Winter is coming and it’s time to review the popular but unwise practice of closing the foundation vents around a home. Many homeowners and maintenance people do this in the belief that they are conserving heat during winter. Instead, they are causing serious building damage and heath problems. Unfortunately, many hardware stores sell products specifically made for closing the vents, adding to the confusion of this potentially harmful misconception.
 
Closure of crawlspace vents is definitely a widespread problem. As a means of winterizing a home, it misses the entire purpose and intent of ventilating the area. Winter is when ground moisture most commonly occurs under a building. It is the time of year when vents are most needed to prevent dampness, condensation, and resultant moisture damage. Closing the vents wrongly assumes that there is a need to retain heat in the sub area. Instead, heat should be retained within the dwelling by installing insulation in the floor framing. The sub area needs to be dry, not warm.
 
A power vent system, in addition to improving venting and moisture removal, serves to vent out other gases, such as those formed from residues in termite treatment, treated wood, and radon gases. They are available for approximately $100, a small expense for the protection gained.

The key points to consider are these:
 
1. Typically, local building codes require cross ventilation of a sub floor space beneath a building, with openings equaling at least one square foot per 150 square feet of floor area. Exceptions are allowed when a vapor barrier is installed on the ground surface or when mechanical ventilation is provided
 
2. Insufficient ventilation can cause moisture condensation, resulting in fungus infection, dry rot damage, rusted hardware and mold infestation. With mold as a consideration, we are therefore concerned with health safety as well as structural damage.
 
3. Insufficient ventilation can also violate combustion air requirements for fuel burning equipment, such as furnaces.