If your fall allergies feel worse at home, your crawl space may be the problem.
For most people, home is supposed to be a safe haven from allergies. You spend a spectacular Charlotte fall Saturday out in the yard, raking leaves and chasing the kids around, but also sniffling and sneezing the whole time. When you come in and shut the door, relief should be there to greet you. But it doesn’t always work out that way.
That same night, the temperature dips and the heat comes on for the first time since March. As the warm air rises, your home pulls replacement air from its lowest level. In a lot of Charlotte-area homes, that’s the crawl space, where humid air has soaked in all summer. And that’s where things get tricky.
Research for the U.S. Department of Energy’s Building America program found that in homes with vented crawl spaces, about 40% of the air inside came from the crawl space. Many Charlotte homes also have vented crawl spaces. If it gets damp down there, which isn’t very hard for it to do considering our climate, the air coming up can carry mold spores, plus the extra moisture dust mites need to thrive.
You may have slammed the door on ragweed and other common fall outdoor allergens when you came inside, but your house could be passing its own allergens up through the HVAC vents and your floors.
Enough With the Allergies Already
If you’re an allergy sufferer, by Halloween, you’re waiting for the tissue packs and allergy pills and seasonal nightmare to end.
Unfortunately, when Charlotte’s warm weather extends into fall, like it has this year, ragweed hangs on into November along with other late weeds like pigweed. Wet leaf piles add mold spores to the mix.
But all of that is outside. Surely, inside has to be better.
Why Coming Inside May Not Help During Fall Allergy Season
For a while, it probably will. But then the sneezing starts again. And your nose gets stuffy. You run an air purifier, swap out the HVAC filter, and still can't figure out what you're missing. After all, you’re inside.
As we’ve already touched on, if your home has a vented crawl space, you may be sitting directly above the problem. Building scientists call the upward pull of air from underneath the stack effect, and it depends on which way the temperature difference runs. In summer, with the AC on, your house is cooler than the air outside, so the upward pull weakens. Once the heat comes on, the house is warmer than outside, and the pull gets stronger.
The DOE research behind the 40% figure measured it in November, so at this exact time of year. If you’re sitting in your living room reading this and your home has a vented crawl space, a good share of the air you’re inhaling probably came from underneath your house.
That research also tested crawl spaces that had been sealed and fitted with exhaust fans. In those homes, the share of indoor air coming from below dropped to about 5%.
So, the bad news is that crawl space air quality becomes part of your home’s indoor air quality. Whatever’s going on down there spreads. The good news is you can improve it.
How Crawl Space Allergies Reach Your Living Room
In a vented crawl space, humid Carolina air comes in through the vents all summer and settles in. Mold is more likely to grow once humidity tops 60%, which is easy work for a Charlotte crawl space in the summer.
People often blame mold allergies in the fall on wet leaves outside. But a damp crawl space keeps mold growing long after the last fall leaves are bagged, and that mold doesn't always stay where it starts.
In a study of 238 North Carolina homes, researchers found crawl space mold spores traveling into the living space in about 1 in 5 homes, and they pointed to the heating and cooling system as a popular transport system. In many homes, the ductwork runs right through the crawl space, and gaps in the ducts can pull the air straight into the system.
Dust mites don’t live in your crawl space. They’re found in bedding and upholstered furniture, and are among the most common indoor allergens. What they need is humid air. Dust mites do well once indoor humidity climbs past 50%. (The Environmental Protection Agency recommends keeping indoor humidity levels between 30% and 50%.) When damp crawl space air rises into your home, it brings that moisture with it and creates a welcoming environment for the mites.
Signs Your Crawl Space May Be Giving You Allergy Grief
Anyone with allergies knows how miserable they can be. What’s harder is noticing where and when they flare up. If you want to see if you have an indoor allergen problem, watch for these signs, with the first one being most obvious.
- Your symptoms are worse inside than they are out in the yard/world.
- Your symptoms linger even after the first frost of the year, which is when ragweed is typically done for the season.
- You notice a musty smell in your house, especially when the heat first kicks on.
- Your indoor humidity level reads above 50% consistently.
- You see condensation on windows or ductwork.
None of these prove your crawl space is to blame. Seeing an allergist and getting tested can help pinpoint what you’re allergic to. However, if a few of these signs show up together, you should take a closer look at what’s happening in your crawl space.
Making Home an Allergy-Free Zone
No matter the season, moisture is almost always the culprit when it comes to problems in your crawl space or basement. The best place to start fighting it is with a humidity monitor. If readings stay above 50% consistently, you know you have a moisture problem, and it’s probably best to call in the professionals.
A professional inspection measures moisture and checks for mold. It should also identify where outside air and water are getting in so you can eliminate the sources. This should be part of any estimate you receive. If a waterproofing company doesn’t include eliminating the moisture source in their estimate, find yourself another company.
The prescribed fix depends on what the inspection turns up. For some homes, a vapor barrier is enough. Others need full crawl space encapsulation, with a dehumidifier to hold humidity in the right range. Our comparison of vapor barriers vs. encapsulation walks through the difference between the two and should help you understand the benefits of each option.
Breathe Easier
In their most tolerable form, seasonal allergies are still really annoying. At worst, they can pose serious health problems for an allergy sufferer, especially layered on top of underlying conditions.
When you go outside, you can’t expect to avoid allergens completely. That’s not the way Mother Nature works. But the expectations for inside your own home should be different. Inside, you’re in control, or at least you should be.
Moisture Loc has worked in Carolina crawl spaces for nearly 40 years. If your allergies aren’t improving significantly when you move from the front porch to the master bedroom, schedule a free crawl space inspection.
We'll show you what's going on down there and how you can make your home the safe, sneeze-free space it should always be.