What Should I Know About My Crawl Space Vents in South Carolina?

Jan 4, 2018

Categories: Uncategorized

As the premier foundation repair company, located in Columbia and Charleston, South Carolina, we are often asked about crawl space vents. Homeowners most often seal their vents due to excess moisture in the crawl space, which can lead to a multitude of expensive problems, including bowing floor joists, mold, and insect infestation. There are a number of important considerations and remediating the issue may require other steps aside from closing your vents. In this article, we will discuss why a crawl space is essential for a South Carolina home, opening/closing crawl space vents during the winter and summer months and the pests each season attracts to your home’s crawl space.

Why is the Crawl Space Important to My South Carolina Home?

Crawl space facts:

According to a study by , homeowners can expect to reduce their energy bills by 15–18% by sealing off their crawl space. They also determined that homes with vented crawl spaces were 19 times more likely to experience relative humidity levels in excess of 70% than homes with encapsulated crawl spaces.
As much as 50% of the air in a home’s living space originates from the crawl space.
Most pests are attracted to moist environments; as a result, moisture control is an important part of any fully integrated pest management system.

Should I Close My Crawl Space Vents During the Winter Months in South Carolina?

There are a few reasons for closing crawl space vents during the winter with the first being to prevent frozen water lines and/or snow from entering. The second biggest issue has is the stack effect. The stack effect occurs when excess moisture, introduced by way of unsealed, vented crawl spaces, contributes to wood rot, mold growth and increased pest activity, including infestation and colonization. Moisture in crawl spaces often migrates to the upper levels of the home through a stack effect.

In essence, whatever air is below the house is also inside the house. As warm air rises and escapes through the upper levels of the home, new air finds its way into the home to replace what has been lost. Intake air comes in at the lower levels — through unsealed crawl spaces. This may lead to costly problems such as cupping of hardwood floors, mold growth, increased air conditioner loads, and swelling of millwork/cabinetry. Air infiltration from the crawl space often carries odors and may contribute to poor indoor air quality and uncomfortably high humidity levels.

Excess moisture in crawl spaces has also been associated with contributing to increased energy consumption. Wintertime ventilation cools the crawl space contributing to heat loss from the home. In the summer, introducing warm outside air under the home contributes to heat gains, increasing cooling loads. Ventilation of a crawl space to control relative humidity only works consistently in an arid climate. In most climates, ventilation can actually add significant quantities of moisture during humid times.

During the winter months, leaving the vents open reduces the energy efficiency of your home by allowing cold air to leak in from the outside. Also, if temperatures routinely drop below freezing, pipes in the crawl space are more likely to freeze if the vents are open. One school of thought has always been to close vents during the winter and open them during the summer to allow moisture to escape. However, it’s not quite that simple.

What Types of Wintertime Pests Can Invade My South Carolina Home Through Crawl Space Vents?

Nobody wants a small village of pests and/or rodents living under their home, especially with young children or pets around. But pests and rodents are naturally drawn to places that are warm, infrequently visited, and have access to food. Not only are these creatures creepy and crawly, but they can damage electrical wiring and ductwork, which can cause major issues or result in total power loss. They can even enter the house and leave unwanted droppings on any available surface (including your food), increasing the chance of diseases and dramatically lowering the air quality of your home. You can stop the spread of mice, rats, squirrels, roaches, spiders, and all other pests by hiring a professional to clean the space and do some serious pest control.

These pests include:

House Mice. The house mouse is the most commonly encountered rodent in the United States. House mice usually nest in dark, secluded areas like attics and crawl spaces. This rodent can cause serious property damage by chewing through drywall and also wires that can then spark an electrical fire. House mice are also known to contaminate food and spread diseases, including Salmonella and tapeworms.

Brown Recluse Spiders. Brown recluse spiders prefer to spin webs in undisturbed places, such as closets, attics, crawl spaces, and basements. Like other types of spiders, the brown recluse is frequently found inside cardboard boxes, along window moldings and in seldom-used clothing and shoes. These spiders can bite and inject venom if disturbed, making them dangerous to humans.

Norway Rats. Norway rats often nest in basements, crawl spaces, piles of debris and other undisturbed materials. They are known to gnaw through almost anything – including plastic or lead pipes – to obtain food or water. Norway rats are also a vector of many diseases like jaundice, rat-bite fever and cowpox virus.

Should I Close My Crawl Space Vents During the Summer Months in South Carolina?

During the summer, especially during July and August, it may be wise to close foundation vents to prevent the muggy air from entering the crawlspace and condensing on cool surfaces, especially air conditioner ductwork and associated equipment. This “sweating” can be more severe when occupants maintain indoor temperatures less than 75 degrees or so. Since insulation, floor joists and ducts are porous and readily wick water vapor from the air, the crawl space can quickly trap large amounts of moisture.

If you keep the interior of your home cool in the summer, this can increase the amount of water pooling in the crawl space due to condensation. While leaving the vents open theoretically creates an escape route for moisture, a cool crawl space may, in fact, be drawing outside moisture in through the vents. If you live in a region where the relative humidity is high for most of the year, chances are you would benefit by completely sealing your crawl space.

What types of Summertime Pests Can Live in My South Carolina Crawl Space?

Centipedes. Centipedes are easily identified by their multitude of legs and ability to quickly dart around rooms. They are especially drawn to crawl space during the summer months because of the moist, dark environment that often exists.

Crickets. Camel crickets, house crickets, and spider crickets are among some of the most prominent basement bugs. Most clients can easily identify cricket infestations by hearing the loud chirping at night time that is unique to crickets alone. Crickets can cause damage to clothing by creating large holes in fabric and synthetic materials. This type of activity can exponentially increase as the weather changes from warm to cold. Crickets the migrate indoors to seek shelter and most importantly, moisture, in potentially very large groups in the thousands. You are most likely to find these pests hiding in dark, damp environments such as basements and crawl spaces.

Wood-boring Beetles. Perhaps the biggest concern with wood-boring beetles is they can infest the framing of homes and jeopardize the structural integrity of wooden buildings. Because the damaging insects thrive in particularly moist wood, homeowners should fix any plumbing leaks and eliminate the presence of excess moisture in the crawlspace and other locations where the wooden framework of the house remains most susceptible to attack. Reducing moisture levels may help prevent infestations.

If you are considering opening or closing crawl space vents for the season and have questions or concerns, contact the professionals at
CNT. With over 15 years of experience solving foundation and crawl space issues, we can help.