6 Essential Areas to Insulate in a Vented Crawl Space

[@keeblerkelloggs]

Excellent video with great information! Thank you, Michael!

[@BVSwanson]

Thanks, Michael. Very informative video.

[@CrawlSpaceNinja]

I'm glad it was helpful! Thanks for watching.

[@mikegreenamyre58]

Thanks!

[@CrawlSpaceNinja]

Wow. Thank you so much!!

[@jimbo8743]

This guy is the best 👍

[@CrawlSpaceNinja]

Thank you Jim Bo

[@anon31415]

wow. Greaat video. I do have a question. Why not have a guy spray the entire under subfloor and joists? I am buying a house in Georgia. The inspector's report showed all the fiberglass insulation had fallen or was taken down. There is some mold on the subfloor and joists. The relative humidiity was 80%. I would like to convert it from a vented to an unvented crawl space or at least spray the entire undersurface.

[@CrawlSpaceNinja]

The first thing we'd suggest is taking a look at that mold. Please check out these videos we have on the subject. kzbin.info/www/bejne/lXiXnYloqsqffsk kzbin.info/www/bejne/epXOn3t9e6p-fpo

[@latebloomer7191]

Michael, love your videos! I live in Virginia and plan to leave my crawl space vented, and unencapsulated. So this video is very helpful. You don't mention the vapor barrier. Is it correct to assume that would be my last step, after I cover all the steps you explain here? (Plus, insuring my crawl space door is sound.)

[@CrawlSpaceNinja]

Hey Latebloomer! You shouldn't use a vapor barrier to cover the insulation but laying a vapor barrier on the ground is still advised. Check out this video "Should You Install Vapor Barrier on Crawl Space Ground" for more information: kzbin.info/www/bejne/oH3WiJinp6iIg5Y

[@golsco1]

Would you recommend using foam board fastened to the bottom of the joists after the kraft faced insulation is in place in a unheated yet insulated enclosed porch. Three sides will be open except for nonairtight decorative skirting.

[@CrawlSpaceNinja]

We would like to go deeper into this. Please fill out a Ask a Ninja form here - crawlspaceninja.com/ask-a-ninja/

[@jaygobolos5563]

great info...thank you

[@DarkerSideOfDawn]

Dude! Thank you for the education. I never thought I’d need it :( My neighbor did some serious reconstruction and all his rainwater started pooling into my crawl space . I think he did it on purpose . Well this bitch is making lemonade. I already redirected the surface water down and around my fairy garden .. my serpent now has a moat lol and once this cold snap passes im going down into my crawl to take a peek. What I have learned is that my ex didn’t care too much about his grandmas little house .. well I do.. I’m going to find a way to hook up my sump pump to a rain barrel to water my other plants .. and I’m upping my native rain garden game .. Muahaha!!

[@CrawlSpaceNinja]

Happy to see you got it down! You got this!

[@VitaKet]

Love the videos, have a question. I live in VA and my crawl space has insulation that I am going to be replacing and was thinking about laying a vapor barrier down as well. Did you say not to use a vapor barrier if you have insulation? As in don't used backed insulation or don't use a vapor barrier if I'm insulating the floors?

[@CrawlSpaceNinja]

You shouldn't use a vapor barrier to cover the insulation but laying a vapor barrier on the ground is still advised. Check out this video "Should You Install Vapor Barrier on Crawl Space Ground" for more information: kzbin.info/www/bejne/oH3WiJinp6iIg5Y

[@chipfornaris]

Hey there, what about using thick poly to put on the floor of the crawl space. The idea is to stop the moisture from seeping up through the ground ....also why not just not have any insulation if the crawl space is open on all sides and has great airflow.

[@CrawlSpaceNinja]

That would work in dry mild climates but does not work where we are as far as letting air flow. Good vapor barrier is recommended as you suggest. Thanks for watching.

[@smallfeet4581]

​@@CrawlSpaceNinja I'm in UK and need to leave air flow up between lathe and plaster so can I just put insulation to edge of floor between joists , the crawl space is about 4ft with tar on the ground or something like that but not earth anyway , there are 4 vents below the floor level (never thought I could cover them in winter , will try that till spring ) , I do need to insulate my walls at some point , I just am not sure of what insulation to use , health-wise fibre glass is not good for asthmatics , wool sounds good , eco is plastic and I'm hearing things about plastic micro pieces in the air not being good so reluctant but wool is expensive but my best option I think , don't think I can stop airflow around the house but I'm just not sure , oh wow it's not easy when you don't know things lol

[@confidentlocal8600]

I'm insulating the subfloor above my vented crawlspace. The goal is to use an ATMOX system with louvered fans and dehumidifier to separately condition the space. (I close the vents and run dehu when outdoor humidity is high.) I have air sealed all subfloor penetrations and am using rock wool to insulate the subfloor. A mold remediation company placed batt insulation against the rim joists. I later found it stuck to the wood with black staining behind it, I assume from condensation on very cold winter nights, so I've removed it. As I install the rockwool, I've been leaving an inch gap between the batts and the band joist to prevent further condensation. Is this a good idea, versus running the batts all the way? I do not want foam against the band, because it is possible for it to get wet if the brick gets soaked (has happened), and I want it to be able to dry to the inside. The sill is not pressure-treated, either.

[@CrawlSpaceNinja]

It is common for rim joists (also known as band joists) in older homes to be uninsulated, despite being only separated from the outdoors by sheathing and siding. As rim joists are above grade, it makes sense to insulate them to the same level as above-grade walls. Rim joists connect many building components - foundation walls, mudsills, rim joists, subfloors - so securing all cracks is essential. Fiberglass batts are no longer recommended as a method of insulating rim joists. The air permeable nature of fiberglass batts means that warm, humid interior air can still reach the rim joists. When the rim joists are cold in the winter, condensation can cause mold and rot. In order to avoid these problems, only rigid foam or spray polyurethane foam should be used to insulate the interior of rim joists. A second ring of rim joists usually runs above the ceiling on the first floor of a two-story home. A cellulose-insulation contractor should be hired to insulate these rim joists.

[@erikmiller2317]

what's best practice in the mountain west? seems most crawlspaces are vented and humidity is rarely an issue. I just bought a 1978 home in the Sierra Nevada. critters had gotten into the crawlspace so I need to reinsulate. Should I stick with the vented system in place? Would there really be any benefit to converting it to an encapsulated crawlspace?

[@CrawlSpaceNinja]

Hey Erik, Check out this video about the benefits of Encapsulation: kzbin.info/www/bejne/aqmTg3-fbax2a6M Thanks for watching!

[@johncosenza3567]

I am replacing all the subflooring in house. The subflooring is removed and the original insulation has settled and has been compacted over the years. Is it wise to use blow in cellulose insultation on top of the fiberglass to fill the gaps and the spaces up to the top of the joist? Then lay down the subfloor. The crawl space below is dirt and vented.

[@CrawlSpaceNinja]

In a vented crawl space the insulation is supposed to touch the subfloor. Your way of doing it is not the usual way but I don't think it will hinder your project. My only concern is if moisture gets into the insulation but moisture is always my concern :).

[@adamtki]

How should we insulate next to the crawl space vent? Just cut the insulation about two feet from the opening?

[@CrawlSpaceNinja]

Yes, that can be done. I've also seen insulation over a sealed vent partially or fully covering it as long as there was no need to access it in the future. Hope that helps. Thanks for watching.

[@Lagunas88]

Hi there. I live in Los Ángeles with vented crawl space.. would you recommend adding some rock wool and then attic foil across? Do you think the attic foil would help in any way in a crawl space? Thank you.

[@CrawlSpaceNinja]

Hey Act Sxazon! Thanks for the question. Rock wool is made from recycled stone dust and does not burn or need to be covered to prevent fires. Since mineral wool cannot act as a vapor barrier, it is best to apply a poly membrane first. In terms of radiant barrier foil in a crawlspace, it is beneficial if you lose heat in the winter through the floor of the house into this crawlspace. Attic foil and rock wool can help reduce heat loss through air gaps from the flooring to the ground outside. Let us know if you have any other questions. Thanks for watching and have a happy and blessed day.

[@Alice-bm1lj]

I'm working with a contractor and want to make sure it's being done correctly. For air sealing the subfloor gaps and rim joist- is it OK to use open cell in the vented crawlspace or will that just be inviting wood rot? I also plan to use rock wool to insulate the subfloor.

[@CrawlSpaceNinja]

Feel free to submit a Ask a Ninja Form for expert advice from us - crawlspaceninja.com/ask-a-ninja/

[@justinhubbard8355]

Any advice for sealing around dryer ducts that come down through the floor and out through a vent? Looking to DYI my crawlspace in the coming months and was curious about how best to tackle this concern. TIA

[@CrawlSpaceNinja]

You will need to check with your local code to make verify, but I don't think dryer vents require fireproof caulk. If so, then spray foam should still work fine.

[@TNE2013]

Hi! We have a crawl space with vents. The crawlspace is approximately 12” deep. The contractor placed fiberboards beneath the 2x10 joists, so there is an appx 2” space from the fiberboard to the subfloor. The plan is to place open cell insulation R30 within the joists. (The 2” space beneath will have nothing). Is this normal and do you recommend this? We live in NYC - climate zone 4.

[@CrawlSpaceNinja]

Typically in our area subfloor insulation is applied up to the subfloor with no gaps. The air gaps can trap moisture potentially.

[@seanoramaa]

What if a home does not have a sill plate? Old home with rim joist is directly on cinder block.

[@CrawlSpaceNinja]

Very intresting. Feel free to submit a Ask a Ninja form so we can dive into this together - crawlspaceninja.com/ask-a-ninja/

[@davericard2020]

Question Is there a reason not to just spray foam the entire subfloor? Is it because of cost or is there another reason. I am in Portland OR and contractor was going to spray foam rim with 4” and bottom of subfloor with 1-2” spray foam and then use rock wool R19 batts. Vented Crawl Space by the way

[@CrawlSpaceNinja]

You can spray foam, I did a video with some warnings and advice. I hope it helps you: kzbin.info/www/bejne/g4jTm5d_ZpmpipY

[@davericard2020]

Thank you!

[@MrNiceGuyMEGA08]

Although pipes in an encapsulated crawl space might not need to be insulated to keep from freezing, it's probably a good idea to do so (especially for the hot water line) if they are accessible. One never knows with freezing weather, and the insulation on the hot water lines might save some water and save some energy over the long run.

[@CrawlSpaceNinja]

Great advice! It does not hurt to be prepared for worst case scenarios so you're not dealing with a headache after the fact.

[@bch5513]

I see bigger issues with temp swings and cold pipes sweating bad here. Doing it now here bad. But I have open space working on encapsulation step by step.

[@Brandon-no3vc]

why use insulation with paper?

[@oscarlemos8663]

I have a vented crawl space and I realized from your video all of my subfloor joists have the insulation installed backwards. Should I flip it all the correctly or let it be? I have no idea how long it’s been this way. Only the addition of my house has the crawl space and I notice part of the house with the crawl space, has problem holding heat/ ac.

[@CrawlSpaceNinja]

Don't be concerned if the vapor barrier is silver rather than brown. In contrast, if you see brown paper, you know the insulation is installed backwards, so it doesn't provide much insulation. You would need to install the insulation correctly in order for it to work effectively.

[@stylicho]

What's your take on a number of videos saying to remove regular batt insulation in your crawlspace and just leave it like it is with no insulation? Thanks

[@CrawlSpaceNinja]

We can say we install foam board insultation on the walls and rim joist!

[@barbershop7277]

I would like to know what do you recommend to seal where the pipes and electrical wires come through the floor. I live in FL. Thank You.

[@CrawlSpaceNinja]

We recommend using spray foam.

[@barbershop7277]

@@CrawlSpaceNinja cool thanks. I used that stuff for the first time a few days ago, gosh I pulled the skin off my hands trying to get it off.

[@phil-spinelli]

Could you attach Tyvek to the underside of the joist? Tyvek is suppose to breath, unlike plastic

[@CrawlSpaceNinja]

Hi Phil, we do not recommend having anything attached to the floor joists that would hide a potential leak.

[@FirstnameLastname-qc3xx]

What about insulating the walls as well? Or is it pointless unless the area is encapsulated?

[@CrawlSpaceNinja]

No it isn't pointless! Normally Foam Board Insulation goes on the walls and then a layer of Vapor Barrier up the walls on top of it!

[@laurajones2032]

It’s scary out there in repair land 🍵

[@charlesgreene4347]

What about a vented crawl space in foothills of N.C. I have a aprilaire Dehumidifier already plumb outside for my 1200sq ft. Wanting to encapsulate but not there yet. Thinking about putting on timer for 12hrs on 12hs off to see if Humidity levels can be Tolerable %%%. What are your thoughts?? And what levels should I try for.

[@CrawlSpaceNinja]

If your vents are open there is not much point in running the dehumidifier. The humid air from the outside will make its way in as quickly as the dehumidifier removes it. If you're wanting to encapsulate eventually, go ahead and close your vents, install an active ventilation fan like we talk about in our videos, and set the dehumidifier to around 50% humidity to begin drying out your crawl space. Once the humidity and wood moisture levels are under control, you can remediate mold and encapsulate.

[@charlesgreene4347]

@@CrawlSpaceNinja single or double fan for vent?

[@CrawlSpaceNinja]

This is the fan we install and recommend: diy.crawlspaceninja.com/lomanco-pcv1-foundation-vent-fan/

[@charlesgreene4347]

@@CrawlSpaceNinja Thank you Michael

[@SUNSHINE-bf3bw]

I'm on a 12 inch insulated cement slab, is this called a crawl space too...I have 18in to crawl under there😅

[@CrawlSpaceNinja]

Home foundations can be built on slabs or crawl spaces, depending on your needs. When soil shifts, slabs are more prone to cracking. On sloped properties, crawl spaces work better, but they are more expensive. In earthquake- and flood-prone areas, slabs are more durable, while crawl spaces are more resistant. You shouldn't have any major problems if the crawl space is at least 18" high. In most cases, this is the minimum that a contractor must do to enter your crawl space, assess it, and determine whether or not repairs need to be made. It’s a tight fit, so you might want to skip breakfast before heading in there lol Let us know if you have any other questions. We appreciate you watching and hope you have a happy and blessed day.

[@christianjohnson6519]

Rim joist