Crawlspace ventalation

I was speaking to a local contractor this week and he told me the building industry is moving toward not ventalating crawlspaces. He said this does not allow the humid air from the exterior to enter the crawl.

Has anyone else heard this? ANd how are you reporting unventalated crawlspaces?

I am looking for oppinions either way on this.

Thanks in advance for the input.


Do a google search and you can find more info. Here are just a sites few I came across regarding unvented crawlspaces.


very helpful


Very expensive. Generally speaking, you won’t see many conditioned crawl spaces, except for high end homes.

Then…the vented crawlspaces should have HUGE vents so that the vent space will be able to maintain the temperature of the outdoor air. Without the big vents, the cool temps in the crawlspace will encourage condensation of the warm, humid air entering, leading to mould and possibly wood framing rot.

All these system start off nice…look nice… and hold down the odors and stuff… but then as time passes we see problem pop up. if the sub-ar was subject to water before we will find water under the covering and on top of the covering. this starts off as a moist area with (NO) ventilation an stuff starts to grow under the covering. Sub-termite can Gerta foot hold into the framing. the can make finding them harder and then treatment is now harder to do and cost more. In my area north of San Francisco these are just some of the problems I see with the sub-area covering.

Mold and other fun stuff
Sub-termite infestation
Harder to do soil treatments for termites
Standing water on top of the plastic or covering
No access to the soil for inspection of the ground condition



lower end homes here built for low income are adopting this practice here, seems fine so far