To Vent or Not to Vent

Cottage Country has numerous structures that do not have basements. Many of these are on piers or have a closed crawlspace with foundation walls. There are many aspects about these situations I could talk about. Today we are going to address ventilation of a crawlspace.

First of all lets determine what a crawlspace is.  A crawlspace would be considered the area beneath the main floor of the structure that does not have sufficient height, or depth depending how you want to look at it, to walk comfortably. Having said that there are plenty of basements, or cellars as we older people like to call them, in old houses with rubble stone foundation walls that I cannot walk comfortably in.

There are two types of crawlspaces - open and closed. The open crawlspace (fig 1) has no foundation walls to support the structure. Piers and beams support the structure. The closed crawlspace (fig 2) has foundation walls around the perimeter that support the structure with possibly some piers and beams inside, depending on the size of the structure. The closed type of crawlspaces can be divided into sub categories of conditioned and unconditioned. A conditioned crawlspace (fig 3) is one that maintains a minimum temperature of 10 degrees Celsius and of course an unconditioned crawlspace has no heat source.

Fig 1
Fig 1

Fig 2
Fig 2

Fig 3
Fig 3

What we want to talk about today is ventilating a crawlspace. Let me start by saying that there is no good way to ventilate a crawlspace. History has taught us that the idea of ventilating a crawlspace in the warmer months to rid it of humid moist air and dampness that can cause wood rot does not work. The intention was good but the result was not there. The problem is in the warmer months the outside air is usually quite humid. The vents allowed this warm moist air to enter the cooler crawlspace and condensation occurred adding to the problem of dampness and eventually wood rot.

If your cottage is on piers it is best to keep it as a completely open crawlspace with no skirting around it. Let the air flow freely.

If your cottage or home has perimeter foundation walls with a crawlspace and there are vents in the walls that you typically close in the colder months and open in the warmer months I recommend creating a completely closed and conditioned crawlspace. Seal the vents and insulate the foundation walls. Install vapour barrier over the dirt floor. Then heat the crawlspace to maintain a temperature of between 10 and 15 degrees Celsius.

I will talk about proper insulating and vapour barriers in future articles.   

For more information on Steve Bowman and Top to Bottom Home & Property Inspections:



Telephone: 705-380-2578


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