05:57AM | 12/17/02
Member Since: 12/16/02
1 lifetime posts
I live in Michigan. In September of this year, I started building a new 3-bedroom ranch on a crawl space.

I insulated the crawl space walls and bonds with Polyurethane spray foam 3 inches thick.
The heating ducts run through the crawl space and are not insulated.
I have an open heat vent in the crawl space area.
The cold air returns are in the attic and they are insulated
I did not install any outside vents, figuring this would be a "conditioned" crawl space.
I am still finishing inside the house and no insulation is on the walls of the house yet
I heat the house only on weekends while working inside.
I have 3 inches of pea gravel over a dirt/clay ground
I have not yet covered the pea gravel with 6 mil plastic, but plan too.

I've noticed condensation on PVC drain pipes and on the underside of the flooring between joists starting just inside the insulated bond area. It has only been about a 1-1/2 months and already I am seeing some mold/mildew forming on the underside of the flooring between the joists.

I am concerned with the mold/mildew forming so quickly, so I was considering spraying the flooring between the joists (using a garden sprayer) with bleach or TSP to eradicate the freshly formed mold/mildew. I would do this before covering the pea gravel over with a 6 mil plastic vapor barrier. Once that was done, I was going to seal up the entry.

Am I doing all that I can or should do, or do I need to do something more or differently? Any suggestions would be appreciated. Do I need to put a humidifier down in the crawl space for a short period of time to dry it out after spraying or just cover it with the vapor barrier and let gravity deal with the problem? Is the spraying of bleach of TSP recommended or an overkill on my part?

Thank you,

Thomas Miller
[email protected]


03:54PM | 12/28/02
Member Since: 11/06/02
1280 lifetime posts
Spraying a ten percent bleach to kill the mildew is OK. It will probably stop growing once you control thew moisture problem. You don't want a humidifieer which will add moisture. You have ground water rising and evaporating into the air space under the floor and then condensing on the cold surfaces of the wood when you shut the heat off. Alternate cooling and heating encourages this percipitation.
The time to put down a vapour bar on the ground was yesterday. That will prevent moisture from rising. The condensation will happen on the bottom of it. Peastone will likely tear holes in regular plastic when you crawl over it so you will have to double it up with another layer after you are doine working down there and the house is built.
Heating the place all week will also help. Just turn it way down.
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