Crawl Space Fan

[Mr_Luke]

I decided to buy a dual AirTitan T7 fan to exhaust and move the air in my crawl space. It's 80% crawl space there, and a little moldy down there but not bad. I put down a 6 Mil vapor barrier in most of the open part. It's about 20% open and about 80% crawl space.

I think this fan will be a nice inexpensive way to lower the dampness down there, and for a fraction of the cost of some of the other solutions I've looked into. The fan itself was only $99 shipped. I need to mount it on a wooden frame to place it in my only cellar window.
I have 2 other vents that are 6" x 18" on the other end of the house.

My question is, I don't think the cord for it will be long enough to reach an outlet.
Can I use an extension cord or do I need to get someone to install a new outlet?
TIA

 

[JC1]

Is there another outlet or light close by? I would try to run another line with a box and outlet to the location you need. Not sure if you need conduit in your location.

 

[RhondaHonda]

It says it draws 7.2 watts. You are fine running an extension cord to it.

 

[Mr_Luke]

Is there another outlet or light close by? I would try to run another line with a box and outlet to the location you need. Not sure if you need conduit in your location.

No. there is one outlet near it but not close enough.
My heat pump condensate pump is plugged into it.

 

[JC1]

Is the crawl space poured cement floors or dirt? Are you going to run the fan all the time or will there be a thermostat connected?

 

[Mr_Luke]

Is the crawl space poured cement floors or dirt? Are you going to run the fan all the time or will there be a thermostat connected?

It's dirt floors with a vapor barrier.
The unit has temp and humidity settings that I think control how often it runs, depending what it's set at.

 

[WyrTwister]

The correct answer is to install a new receptacle close enouth to the fan . What I would do is to install an extension cord that was just long enough and be done with it .

 

[doitmyself]

Be mindful that the air intake vents on the other side of the crawl space need to be big enough to allow as much or more air into the crawl space that the fan ejects. There should be specs. with the fan literature that shows cubic feet per minute moved. Otherwise you will create negative pressure in the crawl space and conditioned air (cooled/heated) will be pulled out of the living space through cracks.

This site: https://www.hvi.org/resources/publi...uide-articles/how-much-ventilation-do-i-need/ ....has the intake size formula under the power attic ventilator section. It's a place to start. I'm no expert on this topic so YMMV.

 

[Donald]

It won't work. Venting of a crawl space only works if the RH of the outside air is below 50%. I doubt if it is in Tenn during the warm part of the year which is when you want to reduce the RH in the crawl space. Venting is kind of old way of doing things. You need the vapor barrier and a dehumidifier. Preferably one built for a crawl space like SantaFe or AprilAir. Seal up the vents with foam board. Some vent a little once the crawl space is all sealed just to exchange the air. Not to reduce the RH. Get a wireless RH sensor for crawl space so you can see what is going on with the RH. You can go wild and really seal up the crawl space and walls, seams taped, etc. But typically a vapor barrier on the floor and a dehumidifier and sealed vents will do what is needed. You want the crawl space at 45 to 50% RH so no mold will grow down there.

 

[4WD]

Considering you need a protocol to determine if the fan really helps …
a shorter extension cord would start the “test”

 

[JTK]

Your plan is better than having no fan in there.

The amp draw of that little guy will be no problem with an extension cord. Not the best or prettiest method, given extension cords are intended for temporary use, but workable.

 

[4WD]

Your plan is better than having no fan in there.

The amp draw of that little guy will be no problem with an extension cord. Not the best or prettiest method, given extension cords are intended for temporary use, but workable.

Plus a dehumidifier can be expensive to run … learned that the hard way at my bay house and went back to dollar store versions of Damp Rid … (not applicable to this)

 

[Donald]

The key is to determine what the RH is in the crawl space and what it is outside. The average RH in Nashville Tenn is 69.9%. So the summer is higher and winter is lower. Where is the source of air below 50% RH that you want to vent into the crawl space to drop the RH in the crawl space?

No argument that a dehumidifier is more expensive than a fan. The better sealing the less dehumidifying.

 

[doitmyself]

Donald's suggestion is excellent and deserves more attention. A quick Google search shows that sealed vs. vented crawl spaces is more critical in certain regions and that there is research supporting sealed crawl spaces for many. There also seems to be a lot of controversy (maybe hesitancy to change old school thinking) about the subject.

During seasons when the ground and lower building structure is very cool, I could see the hazard of drawing in very humid warm air (condensation).

 

[SubieRubyRoo]

Yes, Donald is correct. If you do some research on energy efficient and upscale homes that are built to last, the crawl is treated just like part of the living space. There is a heavy duty vapor barrier all the way up to the sill plate with 100% thermally sealed seams, roll insulation from the sill plate down to ground level covering all of the brick/concrete foundation, no insulation between the crawl air and the underside of the first floor, ZERO crawl space vents to the outside, and the crawl has HVAC vents just like the living area of the house. In summer, AC goes into the crawl, and in winter, heat. The goal of this is always to minimize the temperature differential for the framing in the crawl, which will preserve the wood and make it less likely for mold or condensation to form. It also increases the comfort level when walking barefoot on the first floor since it is always kept at the same temperature as the rest of the house since it's heated and cooled identically.

 

[Donald]

Yes, Donald is correct. If you do some research on energy efficient and upscale homes that are built to last, the crawl is treated just like part of the living space. There is a heavy duty vapor barrier all the way up to the sill plate with 100% thermally sealed seams, roll insulation from the sill plate down to ground level covering all of the brick/concrete foundation, no insulation between the crawl air and the underside of the first floor, ZERO crawl space vents to the outside, and the crawl has HVAC vents just like the living area of the house. In summer, AC goes into the crawl, and in winter, heat. The goal of this is always to minimize the temperature differential for the framing in the crawl, which will preserve the wood and make it less likely for mold or condensation to form. It also increases the comfort level when walking barefoot on the first floor since it is always kept at the same temperature as the rest of the house since it's heated and cooled identically.

One can certainly do that (HVAC with s supply and return in crawl space). But with heating & cooling your typically turning it on/off via temp. In the case of the crawl space you want it done to a certain RH not temp.

 

[Strokenmerc]

I have recently (1 year) done what Donald described to my crawl space (1900 sf rancher) as a test with great results. I am using 2 box fans (opposite corners in theory stirring the air) and a standard large dehumidifier. I closed and sealed the vents with armaflex. This was a inexpensive test to see the difference so now i need to find the correct dehumidifier for the space and install it permanently.

 

[wpod]

Pull aside the vapor barrier and spread lots of 20 mule team Borax or look at the Boracare product and spray the dirt and the wood. Then look into crawl space vent fans.

 

[Donald]

Pull aside the vapor barrier and spread lots of 20 mule team Borax or look at the Boracare product and spray the dirt and the wood. Then look into crawl space vent fans.

Crawl space vent fans will only work in the winter when the outside air has a low RH. Never in the summer.

 

[Mr_Luke]

I realize it's not going to be a perfect solution year round but for $100 I think it will help most of the time to at least move the air around and remove possible radon. When it's dry air outdoors it will also help to lower the RH down there.