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Open Crawl Space Vents

Due to moisture, mold growth, and flooring system failures, builders are discouraging open crawl space vents these days. Find out more.

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It’s not unusual for homeowners to change their minds about something and open crawl space vents are one of those things there has been some debate over.  

We see crawl space vents every day, but we never give them much thought. We also rarely question their functionality. In reality, improperly installed, open, or loose crawl space vents are behind some serious home issues you may be facing.  

Here, we will explain why crawl space vents are problematic. We’ll take you through the ins and outs of crawl space vents in hope of helping you realize why you should seriously reconsider how you use them. 

open crawl space vent

Crawl Space Vents 101: What Are They? 

Before we go into the pros and cons of opening your crawl space vents, it’s essential to explain what they are and what their purpose is.  

Crawl space vents are fixtures on foundation walls. Building codes across the country require every home with a below-grade level to have them. That means that if you have a crawl space, you likely have one. 

Their one and only purpose is ventilation. It makes sense to say that every closed space should have a vent enabling necessary airflow. Unfortunately, what sounds great in theory doesn’t always apply to real-life situations. The same goes for crawl space vents as they’re the reason behind moisture-related problems homeowners experience in below-grade areas. 

Also, crawl space ventilation can contribute to the stack effect. This is because open crawl space vents add to the undesirable movement of air from the bottom to the top of your home. And since below-grade areas aren’t the cleanest of places, they’ll spread mold spores, dust particles, and allergens throughout your home. 

So, Should You Seal Your Crawl Space Vents? 

It’s a logical question to ask whether you should seal your crawl space vents since they’re behind so many problems. But before we say yes, we think it’s only fair to go into detail and explain the issues that below-grade ventilation can cause. 

What Happens If You Leave Them Open? 

The original purpose behind these vents was to allow air to circulate beneath your floor in the crawl space. The idea was to prevent moisture from building up, but unfortunately, things didn’t turn out that way. Moisture is the reason why you might experience mold and rot in the lower level of your home. But that’s not all. 

Another common issue homeowners with open crawl space vents have trouble with is bursting pipes in the winter. When the temperatures begin to drop significantly, vents allow cold air to enter your crawl space. This further cools down already cold areas, seriously damaging the pipes as they will burst due to low temperatures. 

Common Problems 

But as bad luck would have it, the problems we mentioned above are not an exhaustive list. Here are four other open vent problems you might face: 

  • Prompts moisture — Keeping your crawl space vents open will allow humid air to enter the lower level of your home. Once it does, it will affect the level of humidity in the crawl space, allowing mold, mildew, and wood rot to take over and endanger your structural safety. Also, mold spores, allergens, and numerous pollutants can impact the air quality throughout the rest of your home. 
  • Encourages pests — Like us, critters also need to keep warm when the cold weather arrives. If you keep your vent open, you’re saying come on in and enjoy yourselves. A mouse only needs a quarter of an inch of space to squeeze into your crawl space. But mice aren’t the only critters who’ll get that idea as numerous other animals are always on the lookout for a place to hang out during winter. 
  • Creates inefficient energy use — Open crawl space vents will affect the energy efficiency of your home. The flow of cold air will make your furnace work harder to keep up an optimal temperature inside. While doing so, it will use more energy, making your bills much higher than they should be. The same goes for hot summer days as your air conditioning will have to keep up with the rising temperatures. 
  • Affects air quality — Leaving your crawl space vents open means that they’ll allow polluted air into your home. The air will carry dust and other particles throughout your home. Unfortunately, low air quality means a higher risk of asthma or frequent respiratory infections. 

How to Seal Crawl Space Vents 

We recommend that you seal your crawl space vents before winter. The best way to do so is to use airtight vent covers. With them in place, you’ll be able to keep the lower level of your home nice and dry. 

Numerous studies suggest that a closed crawl space means a drier and overall healthier home. But besides keeping your home structurally safe and compact, you won’t experience mold-related problems, and you’ll keep your bills lower because of higher energy efficiency. Sealing vents will keep the humidity levels under 60%, which is what you should aim for. 

Crawl Space Encapsulation 

Sealing your crawl space vents is a great first step, but it won’t be enough to eradicate all your crawl space moisture problems. Nevertheless, it’s a step in the right direction. 

Complete crawl space encapsulation can do a lot for your below-grade areas and home overall. Have a professional cover the walls and the floor of the crawl space with a 20-mil plastic vapor barrier. This will lock out the outside humid air, preventing it from entering the lower level of your home and causing harm. 

If you’d like to encapsulate your crawl space and cover the vents, contact Tar Heel Basement Systems in North Carolina to help you out. We offer a free inspection and repair quote as well. Don’t hesitate to give us a call — keep your crawl space safe and secure with our help. 

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