Crawl Space Ventilation

Your crawl space is perpetually wet. Wet soil. Wet insulation. Dripping pipes. Evidence of rot on joists and rust on ducts. Your problem may be that you still think that you should be ventilating your crawl space. Don’t feel embarrassed. Not so long ago, building officials thought so, too.

Old crawl space thinking and old building codes had builders placing crawl space vents on opposite sides of the house hoping that outside air would enter a vent on one side of the crawl space and exit out the vent on the other side. The idea was that this would remove damp, musty crawl space air with clean outside air.

That's not how it works

Telltale signs of too much ventilation

  • Soggy, sagging insulation in summer
  • Cold first level floor in winter
  • Muddy crawl space floor
  • Evidence of rot on framing
  • Rusty duct and metal posts

Air movement moves upwards in a house, like a chimney. Called the stack effect, it draws air inward from crawl space vents and into the living space of the home, eventually exhaling this air out of the upper levels.

During humid summer months, the air drawn into the crawl space would dump its moisture, in the form of condensation on every cool surface it passed. Crawl space vents also increase associated heating costs in the winter by sucking in cold outside air. It was lose/lose situation.

CrawlSpace Ventilation Diagram

A better way

Closing crawl space vents and encapsulating the crawl space with a vapor barrier has proven to be the best solution to handling crawl space moisture problems. The crawl space walls and floor is sealed with the vapor barrier, and so are gaps or holes to the outside. Basement Systems has designed an array of products to get the job done right, including its tough CleanSpace liner, airtight vent covers and hatchway doors.

Get the Facts

Gas or oil fuel burning appliances need adequate air to operate properly. Without it, a hazardous situation can occur.

Call for a free estimate and inspection from a certified CleanSpace installer. Ask your CleanSpace technician about drawing combustion air from outdoors.

Conditioning the Crawl Space Air

In many cases, encapsulating a crawl space is all that’s needed to bring humidity levels to normal levels. In some regions, however, you may need more. Ask your certified CleanSpace installer for recommendations. There are two good options for conditioning a crawl space. One is to dehumidify the space with an energy-efficient and cost-effective dehumidifier such as the SaniDry CSB crawl space air system. A less expensive option is to draw conditioned upstairs down into the crawl space with a fan, such as the Crawl-O-Sphere crawl space conditioning unit.

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