The 5 Critical Steps to Mastering Crawl Space Humidity

The hidden world beneath your home could be quietly undermining your family's health and your house's structural integrity. Crawl space humidity isn't just an "out of sight, out of mind" problem—it's directly connected to issues like mold growth, wood rot, and even childhood asthma triggered by dust mites thriving in moist environments.

Michael Church from Crawl Space Ninja takes us through the five non-negotiable elements of effective crawl space humidity control that many contractors surprisingly overlook. Starting with proper vent sealing using R10 foam board and spray foam insulation, he explains why simply stuffing old blankets or taping cardboard over vents won't protect your home. The foundation vent fan might seem counterintuitive in a sealed system, but it's crucial for directing soil gases outside instead of up into your living spaces—a recommendation straight from the EPA to protect your family's health.

The technical aspects of vapor barrier installation make a world of difference in performance. From extending the barrier high up foundation walls to the specific overlapping and taping techniques that prevent ground moisture infiltration, these details determine whether your system succeeds or fails. The often-overlooked crawl space door requires careful air sealing, while a quality dehumidifier with a condensate pump completes the moisture control strategy. Each component works together to create a comprehensive system that protects your home's structure, improves indoor air quality, and creates a healthier living environment for your family.

Chapters

• 0:00 Introduction to Crawl Space Humidity Control
• 1:17 Why Controlling Humidity Matters
• 3:30 First Step: Sealing Crawl Space Vents
• 6:05 Installing Foundation Vent Fans
• 8:07 Proper Vapor Barrier Installation
• 10:21 Air Sealing Crawl Space Doors
• 11:48 Dehumidifiers and Final Recommendations

Transcript

Speaker 1: 0:00

Michael Church with Crawl Space Ninja, and today I want to talk to you all about the five crucial things that we here at Crawl Space Ninja feel like every crawl space should have in order to control humidity. Stay tuned, okay. So if you're new to Crawl Space Ninja, we talk about everything related to basements, attics, crawl spaces and duct work, so we hope you'll subscribe to our channel and ring that notifications bell. Okay, so what we're going to talk about today is the five crucial items we feel that every crawl space encapsulation company should utilize whenever they're trying to control humidity in the crawl space. And, believe it or not, a lot of companies miss one, if not more than one, of what we feel are these five crucial steps. So we hope this will help each of you know whether you're going to DIY your own crawl space encapsulation or hire a contractor to take care of that for you. We feel like these are things that everybody should do as a minimum in order to control humidity in their crawl space. So let's get started, all right. So the first thing you want to look at is why do you even need to control humidity? Okay, you know everybody's talking about controlling humidity, but why do you need to control humidity in, particularly the crawl space. Well, if you think about it, most people that maybe are unfamiliar with crawl spaces don't necessarily realize that the crawl space is actually part of the home. I mean, just because it's under the house does not mean it cannot affect the house. It can affect your home in different ways, like high humidity. I know I didn't list it here, but it can cause your hardwood to begin to cup because that high humidity gets absorbed inside the wood of the subfloor and the joists and creates a moisture problem even up into the hardwood. The main reason why you should control humidity is I've listed four main reasons right here. You should look at controlling humidity to prevent mold. Here's a great picture of what humidity can do to your crawl space. Look at that. That is just horrible mold all over these floor joists and probably behind the insulation as well. But if you think about it, there's no standing water here, there's no leak or anything like that. This is all from humidity, high humidity, getting absorbed by the wood and by the insulation, and then this is probably some kind of brown wood rot fungus that can even eat away at the wood itself and destroy the foundation of your home, make structural problems for you if you hear a lot of squeaking floors and things like that. But another thing that's overlooked about humidity is it also causes dust mites to grow uncontrollably. For some of you that don't know, dust mites are actually the number one cause of asthma among children. So if you're like me and you have kids and you want to protect the indoor air quality of your home, whether you have a basement, whether you have a slab or whether you have a crawlspace, you should control humidity. And these are going to cover the five things that we feel like you should do to control humidity. But before I get into that, how do you even know if your humidity is out of control?

Speaker 1: 3:39

We got a couple of devices right here that we recommend. That's on our DIY store is you can get a handheld humidity reader. Now, this is more for someone like recommend. That's on our DIY store is you can get a handheld humidity reader. Now, this is more for someone like us that's going in to inspect a crawl space. You can go in and you can like open this up and and test the humidity, go to different parts of the crawl space and things like that. But if you're looking for a consistent way to check humidity. We recommend the ThermaPro humidity reader right here. And these are the bases. Now, you can get several of these. You can have one in, maybe, a basement, one up in the attic, you can even put one outside and then obviously, one in the crawl space. It will handle, I believe, four total bases, but you can check out the DIY store for that, and then you can choose which base you want to look at whether it's the living space or the crawl space of the outside and, plus, this base right here will also check the humidity. So this is checking the humidity of where it's located. A lot of people put it in their kitchen or something like that, so that way you can keep an eye on the home's humidity all the time. Winter, spring and summer and fall obviously different times of the year your humidity levels may be different.

Speaker 1: 4:50

So let's look at the first reason, or the first thing you should do to control humidity, which this may seem like a dumb number one, but, believe it or not, we go to homes a lot of times, whenever they have hired someone did not seal the vents. They'll put in a dehumidifier even and did not seal the vents, as you can see right up in here. We seal them that's the important part Just cutting a piece of foam board, or I've even seen people shove comforters inside crawl space vents, or maybe they'll take a piece of cardboard and some tape and tape the outside. That's a way to seal a vent, but it's not the way we would seal. So we use our R10 foam board so that way we've got some insulation there in the vent, as well as using a spray foam sealant, or what they call spray foam insulation, to seal around that so that air and high humidity can't come into those vents.

Speaker 1: 5:57

Okay, so now this one may seem like a weird thing to say, but, believe it or not, this doesn't do really anything to control humidity. But if you're going to control humidity, according to the EPA, by sealing the vents and installing a dehumidifier, you should have a foundation vent fan installed to blow air out of the crawl space. Believe it or not, if you do not do this, you could be creating a soil gas problem. If you have an open or vented crawl space right now and then you seal up every single vent without putting some kind of foundation vent system in there to basically get that air out of the crawl space. It's got nowhere to go but up in your living space. Now, not everyone has radon, but typically soil gases are in every part of the country that could be even weird smells methanes and different things like that. So you want to try to divert those soil gases out of the crawl space while controlling humidity, which is what some people would call a hybrid encapsulation system. So this is very effective. It's what we typically do every single time because, as I mentioned before, it is recommended by the EPA to control soil gases. It's one CFM cubic feet per minute of air for every 50 square feet of crawl space.

Speaker 1: 7:21

Now these Lamanco PCV1s are our go-to foundation vent fan. You can get these on our DIY store, but I want you to also take a look. We've sealed the top. You just don't throw this in here. You also, if you've got an opening up here, you want to make sure that you seal the top of this as well with a spray foam sealant and then make sure that you don't have a lot of backflow coming in because of this fan. I would recommend you set it's got different humidity settings. We turn it to the on position, so that way it's constantly running year round to get all of those soil gases out of your crawl space. Again, that has nothing to do with controlling humidity, but it is part of our humidity control procedure.

Speaker 1: 8:07

Okay, this is a huge one. You've already seen this picture when I talked about sealing the vents. But look at this right here. See how we took the vapor barrier all the way up and covered as much cinder block or concrete depending on what your foundation walls are made of as possible with the vapor barrier, or the plastic, as some people would call it. The reason why we do this is because if you've got dirt on the other side of this foundation wall and you get moisture penetrating through the CMU, the concrete or whatever it is your brick, your stone, whatever that foundation wall is made of then that moisture is going to evaporate or try to evaporate, causing humidity spikes, especially during thunderstorms and different things like that. So taking the plastic as high up the wall as you can and attaching it near the sill plate is the better way to handle it.

Speaker 1: 8:59

Now we have to leave this gap. Here in Tennessee it's a minimum of three inches. Now check with your local codes to see if you require that gap or not, but here in Tennessee it's three inches In Georgia it is six inches and then we're also going to overlap and tape the vapor barrier. Okay, a lot of companies they'll just throw it down and even the white, pretty vapor barrier, they'll just throw it down, won't overlap and tape it, as you've seen in many of our videos. So if you don't overlap this a minimum of six inches, but a little bit more is better you want to overlap and tape this. You can see this tape seam right here. So we got it overlapped and you can almost see we took it all the way to here on the overlap. The reason why we did that is because, in case there's any standing water underneath this plastic, it has to travel further before it can come back and get on top of our vapor barrier. So we overlapped it and taped it quite a bit and that way it keeps all that moisture behind the plastic and makes that dehumidifier run less.

Speaker 1: 10:05

Okay, here is another very important thing you should do I believe this would be number four in our reasoning or our things that we should do to seal the crawl space up and control humidity, and that would be air sealing the door. As you can see, this is a before we went and built a frame all around this door frame, okay, and then we used a caulk and different adhesives like that that and then installed a new door all the way around it. We used gaskets and also insulated the inside of this door. So you want to make sure you air seal the door as best you can. Now you don't need to, obviously, build a new door if you don't have to, but you can get some of those air sealing gaskets and things like that at Home Depot and Lowe's and make sure you air seal this door as good as possible.

Speaker 1: 10:55

Before I move on to the last thing, I want to ask you to please like and subscribe this video. We hope this is being good information for you all out in crawl space, ninja land, and also leave a comment below. I am obviously not covering every single thing about controlling humidity. If you had a unique situation with your crawl space, that maybe you did all of these things, but there was one more like. For example, if you have standing water, you may want to install a sump pump or things like that. Whatever comments you want to leave down below, and if you need to request a quote, go to crawlspaceninjacom and get a free quote up there as well, as if you're a DIYer and you need some of these dehumidifiers or vapor barriers or things like that, you can go to diycrawlspaceninjacom and purchase that for yourself. The last thing, the last thing and this is probably the question we get the most is do you need this? And many of your crawl space companies will not install it, and that, of course, is the dehumidifier.

Speaker 1: 11:55

Now, we prefer the Aprilaire dehumidifier. It's been great for us. It uses aluminum coils, it has less corrosion and things like that because of that. But you can also see the dehumidifier in the condensate pump. Typically, your crawl space is lower than the rest of the house, so having the dehumidifier drain into the condensate pump and then taking that water up and out of the crawl space is the final thing. So if you'll do those five things, if you'll start there and control humidity in your crawl space, then that is a great start. And, like I said, let me know down below if you've got another thing that you feel like homeowners could do to improve the humidity in their home. My name is Michael Church with Crawl Space Ninja, and we hope you make it a happy and blessed day. We'll see you later.