Your crawl space vents should always be closed and sealed from outside elements. Venting your crawl space can lead to a variety of issues. First and foremost, open vents allow moisture to enter your crawl space, creating the perfect environment for mold growth and mildew.
Vote: seal off crawl space vents
"Properly sealing the crawl space and removing the moisture from the ground and air is part of the solution that helps provide a mold-free and insect-free environment, which leads to a more energy-efficient and healthier home," says Waltz.
If you add a dehumidifier to the crawlspace, you will need to seal the vent, and the entire crawl, otherwise you are attempting to dehumidify the outdoors.
#1: Don't open them
But the Carolinas are well known for their hot and humid summers coupled with very mild winters. In a regular climate, the hot/humid summer air will add moisture to the crawl space, but before anything bad can result, the season changes to winter.
Your crawl space vents should always be closed and sealed from outside elements. Venting your crawl space can lead to a variety of issues. First and foremost, open vents allow moisture to enter your crawl space, creating the perfect environment for mold growth and mildew.
Close your vents… at least in the hot, hot Summer and the cold, cold Winter. Perhaps if you want to allow some fresh air (along with the moisture/humidity) into your crawl space then do it in the milder months of Spring or Fall.
It is always a good idea to block the vents when the crawl space has uninsulated water supply pipes if the temperature gets below freezing. Frozen, busted pipes result in paying for plumbing repairs and possible water damage.
Even if your crawl space is encapsulated, you still need to dehumidify it. This helps ensure that moisture levels are kept in check and prevents the growth of mold and mildew. It also helps control indoor air quality by reducing allergens in the air and prevents rust and corrosion of metal objects.
You don't want moisture in a crawl space because it will lead to mold growth, wood rot, and attract wood-eating pests. All this will eventually affect the structural integrity of the wooden structures in the crawl space, and your home as well since it's sitting atop the crawl space.
Crawl space encapsulation costs homeowners an average of $5,500 but typically ranges from $1,500–$15,000. See which factors will impact your total cost. Mark Howey is a licensed California building contractor with more than four decades of experience in the construction industry.
Top 4 Benefits of Sealing Crawl Space Vents
Deters deter condensation, mold growth, and pests. Heating costs could go down by about 15% Indoor air quality will improve. Your crawl space will remain dry and comfortable all year round.
When you know you've got a really bad cold front coming in, many folks recommend blocking off and insulating your crawlspace vents for those couple days. This can be done by taking a small trash bag, stuffing it with insulation, then placing it within the vented area.
It's important to remember that static vents serve a purpose, especially in older homes. They provide ventilation to indoor spaces, help regulate indoor temperatures and prevent the build-up of excess moisture in wall cavities and rooms which can lead to mould outbreaks and damage to building materials.
Crawl space encapsulation has a few negatives worth considering. Initially, the process can be costly and may not fit every budget. Moreover, if not done correctly, it could trap moisture already inside the crawl space, leading to mold growth and wood rot.
Experts suggest keeping your crawl space moisture levels below 28%. Anything higher can lead to wood rot and mold, turning your crawl space into a damp and musty environment. High moisture levels can damage ductwork, wiring, and insulation, leading to costly repairs.
In winter, particularly in cold climates, closing crawl-space vents can help prevent cold air from entering the space and potentially freezing pipes. The simplest way to close foundation vents for the winter is to plug them from the outside with foam blocks made specifically for this purpose.
Keeping it running even in winter might seem pointless initially, but keeping a dehumidifier running all year long for a crawl space is crucial for several reasons. Here are some of the most important ones: Prevention of Mold and Mildew Growth.
However, after much research and analysis, the consensus nowadays is that crawl space vents should be closed. While it may seem reasonable to keep them open for ventilation, it's quite the opposite. Open vents can lead to various issues, including moisture buildup and insect infestations.
While the idea may be to close off one area in order to make another area more comfortable, surprisingly, doing this can cause damage to your HVAC system, increase the energy needed to heat your home, and in turn, cost you more money.
Regardless of the choice, specific conditions must be met to comply with these codes. However, we firmly advocate for closing the vents year-round, as it is challenging to regulate summer humidity levels in an open crawl space, leading to potential moisture-related issues.
Don't do it.
We almost never recommend closing or sealing your crawl space vents; the architect and engineers who designed your crawl space ventilation system designed it that way for a reason. That said, our recommendation really depends on how well your space is insulated.
Summer months aren't just notoriously hot, but extremely humid. Moisture levels can shoot up drastically and remain above 60% for days. This sets the stage for crawl space condensation, a situation where warm and moist air from the outside gets inside and comes into contact with cold air.
Shutting Heating Vents in the Summer to Conserve Energy
Leaving vents closed for extended periods can cause damage and expensive leaks. That's why we recommend rotating which vents you close every few days. Doing so will help keep your HVAC system in great shape and lower your monthly energy bill.