August 18, 2025 • 12 mins
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.
Check out Michael's book, "Crawl Space Repair Myths-Busted" now available on Amazon!
Schedule a consultation: https://buymeacoffee.com/csninja/extras
Need help: https://crawlspaceninja.com or https://supply.crawlspaceninja.com
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
Michael Church with Crawl Space Ninja, and today I
want to talk to you all aboutthe five crucial things that we
here at Crawl Space Ninja feellike every crawl space should
have in order to controlhumidity.
Stay tuned, okay.
(00:31):
So if you're new to Crawl SpaceNinja, we talk about everything
related to basements, attics,crawl spaces and duct work, so
we hope you'll subscribe to ourchannel and ring that
notifications bell.
Okay, so what we're going totalk about today is the five
crucial items we feel that everycrawl space encapsulation
company should utilize wheneverthey're trying to control
humidity in the crawl space.
And, believe it or not, a lotof companies miss one, if not
(00:54):
more than one, of what we feelare these five crucial steps.
So we hope this will help eachof you know whether you're going
to DIY your own crawl spaceencapsulation or hire a
contractor to take care of thatfor you.
We feel like these are thingsthat everybody should do as a
minimum in order to controlhumidity in their crawl space.
(01:15):
So let's get started, all right.
So the first thing you want tolook at is why do you even need
to control humidity?
Okay, you know everybody'stalking about controlling
humidity, but why do you need tocontrol humidity in,
particularly the crawl space.
Well, if you think about it,most people that maybe are
(01:38):
unfamiliar with crawl spacesdon't necessarily realize that
the crawl space is actually partof the home.
I mean, just because it's underthe house does not mean it
cannot affect the house.
It can affect your home indifferent ways, like high
humidity.
I know I didn't list it here,but it can cause your hardwood
to begin to cup because thathigh humidity gets absorbed
(02:02):
inside the wood of the subfloorand the joists and creates a
moisture problem even up intothe hardwood.
The main reason why you shouldcontrol humidity is I've listed
four main reasons right here.
You should look at controllinghumidity to prevent mold.
Here's a great picture of whathumidity can do to your crawl
(02:24):
space.
Look at that.
That is just horrible mold allover these floor joists and
probably behind the insulationas well.
But if you think about it,there's no standing water here,
there's no leak or anything likethat.
This is all from humidity, highhumidity, getting absorbed by
(02:44):
the wood and by the insulation,and then this is probably some
kind of brown wood rot fungusthat can even eat away at the
wood itself and destroy thefoundation of your home, make
structural problems for you ifyou hear a lot of squeaking
floors and things like that.
But another thing that'soverlooked about humidity is it
(03:05):
also causes dust mites to growuncontrollably.
For some of you that don't know, dust mites are actually the
number one cause of asthma amongchildren.
So if you're like me and youhave kids and you want to
protect the indoor air qualityof your home, whether you have a
basement, whether you have aslab or whether you have a
crawlspace, you should controlhumidity.
(03:31):
And these are going to coverthe five things that we feel
like you should do to controlhumidity.
But before I get into that, howdo you even know if your
humidity is out of control?
We got a couple of devices righthere that we recommend.
That's on our DIY store is youcan get a handheld humidity
reader.
Now, this is more for someonelike recommend.
That's on our DIY store is youcan get a handheld humidity
reader.
Now, this is more for someonelike us that's going in to
inspect a crawl space.
You can go in and you can likeopen this up and and test the
(03:54):
humidity, go to different partsof the crawl space and things
like that.
But if you're looking for aconsistent way to check humidity
.
We recommend the ThermaProhumidity reader right here.
And these are the bases.
Now, you can get several ofthese.
You can have one in, maybe, abasement, one up in the attic,
you can even put one outside andthen obviously, one in the
(04:16):
crawl space.
It will handle, I believe, fourtotal bases, but you can check
out the DIY store for that, andthen you can choose which base
you want to look at whether it'sthe living space or the crawl
space of the outside and, plus,this base right here will also
check the humidity.
So this is checking thehumidity of where it's located.
(04:36):
A lot of people put it in theirkitchen or something like that,
so that way you can keep an eyeon the home's humidity all the
time.
Winter, spring and summer andfall obviously different times
of the year your humidity levelsmay be different.
So let's look at the firstreason, or the first thing you
should do to control humidity,which this may seem like a dumb
(04:59):
number one, but, believe it ornot, we go to homes a lot of
times, whenever they have hiredsomeone did not seal the vents.
They'll put in a dehumidifiereven and did not seal the vents,
as you can see right up in here.
We seal them that's theimportant part Just cutting a
(05:22):
piece of foam board, or I'veeven seen people shove
comforters inside crawl spacevents, or maybe they'll take a
piece of cardboard and some tapeand 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 sothat way we've got some
(05:47):
insulation there in the vent, aswell as using a spray foam
sealant, or what they call sprayfoam insulation, to seal around
that so that air and highhumidity can't come into those
vents.
Okay, so now this one may seemlike a weird thing to say, but,
believe it or not, this doesn'tdo really anything to control
humidity.
But if you're going to controlhumidity, according to the EPA,
(06:10):
by sealing the vents andinstalling a dehumidifier, you
should have a foundation ventfan installed to blow air out of
the crawl space.
Believe it or not, if you donot do this, you could be
creating a soil gas problem.
If you have an open or ventedcrawl space right now and then
(06:31):
you seal up every single ventwithout putting some kind of
foundation vent system in thereto basically get that air out of
the crawl space.
It's got nowhere to go but upin your living space.
Now, not everyone has radon,but typically soil gases are in
every part of the country thatcould be even weird smells
(06:53):
methanes and different thingslike that.
So you want to try to divertthose soil gases out of the
crawl space while controllinghumidity, which is what some
people would call a hybridencapsulation system.
So this is very effective.
It's what we typically do everysingle time because, as I
mentioned before, it isrecommended by the EPA to
(07:13):
control soil gases.
It's one CFM cubic feet perminute of air for every 50
square feet of crawl space.
Now these Lamanco PCV1s are ourgo-to foundation vent fan.
You can get these on our DIYstore, but I want you to also
take a look.
We've sealed the top.
You just don't throw this inhere.
You also, if you've got anopening up here, you want to
(07:34):
make sure that you seal the topof this as well with a spray
foam sealant and then make surethat you don't have a lot of
backflow coming in because ofthis fan.
I would recommend you set it'sgot different humidity settings.
We turn it to the on position,so that way it's constantly
running year round to get all ofthose soil gases out of your
(07:59):
crawl space.
Again, that has nothing to dowith controlling humidity, but
it is part of our humiditycontrol procedure.
Okay, this is a huge one.
You've already seen thispicture when I talked about
sealing the vents.
But look at this right here.
See how we took the vaporbarrier all the way up and
covered as much cinder block orconcrete depending on what your
(08:22):
foundation walls are made of aspossible with the vapor barrier,
or the plastic, as some peoplewould call it.
The reason why we do this isbecause if you've got dirt on
the other side of thisfoundation wall and you get
moisture penetrating through theCMU, the concrete or whatever
it is your brick, your stone,whatever that foundation wall is
(08:43):
made of then that moisture isgoing to evaporate or try to
evaporate, causing humidityspikes, especially during
thunderstorms and differentthings like that.
So taking the plastic as highup the wall as you can and
attaching it near the sill plateis the better way to handle it.
Now we have to leave this gap.
Here in Tennessee it's aminimum of three inches.
(09:04):
Now check with your local codesto see if you require that gap
or not, but here in Tennesseeit's three inches In Georgia it
is six inches and then we'realso going to overlap and tape
the vapor barrier.
Okay, a lot of companiesthey'll just throw it down and
even the white, pretty vaporbarrier, they'll just throw it
down, won't overlap and tape it,as you've seen in many of our
(09:27):
videos.
So if you don't overlap this aminimum of six inches, but a
little bit more is better youwant to overlap and tape this.
You can see this tape seamright here.
So we got it overlapped and youcan almost see we took it all
the way to here on the overlap.
The reason why we did that isbecause, in case there's any
standing water underneath thisplastic, it has to travel
(09:49):
further before it can come backand get on top of our vapor
barrier.
So we overlapped it and tapedit quite a bit and that way it
keeps all that moisture behindthe plastic and makes that
dehumidifier run less.
Okay, here is another veryimportant thing you should do I
(10:09):
believe this would be numberfour in our reasoning or our
things that we should do to sealthe crawl space up and control
humidity, and that would be airsealing the door.
As you can see, this is abefore we went and built a frame
all around this door frame,okay, and then we used a caulk
and different adhesives likethat that and then installed a
(10:32):
new door all the way around it.
We used gaskets and alsoinsulated the inside of this
door.
So you want to make sure youair 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 canget some of those air sealing
gaskets and things like that atHome Depot and Lowe's and make
sure you air seal this door asgood as possible.
(10:55):
Before I move on to the lastthing, I want to ask you to
please like and subscribe thisvideo.
We hope this is being goodinformation for you all out in
crawl space, ninja land, andalso leave a comment below.
I am obviously not coveringevery single thing about
controlling humidity.
If you had a unique situationwith your crawl space, that
maybe you did all of thesethings, but there was one more
(11:16):
like.
For example, if you havestanding water, you may want to
install a sump pump or thingslike that.
Whatever comments you want toleave down below, and if you
need to request a quote, go tocrawlspaceninjacom and get a
free quote up there as well, asif you're a DIYer and you need
some of these dehumidifiers orvapor barriers or things like
that, you can go todiycrawlspaceninjacom and
(11:39):
purchase that for yourself.
The last thing, the last thingand this is probably the
question we get the most is doyou need this?
And many of your crawl spacecompanies will not install it,
and that, of course, is thedehumidifier.
Now, we prefer the Aprilairedehumidifier.
It's been great for us.
(12:01):
It uses aluminum coils, it hasless corrosion and things like
that because of that.
But you can also see thedehumidifier in the condensate
pump.
Typically, your crawl space islower than the rest of the house
, so having the dehumidifierdrain into the condensate pump
and then taking that water upand out of the crawl space is
(12:22):
the final thing.
So if you'll do those fivethings, if you'll start there
and control humidity in yourcrawl space, then that is a
great start.
And, like I said, let me knowdown below if you've got another
thing that you feel likehomeowners could do to improve
the humidity in their home.
My name is Michael Church withCrawl Space Ninja, and we hope
you make it a happy and blessedday.
We'll see you later.
Michael Church with Crawl Space Ninja, and today I
want to talk to you all aboutthe five crucial things that we
here at Crawl Space Ninja feellike every crawl space should
have in order to controlhumidity.
Stay tuned, okay.
(00:31):
So if you're new to Crawl SpaceNinja, we talk about everything
related to basements, attics,crawl spaces and duct work, so
we hope you'll subscribe to ourchannel and ring that
notifications bell.
Okay, so what we're going totalk about today is the five
crucial items we feel that everycrawl space encapsulation
company should utilize wheneverthey're trying to control
humidity in the crawl space.
And, believe it or not, a lotof companies miss one, if not
(00:54):
more than one, of what we feelare these five crucial steps.
So we hope this will help eachof you know whether you're going
to DIY your own crawl spaceencapsulation or hire a
contractor to take care of thatfor you.
We feel like these are thingsthat everybody should do as a
minimum in order to controlhumidity in their crawl space.
(01:15):
So let's get started, all right.
So the first thing you want tolook at is why do you even need
to control humidity?
Okay, you know everybody'stalking about controlling
humidity, but why do you need tocontrol humidity in,
particularly the crawl space.
Well, if you think about it,most people that maybe are
(01:38):
unfamiliar with crawl spacesdon't necessarily realize that
the crawl space is actually partof the home.
I mean, just because it's underthe house does not mean it
cannot affect the house.
It can affect your home indifferent ways, like high
humidity.
I know I didn't list it here,but it can cause your hardwood
to begin to cup because thathigh humidity gets absorbed
(02:02):
inside the wood of the subfloorand the joists and creates a
moisture problem even up intothe hardwood.
The main reason why you shouldcontrol humidity is I've listed
four main reasons right here.
You should look at controllinghumidity to prevent mold.
Here's a great picture of whathumidity can do to your crawl
(02:24):
space.
Look at that.
That is just horrible mold allover these floor joists and
probably behind the insulationas well.
But if you think about it,there's no standing water here,
there's no leak or anything likethat.
This is all from humidity, highhumidity, getting absorbed by
(02:44):
the wood and by the insulation,and then this is probably some
kind of brown wood rot fungusthat can even eat away at the
wood itself and destroy thefoundation of your home, make
structural problems for you ifyou hear a lot of squeaking
floors and things like that.
But another thing that'soverlooked about humidity is it
(03:05):
also causes dust mites to growuncontrollably.
For some of you that don't know, dust mites are actually the
number one cause of asthma amongchildren.
So if you're like me and youhave kids and you want to
protect the indoor air qualityof your home, whether you have a
basement, whether you have aslab or whether you have a
crawlspace, you should controlhumidity.
(03:31):
And these are going to coverthe five things that we feel
like you should do to controlhumidity.
But before I get into that, howdo you even know if your
humidity is out of control?
We got a couple of devices righthere that we recommend.
That's on our DIY store is youcan get a handheld humidity
reader.
Now, this is more for someonelike recommend.
That's on our DIY store is youcan get a handheld humidity
reader.
Now, this is more for someonelike us that's going in to
inspect a crawl space.
You can go in and you can likeopen this up and and test the
(03:54):
humidity, go to different partsof the crawl space and things
like that.
But if you're looking for aconsistent way to check humidity
.
We recommend the ThermaProhumidity reader right here.
And these are the bases.
Now, you can get several ofthese.
You can have one in, maybe, abasement, one up in the attic,
you can even put one outside andthen obviously, one in the
(04:16):
crawl space.
It will handle, I believe, fourtotal bases, but you can check
out the DIY store for that, andthen you can choose which base
you want to look at whether it'sthe living space or the crawl
space of the outside and, plus,this base right here will also
check the humidity.
So this is checking thehumidity of where it's located.
(04:36):
A lot of people put it in theirkitchen or something like that,
so that way you can keep an eyeon the home's humidity all the
time.
Winter, spring and summer andfall obviously different times
of the year your humidity levelsmay be different.
So let's look at the firstreason, or the first thing you
should do to control humidity,which this may seem like a dumb
(04:59):
number one, but, believe it ornot, we go to homes a lot of
times, whenever they have hiredsomeone did not seal the vents.
They'll put in a dehumidifiereven and did not seal the vents,
as you can see right up in here.
We seal them that's theimportant part Just cutting a
(05:22):
piece of foam board, or I'veeven seen people shove
comforters inside crawl spacevents, or maybe they'll take a
piece of cardboard and some tapeand 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 sothat way we've got some
(05:47):
insulation there in the vent, aswell as using a spray foam
sealant, or what they call sprayfoam insulation, to seal around
that so that air and highhumidity can't come into those
vents.
Okay, so now this one may seemlike a weird thing to say, but,
believe it or not, this doesn'tdo really anything to control
humidity.
But if you're going to controlhumidity, according to the EPA,
(06:10):
by sealing the vents andinstalling a dehumidifier, you
should have a foundation ventfan installed to blow air out of
the crawl space.
Believe it or not, if you donot do this, you could be
creating a soil gas problem.
If you have an open or ventedcrawl space right now and then
(06:31):
you seal up every single ventwithout putting some kind of
foundation vent system in thereto basically get that air out of
the crawl space.
It's got nowhere to go but upin your living space.
Now, not everyone has radon,but typically soil gases are in
every part of the country thatcould be even weird smells
(06:53):
methanes and different thingslike that.
So you want to try to divertthose soil gases out of the
crawl space while controllinghumidity, which is what some
people would call a hybridencapsulation system.
So this is very effective.
It's what we typically do everysingle time because, as I
mentioned before, it isrecommended by the EPA to
(07:13):
control soil gases.
It's one CFM cubic feet perminute of air for every 50
square feet of crawl space.
Now these Lamanco PCV1s are ourgo-to foundation vent fan.
You can get these on our DIYstore, but I want you to also
take a look.
We've sealed the top.
You just don't throw this inhere.
You also, if you've got anopening up here, you want to
(07:34):
make sure that you seal the topof this as well with a spray
foam sealant and then make surethat you don't have a lot of
backflow coming in because ofthis fan.
I would recommend you set it'sgot different humidity settings.
We turn it to the on position,so that way it's constantly
running year round to get all ofthose soil gases out of your
(07:59):
crawl space.
Again, that has nothing to dowith controlling humidity, but
it is part of our humiditycontrol procedure.
Okay, this is a huge one.
You've already seen thispicture when I talked about
sealing the vents.
But look at this right here.
See how we took the vaporbarrier all the way up and
covered as much cinder block orconcrete depending on what your
(08:22):
foundation walls are made of aspossible with the vapor barrier,
or the plastic, as some peoplewould call it.
The reason why we do this isbecause if you've got dirt on
the other side of thisfoundation wall and you get
moisture penetrating through theCMU, the concrete or whatever
it is your brick, your stone,whatever that foundation wall is
(08:43):
made of then that moisture isgoing to evaporate or try to
evaporate, causing humidityspikes, especially during
thunderstorms and differentthings like that.
So taking the plastic as highup the wall as you can and
attaching it near the sill plateis the better way to handle it.
Now we have to leave this gap.
Here in Tennessee it's aminimum of three inches.
(09:04):
Now check with your local codesto see if you require that gap
or not, but here in Tennesseeit's three inches In Georgia it
is six inches and then we'realso going to overlap and tape
the vapor barrier.
Okay, a lot of companiesthey'll just throw it down and
even the white, pretty vaporbarrier, they'll just throw it
down, won't overlap and tape it,as you've seen in many of our
(09:27):
videos.
So if you don't overlap this aminimum of six inches, but a
little bit more is better youwant to overlap and tape this.
You can see this tape seamright here.
So we got it overlapped and youcan almost see we took it all
the way to here on the overlap.
The reason why we did that isbecause, in case there's any
standing water underneath thisplastic, it has to travel
(09:49):
further before it can come backand get on top of our vapor
barrier.
So we overlapped it and tapedit quite a bit and that way it
keeps all that moisture behindthe plastic and makes that
dehumidifier run less.
Okay, here is another veryimportant thing you should do I
(10:09):
believe this would be numberfour in our reasoning or our
things that we should do to sealthe crawl space up and control
humidity, and that would be airsealing the door.
As you can see, this is abefore we went and built a frame
all around this door frame,okay, and then we used a caulk
and different adhesives likethat that and then installed a
(10:32):
new door all the way around it.
We used gaskets and alsoinsulated the inside of this
door.
So you want to make sure youair 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 canget some of those air sealing
gaskets and things like that atHome Depot and Lowe's and make
sure you air seal this door asgood as possible.
(10:55):
Before I move on to the lastthing, I want to ask you to
please like and subscribe thisvideo.
We hope this is being goodinformation for you all out in
crawl space, ninja land, andalso leave a comment below.
I am obviously not coveringevery single thing about
controlling humidity.
If you had a unique situationwith your crawl space, that
maybe you did all of thesethings, but there was one more
(11:16):
like.
For example, if you havestanding water, you may want to
install a sump pump or thingslike that.
Whatever comments you want toleave down below, and if you
need to request a quote, go tocrawlspaceninjacom and get a
free quote up there as well, asif you're a DIYer and you need
some of these dehumidifiers orvapor barriers or things like
that, you can go todiycrawlspaceninjacom and
(11:39):
purchase that for yourself.
The last thing, the last thingand this is probably the
question we get the most is doyou need this?
And many of your crawl spacecompanies will not install it,
and that, of course, is thedehumidifier.
Now, we prefer the Aprilairedehumidifier.
It's been great for us.
(12:01):
It uses aluminum coils, it hasless corrosion and things like
that because of that.
But you can also see thedehumidifier in the condensate
pump.
Typically, your crawl space islower than the rest of the house
, so having the dehumidifierdrain into the condensate pump
and then taking that water upand out of the crawl space is
(12:22):
the final thing.
So if you'll do those fivethings, if you'll start there
and control humidity in yourcrawl space, then that is a
great start.
And, like I said, let me knowdown below if you've got another
thing that you feel likehomeowners could do to improve
the humidity in their home.
My name is Michael Church withCrawl Space Ninja, and we hope
you make it a happy and blessedday.
We'll see you later.
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