspaces clean and dry. Indeed, venting will only help increase moisture levels if the outside air is dryer than the air inside, or when enough hot outside air enters and warms the area. New studies have shown that as air enters the crawlspace through the foundation vents and comes in contact with surfaces that have been cooled by the cold air in the ducts, the dew point is reached and condensation occurs. And when condensation forms on various surfaces within the environment, you have the ideal environment for mold, mildew, and the accompanying problems they create in your home.

Installing a high-performance vapor retardant material to cover the crawlspace floor can help solve the problem. In a vented crawlspace, our system can be used to keep much of the ground moisture out of the living space. The Your Crawlspace vapor barrier effectively blocks water vapor and eliminates the need for vents altogether. As some building codes still mandate these sorts of vents, contractors must check local building codes prior to installation.

Contractors Will Recognize These Common Crawlspace Terms

Crawl Space Insulation

As many of us know, homes that are built over a crawlspace often suffer from moisture related issues due to the crawlspace’s surroundings. Naturally, when moisture mixes with wood it creates a recipe for mold and other problems like termite infestation, which often lead to the deterioration of a home. Because indoor airflow naturally rises, using a vapor barrier and dehumidifier together in the crawl space can dramatically decrease the amount of moisture and soil gas present in the crawlspace. This can greatly reduce the risk for:

  • Mold
  • Mildew
  • Wood rot
  • Floor failure
  • Decreased insulation R-values
  • Increased heating & cooling bills
  • Odors
  • Insects
  • Dust mites
  • Aggravated allergies
  • Poor storage environment
  • Poor indoor air quality (IAQ)


Water can permeate the crawl space through the earth around the customer’s home, from any number of plumbing issues or through moisture entering the crawlspace vents. What results is a transformation from a crawl space to an actual breeding ground for mice, rats, snakes and other creatures that can thrive in this damp, dark habitat. Keep in mind that as warm air rises through a customer’s home and leaves through the upper levels, crawlspace air is pulled up into your home with it. As the warm air rises, there is nothing to stop the humidity, mold spores, dust mite waste, and odors coming up with it.

Insulating a crawlspace that is vented is a sticky situation. Insulation will not keep humid summer air or cold winter air away from a structure’s floorboards. Most standard insulation vapor barriers will allow moisture and mold to soak through the material, weighing it down and causing it to crumple onto the floor. And, as we all know, that is no good for a home.

Some contractors usually lay down a very thin, non-fire-retardant 4 or 6-mil plastic liner that does very little good since air can still enter from crawl space doors, vents, pipes or other permeable openings. Furthermore, most standard vapor barriers will either be attached by a seal tape or be stapled to the wall. The problem with this is that in one case it defeats the purpose of a liner by injecting holes into it. And the other creates a rumpled-looking effect in the crawl space. Utilizing an adhesive liner not only ensures longevity, but customers will also appreciate the cleaner and tidier aesthetic. The vapor barrier must cover all areas, including the foundation walls and piers.

The bottom line is that a durable, 12-mil, adhesive strip, water-proof, anti-microbial, fire-retardant and puncture resistant vapor barrier like the Your Crawlspace system can transform a moist, unhealthy crawlspace breeding ground into a clean, sanitary environment that no longer promotes mold, odors, pests and even potential infestation. The customer can rest assured that the crawlspace can even be used for storage purposes and ultimately fulfill its purpose of promoting healthy air circulation and reducing overall humidity in the house. And, of course, a vapor barrier just makes the crawlspace look a whole lot more attractive!

Your Crawlspace FAQ

Where can I find a reputable contractor to do my installation?
We are in the process of putting together a list of contractors who install the Your Crawlspace vapor barrier and encapsulation systems. It will be posted on our website shortly. In the mean time, give us a call (877-442-7295) and we’ll put you in touch with an installer who uses our system. Or email us at

How do I know if the job will require a sump pump?
A sump pump is typically used to discharge excessive water build-up that accumulates in the crawl space. It’s usually only required if drainage by gravity is not possible. As you probably know, some sub-areas have what is called a “drain to daylight” drainage system that allows water to pass through or under the foundation wall.

Where can I find information regarding crawl space building codes?
Our Research & Resources section provides access to documentation regarding most crawlspace issues, including building codes and research and reports. Always check with the local building department, however, for specific codes relevant to your job site’s area.

I want to share my Your Crawlspace experience. How do I do that?
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Your Crawl Space, Inc, Waterproofing Materials, Mount Pleasant, SC