Here in easterm Nc i see a lot of insulation contractors going through the trouble of encapsulating a crawlspace and then they leave fiberglass batts at the rim joist. This is the right way to do it. Nice work
I just had fiberglass batt in the rim joist cavities. Pulled it out and put in foam board and spray foam to seal (like you showed), then put the fiberglass back in... no harm and adds just a bit more R-value. My suggestion for even better performance, especially in a crawl space or unheated basement... staple and seal "double-bubble" (Reflectix) insulation sheet to the bottoms of the floor joists and seal those joist cavities across the entire crawl space or basement. Greatly helps keep the floors warmer. Cheap and very easy to install.
Thanks for the great info. Great job. Just one safety suggestion. Cutting foam like that with a miter saw can cast thousands of micro particles in the air that you breathe. You may want to wear a mask (didn’t look like I saw one, I could’ve missed it). Can’t be good for you.
isnt is also better to take EPS instead of extruded styrofoam ? Simply because of the lower cost of EPS, but also because of the off-gassing from the extruded foams.
I hit the top plate edge where I could to seal that. No gaskets installed in older home. I used DAPtex Plus Multi-Purpose Foam Sealant, which is water clean up, and a partially used can is reusable months later. Around the rigid foam board edges I use standard expanding closed cell foam.
I had a 2005-built house with block foundation and many parts in the area you mention had nothing over them; was a ferocious source of heat loss until I glued foam over them and great stuffed the gaps.
my concrete block walls are empty and if you try to put in spray foam it just falls down in the walls so i tried a few ways of filling walls with Styrofoam peanuts or perlite poured in that stuff is awful to work with if you breath some in it chokes you terribly.
You need to use 4" foam boards or 2 time 2", home depot has 2" foam that is R13 so 4" gives R26, code is I think R30. Cut foam 3/4 less than rim joists size and attach transparent flexible plastic tube to foam gun so you can easly access everywhere... When you have 3/4 space you make 5/8 from each side so foam can go all the way towarst wood, this way you dont let air movements in front of the foam and also you dont need caulk.
I wonder about this. I think where I’m at there is a potential for condensation between the joist and the foam board, which (if you seal that up) will just sit there.
I think the latest advice is to not have fiberglass insulation at all in the basement. Better to add another layer of foam board with foil backing for both fire code and higher r values. Otherwise, great job!
All rigid foam board I use specifically state they are combustible, and need to be covered. Plywood or drywall is enough. Drywall obviously if you finishing an area but for shops etc plywood is good too. But the foil face only adds vapour/air barrier nothing to do with fire code.
Roxul will fit the bill. I took out all of fiberglass and replaced it with Roxul. Recently there was a house that went up in flames. It took less than 20 minutes for the whole house to be destroyed by fire.
Question: In the video at the end you see the end joist with caulking but no foam board. Is that right or should you air seal the end joist as well? One of my end joists is damn near impossible to access because of the foundation and an adjoining joist are like 2 inches apart. Previous homeowner stuffed a bunch of fiberglass up there which isn’t doing much for air seal. Any thoughts?
I use a similar method to air seal and insulate rim joists here in Maine. However, I prefer mineral/rock wool over fiberglass. It has a higher R value per inch, is denser so it is easier to cut and stays in place better than fiberglass, it is hydrophobic, and it is non combustible so it does not have to be covered in a finished basement.
Here in 🇨🇦, you just need to pony up and get the job done right, spray foam!!! Specifically, closed cell spray foam... completely seals everything, waterproof so it's a vapor barrier, adds structural rigidity and is an r7 per inch!!! It's biggest asset being how well it blocks air leakage!! If interested, check a dude named spray Jones from Saskatchewan canada, ge has a wicked pages with a stupid amount of information!! Hours upon hours of information comparing myths with facts back by data from educated sources along with his experience! Super amazing, even goes to say r values should be shot out the window when it comes to closed cell spray foam as your not getting a return after a certain amount of inches(here in canada were an r21 in walls)... that being 2inch at something like 86% efficiency while 3inches will only give you 88% and 4 90%!! Just does make sense to pay more for a few percent... dudes very, and I mean very educated on thus subject, probably one of the best in the industry from what I've seen!!! If not the best, no ones pulling the wool over this dudes eyes, that's for use!!
@@jimhendrix7776 Closed cell spray foam is my first choice and it is what I recommend to clients. However, the flash & batt approach can be less expensive so many clients choose this method. When you use closed cell spray foam how many inches do you use and do you add some batt insulation to get desired R value? Thanks
@@jimhendrix7776 I follow Spray Jones and agree regarding his videos. I also agree regarding the short comings of relying on R value alone in deciding on what to use for insulation, and how much to use.
Do you use foamboard with backing attached? I used multiple layers with covers already attached and now I'm worried about mold and rot. Help anyone; I need advice. Do I pull it and try again? The NE is COLD.
I've used flash and batt techniques to seal the rim joist on a number of projects. I think the 2" foam board spray foam is ideal. Less than 2" on XPS and I don't think you have a vapor barrier but instead a vapor retarder which could lead to rot on the rim joist. And the caulk seems superfluous if you seal with foam spray. I don't use any fiberglass in the basement and hopefully no where else. But rather fill the joists with mineral wool. It's easier to work with, hydrophobic, fireproof to 2200 F and deters pests. And so much easier on your lungs.
Would like to just clarify-on the ends you use the foam boards and then in the joists themselves that run under the floors you use mineral wool? I have mineral wool on my end joists right now with no caulking so it's clearly not as good as this setup and I don't have anything under the floors. Thanks for the help!
The University of Alaska Fairbanks did an informational video on insulation in rim joist. They went into numerous crawls spaces when the temperatures were well below zero and every place they went where fiberglass was used it frosted up from moisture. They went to houses that used closed cell foam and drilled small sample cores to test for moisture and found none. We did our place with 4” closed cell rigid foam on the outside of the foundation and 7” of sprayed closed cell foam from the rim joists to the top plate(double stud walls). We only used fiberglass in the ceiling and I used R-38 Batts with R-21 batts between the ceiling part of the trusses. I sealed the ceiling vapor barrier with acoustic seal. We don’t pay much for heat as we have about 200 sqft of glass on our south wall with the east horizon about 20 miles away and the west horizon 45-90 miles away.
@@megdahlin1118 I use foamboard to directly seal the rim joist. It is better at minimizing thermal bridging than fiberglass or mineral wool. Then I put mineral wool behind it. Mineral wool is so much better than fiberglass because it's hydrophobic, less itchy and is a great sound absorber. And don't forget to foam seal the sill plate. Even in a relatively modern construction there's a lot of air leakage through that area.
It wet regions it's beneficial sometimes to not insulate the rim joists at all. I've found rot behind foam board and batt insulation. We removed it and let it breathe, no more condensation issues. 🤷♂️
You're right. In Ga, this is not a beneficial practice. We have high humidity and this method would allow condensation to form behind the foam and against the ridge board causing rot. My home is 60 years old and is dry as a bone. Sealing edges and cracks however is necessary.
Batt insulation should never be used for rim joist because the rim joist is in the ideal place to collect moisture because moist air is lighter and rises and the rim joist will be colder. If you use closed cell foam you won’t get moisture. You should also use silicone caulk versus latex as it bonds to the surface better for a seal. Our house was sprayed with closed cell foam to get R-40 from the rim joist to the top plate of interior walls.
@@eyehear10 Spray foam is the better alternative. My home is over 60 years old and has zero insulation and there has been zero moisture problems. However, I'm pretty certain we're getting heating and cooling loss in those areas without a properly sealed insulation foam, Which we plan on doing this year.
He's creating a moisture trap and a termite's paradise. They WILL get behind those foam boards and he will never know they are there. Caulking the top seams is a good practice. It will stop air flow and dust penetration, but the foam isn't doing anything. Am I missing something here?
i have been trying different ways of doing this on my house but I did not want to leave foamboard exposed because of fire rules saying it can't be exposed to living space so smake doesn't poison people if it catches fire.
all depends on where you live if ground is wet you might want plastic over ground is there vents between ground and floor in cold north people put vapor barrier towards house in south they put it towards outside for hot moist outside air.
@@ranger178 that's actually how i insulated the walls. 2" XPS against the foundation and Roxul R14 batts between the 2x4 studs. It's all covered in drywall for fire barrier.
do you have a really old brick house with thick walls they used to actually put the joists into the brick wall, and it sat on the foundation to support the joists new houses just have one layer of brick over a wood framed house as a siding its not structural. you could put insulation over the bricks to seal it up.
In cold environments none of alternatives using fiberglass or foam board or spray foam are ideal. Moisture will travel through the wood joists (or the inevitable holes and gaps missed) and deposit on the cold surfaces of the rim joist. Now that the water is trapped, it begins to rot the wood. Ever wonder why it's impossible to keep paint on the exterior surfaces of wood windows? It's the same process .... moisture transits through the wood from inside the home and deposits between the wood and the paint on the exterior .... and voila .... the paint peels!! The only way to stop rim joist damage is to stop the rim joist from getting cold in the first place. This is done by insulating the "exterior" wall, rim joist and concrete foundation from the outside to keep it warm so moisture cannot get deposited on it from the inside. It took me years of research and thousands $$ in damage to figure this out and finally get control of the situation :)
Anything showing daylight or having obvious air movement should be sealed with caulk, preferably from the outside whenever possible. Larger holes should be closed with tin or wood shims and sealed with caulk and then insulated. Insects and vermin will chew through foam. The best practice would be to use closed cell spray foam approximately 3 inches depth and do a continuous spray from floor to ceiling. Also, the most recent data leans toward not using fiberglass bat insulation in basements as it will trap and hold moisture. Rigid foam board is a good DYI solution, it’s cheaper than spray foam but only if your doing the labor. Some areas require foil backed foam board to function as a fire barrier. Something else to look into is breaks. Most codes require fire breaks between each horizontal level of the building and vertical breaks at least every 10 feet of linear wall when using foam. In most areas 2 inch rigid foam insulation meets the R10 minimum insulation value for basements. Check with your local building codes before you start any work.
I won't lie, it's very confusing what fire breaks I need if I do continuous spray foam across the entire wall and into the rim joists as well. (In a basement)
@@simland yup. And the code varies in different areas, although most areas, cities follow international building codes. In my area foil backed foam is not required, but the next town over says you have to have it. Most areas require fire rated sheathing at least 7/8 thick with a minimum of 1 inch overlap with 2X4 or floor joists. In most cases the flooring covers the between levels requirement. For the running wall breaks 10 foot is considered the maximum span. Mine are set at 112 (if I remember correctly) something around the 9 foot mark lands on a stud. The break is scribed to the wall and nailed to stub with a three inch overlap. In theory that gives me a 45 minute burn through. We’re not required to have foil backed foam as long the wall has fire rated Sheetrock. Like I said, check with your local building inspector before starting anything.
Every XPS product at all the stores mention they cannot be left exposed in an indoor application. Must have min 15min fire break. I've also seen another RU-vid channel even compare closed cell, open cell, fiberglass, and rockwool insulation to see which burns faster. Quite alarming.
The pieces of foamboard act as a vapour barrier as well. So shouldn’t any batts of insulation be on the cold side (outside) of the foamboards? Standard building rules for cold climates says vapour barriers go on the warm side. If you use a polyethylene barrier afterwards, say when finishing the basement, aren’t you basically sandwiching fiberglass batts between two vapour barriers?
No. Fiberglass on the outside would cause condensation problems within the fiberglass. So, you want the fiberglass to be on the warm side. That way, the condensation point/dew point is within the foam (i.e., no moisture within the foam, so no condensation will occur). There is a formula to determine your foam to fiberglass ratio, and it depends on your location. Not enough foam (r-value) and moisture will condense outside of it. And too high of a ratio of fiberglass will move the condensation point farther inside (dont want that happening in the fiberglass). In other words, you ALAWYS need enough foam to keep the dew point inside the foam. It would also be bad practice to encapsulate fiberglass, or anything for that matter.
if air can't get through closed cell foamboard which is a vapor barrier from house side then the fiberglass would be better towards outside so the wood beams can dry out if moisture get into them from outside air can circulate around wood@@Myles_to_go
I did an entire basement like this. It works well but man is it super time consuming. Before I finish my current house I doubt I’ll bother; likely just nicely tucked fiberglass like 99% of people do before finishing.
@@zachgoestoeurononsense. In follow up the basement already had fiberglass in all the joist cavities, and it stays in place with friction. In my prior house, to which I earlier referred, it also was a new build with fiber and before I foamed it never once had an issue with rodents. Like I said: 99% of homes here have either no insulation in these bays or fiberglass. Foam is ideal but it’s something you’re more likely to find on RU-vid than in real life. In fact the only home I’ve ever seen to have it was mine, which is also a reason I didn’t bother this time around; inspectors don’t care and home buyers don’t value it. That same home I had sheeted all my basement walls with foam and tightened the hell out of all the seams. When I sold I don’t believe anybody cared. People don’t value what they don’t understand. If you have rodent problems you need to address that. I’ve never had a mouse in any home I’ve ever lived in. Properly built house has raised entrances and clearance to ground, making ingress of rodents unlikely.
On a different point, the access holes for your services should not be where they are, they should be drilled on the central axis of the joints. By locating them as is, the joists loading capacity will be reduced.
When using spray foam your supposed to spray a little water on the surface your foaming, then one time over the foam again. Almost noone knows or does this. And also make sure the wood have no way to get wet from the outside, since now it will loose its ability to dry on its own.
never and i repeat NEVER have standard fiberglass batts in the rim joist cavities. If those cold condensating rim joists have any warm air meeting them in extremely cold months, it's a disastrous condensation/mold/mildew issue and learning that from experience with a new home build. from doing this project entirely myself, i would strongly recommend cutting foamular pieces, angling all edges (so foam expands better on all corners, gluing the foamular to rim joist FIRST with loctite PL 300 adhesive and once dried go back and foam the edges to seal it out. The foam board doesn't always rest tight against rim joist when foaming the edges i found they would sometimes pop out and not sit flush. Gluing first is definitely the way to go.
@@zachgoestoeuro yes, the foam board glue is just a bead to fasten the foam board securely in place against the rim joist. if you don't, the board will slide all over while trying to foam the outer edges and it can be messy. spray foam doesn't firm up for quite some time either. you can always cut out the foam at a later date and easily replace it too.
@@zachgoestoeuro welcome! i would suggest rockwool on the inside once foam board is sealed, it's a MUCH more superior product to fiberglass batts, moisture and fire resistance, etc.
@@slo232000 thanks. Two questions on using rockwool: 1. Does it simply “float” on top of the foam board or do you somehow glue it to the foam board? 2. I’m seeing some people use aluminum tape the four sides of the rockwool to the joists to limit intrusion of rodents. Seeking your general impression on that. I’m fine with the extra expense.
I just found out a half sheet of plywood was missing behind a exterior wall to roof . The draft allowed my pipe to freeze this weekend . Great job thanks for tips !!
My basement has no sill plate (probably 100 years old. All the wood sits directly on the blocks. Three sides are below grade and one above grade. How do I insulate that?
I pulled the batt insulation away from the rim joist to locate a huge snake and the rim joist were covered with ice. So I left the insulation out of this area so the board could breathe.
Mineral wool would have been a lot better on top of the foam. It is more fireproof, more inert, and especially a lot better for you in a fire since it will protect the foam from fire better than fiberglass. Highly recommend redoing the video to add mineral wool in addition to what you have already.
Roxalls just better all round lol!! Higher performance, more environtal, no moisture issues, stiffer, MORE of an air barrier(for what fiber insulations re worth lol), and one of the biggest in my opinion, that shit snuffs out fires 🔥 if on unfortunately happens!! That's its BIGGEST asset right there!!! $ !-! ][ + DONT BURN!!!
but if you put ROXUL on inside of house against foamboard warm moist air will go through ROXUL and condense on foamboard making ROXUL wet. the fibers are waterproof, but the empty air space can fill with water. mineral wool is not a vapor barrier it repels water sprayed on it but can get condensation in it.
I simply ask my insurance company what is covered before buying materials. They might deny your claim especially if it's a DIY. The air bubbles inside expanded polystyrene board stop heat transfer but can accumulate moisture making it ineffective. Any type of the foam crap will melt and drip fire. I just pay the high utilities and let my house breathe. Better than wasting your time and money creating your own mold problem!
Don't forget to turn the water heater pilot light off the flammable gasses are no joke unfortunately the best way to clean uncured foam off you is flammable liquids like gas or acetone ect.
@@garettbenham5312 depends. I had a house I flipped where they came up between the stone veneer and the foundation. Had the house inspected by my pest control company prior to purchase. I Noticed a stone coming loose by the front door. Pulled it off to add some mortar behind it and regrout. Immediately discovered mud tunnels behind that stone. Termites had eaten up the rim board, the sheathing, the mudsill, bottom plate of the wall above, and a few of the studs. They made it all the way up some of the studs to the header of the window, fortunately stopped right at the end of the jack studs and didn’t make their way into the header. They had even gotten into some of the hardwood floors right by the wall. Also discovered that someone had scabbed on studs onto the termite ridden studs in the past 🤦♂️. Had to reframe that whole wall. Luckily the floor joists were running parallel to the rim board on that wall so they didn’t get into the joists.
@@garettbenham5312 yep. Right to it. House was built in the late 80’s so someone could have backfilled more dirt later but who knows 🤷♂️. Fortunately that bump out wall on the front was the only stone veneer on the house as an accent. Rest was siding so that was the only termite damage.
Caulking is a waste of time and not particularly suitable to confined spaces. I you spay with closed cell foam properly it will seal well. If you want to go an additional step use Henry Stop Leak spray.
