5 Ways to Lower Crawl Space Humidity

[@Tom-ej8bb]

Took us a couple years here in Michigan to seal and insulate the rim joists and walls. All that was left was to encapsulate with plastic. Had your prices for materials. Called a well known Michigan foundation specialist to see what it would cost to finish using their special 120 mill plastic that is almost indestructible. Son in law used it in his basement to cover area over gravel and it’s awesome but also proprietary so I couldn’t buy. Well their cost to install just that plastic was $6300. Now I figured the plastic cost was probably 3k. But the next day we ordered all your 14 mill if I remember correctly and tape to install ourselves for $900 Took us (65 year old) 3- 6 hour days to install with excellent overlap and the took me more time over the winter to seal the foundation supports and around our tanks etc. couldn’t be happier! Saved so much the entire floor I covered with those 2’x2’ connectable foam floor stuff tiles so I don’t damage the plastic when under there. Going to get the dehumidifier going ! Thanks 🙏

[@scottieashe63]

Hey man I'm in Virginia Beach. I have worked for a distributor of basement systems. And I've also worked for an independent. And also worked for a groundworks company. For the past 10 years. And I know my stuff LOL.. I love your videos. I like hearing new ways and seeing new ways to do things thank you

[@JohnS-jj9by]

Great information for the owner of a new house with a crawl space.

[@bonniebaker8527]

We sure appreciate you sharing your knowledge on this important topic. Wish you covered our our state (SC). We are in the middle of getting estimates on our home crawl space and your videos have helped a great deal in asking the good questions.

[@christianjohnson6519]

#2 I have a foundation vent fan. Should I install a foundation vent fan on the other side of the crawl space for cross ventilation or should I just cover that up and seal it?

[@stevepickett4258]

This is very educational thank you so much

[@pead7515]

Information is great. With it sealed up as much as possible, how do you handle make up air

[@CrawlSpaceNinja]

A Foundation Vent Fan will circulate air out of the crawl space without increasing the humidity!

[@zzubuzz]

Thank you for this helpful information.

[@sergii_contractor]

I got a question, if technically crawlspace is encapsulated/sealed, why do you need a fan to blow the air out that allegedly builds up out of soil gases if it's underneath the sheets? They are technically outside of house envelope(excluding foundation) and still in the soil if proper job is done with insulating crawlspace by vapor barrier. If that's the case, technically in 10 years after encapsulation you get a knife and make straight cut in your poly sheet so you will have a surge of gases running through it that was accumulating between the vapor barrier and soil and wall foundation for 10 years lol That's how I see it.

[@CrawlSpaceNinja]

Soil gases can get through and around vapor barrier same way it gets through and around concrete in a basement. Vapor barriers are retarders (not barriers), if vapor can pass through so can gases. Hope that helps, thanks for watching.

[@aaronwalker2571]

Great videos! Thank you for sharing Michael & Crawl Space Ninja!

[@stephenporter7252]

This is fantastic! Thank you for making this!

[@CrawlSpaceNinja]

Glad you enjoyed it!

[@gettngoatiefarms7199]

Thanks for all the great advice!!

[@jsomnes]

Thank you for good information in this video. I was vondering if you have any videos with dehumidifier who sends moist-air outside the crawlspace instead of water through a pump?

[@automatic12ga4]

Thanks for the video! I ordered all my material. I'm from Tennessee, what is the 3 inch? From the top of my cinder block?

[@CrawlSpaceNinja]

3 inches from the Sill Plate! Check your local code to see if that code is in place!

[@automatic12ga4]

@@CrawlSpaceNinja in East Tennessee we make our own code lol

[@automatic12ga4]

@@CrawlSpaceNinja I'm going to make it 3 inches. Thanks for getting back to me!

[@chuckb4375]

I already have a vent fan, and am considering adding one of your 1830 dehumidifiers. Where do you prefer to position dehumidifiers in relation to vent fan? I get that wet air tends to migrate toward dry air, but it would be sad if the vent fan pushed out the driest air in the crawl because it's too close to the dehu. Should I centrally locate the dehu, or get it as far away from the vent fan as possible?

[@maryquayle7305]

Thank you for this helpful information. We’re trying to make decisions about sealing our crawlspace, and I have a question about the vent fan you discuss in the video. If this moves air out, how is air replaced in the crawlspace? Thank you.

[@houseonahillok]

Had the same question. The air will be replaced from somewhere. If everything is truly sealed, it would create a vacuum. Air has to replace the air moving out. Would it be best to replace it with a vent from the inside of the house? Maybe that air would be less humid?

[@Horrrrrribleboy]

@@houseonahillok what I don’t get is, if one has the vapour barrier sealed properly, why would the gases from soil penetrate ?!

[@sergii_contractor]

@@Horrrrrribleboy The same lol But I guess precaution if poly sheet peels off somewhere?

[@kavendaneault2305]

Always good information with Crawl Space Ninja. I have 8 open vents and the under of the house (the subfloor) is fully rap in a vapor barriers from factory (Canada) on a 4 foot frost wall . There is nothing on the wall. They put at the base of the wall some isolation foam. I have a subpump. The under of the house in summer is very humid. Something around 2months during the year. The vapor barrier is dripping with water. At least is not touching the foundation due to the vapor barrier. Do you think that sealing the vent and putting a demystified and a negative pressure will help enough?

[@freemontstudios2914]

I have a crawl space that has a sump pit/pump. How would you apply vapor barrier in this situation? would you just run plastic vapor material up to the edge and then fasten down? Also how would you run vapor barrier under or around a well pressure tank in a crawl space. These are both obstacles I'm facing. Maybe a new video idea? Thanks for your help and awesome videos. I enjoy learning all your tips and tricks for my home.

[@CrawlSpaceNinja]

You will want some of the vapor barrier to go down into the pump with the lid secured on top to help with any potential flooding from above. For the pressure tank, you could just go around it if you are unable to get the vapor barrier under it. Thanks for your support!

[@Alex-gx5mb]

Thanks for the great videos! Do you recommend an encapsulation contractor in Hickory NC. ?

[@CrawlSpaceNinja]

Thanks for watching! We do not have any recommendations in that area as of 4-28-21.

[@amyclutter7259]

We have a lot of moisture problems in our 1950 concrete block house. I'm not sure if we can manage encapsulation right now. Would sealing the vents help bring down the humidity level even with a crawl space that's not encapsulated? (We live in Northern PA... cold winters with cold uninsulated wood floors and humid summers with no central air.) We're just trying to figure out the first step that we should take to start dealing with these moisture issues. Thanks!

[@kirkhall2099]

i would like to know if i can apply the 4x8 sheets of foam insulation on bottom of floor joists after replacing the old insulation with new. I would then tape the seams with aluminum duct tape

[@doogiehowser1124]

i have a dumb question. i've watched a bunch of videos on crawlspace dehumidifiers. WHERE does the PVC tubing connect to so that it could push the water out??? am i supposed to drill a hole thru the concrete to snake the tubing thru??? or do i drill a hole in the sink drain PVC pipe and fit the tubing in there??? WHERE does the water drain??? NOBODY seems to point that out! Thanks for any help.

[@CrawlSpaceNinja]

Directly drain your dehumidifier into a sink or into a pipe. If your dehumidifier has a motorized pump, connect a water hose to its drain pump hole. Next, insert the other end of the drain hose into a sink, drain, or drainage pipe.

[@dspeer11]

Great videos. I have an older house with damp crawlspace. The crawl space is so shallow that I can only get to about 2/3 of it. Should I install vapor barrier in 2/3 of the crawl space?

[@CrawlSpaceNinja]

It would definitely be better than no vapor barrier at all. Thanks so much for your support!

[@candizwerle6449]

I live in KY. I just bought a house in Strunk where the walk in crawl space is moldy & horrible. I bought some Borax powder which will treat the mold in the dirt floor I'm hoping. The house is 20 yrs old & they had to replace the electric panel which is down there. I thought that was weird. So I'd like to get your input re how I can seal this space & waterproof. We spotted termites too. A couple channels. I sprayed so we'll see if that worked. I'm working on drainage away from house & appreciate your videos. So what's next???

[@doziboy803thethird6]

Just checking to see what you did to prep your house to get water out from under it and proper drainage any tips that you can give me

[@thjbird]

This guy is a pro

[@CrawlSpaceNinja]

Thank you.

[@mattleggieri7264]

I bought a double wide mobile home. It is on a brick foundation. I'm in Richland's n.c. the crawl space has vents all around the foundation. It also has a black plastic? Barrier covering the joists and floor . It does have a vapor barrier on the dirt floor which does need work . It's about 2500 sq ft. . Do I seal the vents ? What dehumidifier do you recommend and will l need anything else . Thx Matt

[@CrawlSpaceNinja]

If you are wanting to control humidity, yes you will want to seal the vents and install a dehumidifier (we recommend Aprilaire). You'll also want a ventilation fan in one of the vents. Check out our guide to encapsulation and our other videos for more details on DIY encapsulation: crawlspaceninja.com/encapsulation/essential-guide-to-crawl-space-encapsulation/

[@sandys2672]

Its January in Northern Minnesota. My Crawlspace humidity is at 73%. Would you suggest installing and running a Dehumidifier to dry it out before encapsulating?

[@CrawlSpaceNinja]

Sandy - great question! Michael actually did a video on this very subject: kzbin.info/www/bejne/qae3i4d3i81_idU

[@buildwithchris]

I suppose that if a radon system is present the foundation vent fan is no longer required?

[@CrawlSpaceNinja]

That is correct, Makers Zone. Because the air pressure inside your home or office is lower than outside, radon is drawn in like a vacuum. Air pressure is further decreased by exhaust fans, so their use actually increases radon concentrations. Great question. Thanks for watching and have a happy and blessed day!

[@anthonyrobinson973]

I have heard vents should be open in the summer and closed during winter months..if you completely seal them, you won't be able to open them in the summer

[@CrawlSpaceNinja]

We have done a video about opening and closing vents in the summer and winter. Have you had a chance to watch that?

[@anthonyrobinson973]

@@CrawlSpaceNinja will do now

[@richardlemke4240]

Question, does April air make a indoor controller for their dehumidifiers that are either in the attic or in the crawl space that will read the humidity level in the area where the dehumidifier is placed?

[@CrawlSpaceNinja]

Here's a link to our 76 controller diy.crawlspaceninja.com/aprilaire-model-76-dehumidifier-control/ Also, check out this video, Hope that helps. kzbin.info/www/bejne/rmO3mpiGpa94e7c

[@richardlemke4240]

@@CrawlSpaceNinja yeah the instructions on the 76 controller states that it reads the RH of the room in which the controller is placed it does not relay to you the humidity that the dehumidifier is reading and it's designated placement in the house or below.

[@CrawlSpaceNinja]

@@richardlemke4240 Dehus are displayed as RH as well, of which the controller is connected to, so a controller will only read RH

[@richardlemke4240]

@@CrawlSpaceNinja I don't mean to be a burden nor be this dead horse, so aprilaire 76 only displays the RH at the dehue? If I'm putting it in the crawl space my goal would be to know what the RH level is in the crawl space I don't care about the RH in my house as much as where the dehue is

[@richardlemke4240]

@@CrawlSpaceNinja see when I read the instructions I read it wrong I assume I assumed there was an RH sensor on the controller not that it was reading the information from the dehumidifier.

[@rosemcommm]

I planned on putting an ERV exhaust vent on the far end of the crawlspace to vent soil gases, will that work?

[@CrawlSpaceNinja]

Hey Mike, Check out this video we did about vent fans. kzbin.info/www/bejne/hYbZh4WbnMiXY8U

[@azncooler]

If you're removing mold do you leave the vapor barrier after you soda blast?

[@CrawlSpaceNinja]

Great question. Depends. If we are encapsulating we remove it. If homeowners hired us to only soda blast, we'd leave it.

[@John-mh6mi]

Can you dig out your foundation on the outside and use sealer paint to help on the cinder block, to keep moisture out from the outside of a foundation to help?

[@CrawlSpaceNinja]

If you have the time/resources, yes, but those can still fail over time as well. I'd recommend doing a lot of research to make sure you install a quality product.

[@rebeccajohnson1368]

Checkout the stuff posted by Apple Drain

[@willowmobilesystems4008]

Great information! I think its funny that a space you can clearly stand up in is called a "crawl" space! It would be good to hear your opinion of WHAT is high humidity. A quick search suggests above 60%. Is that your experience?

[@maxmanx1294]

I'm pretty sure the wood shouldn't register more than 15% moisture using a moisture reader. Indoor air humidity should be 30 - 50%. I would expect the crawlspace to be the same.

[@maxmanx1294]

My crawlspace is 18" tall. I can't even crawl; I slither.

[@willowmobilesystems4008]

@@maxmanx1294 I agree...based on the knowledge I have acquired over the past year. I have a sensor in my "crawl" space and it now regularly registers 90% humidity. It is a house on piers and last year I encapsulated the space with 4 inches of rigid foam as skirt insulation - to keep pipes from freezing. It does its job but I now need to mitigate the humidity problem - which I knew going into it, just not looking forward to it.

[@maxmanx1294]

@@willowmobilesystems4008 its wise of you to get the humidity sensor. I definitely need to get one. 90% is high. Have you ensured all your soil slopes away from the foundation, installed downspout extensions that discharge water downhill as from your foundation as possible (minimum 6' , ideal 20'), verified that no gutters overflow? If all that is taken care of, could you have a plumbing leak in your crawlspace or under your crawlspace? Plumbing leaks can be tricky. Even a periodic drip adds up.

[@willowmobilesystems4008]

@@maxmanx1294 I'm using the Govee Temp and Humidity sensor(H5179), less than $34 (no additional costs) and connects directly to WiFi. Gives readings up to the min, if you want, and reports to downloaded app. I can check status anywhere I have internet. Alerts can be configured for both High and Low. I also use it to monitor winter temps in the crawl space and then can remotely turn on a heater (via Wifi plug) if needed.

[@tadmccalister2234]

Does "closing" the vents serve the same purpose as "sealing" them?

[@CrawlSpaceNinja]

Closing the crawl space vents will prevent most of the outside air from getting into your crawl space, but it will still be able to get in if it's not totally sealed. Here is a video on how we recommend sealing crawl space vents if you're interested: kzbin.info/www/bejne/eJnSYaNjmJhkras

[@markw5985]

I'm looking to build in NC. I was wondering if you can use a regular store bought dehumidifier or do u have to use one that you guys use

[@maxmanx1294]

You need one made for crawlspaces.

[@deborah2351]

Helpful

[@jesstrix]

Why not create small vaccum beneath the floor plastic with a fan to pull the radon before it enters the conditioned space?

[@CrawlSpaceNinja]

Natural ventilation in any type of house should not be considered radon mitigation since it is only a temporary strategy to reduce radon.

[@wiros8101]

5:10 start

[@johnbeau5086]

You said to seal all the vents and air seal the door, but you also said to install the foundation fan. Does that mean that one vent is left unsealed for the fan to exhaust through?

[@CrawlSpaceNinja]

Not unless it is required by your local code. We want to create negative air pressure in the crawl space. Here is a video talking about makeup air if you are interested: kzbin.info/www/bejne/r4S3mIJqhbaHba8

[@johnbeau5086]

@@CrawlSpaceNinja Perhaps i wasn't clear with my question. From the video i assume ALL vents are sealed except the one with the ventilation fan. Is that correct?

[@CrawlSpaceNinja]

That is correct, unless your local building code requires differently.

[@johnbeau5086]

@@CrawlSpaceNinja Thank you sir.

[@tashagirl5]

If you need to treat mold, after the source has been addressed, do you treat before you install vapor barrier? Is it helpful to run dehumidifier before you treat the mold? This is minor mold I was hoping to treat with concrobrium as the soda blasting unaffordable and not something I want to attempt myself. Thank you.

[@CrawlSpaceNinja]

Yes and yes. You want the wood moisture level to be at least below 15% and above 6% before treating mold. Typically that means running a dehumidifier for a few days/weeks before treatment. We recommend installing vapor barrier at the very end.

[@benjaminlew7003]

If your home has automatic temperature vents in the crawlspace (which open or close based on temperature), would it still need (or be a good idea) to get a dehumidifier? My thought was that the most humid months are usually the hottest, so the vents would be open during that time. As such, they would allow airflow to come in and out and reduce a kind of "stale" air and stale "humidity" in the crawlspace, no? Wondering what your thoughts might be. :)

[@vvsmixing]

after researching a bit I've come across the fact that having a vent in the summer months where the outside air is hotter than the crawlspace air is detrimental because the hotter air holds more moisture and once entering the crawlspace it cools down and loses its ability to hold the moisture and deposits it as condensation which is Not good!

[@george9710]

Automatic vents are great but if they are controlled by temperature alone they are pointless. Vents are used to control humidity not temperature. In fact, the reason why you'd want to close them is to reduce heat loss/gain. Venting in high heat can also mean that you are letting in wetter air which is again no good. So you really want vents that are controlled by humidity with a temperature override. But it's actually easier to do all of this with a dehumidifier and mechanical air extraction/input i.e. fans.

[@FerintoshFarmsPhotography]

Wouldn't it get pretty gross and moldy under the plastic?

[@CrawlSpaceNinja]

You'd want to ensure you've removed all debris and organic material that would continue to decay and smell before laying the plastic. That way it just keeps out the moisture like it's supposed to.

[@dwestley74]

Why have vents if you need to seal them?

[@CrawlSpaceNinja]

Its just the way builders build the homes. Not all builders add vents but most do.

[@metablue4454]

Great show!! And helpful!! I've watched a lot of presentations from different companies and there is one thing that most never, ever talk about - keeping as much water away from the house in the first place... by using things like attachments to downspouts to channel water away from the structure. Not sure why this info is not mentioned.

[@CrawlSpaceNinja]

Hey! Thanks for commenting. Sometimes there just isn't time to cover every detail in one video, which is why we have so many! Here is a video discussing more about the topics you mentioned: kzbin.info/www/bejne/b5rbh3adgtuIr80

[@metablue4454]

@@CrawlSpaceNinja Thanks dude. Fortunately, and after watching your recommendation, I've got the exterior issues covered. My next step is to put a dehumidifier in the crawlspace. Vapor barrier is already down, with a little more work to do. I was hoping to get a price for installation on an Aprilaire but there are no dealers here in SW metro Atlanta, so I'm likely having to go with something like a Santa Fe. I did notice you have a shop in Alpharetta, but that's way up in NE metro Atlanta... which is a very long way away (FYI, the 29-county metro Atlanta area is about the same square miles as the state of New Jersey). Hopefully the Santa Fe will work ok. I do enjoy watching your channel. Thanks again.

[@CrawlSpaceNinja]

Did you check Aprilaire's website to make sure? They have a vendor list and there may actually be someone in your area who can help! www.aprilaire.com/find-a-pro

[@metablue4454]

@@CrawlSpaceNinja I did that. The only company handling Aprilaire is a long way off. I did find a local company that sells Santa Fe. I checked those reviews and found them reasonably good.

[@rubyb6455]

Should a crawl space be vented?

[@gabrieltaylor5501]

Company wants to charge me $13,000 for an encapsulation. Is this the going rates? Currently waiting on more quotes.

[@CrawlSpaceNinja]

That sounds about average depending on the size of your crawl space and scope of work. We did this video discussing potential costs of crawl space repair that you may find helpful: kzbin.info/www/bejne/rYrSlaKXnZeklc0

[@thomas13livingston]

Soooo........ Who won the dehumidifier?

[@CrawlSpaceNinja]

Announcement video is coming tomorrow!

[@meredithlittles6556]

How many fans should you have?

[@CrawlSpaceNinja]

It depends on how big your crawl space is. Check out this video: kzbin.info/www/bejne/Y2m0kJ2NqreAp9k

[@brentonwilks]

I thought air movement under the house was good

[@CrawlSpaceNinja]

In order to control the humidity level in the home, air movement is very important. Air movement inside the house creates a stack effect, allowing air to circulate from the lower floor to the upper floor. Movement of air can allow moisture to circulate throughout a room.