Everything You’d like to Know About Crawl Space Ventilation

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Until recently, many homes with vented crawl spaces were constructed with almost no regard to moisture sources. Moist outside air would get into the crawl space, accumulate, then condense on the wall, floor, and insulation. This would set the stage for mold growth and other problems.  

Some people are still skeptical about the effects of crawl space venting on their homes. If you’re among them, read on and see how venting affects your crawl space and home. We’ll also show you how to curb moisture. 

History of Crawl Space Venting 

Crawl space ventilation remains a gray area for many people. From the 1930s until recently, homeowners observed certain building codes. Crawl spaces in Moberly, MO, were built using hollow masonry blocks or poured concrete, and their foundations were fitted with permanent vents that went outdoors. The HUD standard recommended four crawl space vents on every floor area with the ground uncovered. People were also encouraged to set up two vents on opposite walls.  

These fixtures were designed to promote cross-ventilation to curb moisture buildup. What most people didn’t know was venting contributed to moisture buildup, which triggers severe structural damage and health hazards.  

Where Do Air Leaks Come From? 

Air leaks in your home come from different sources. The first is the junction of the floor/ceiling with the external wall. Another source is the junction of the separating walls with the external wall.  

Air also penetrates through gaps in your electrical and plumbing installations. Chimney and ventilation ducts that go through the air barrier can also let in air. Other sources are leaks around electrical sockets, windows, and doors. 

Crawl space standards required ground cover to be used together with ventilation. Despite the fact that builders still use ventilation codes from the 1930s, they have some leeway on how they can control moisture.  

Dealing with Crawl Space Moisture 

Combining ground covers and air change has always been the accepted method of regulating crawl space conditions.  

Some local contractors use a light sheet of expanded polystyrene together with an increased air exchange rate in summer. An alternative solution is covering the ground with polystyrene and reducing the air exchange rate to 0.5 ach. This solution results in lower RH values and mold growth.  

Building experts generally recommend these tips to eliminate moisture problems: 

  • Seal all the ductwork and create proper return pathways for air. 
  • Set the AC thermostat above the dew point. 
  • Resolve long-standing negative pressures associated with ventilation equipment or air handler fans. 
  • Fast-track moisture removal by correctly sizing and maintaining the equipment. 
  • Remove ground surface water and apply an ample moisture and vapor barrier
  • Remove the improperly placed barriers and position them correctly. 

Experts no longer advise their clients to use passive venting or temperature-controlled venting. If an inspection reveals a perennial moisture problem, the right thing to do is seal the crawl space with vent covers and a vapor barrier and condition it. But that’s not enough. You’ll need to dry out this area and add some heat. 

Should You Ventilate the Crawl Space? 

Numerous studies have shown that venting the crawl space is a bad thing. Venting lets in moisture-laden outside air, which leads to higher humidity. Moisture buildup also sets the stage for condensation, mold growth, insulation damage, wood rot, and pest infestation.  

A study that was done in 1985 showed a significant volume of air moved from the crawl space to the living area. Worryingly, crawl space vents nearly doubled radon gas contamination, the bulk of which ended up in the living space. 

That’s not all. Indoor air will turn acrid. Heating costs will go up too. If you don’t want to endure any of these unpleasant consequences, seal the crawl space, and condition it from inside. Another useful solution is an energy-efficient dehumidifier that cleans and filters the air, controls moisture and humidity, and reduces odors and the potential for mold growth. 

Benefits of Sealing the Crawl Space 

Sealing your vented crawl space and conditioning it is beneficial in a number of ways. Since there’s no outside air, you won’t experience condensation and mold growth. Your crawl space will become warmer and the quality of air inside your home better. Heating costs will go down too. Best of all, you’ll get a dry, clean space you can use for anything. 

Interestingly, people still debate whether to seal the crawl space vents or not. Research has consistently shown us that outside venting is a conduit for crawl space moisture in humid weather. Don’t let crawl space moisture cause you sleepless nights. Get in touch with the experts at Foundation Recovery Systems for a free crawl space inspection and quote. We can help you evaluate the interior and exterior components of your home and take remedial measures to combat unwanted moisture.