Tjernlund Crawlspace Ventilators

UnderAire crawlspace ventilators are used to help reduce excess moisture that causes mold, mildew and wood rot. Help vent radon, off-gassing, and odors that might otherwise migrate into living areas. 1 fan model will ventilate up to 1650 cubic feet. For larger spaces use multiple units or multiple fan model.

1 and 2 fan models available. 1 fan model rated at 110 cfm and 2 fan model rated at 220 cfm. Complete with 6 foot cord and dehumidistat. The dehumidistat is adjustable from 20 to 80 percent RH. Thermostat shuts fan off at low temperatures. ETL Approved.

model description usually ships price QTY
V1D Tjernlund crawlspace and foundation ventilator. 18x9 inch backplate. Quiet 110 cfm ball bearing motor. 120 VAC, 0.3 amp. Humidity sensor and 6 foot power cord included. ETL approved. 1 Day. In-stock $124.00
V2D Tjernlund crawlspace and foundation ventilator. 18x9 inch backplate. Quiet 110 cfm ball bearing motors (2 fans for a TOTAL OF 220 cfm). 120 VAC, 0.6 amp. Humidity sensor and 6 foot power cord included. ETL approved. 1 Day. In-stock $162.00
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Click on the ? image on the left or this link to ask us your questions!
#1 Q:   Can the V2D be manually set to run continuously rather than controlled by humidity or temperature?
A:   Yes, the humidistat can be set to not turn off the unit. The low temp snap switch will still turn off the unit around 35F.

       Asked on 2022-07-06 by James
#2 Q:   I have 5 small windows in the chain wall on 2 sides of my house. It is about 1500 square feet. On the back side it is open for about 25. Would this need to mostly closed off if I were to put fans in 1 or two of the other two sides to create a draft?
A:   Ideally you want to create a cross flow through the crawlspace by having openings on one side and exhausting with the unit(s) on the other side. That might mean closing some openings on the side with the fans. If you have openings right beside the fans the air will short circuit and not flow through the entire crawlspace.

       Asked on 2020-09-21 by Byron
#3 Q:   Would it be best to install on the end of the house that retains the most moisture throughout the year? For my home, it is the north side of the house.
A:   Yes, that makes sense. No point dragging the moisture deeper into the crawlspace. Create a cross flow through the crawlspace by having openings on one side and exhausting with the unit on the other side.

       Asked on 2019-10-11 by Karen
#4 Q:   I have the V2D installed in my crawl space and it has done an amazing job of ridding the space from mold. However the humidistat has gotten pretty damp due to a storm which blew water around the crawl space door. Is the humidistat replaceable?
A:   Looks like the dehumidistat is replaceable. Part 950-8351. You might consider replacing the whole unit if the fans and other electronic parts got that wet as well. Parts:

       Asked on 2019-01-05 by B
#5 Q:   I will be using two ventilators. Should I install them both on one wall or place them opposite each other? Like one on the front of the house and one on the back?
A:   Typically we see these on the same side (wall) and openings (intake) on the opposite side. That way you get a nice cross flow through the crawl space.

       Asked on 2018-10-04 by Fiona
#6 Q:   I have a crawl space with 3 outside vents between the floor joist on 16 centers. will the V2D unit fit in the existing opening?
A:   The V2D backplate is 18x9 inches.

       Asked on 2018-09-04 by Ken
#7 Q:   I have an 18x36 crawlspace 2 high, on a concrete slab. Two 2x4 screened openings, one attached at each end, but in opposite corners.1. Which fan do I need?2. Can I mount the fan to one of the openings and would it not only exhaust crawlspace air, but draw a continuous flow across the crawlspace from the other screened opening?
A:   You are relatively close to the V1D model capacity per Tjernlund, so definitely upsize to the V2D. Mount the V2D on 1 of the openings to get a cross flow thorough the crawl space. Their rating does not vary with moisture conditions, etc, so you you might need more fan depending on site conditions.

       Asked on 2018-07-11 by Jim
#8 Q:   Can you please tell me what material the fans are? Are they stainless steel or galvanized?
A:   Painted steel. Not stainless. The blades are plastic. The backplate is galvanized steel.

       Asked on 2018-06-02 by RLS
#9 Q:   My crawlspace has 4 vent openings,2 at front of foundation and 2 at rear,would I need to close off any of the openings for the fan to function properly? Its a small house,so I would only need 1 fan.
A:   Typically you want to create a cross flow through the crawl space. Using your setup, if you were to put the fan at one of the rear openings I would close the second rear opening. That way only front openings are open and air flows through the space from front to the fan at the rear.

       Asked on 2018-05-25 by Bill
A:   The active area where the fans and junction box are is 12x4 inches.

       Asked on 2018-03-08 by ALLEN
#11 Q:   I want to make sure before I purchase the fan - the fan blows air out of the craw space, correct? Not in. I want a fan that blows craw space air out of the craw space to the outside. thanks
A:   Yes, the fans pull air out of the crawlspace and push it outside.

       Asked on 2018-03-07 by ALLEN
#12 Q:   I have two vents in my crawl space, one on each end of the house. I would like to put one on each vent. One pushing air in and the other pulling air out. Can the fans be flipped around to do this?
A:   It would be very difficult to reverse the fans as they are riveted to the backplate. I would start with 1, leaving the opposite vent open, to see how well that works.

       Asked on 2018-02-06 by Gary Davis
#13 Q:   My house has two crawlspaces. One is vented to the outside, the second is only vented to the first. The second is too moist. Would venting from the second to the first alone work?
A:   You would need replacement air (replacing exhausted air) to come from somewhere. Typically we see a crawlspace with fans on one end and openings for replacement air on the opposite side.

       Asked on 2017-08-02 by Gary
#14 Q:   Do these units have temperature controls?
A:   Adjustable humidity control and non-adjustable temperature snap switch to prevent the unit from running below 35F. More specs:

       Asked on 2017-07-05 by RiteWay
#15 Q:   What should the thermostats be set at?
A:   The thermostat is set to 40 degrees and cannot be adjusted. The humidistat can be adjusted, and where will depend on how much moisture is present. Generally these are set to 30-40 humidity, unless you want it to run more, then you would set it very low.

       Asked on 2016-12-08 by Bam
#16 Q:   I was under the impression that these take outside air and blow it into the crawl space (Pressurizing the space) and therefore force the air out the other vents. Is this true or does it suck air out?
A:   These are installed on the inside of the crawlspace and pull air out of the crawlspace.

       Asked on 2016-08-11 by Justin
#17 Q:   I have 1500 Sq ft crawl space. What type and how many fans would I need?
A:   Per Tjernlund: 1 fan model will ventilate up to 1650 cubic feet. So if your crawlspace is 1 foot tall, that would be 1500 cubic feet so 1 V1D fan minimum. For 2 foot tall crawlspace, that would be 2x1500=3000 cubic feet, so 2 V1D fans minimum. If you have a lot of moisture, you will need more than the minimum.

       Asked on 2016-05-09 by CM
#18 Q:   Is there a video showing how to mount these in crawl space?
A:   No video available, but here are the installation instructions:

       Asked on 2015-09-03 by Mike
#19 Q:   what are the sones?
A:   No information is provided by Tjernlund, they arent too bad, more of a higher pitch sound, but they do recommend to place it away from any windows.

       Asked on 2014-11-09 by Martin
#20 Q:   What is the warranty on these fans.
A:   These carry a 1 year factory warranty.

       Asked on 2013-07-11 by Renee
#21 Q:   Is there an off switch?
A:   There is an off switch, you simply turn it the switch all the way to the left. Alternatively, you could switch the 110V outlet the unit is plugged into so you neednt go under the house.

       Asked on 2013-04-05 by Dan
#22 Q:   Is the 2 fan model louder than the 1 fan one?
A:   Not really. The fans are the same frequency and the same fan model.

       Asked on 2013-04-05 by Susan
#23 Q:   Can I mount the V1D on the outside pushing air into the crawlspace?
A:   Theoretically yes, but the unit is not designed with that in mind. Its designed to sit inside the crawlspace where its protected from rain, etc. Also, you probably do not want to blow air into the crawlspace (pressurize the crawlspace). Its better to draw air out instead.

       Asked on 2013-04-05 by Ed

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The PCV1 crawlspace fan is designed to be mounted behind any new or existing crawlspace vent. Humidistat controlled. 1 unit will VENTILATE UP TO 1650 cubic feet of crawlspace.


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