Adjustable House-Air Drying Mechanism (for sealed crawlspaces)

By adam
November 4, 2016   Comments Off on Adjustable House-Air Drying Mechanism (for sealed crawlspaces)

This method is our 3rd choice. Various options are provided in the NC sealed crawlspace code for how to provide a Drying.

1st Choice) Adjustable Supply-Air Drying Mechanism on existing crawlspace plenum or distribution box.

2nd Choice) Adjustable Supply-Air Drying Mechanism “chased down” from the attic or interior duct-work. aka DUCTED DRYING MECHANISM

3rd Choice) Adjustable House-Air Drying Mechanism utilizing a 4″ booster fan and a fan controller.


With no access to any ductwork, we can install a small 4 inch fan, a new register, under the doorway to the coat closet for example, and pull a little air out of the house.


6″ Adjustable House-Air Booster-Fan

This client was awesome, wanted the air to come from the near area by the always cold area in their breakfast nook, / kitchen… right under this location was an exterior outlet and we tapped right into that circuit from the back of the box! This is a brand new home on a vented crawlspace foundation with zero HVAC in it. Both of the air-handlers are crammed into the attic. In need of a “Drying Mechanism” (for the sealed crawlspace) we utilized the “House-Air-Fan”.

If we had been allowed to alter the HVAC during construction of this home we would have run an insulated 6″ flex-duct down from the attic, see this:

…or better yet we would have installed an air-handler(or both) in this crawlspace because there is plenty of room for it and it would have performed better, lasted longer, and the condensate drain would be below the living space.

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The above controller was initially powered via extension cord. You can choose OFF, and as low as 50CFM to as high as 100CFM. An outlet was added later.

fullsizerender-4 All you need is a hole and a flashlight. 

We installed it this way to limit the noise associated with this system.




This fan comes with a nice little controller that allows you to choose OFF or anywhere from 50CFM to 100CFM. The dedicated outlet must be installed almost directly above the fan to reach.