3 Summer Crawlspace Tips

keep your crawlspace vents closed in the summer

If your home has a crawlspace, there’s a good chance you’ve never been in it. It’s just this mysterious, narrow grotto underneath you, that avoid or even forget about until you sell your home, or it presents symptoms of defects. These symptoms can include smells, soft floors, or sticking doors and windows.

3 summer crawlspace tips


When we do an inspection, we inspect the Crawlspace last and everything can be going fine right up until then. The condition of the Crawlspace can make or break the deal. A wet moldy crawlspace can cost several thousands of dollars to address. If it’s been an undetected chronic issue, there can be wood rot or termites that can easily the double the cost of repairs. It doesn’t need to be this way though. A little effort can a long way to preventing costly repairs. That’s why I wrote this blog 3 Summer Crawlspace Tips 

  1. Keep your crawlspace vents CLOSED all year long

We get asked this all the time.

“Should I open my crawlspace vents?” or “When Should I close my crawlspace vents?”

Yes I said keep them closed all year long. Close your crawlspace vents in the summer. Close your crawlspace vents in the winter. Close your crawlspace vents in the spring and fall. CLOSE YOUR CRAWLSPACE VENTS.  Yes, I know your dad doesn’t agree. I’m going to try to break this down Barney style. There are three important things to understand; temperature equilibrium, dew point, and humidity.

Temperature equilibrium is when two spaces of air (or any two objects) transfer energy until they’re the same temperature. The hotter space will transfer its energy to the cooler space.

Humidity – or rather relative humidity is the amount of water in air, in the form of vapor, compared to how much water it can hold. Hot air can hold more moisture than cold air. 

Dew point – this is the temperature air must be cooled to achieve 100 percent relative humidity. Remember, cool air holds less moisture than hot air, so given the same amount of water, as air gets colder, the relative humidity gets higher. This why relative humidity is highest early in the morning (coldest part of the day) and why you have dew in the morning.

One last thing. Crawlspaces are always cooler than the outside temperature in spring and summer because they’re dark and shaded. There also may be an air handler or ducts that keep it colder. 

When you open your crawlspace vents, hot humid air will be pushed into the crawlspace as the two spaces work towards temperature equilibrium. As the hot humid air is cooled in the crawlspace, the relative humidity is increasing, potentially reaching the dew point. Once the crawlspace reaches dew point, you will have condensation forming on all the colder surfaces such as pipes and ducts, but even wood and insulation. 

A wet crawlspace encourages mold growth, rot and decay. 

  1. Improve the vapor barrier 

The vapor barrier is the plastic that is (or should be) on the ground the crawlspace. It blocks water vapor, which is water that evaporated in the soil is making its back into the atmosphere, from going into your crawlspace. Remember, if you’re adding water vapor to your crawlspace, you’re increasing the relative humidity and  runing the risk of allowing your crawlspace to reach its dew point. 

The vapor barrier is never as good as it should be. It should be free of holes and sealed along all the joints and edges. Take an afternoon to improve your vapor barrier. It’s not fun, but neither is a 20k crawlspace repair bill.

  1. Keep an eye on your crawlspace 

It takes a while for moisture to start rotting your joists and damaging other components. Sometimes, you won’t be able to prevent needing to fully encapsulate your crawlspace, but you can prevent thousands in structural repairs. Check your crawlspace weekly for termites, moisture, mold, and leaks. If you see any of the above, you can quickly get it addressed before the problem festers and makes a mess of your crawlspace. 

Perhaps once or twice a year get a professional in there such as termite inspector, or home inspector. 

Check Out Our Post About How to Inspect for Termites in Your Crawlspace