Curabitur felis erat tempus?
Bringing Light
to Tough Subjects
Unfortunately their theory was flawed. But to understand how, you first need to know
that every structure creates a natural chimney or “stack” effect on the air inside.
In other words, hot air rises up and out the attic and roof while drawing cooler
air in from the lower levels. In this manner, the earth beneath a house actually
becomes a “lower level” from which cooler air is drawn into the first level of the
house. This, in turn, draws in outdoor air through the vents. This cycle continues
year-
Ventilating does sound reasonable. Open the vents in the summer…close ‘em in the winter. However, in the summer, crawlspaces are almost always cooler than the air outdoors. When the warm outdoor air is drawn in through the vents (due to the chimney effect), the crawlspace humidity goes up dramatically. Condensation forms on the cool surfaces such as floor joists, the underside of the subflooring, insulation paper backing, debris, etc…
Close the vents during the winter, and the soil continues to evaporate its moisture into the dead air space keeping it damp.
The problem with high humidity is it promotes destructive mold growth and attracts termites, both of which can cause not only health problems but also can attack and destroy the structure itself!
Today, building codes are finally changing to allow the construction of ventless crawlspaces. Instead of insulating the bottom of the main floor, the foundation walls are insulated and a vapor retardant barrier is installed on the earth floor and up the foundation walls. There are no perimeter foundation vents.
Existing structures can be converted by permanently sealing the vents, removing the existing insulation on the crawlspace ceiling (which is the underside of the first floor), insulating the sidewalls, and encapsulating the crawlspace by sealing the