Different Ways To Insulate Your Crawl Space

There are different ways to insulate your crawl space - Understanding the different types will help you choose the best insulation for your crawl space.
Fiberglass Insulation
Fiberglass insulation is the oldest type of crawl space insulation, and is installed between the floor joists and the crawl space ‘ceiling’.
- Advantages: Fiberglass is readily available, inexpensive, and easy to install
- Disadvantages: Can support fungal growth, is ruined by exposure to moisture and humidity, and rodents bed in it
Closed Cell Spray Foam Insulation
Closed cell spray foam is made up of cells that are completely closed. The cells are pressed together so air and moisture are unable to get through the foam.
- Advantages: Fast and effective install, not damaged by water or moisture, and expands to fill in gaps providing larger coverage area
- Disadvantages: Restrictively high cost product, permanent install (can't be easily removed), and must be installed by an experienced professional (overspray creates a messy clean up)
Foam Board Insulation
Foam board is wrapped in reflective foil to create a barrier against water, fungal, and air. The higher the R-value required, the thicker the foam board.
- Advantages: Creates thermal efficiency, no messy install, and is waterproof (resistant to water damage)
- Disadvantages: Can be difficult to install around obstacles in your crawl space and doesn't expand to fill voids
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Think you have an issue in your crawl space? Don’t let things get out of hand, you can call on the trusted local experts at Crawlspace Medic® to provide crawl space encapsulation services that keep your property protected by creating a reliable barrier between your home and the outdoors.
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[@ajsdriver7988]

PRICELESS VIDEO!! I've watched hours of videos. Learned tons on how and why.. but this simplifies it and actual footage is TRULY PRICELESS!! TY TY TY

[@matiasperttula3257]

Great Video! Great information.

[@stevenbusch9336]

Thanks

[@twilde3754]

My home is a 1907 small, brick home in Denver, CO -- very dry and (can be) very cold in the winter. I have an uninsulated crawl space. It's sealed as well. Half the basement is the closed crawl space the other half is a basement that holds the furnace and water heater and storage. The main floor pine floors are chilly when it's very cold outside. I've read that R25 or R30 is best for fiberglass insulation in my region. What do you think about fiberglass versus the other two given the specs of my home? Thank you!

[@JonathonNeville]

Great video! But you don't describe the floor! On a concrete floor* would you install a plastic sheet vapor barrier before installing insulation? I can fit 3'-wide insulation boards thru the opening into my crawl space, but boards are sold 4' wide. What are you using on the floor in the 3rd part of the video? * (45 years old with no cracks, so not likely to develop cracks)

[@chuckhall5347]

IF that was by basement I would caulk the gap between the sill plate and the block wall. I would also caulk all the seams in the band joist then put in mineral wool. Is that needed in a crawl space?

[@timvalli3270]

? We have a cabin, built new 18 years ago, I have a 4’ crawl space with concrete walls, in beginning we had problems with moisture on the gravel floor which did have plastic sheathing underneath, I had 2” spray foam put over entire gravel floor which took care of the moisture problem, I also have all my rim joist insulated and have 2” styrofoam sheets over the concrete walls on entire perimeter of the house. Our furnace and ductwork are down there also, which I have somewhat insulated also, I would like to know if I can add insulation between my floor joists throughout entire area? Some people told me no because of future moisture damage, but I think I have all that taken care of- I would appreciate your professional opinion- cabin is 1500 sf, at the Arkansas-Missouri boarder - thank You

[@ramyswar296]

I laid vapor barrier on my walls and dirt floor. Can I put those foam boards over the wall vapor barrier, or do I have to do it under the vapor barrier like in the video?

[@docphi]

What is best for a vented crawl space? WE live in NJ

[@hughmac312]

Patton Oswalt does insulation?

[@dgriffin6074]

The fiberglass batts between my floor joists are sagging; not overtly wet, but I suspect some moisture transfer. I don't want to insulate the whole crawlspace, but would like a more efficient floor insulation. What is the R value of the foam boards, and can I just fasten them to the bottoms of the floor joists? Would that trap moisture between the foam boards and the floors? If so, what about fastening foam boards against the floors between the floor joists?

[@ambilaevus7607]

I'm curious of this exact same thing.

[@GrandmaD2024]

I just purchased rockwool insulation for the ceiling of my crawlspace. I live on a river and get a little water in my crawlspace. I also have open air vents that I open and close each spring/fall. The fiberglass insulation down there right now is starting to fall down. I have installed a lot of insulation and it looks like it was not cut right nor was it stapled up. However it does appear to look ok as far as thickness etc. So, my question is, should I put a plastic barrier up after insulating? My home is a 1950;s home and IDK how old the fiberglass insulation is so I was just going to remove it. Also, does the spray foam insulation come in a can form? I have only about 2 to 3 feet in height to crawl around down there. Its pretty tight.

[@sandys2672]

I heard only pros of foam and boards - any cons?

[@JOMO_EDC]

The R19 part you had mold right above your head.

[@vinnyp2490]

Great video John and Craig, question, if you have a open crawl space, how many inches of CLOSED CELL spray foam do you need between your floor joist to form a moisture barrier? Thank you in advance.

[@vinniecrisante4920]

You have to spray the home to code for the area you live in, the foam if closed cell is a air sealing material so if applied right you would have no worries. A vapor barrier of code in your area in (NC) it is a 6 mil plastic, my company prefers to use a 10 mil. The barrier will help protect the foam and wood from the ground moisture but if you do not encapsulate it and leave it vented over time the foam my be damage due to the moisture from the vents. Hope this helps

[@alexanderwalsh4086]

Great video! My understanding is that foam board insulation isn't okay (from a fire resistance standpoint) in accessible crawl spaces. Seems like spray foam might also have the same problem since I'm not sure it's as fire resistant as fiberglass. How do you handle the fire resistance issue?

[@viperman300]

Some spray foams are actually more fire retardant than traditional insulation so that can be an added benefit. This does not apply to great stuff type spray cans. Some of these are VERY flammable.

[@xAnAngelOfDeathx]

Actually where I live the building code allows for foam board insulation in an accessible crawlspace however it needs to be covered with 1/2" drywall.

[@vinniecrisante4920]

Some spray foams have a fire resistance mixture in them or that can be applied with or after the application. Spray foam is very expensive and if not done right can lead to a huge loss. Not all crawl spaces have to be encapsulated. It can sometime be a cheaper option companies unlike the one I work for may not explain to you that your floor may be cooler( wood for sure) due to the dehu controlling the CS at 55. Also the fact that we all know cold air and hot air want to meet so with no insulation to stop the transfer guys who gets to handle that bill. YOU its You, lol. Also you have to replace the 20-30 dollar merc 11-13 filter in the dehu at least once a year and some people sell you a two piece dehu with a condensate pump when good WatchDog dehus can do it all for you and are just as compact. Hope this helps

[@footprintsinthesand204]

i live on the water in MD. i have a crawl space. What would you reccomend?

[@Vincegould]

What if it’s wet and there is a sump pump. What kind of insulation do you suggest?

[@mwngw]

Where are you located? Ever see floor joist spacing at 32" on center?

[@scottschmittmusic]

I need to to insulate the ceiling of it

[@charlesgentry4048]

Why are the vents open in the 3rd part of the video? He said it was sealed correct??

[@jfaust97]

Can you please explain more about what a "sealed" crawl space is? In the lest segment of the video with the reflective foam board you state that is a sealed crawl space... but I see a vent to the outside right over your shoulder? Can you clarify? Thanks!

[@yayinternets]

I'm not an expert, but from what I understand, you completely seal up a crawlspace, but also design a way to move air/moisture.. like maybe an air exchanger, dehumidifer, etc. Depends on locale.

[@justinclark3649]

So if I enclose the crawl space then I don’t have to insulate the sub floor ?

[@howtodoitdude1662]

What about spray foam on the ceiling?

[@another1bitesdusty]

That can trap moisture in the boards and cause rot damage. It also makes it very difficult to work on wiring or anything else that runs through the floors joists.

[@creativeorca]

can you install the foam board on the joist over the r19 insulation?

[@zacmullins7811]

yes

[@whtsmonithnkg1]

Mr. Crawl Space Medic, We're in the great cold State of Michigan and is highly considering insulating our roughly 500 sq ft addition/room on the rear of the home. It sits above a nearly 3 ft high uncovered dirt crawl space with two vents. No other insulation exists, nor does pipes exist here. This room offers freezing cold in the winter months. Now, there's 1 heat register, but of course, this room isn't containing heat. For clarification, would using closed cell spray foam (or) 2" inch foam board reflective insulation be useful with adding insulation to the floors boards with R-19 rolls?

[@vinniecrisante4920]

Hello sorry he did respond but I will lol. I would add a product to the inside of the sub-floor (crawl space side) called prodex or a new one called triplex. I don't know to much yet on triplex but I do know its similar so, Predex is a reflective material with spray foam insulation properties, holds an R-value of 16 if you get it from the Pro-Dex company. Always trust the source. It can be applied in many ways some as simple as a staple gun. You can install the batt insulation after that and remeber wire supports to hold it in, I hope this helps

[@reinhardgentz4042]

How to insulate a vented crawl space?

[@drummonk3699]

How did you affix the reflective foam board to the crawl space walls? What is the thickness and brand of the foam board?

[@CalTek]

My guess would be with something like Hilti DX 5 Foam Board Insulation Nail (can see the round disk on the wall over his right shoulder and another on the right edge of the video.

[@strawhatfarms4860]

Should all the vents in the crawl space be sealed off when doing a full encapsulation?

[@pleskbruce]

Yes. Except: I encapsulated a year ago and have been very happy with it. I have a block foundation and sealed my all vents (by filling in the missing block on each) except one, which I had temporarily closed off with wood, "just in case." Turns out I needed to add an exhaust fan for radon remediation to create a slight negative air pressure in my living space. We are in Virginia where temps have ranged from +5 in December to 100 in July and the crawl space temp has never dropped below 59 nor gone above 79. My radon initially measured between 20 and 30 and now averages about 1.4. I use a dehumidifier so no mold issues. Encapsulation is well worth it in comfort, energy savings, and mold prevention. Plus, it's just a whole lot nicer if I have to get under my house - crawling on a sturdy sheet of plastic rather than dirt (creating dust!), so potentially I could it for storage more easily.

[@yayinternets]

Yes, but you will need a way to deal with radon, moisture, etc depending on your locale. So you might reuse that entry for an air exchanger for instance.

[@shannonherb2048]

What about an old home where there is very little room to work, and it's built on cornerstone with very little wall?

[@ckirk1597]

I have a similar issue, did you ever get an answer?

[@shannonherb2048]

@@ckirk1597 nope. The only real solution is to have the house raised 9 to 12 inches and replumb, new steps and hope for the best.

[@peterrobbins6691]

I incapsulated my crawlspace and live in the north east. I have no insulation. now in there..its about 900 sq ft and 4 ft. I have asked different insulation companies what insulation to use. some say foam on the walls and ceiling, some say just bat insulation on the ceiling and some say use foam board on the walls and don't insulate the celing. Now I'm not sure what to do, who is correct. I have no moisture in my crawlspace, its completely dry. humidity is 24% in the winter and below 50% in the Summer.

[@JonathonNeville]

Do you need the dehumidifier even after sealing the crawl space including the floors? Why?

[@KennyFlagg]

Once it’s sealed, then any humidity which gets in the crawl has a harder time getting out. The dehu is mandatory for most climates once things are air sealed

[@michaelblew6019]

Best for stacked stone?

[@CalTek]

Doing this now in my Century Home (stone walls and dirt floor). I decided to install 1/2" rigid insulation on the walls, tuct taped the seams and put down 6 mil VB on the dirt floor and ran the VB 12-16" up the front of the insulation and taped the seams. Now in the process of framing out with 2x4 (16" OC) then once I have encapsulated the area I am going to try to get the moisture under control (sitting at 80% now) with a dehumidifier. Once that is done I will finish with R14 Rockwool bats and VB then a subfloor. Clearance is around 5' and furnace is in there so going to use it as storage for my plastic totes.

[@Horrrrrribleboy]

By leaving that space, cold air will come right above to the subfloor from the sill and exposed foundation walls.

[@johnchapdelaine9698]

IT IS A CODE THING NATIONWIDE

[@Horrrrrribleboy]

@@johnchapdelaine9698 THAT DOESN’T MAKE IT THE CORRECT WAY TO INSTALL IT !!!!

[@shensley011]

Well then how would you do it mike?

[@Horrrrrribleboy]

@@shensley011 insulate the sills properly

[@mikeboston421]

@@Horrrrrribleboy garbage answer, what do you consider properly?

[@charlesdennyjr3089]

Why did you not spray on wood in between floor joist

[@turbosupra2jzdragracingtob249]

No reply?? Lol. They said the gap from the foam to wood is to inspect for termites. That’s shady. Foam attracts termites and shouldn’t be placed within 3 feet of the ground. The gap is to keep the termites in the foam from reaching the wood. It’s not for inspectors. They made that crap up or lied.

[@youknow1334]

You would be incorrect. It’s code. Check your state. I did when I got 5 quotes and all of them left a gap no matter what they were installing up the foundation walls. It’s easier to run your mouth than to educate yourself

[@Travisrogers87]

Nobody is answering the original question here. Charles is asking why not spray a closed cell foam directly onto the subfloor where the r19 was, between the joists? Many of us don’t have sealed crawl spaces and none of the solutions in this video were good for unsealed.

[@mattmiller3985]

You can just not as efficient. If your going to re-do a crawl space make it encapsulated like most newer homes have moved on.

[@kaaytie84]

My sister bought a home with a crawlspace and her home is always freezing.

[@bobbyballbuster9603]

Dude said they were gonna show some bad insulation...never saw it

[@davidmoye2354]

fiberglass in between the joists is usually a bad idea

[@KhmerH20]

@5:09 what's this white stuff on the floor called?

[@KennyFlagg]

Vapor barrier. Don’t know the brand used here. Usually 12-20 millimeters thick depending on the substrate beneath. Some people add dimple mats for draining and longevity

[@EdA-bz3bu]

Did not spray foam around the piers and did not tape the seams on the form boards. 😳

[@turbosupra2jzdragracingtob249]

The “gap” is to keep the termites that get into to the foam from reaching the wood. Foam attracts termites. Not suppose to be sprayed within 3 feet from the ground.

[@pjmuffin]

Foam does not attract termites. The "gap" is there to allow for termite inspection access.

[@breety_boy866]

As a termite technician my main problem with that spray foam insulation is that termites can still get behind it and travel through the cracks in a cinder block. It’s nice that there’s a gap to allow for an inspection, but if termites are spotted all of that material has to be removed, at least where the grade meets the foundation, to allow the soil to be treated.

[@jwxap0p]

​@@breety_boy866 it sounds like you are describing closed cell spray foam on the exterior side of wall that touches soil, correct? Or does the interior foam application of a crawl space need to be removed to treat the soil?

[@rickjames6948]

Can someone address the sinking effect of cellulose please? I had over 10 inches blown in several years ago. They even left the paper sticks showing how much was blown in. Now it's all level with the rafter tops where you walk. Total waste of money. At least bats won't disappear over time like cellulose does.

[@nate456]

i see sunlight

[@JGilbert529]

So don’t insulate my floors in Maine?

[@SUNSHINE-bf3bw]

I am, lol

[@amypaul9687]

Go under geoy

[@xAnAngelOfDeathx]

If the rim joist isn't insulated then the spray foam on the foundation wall is pretty much a waste of money and useless.

[@dionfrutos7997]

Question if you insulate floor framing with r13 insulation rolls you know the kind where they say paper to the people is it okay to board up insulation.

[@allpointsorganized]

He's right about rim joists.

[@ironnads7975]

​@@dionfrutos7997 Wanna rewrite that so it makes sense?