Sealing and Insulating the Rim Joist

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The rim joist, for those who are not familiar with building terms, is the edge of the wood floor framing system. It sits on top of the foundation walls, secured to the sill plate.
In a typical home, the rim joist area is a huge source of energy loss. It often lacks proper air sealing, so outside air is consistently leaking in through the wood joints, corner, gaps and openings drilled in the rim joist for electric wires, plumbing and ducts.
When the rim joists are insulated, it is often with pieces of fiberglass batt, which is not the best choice for this type of application. Fiberglass doesn't stop air flow, so the air still leaks in. Also, fiberglass loses R-value when it is damp. Basements tend to be naturally-damp environments due to ground water evaporating into the space and condensation issues.
The results of poor rim joist air sealing and insulation can be felt throughout the house in the form of cold floors, drafty rooms and high energy bills.
The best materials for rim joist insulation are those impervious to water. When the rim joists are easily accessible, pieces of rigid foam board can be cut to snuggly fit on top of the rim joist, between the floor joists and then air sealed with spray foam.
In this particular job, however, Dr. Energy Saver chose another great option to insulate rim joists on top of stone basement walls: two-part polyurethane spray foam.
Two-part polyurethane spray foam not only provides superior R-value (R-7 per inch), but is also expands to fill gaps and holes in the rim joist, stopping air leakages in one simple step.
In most homes, even new constructions, there is always an area that can use some improvement in terms of energy efficiency. It can be the rim joist, or your attic that need better insulation. It can be doors and windows that are leaky or air ducts that need to be cleaned, sealed, balanced or insulated. There is often an opportunity to save money and energy. Your local Dr. Energy Saver dealer can help you discover ways to improve your home's energy efficiency, while making your home more comfortable and affordable to own.
For more tips on how to save energy at home, watch our "On The Job" video series and subscribe to our KZbin channel for the latest updates.

[@DennisMathias]

This guy is way above most of the 'home tip' characters on YT. Great narration, editing and audio.

[@GabeSchickLive]

I wouldn't argue the effectiveness of the insulation methods described here, but one thing to consider prior to spray insulation in the rim joist cavities is to make sure there is no wood destroying insect activity (i.e. termites, carpenter ants, powder post beetles, etc). I would really recommend spraying all the rim joist areas with Borathor to prevent aforementioned insects from going after wood that will no longer be accessible once the insulation is applied.Other than that, great video!

[@amurizon]

Great tip! I'm about to spray insulate my rim joist, and this will be an excellent item I add to my checklist to make sure I've covered my bases. :)

[@ModeratelySpeaking]

LARRY- I absolutely LOVE your channel. You are a perfect narrator for the topics that you discuss. You somehow balance both expert and novice information without coming off in an ill manner. Its no wonder that you are so knowledgeable and so successful, in your career. Keep up the great work, Larry! You are saving me dollars!! :P

[@amurizon]

This is super helpful. Now I know why my roommates and I have such cold walls upstairs, and how to approach insulating my unfinished basement. Thanks!!

[@davidwood2081]

You're an excellent teacher thank you for your time

[@nyltonandrade8607]

Thanks for your help. Man that makes a big different.

[@roccogambucci7341]

Wonderfully explained! Thank you!

[@ML-lg4ky]

Excellent visual demonstration!!!!!

[@nancyorkeithm1518]

Thank you I think this solved the mystery of My damp Smelling basement. !

[@braddavenport6346]

What application would you recommend for a block and mortar foundation that isn't exactly flush. It's not not structurally sound but I know rigid foam has to be flush with a block wall or it could cause a pocket which leads to air/moisture and mold? Would I be better off going with the closed cell spray in? What about leaving the 3" for termite inspection? Do you not need to leave any space in the rim joist area for a termite inspection?

[@donluchitti]

Great video. I've been trying to google a difference between standard great stuff spray foam versus polyurethane foam. Do you have an opinion or information on this? Thanks.

[@paivasteveable]

What would you recommend for under a gas fireplace ? Man air that comes from that place is crazy . What will work thanks

[@bluelightning0820]

I counted 108 time you said rim joist….. my wife wouldn’t stop laughing your entire video… thank you sir.. lol

[@bobhaddock957]

where do you get the polystyrene foam board with foil on both sides?

[@Steveshappylittletrees]

Great content.

[@booksatthemovies]

great video, I got all the info I needed, Many thanks.

[@groundhog7652]

Does it really matter that much as to whether to use open cell, or closed cell foam like is recommended here?

[@matthewkiser4454]

Close cell is a moisture barrier.

[@jonpaton4449]

I watched another video that cautioned not to insulate that cavity as the rim joist will trap wicked moister from the foundation wall, and then rot.Might it be smarter to just put insulated board under the sub floor?

[@matthewkiser4454]

Use treated lumber

[@CougarLand]

they have sealants for those sill to foundation and sill to rim joist connections when homes get built.....

[@amurizon]

I recently removed the extra fluffy pink insulation that was stuff into the rim joist spaces of my unfinished basement, only to find that some areas had been sealant-covered, but other areas were clearly not. There were even up to 1/4" gaps between the rim joist and sill plate in some areas where I could see the concrete foundation beyond it. And those were probably where rodent pests were able to get into my basement recently... All that sh* is getting stuffed with wire mesh and spray foamed. xD

[@javiermartinez3041]

Where can I find those black board foam extended polystyrene? Thank you.

[@berg8970]

Caulking your exterior wall sheeting from the outside where it meets the foundation will cut down drastically on energy being lost and drafts you feel by outlet plates in your house. Note I said wall sheeting not siding sheeting is what the siding is nailed to.

[@hotrodder62]

correct.. but caulking will do NOTHING to stop thermal tem transference.

[@thebobandtomshowfan]

We spray foam the rim joist then added batt insulation. About 4 years later we found heavy condensation between the spray foam and batt insulation which caused mold. Should we remove the batt insulation, leave the spray foam insulation, and just dry wall over the basement wall and basement ceiling?

[@stifflers69mom1]

thebobandtomshowfan ARE YOU KIDDING ME I just spent all yesterday installing ridged foam and sealing the edges it with great stuff and I put some fiberglass batt insulation...are you telling me that I’m gonna get moisture problems? ..........is your ridged foam sealed on the edges?

[@thebobandtomshowfan]

No Name: I'm probably going to have to post a video to show all the problems we unveiled after 4 years of construction to our basement. I could not believe the amount of condensation generated between the spray foam and Batt insulation. We had so much moisture created it ran down the basement walls and pooled on the basement floor. Please note our house was built 4 years ago and I have been told moisture will come out of the concrete for several years while it is curing. I'm not sure if that caused all the water or not. We do have a humidifier running and have it set at 35% which is pretty dry but still have lots of condensation dripping from the spray foam that is combined with Batt. Where I removed the Batt, the spray foam stays dry.

[@thebobandtomshowfan]

I really recommend this youtube channel regarding this topic "Home RenoVision DIY". Check out this video which has helped us. kzbin.info/www/bejne/gXjNgGStmcmLbaM

[@stifflers69mom1]

thebobandtomshowfan our house is 30 yrs old and the last owner had just stuffed batt insulation in the joist rim which I was told was a no no because it will create moisture so I took it out to find a HUGE mouse infestation.... but surprisingly absolutely no signs of moisture so I cleaned all the mouse feces up blocked the hole they were getting in at and installed rigid foam and new insulation on top of that hoping that it will be OK.....I hope that your problem was just the new concrete ......Oh yeah I have a block foundation with a basement

[@ShakzT]

Hey guys, schoolboy question from me. Doesn’t something like this raise concern? Say you have below you have a timber floor, and between the sub floor and downstairs ceiling plasterboard, between the cavity you already have rock wool insulation, and now you are sealing the gaps around the joist-to-plasterboard… Shouldn’t you leave some gaps for airflow?

[@donluchitti]

Doctor, the top of my foundation is much more exposed than the drawing of the rim joist area in the beginning of your video. There's like 4-5 inches of cinder block exposed before the sill plate and rim joist. I've insulated the rim joist and foamed where the sill plate meets the foundation but should I cover the top of that cidnerblock?.

[@jl2w711]

I have this same problem.

[@stevescherer6602]

I plan to cover the top openings in the cinder block with PVC trim brad-nailed to the sill plate, then caulked. This is not so much for insulation purposes but to block an insect pathway through the foundation into the house.

[@DrEnergySaver]

Sealing and Insulating the Rim Joist (video) buff.ly/1H2p3cX #energyefficiency #saveenergy #homeimprovement

[@krisbostrom4811]

I want to seal the rim joists around my house, but the basement is finished. Is there anyway of doing this from the outside? Maybe spray foam? Can't take off the sheetrock walls and ceiling on the inside, but I have very high energy bills and very cold floors around base of the house.

[@hotrodder62]

NO this can not be doe from the outside. It would just keep spreading out and over the ceiling and you wouldnt be able to see anything.

[@paulmryglod4802]

Kris Bostrom did you do anything about it?

[@gsb5050]

Would utilizing this method also apply to a balloon framed structure?

[@monkknom6919]

Got to fix that basement wall

[@musicmusic5407]

Where is the power meter?

[@johnward5890]

Loosing the heat out the rim joist isn't the real danger, it's the Moister than build up on the Rim joints and rots the Would and creates a black mold or dry rot. then the bugs move in. Builders have to start properly sealing from the start. There needs to be a cap that go in these spots that clamps on the wood Rim joist and has a sealant built in keeping Cement block and wood apart and seals it at the same time. Something that sits on the Block wall and rim joist sit on it and be high enough to be nailed to the studding and be thin enough to nail sheeting over top. A large Plastic L shape 12" x 12" This could act like the Foam seal and tuck taped to the House wrap for a complete seal. I find rock wool the best insulation it maybe expensive but in the long run much better savings fir resistant to 2100 degree Fahrenheit and get wet doesn't interfere with it's insulating values like Fiberglass because rock wool repels water.

[@matthewkiser4454]

Should be using treated lumber on sill and rim joist. Even on joist themselves. More cost and maybe little less straight causing more work but best long term

[@justwaiting471]

Spray foam encapsulates the wood forever. How do you know if termites or carpenter ants aren't behind it eating the rim joist up? You won't, until it's too late.

[@bobbywanger8123]

👍👍👍🔥🔥

[@CUSTOMWORKS7.3PSD]

WHAT ABOUT THE RIM JOIST ROTTING OUT FROM NO AIR CIRCULATION ?

[@PastorManningPhD]

+allyn bubolz was just thinking this

[@zaphix1367]

Watch TGSNT & Hellstorm z K

[@1PITIFULDUDE]

That's what prevents moisture stacking, stopping the influx of humid air.

[@hotrodder62]

Why would that happen? .. no such thing.. if the spray foam is STOPPING heat loss it ALSO stopping condensation. Thus NO rot. With that thinking why insulate at all ? And just let AIR CIRCULATION run rampante thru the entire home?

[@douglashughes2331]

This can happen. The sill plate sits on the top of the foundation, the foundation is in the ground at 100% relative humidity, insulate the inside wall of the basement, then the rim joist, the moisture in the foundation will have no where to go but up into the sill plate and it will not evaporate because you have removed all air flow from the rim joist bay. The sill plate will be sitting on damp concrete all the time.

[@terryblakesley2670]

I received a quote this week for my 1,000 sq. ft basement, $1200 plus taxes. Last week, an HVAC contractor quoted $1200 to apply rigid foam.

[@jamestroske2513]

Yes these guys are a rip off. $12,000 to do the same job I already had quotes of $6200. Guy came over and wasted 4 hours of my time. Yes this guy is great speaker and they send you a lot of useless waste of money paper materials. This company is greedy and spends a lot of money on videos, decorating their cars, and bullsh*t brochures. I do not recommend this company. $2066 just to vacuum out the 5 inches of old insulation. $600 for a dumpster!!!! 1000 sq. ft. Just use them for a guideline. Good info but, if you have them do it. There is no way in hell you will ever cover half the cost.

[@hotrodder62]

IF they just did they band joist AND it was a BASEMENT and not a crawlspace. Our cost would have been around 450.00 using closed cell

[@mattamal1]

what the average cost

[@amurizon]

I see this is 5 yrs ago, so, not sure if you still need an idea, but you can get $5-6 cans of spray foam insulation from a local hardware store. I've started using that, and it seems helpful (I can no longer feel a breeze when I put my hand near the area I've sprayed). The stuff is super sticky when drying, however, so I'd advise wearing disposable gloves that you can just take off and throw away after using it.

[@mikerodriguez1963]

Great video and explanation. Valuable information, but I would rename the video for more traffic. I didn't find this video until I learned what a rim joist was and searched for it. Most DIYs like me likely don't know the terminology.

[@ericbaker6542]

Why do u have ducks in there?😳

[@kurtcooper3699]

Older homes could certainly benefit from any structural & insulation upgrades where practical. I'm always suspect when an additional method of insulation comes to a well built home & the spray foam has to be added with a protective oxygen mask. I'm sure many here are aware of the spray foams causing serious medical issues when even applied by contractors incorrectly the foam to thick. The more we make our homes air tight the more we have to spend to get fresh healthy air handlers to blow from outside back into our homes due to these tighter insulation methods which create an industry for fresh air handlers. I believe there's a balance know doubt in efficiency vs cost savings but, fresh air is more vitally important than air tight foam insulation. Some of The longest standing homes built which many have little in the way of insulation can @ least not pose a health threat due to chemical foam insulation.

[@hotrodder62]

This is WAY off in its idea. Building science has PROVEN that there is no such thing as "to tight a house" The fresh air you speak of leaking in and out ALSO brings with it.. contaminates, dust, pollen and just plain over all poorer air quality. A blower door test can prove all this.

[@kurtcooper3699]

hotrodder62 I guess we all have an opinion. Some have more experience than others & science would argue with to tight of house theory I'm afraid..... science, yah there still trying to prove what they don't understand & can't figure out but put there opinion in it anyway. U can use passive solar & landscape properties to keep a home cool in the summer & versa in the winter. Keep selling your products people will buy Dr energy savings due to balloon framing before they learn of the next great mouse trap idea. U seal your cracks all u want keep your contamination away from sound, quality craftsmanship in any home built with common sense & good design Dr energy!

[@hotrodder62]

30 yrs in the buis, BPI certified, and over 7000 homes insulated IS my experience.....soooooo........

[@kurtcooper3699]

hotrodder62 last reply- I'll venture those homes are mainly in the city stacked up against one another. When a man boast about what others build for him under a contractors name I'm not impressed. Building homes like they were stamped out all identical in there infrastructure in just under 90 days or less is not building a house in harmony with the lands natural timbers & earths landscape surroundings. If your willing to dispute the oldest most efficient use of passive solar design, earth's natural insulation, & using the tragetory of the sun In each season to allow the natural resources to manage the balance for healthy efficient energy homes that are proven to be nearly 0 loss in energy waist & requiring no manufactured producing resources for consumption year around then it's obvious your determined & would rather spray your cancer causing synthetic chemicals all over your home. So please, by all means be my guest. Enough said!

[@hotrodder62]

And like most that you have spewed .. you would venture WRONG.

[@crushsmith7534]

lol worried about insulating when you have 2 big metal doors leading right outside... scam artist at its finest

[@parkerhibbs9956]

my favorite part of this video is how you try and use all those darn fancy words and all that quick talkin to the good ol folk to sell that daggarn product. man r7?! wow! LOL