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Crawl Space Ventilation 101- A Handy Guide for Homeowners

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poor crawl space ventilation

For many years, conventional crawl space ventilation wisdom meant home construction specs in Denver, CO, had to be consistent with building codes. That’s what many people did. No one questioned the logic of having crawl space vents. However, things started changing in the mid-1980s.

If you’re struggling to make sense of crawl space vents or looking for ways to protect the crawl space and still condition it, you’re in the right place. This post will shed some light on crawl space ventilation, help you understand what makes your crawl space moist, and measures you can take to resolve the problem.

Crawl Space Ventilation Research

Experts have studied crawl space ventilation and air movement for years to understand the effects our building choices have on indoor air quality, energy costs, and moisture levels. They observed that venting was ineffective, depending on the source and amount of moisture. Here’s what they found out. When warm, moisture-laden air got into a cool crawl space in summer, moisture levels and condensation increased drastically. This worsened the moisture situation in the crawl space instead of alleviating it.

By 1985, research had conclusively shown there was significant air movement from the crawl space to the living space. And where crawl space vents were present, radon gas contamination doubled. Fifty percent of the gas ended up in the living space. A 2013 study has shown that vented crawl spaces in hot and humid areas tend to experience a surge in moisture levels instead of a decrease.

What is Behind Crawl Space Moisture?

Experts were eager to uncover the source of moisture in homes with vented crawl spaces. So, they conducted studies in 1999-2000 involving 25 moisture-damaged homes. This is what they discovered:

  • Lower AC thermostat setting (below the dew point)
  • Negative pressure from duct leakage, inadequate return paths, and door closures
  • Oversize air conditioners
  • Inadequate moisture removal from detached return ducts
  • Moisture infiltration from the ground due to poor drainage
  • Improperly placed vapor barrier

Best Ways to Control Crawl Space Moisture

Seal the crawl space vents with vent covers (to block outdoor air) and convert it to a conditioned space. Depending on the weather conditions in Denver, CO, heating up this area can help keep it dry and prevent freezing.

Next, seal interior leaks. Close off openings around wiring, pipes, or framing between the crawl space and overhead areas. By doing so, you’ll stop cold air from getting into occupied spaces. This step also stops mold, allergens, and moisture from floating into your home or building.

Determine and cure moisture sources such as gutter spill and downspout effects around your foundation. Coupled with in-slope grading, this will keep the foundation dry.

Install a 20-mil vapor barrier over the crawl space floor and over the walls and have your crawl space inspected at least once a year to ensure the vapor barrier is working properly.

Having an energy-efficient dehumidifier also will help keep excessive moisture and humidity in check. Opt for a dehumidifier that will also clean and filter the air, as well as reduce odors and the potential for mold growth.

What Can You Do with a Sealed Crawl Space?

Converting a vented crawl space into a conditioned space without vents offers you the same benefits as any homeowner with a basement. You’ll enjoy greater energy savings, better comfort, and bring moisture under control. What’s more, your loved ones will live and breathe easy, as the air is fresh. Because the crawl space stays dry, it will remain intact for many years.

Crawl space ventilation codes from the 1930s are still in use today and remain unchanged. However, they provide builders with flexibility in moisture control methods. Get in touch with Complete Basement Systems for a free crawl space inspection and quote and find out the best way to create a dry, clean, and warm crawl space.

Serving Greater Denver area, Colorado Springs, Eastern Colorado, and parts of Nebraska and Wyoming

Colorado Springs, CO

707 County Line Rd.
Palmer Lake, CO 80133

Denver, CO

4686 Ivy St
Denver, CO 80216