Let’s be real — not many of us invite our friends over and say, “let’s go check out the crawlspace.” They are areas that are historically dark, dank, and full of mold and critters. Have you ever seen a camel cricket? It’s enough to make you never want to visit your crawlspace again.
So what is the issue and how can we turn the crawlspace from a dungeon of doom into a clean, healthy environment for our home and air exchange systems?
The main issue with crawl spaces in North Carolina is moisture. A damp crawl space can be a breeding ground for issues like mold, pests, rot, and high energy bills. Because our heating and cooling systems are often located in the crawl space, the air in our homes can be polluted by the conditions of the crawl space.
An unhealthy crawl space can exacerbate conditions such as asthma or allergies, resulting in unhealthy people. Studies have shown that high moisture levels in vented crawl spaces in the Southeast were linked to high mold counts inside the living space.
Turns out, keeping a vented crawl space dry in North Carolina is really hard which is why we recommend a sealed crawl space strategy.
If you have a vented crawl space, the original guidance for vents was to close the vents in the spring when you start using the AC and open vents in the fall when you switch the heat back on. Unfortunately, this crawl space strategy just doesn’t cut it when we consider the impact of a year-round humid climate in North Carolina. Through building science, we can see the true reasons that vented crawl spaces are so troublesome in the Southeast. Spoiler alert — it’s about more than just opening and closing the vents.
It is also advisable not to use your crawlspace for the storage of any potentially hazardous or noxious chemicals such as paint or gasoline. Even in a well-air sealed house, there is often connectivity between the air in the home and the crawlspace. Don’t store any chemicals in the crawlspace that you would not store inside of your home.
Sealed crawl spaces create a much friendlier environment for you & your home. There are many benefits to having a sealed crawl space, especially in our humid North Carolina climate. These are the top 3 benefits of a sealed crawl space:
From an energy standpoint, since all your ducts are in a nice conditioned environment, rather than an unconditioned crawl space or attic, you’re getting a lot of benefits. If you have your ducts in an unconditioned space, they’re fighting the outdoor air temperature while trying to condition the air that’s going into a house, which causes your equipment to work harder.
Moisture management is one of the number one issues we face in North Carolina. (More on moisture management in the humid southeast.) Sealing a crawl space offers the ideal strategy for starting at the ground up in managing humidity and the moisture coming through the ground to the building structure. Less moisture means less risk to the structure, which creates a much friendlier environment for your building structure.
Believe it or not, air entering the house can come up through the crawl space, so by managing the air quality in that space, you’re contributing to the indoor air quality inside the home.
So long as you’ve thoroughly air sealed the crawl, are supplying adequate supply air, and are monitoring moisture levels an active dehumidification system shouldn’t be necessary. Should you see levels spike or have challenges with maintaining healthy humidity levels a dehumidification system might be something you’d want to explore.
Here are the components to creating a properly sealed crawl space:
By grading to the lowest point and adding a drain (like a French Drain), we can provide a drainage path for any water that gets in the crawlspace. This is a critical failsafe should a leak occur.
Adding conditioned air to the space regulates the temperature but more importantly, it creates positive pressure, which keeps vapor from coming in. Air and moisture want to move from high to low pressure so think of the space like an inflated balloon.
Mechanical dehumidification (dehumidifier) is the alternative to supply air. As mentioned above you don’t need both, but you need one of the two. A dehumidifier offers more control of humidity levels.
Closed crawl spaces will have the lowest year round cost of operation when compered to a vented crawl. A HERS score can drop about 3 HERS points when changing a vented to a closed crawl in the average 2,000 sq ft home (assuming ductwork moves to a conditioned space).
As with most things in life, the devil is in the details — especially when it comes to crawl space encapsulation. Having a third-party energy rater inspect the installation and performance test the home helps ensure all the components are working as intended.
If you’ve got a spooky crawl space or questions about your building strategy, don’t hesitate to reach out! Schedule a meeting with one of our building science specialists or fill out the form to get started.
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