2-10 – Crawl Spaces :: The Construction Management Pro

2-10 – Crawl Spaces

On 1-4-10 I wrote a post conering the USGBC recommendation regarding ventilation of crawl spaces. I have done some additonal research on the subject. The main problem with crawl spaces come from moisture and temperature variances. Comparative studies conducted on crawl spaces conclude that encapsulation and conditioning systems perform better than crawl space vents in preventing moisture problems, and improve a home’s energy efficiency and indoor air quality. Vented crawl spaces have been the norm for many years. One paper shows why this traditional building technique is now problematic. Read more 

To keep moisture out of crawl spaces, the walls and floors need to be sealed with a vapor barrier. If ductwork is installed in the space, it should have its seams properly sealed. This is done to prevent the introduction of humidity. In addition, the floor above should be insulated. The floor acts like a heat sink causing the occupants to feel colder. Floor insulation then reduces the tendacy to increase the ambient air temperature. lastly, the crawl space should be provided with conditioned air from the homes HVAC system. Ok, what if the home has no central air or hot air system? Conventional wisdom is that if properly sealed, conditioning the crawl space in older homes is not necesarry. However, the space does need a dehumidifier to ensure low relative humity.

With a properly sealed crawl space, the accumulation of noxious gases could be a problem (radon and carbon monoxide). This space needs to be monitored and if this becomes a problem it would be necessary to follow the EPA recommendations for the mitigation of radon gas. This means the installation of an exhaust fan; and you thought this was going to be complicated and costly :~)

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