Flash and Batt 2 | Can you put batt insulation over spray foam insulation? 

One small, niggling thing. I agree that spray foam is a superior product. And if I ever have to insulate a home, spray foam will be my very first choice. (Giant, Gulliver-sized) BUT, if you're doing primary air/vapor control and temperature control on the "cold side" of the wall assembly with 1-2 inches of foam, what is the performance of a batt under THOSE conditions i.e. shielded from the worst by the foam shell? Because you're talking about Flash & Batt or "Flash & Fill", but the research you're citing is all "all foam" vs "all fill/batt" systems. And treating a hybrid setup like a uniform assembly is a reach and an incorrect comparison. So, sorry if I'm peeing in your cornflakes here. It's just one of those "Because I really wanna know!" type things.

Your videos always blow my mind. What flash and blow (cellulose)?

That's a super good video!! Have you heard of a good company in missouri, usa?

I think you will trap moisture if you use 1 or 2 inches of foam and batt on top, go one way or the other. Spray foam will cost about three times as much, but will save in the long run

2 by 6 wall used for wind or earthquake strength. Back of shear wall has 2 inches of spray foam so we have air, vapor control, insulation and a much stronger wall. PROBLEM we have a 3.5 inch chimney for fire to race up. Answer put in 3.5 inch rockwool batts, not for insulation, but to slow spread of fire up walls and provide a better sound barrier. Wouldn't this be best practice?

2 reasons to use flash and batt: meet the arbitrary R-value and the cost associated. I think 2" of closed cell and then fill the cavity with open cell to meet the R-value code is the way to go unless you can afford to do straight closed cell.

It’s because of the echo and air space behind the wall is what I was told

The cost of spray foam can become way beyond unrealistic. Upwards of 15 grand for 600 sq ft with a 2x6 non vented vaulted ceiling in my tiny shed home in Washington state. I’ll send you some info so you can send that excess income you got my way. 😂

If builders sheathed houses better you wouldn't have air flow in the walls.

There is absolutely nothing wrong with flash and batt. The foam seals the house and then fiberglass is added for more R value AND at a cheaper price. It makes no difference that R19 fiberglass is actually R17 or some other number. You are still getting more insulation for less money. You just have to know up front that R19 isn't going to actually be R19 and plan for it if that is a problem.. Most people don't take into account "whole wall" R value anyway so losing another R1 or R2 is nothing.. You also have to take into account the ratio of foam to fiberglass to prevent moisture. You can't just throw 1" of foam and then add batts willy nilly. I just had a house built in Colorado and the ratio there of foam to fiberglass needs to be 50% to avoid condensation. In the walls I went with flash and batt and saved $4000 by doing so. My walls are 2" of high density foam and R15 unfaced insulation. This give me approximately a r value of R26 vs 4" of foam giving me R28 (ignoring whole wall R values). Do you think a R value of 2 is going to make any difference? NO. I am not dishing spray foam but it's expensive and if a person wants a higher R value flash and batt is the cheaper way to go. You yourself showed charts in other videos saying that even 2" of foam stops 86% of heat loss. If the foam can do that the fiberglass on top is just icing on the cake. Thanks for the videos, just keep the bias out of them...

First off I just want to thank you for the videos and information you have been putting out. I think its amazing and you obviously take your time and or have already done the research in the past and are just sharing it with the world now. Although I don't actually know what the purpose of this video was? You say your going to talk about Flash and Batt but honestly all you talked about is how inefficient fiberglass is compared to spray foam - something I don't think anyone can argue against. I unfortunately don't think you covered the topic of your title. Now if your just gaming the system, okay, but I don't really think that is what your here for. I think you should consider changing the title to match what your really talking about. If you were going to talk about Flash and Batt, and try to show why its an unacceptable practice I think you need need to cover the subject in a drastically different approach. You ignore the fact of just how much more spray foam is to the other products, or to the fact that when your applying your foam, and calking studs, (stopping air flow) that the other products do work well. You ignore that not everyone can just spray foam themselves. Currently the only cost effective route is to hire someone. When it comes to caulking, and placing batts, or even blowing in fiberglass, or cellulose. Those are things people can do cost effectively themselves as well. I'm not going to keep going here because just like the video would take a long time, there is ALOT more involved in why people choose to flash and batt, and it certainly isn't because people think fiberglass batts are amazing compared to closed cell foam. Anyway thanks again for the information in this video and all your past ones. I've learned a ton, am subscribed, and look forward to more videos. I just think you really dropped the ball here if you were trying to argue why flash and batt is bad, or even why its bad.

Could we spray foam my neighbors' doors and windows while they're in there? Like to entomb them in their apartment?

All you stated was results from either spray foam or batt insulation. That was not the question. The question was what would the results be if combined, which you provided no actual real life test results. If you would use spray foam on the outside wall or roof deck, then that solves the issue of why batt insulation would perform bad in the same conditions you sited individually in those test, and therefore would not have air infiltration issues if added after the foam was applied, wouldn’t it?

I know a contractor that frames high end homes with 2x8 24" on center. Sprays 2-3" closed cell followed by rockwool. He told me the foam is basically a air and water barrier and helps stiffen things up, then and the rockwool for sound. Also makes it really easy to run all the utilities after the foam is done. Rock wool is easier to deal with in the event you want to do a remodel or have a problem.

Hi Mike, Great video. You’ve affirmed everything that I’ve always thought about Sprayfoam insulation. My newer build cape in upstate NY is 100% Sprayfoam, 2-1/2” in the walls and 4” in the rafters. The performance is fantastic in every way, inexpensive heating in winter and cooling in summer. The one thing that surprised me was it’s noise dampening characteristics, or lack of. Our music or loud movie watching can easily be heard outside the home. I’m considering adding 3” fiberglass to my bonus room , also sprayfomed, just for noise dampening. It’s been unfinished for two years and I feel we’ve found and sealed any leaks in the envelope, identified by ice on the exterior during winter. Is there anything that would concern you about doing this, or maybe a better product? Thank you, Wayne

I think what this does not address is the fact that when we’re looking at close cell foam then finished off with bats is that the closed cell foam is going to probably insulate well enough to make sure that the thermal drift inside the fiberglass is already a lot lower, making sure it performs more closely to rated R value. Unlike in the paper which is pure fiberglass insulation. therefore the aforementioned occurrence of cold air dropping down and therefore making the insulation fairly useless don’t happen because the spray foam will guard the fiberglass from this problem, really we’re only going from say 20° inside the house to maybe 10° towards the spray foam and then have the rest of the transition of outside temperature happen within the spray foam. Fundamentally that means that it’s like adding more foam than 3 inches you get diminishing returns but in this case using fiberglass is good enough given we are making sure the foam is handling the difficult part of the equation namely the initial frost and dewpoint.

Well Mike, its now 4:30 am. Thanks a lot for making spray foam insulation so damned interesting that I did not go to bed last night! I need to peruse your video offerings to see what is the right application for the south western state of Arizona buildings applications. I like your style precise, succinct, and to the point.

One of your comments doesn't seem correct. You state that the spray foam is doing 90%+ of the work when you do this system, which contradicts your initial approach of talking about fiberglass insulation's efficiency (or lack of) from a mathematical approach. Let's assume 2x6 wall construction. 2" of R7 closed cell is R14. That leaves 3.5" of void, which is typically R13, which is then reduced 28% as per your source to R9.36. We'd also hope that the spray foam installer would go ahead and fill voids which cannot be easily filled with batt insulation so let's take that out of the equation. By my pretty simple math, that makes the system an R23 wall with the spray foam acting as 61% of the insulating factor. Lastly, in this scenario, we're assuming perfect application of the spray foam and "common" installation of the fiberglass. We should really drop that R14 number down to R10 or R11 to account for human error and spec sheet marketing. If we do that, the wall is now an R20 approximately, and we're talking about close to a 50/50 ratio.

There are some benefits you are missing. Fire resistance. First the cavity must be completely filled to slow down heat and flame travel. That can be done with either, but at much greater cost with all foam. Second the point at which the product breaks down and allows flame propagation. The foam melts/burns at a much lower temperature meaning that flames against the inside wall will burn the foam away before it burns through the drywall, and then travel freely up the now empty cavity behind it when it breaks thru. The fiber glass will resist longer. Third the burning foam is very toxic. having the inner surface covered with nontoxic material makes it more likely you will get out before the nasty smoke is produced from the foam behind it. Fourth it would leave a cavity of material that is easier to displace when renovating or trying to fish new wires and pipes. Fifth, the combination provides better sound deadening. Sixth, the glass R-value isn't compromised as much due to the superior air sealing of the foam keeping any pressure gradient away from the batt. Seventh it still provides 80% or so the R-value stated even by the studies you quoted, but then later dismiss that value, attributing all the effort to the foam without any study as basis. All of those still leave a decent reason to add it, so long as it doesn't cause other problems like condensation. Yes it is superior in most ways, but also far more expensive. Wet spray in cellulose would probably be a better match than fiberglass. It would conform to the uneven shape and fully fill. The fire retardant would help keep fire from propagating, and the ash gets in the way even after it burns.

I love hearing about this information man keep it up people are listening! Nice job

Spray contractors in my area want to do 2 inches closed cell in cathedral ceiling and fill the rest 2x8 with open cell. What are your thoughts on this? If it can be done does there need to be a cure time in between layers? My quote is 8500 with all closed cell and 6000 with the hybrid.

Excellent content! It’s refreshing to see a professional that truly cares about the product they are Installing and understands the science behind it. I appreciate you sharing your knowledge and educating others in all your videos!

Using the flash and batt approach you can more cost-effectively leverage the attributes of two types of insulation. I would have selected Rockwool batt in lieu of Fiberglass batt. The closed cell spay is providing air infiltration protection and high R-value at a premium price. The batt insulation in a sealed cavity is providing a mid-range R-value at an affordable price.

I have a question concerning a post frame shop building: would adding 1 1/2 inch foam board between the 2x4 or 2x6 girts that the outside metal sheeting is attached to and then spraying 1 or 2 inches of closed cell spray foam over the top of them be worth the added expense?

Two questions, you talk alot about how inferior fiberglass is, what about a flash and bat with a product like rockwool or a blown in cellulose (somthing that is relying on the properties of the material and not the air inside the material to insulate)? Also if you did the flash and bat and had the kind of water issues in said video, that would also lead me to believe air intrusion plays a large role, so shouldn't the spray foam (when properly installed) help to seal up the structure against air intrusion. I get you are saying only use spray foam and I'm glad you believe in the product you are selling (and it is by all account a far superior insulator). But spray foam is expensive and not every one can afford to do a whole house in full depth foam and they have to conform to code somehow? So how would you suggest that happen if all you could afford in spray foam would be 1", do it? Or don't do it? And if you do it how do you meet code? Not trying to argue just trying to see what you think the best option would be.

Wouldnt the batt be good for sound tho. Maybe not fiberglass but stone wool or dense pack cellulose? I know my metal building is closed cell and it can get loud even with 3/4 plywood as wall and ceiling. I know u could do open cell on top too.

I agree on the air sealing with foam but also see an advantage to rockwool over 2 inches of closed cell foam for the fire rating.

Man, I've watched so many of your vids! I just erased my 2 minute comment by reading a response you gave someone below. Im a DIY building my last home in October. So, here in the Ct I believe we need an R30 in wall cavities. Is that 4 to 5 inches of SF? And an R60 in the cathedral ceiling. 12 inches????

This is dumbfounding! I'm astounded at the results you are presenting with these studies. I was just watching through Marshall Build and their struggles with the Hybrid approach they did and the resulting trouble. This all makes me think twice about the entire thing. One question though, all this studies presented compare fiberglass with foam, what about a product like Rockwool?

One issue for some is wanting to block sound and noise transfer coming through the walls. I heard closed cell does not block sound well and actually can act like a conductor to transfer sound like wood does. That a good way to block sound would be to go with 2 to 2 1/2 inch of close cell then use quiet rock insulation over that if you're building with 2x6 walls. What is your thoughts on that?

Hello Mr Spray Jones. I like your videos very much. My Pops and I run a full spectrum insulation business although I would like to nix the glass. What would be helpful for knowledge junkies like myself would be references. In many of your videos, you show documents, research papers, IBC, etc on screen. Being able to get the full article and/or print it to be able to provide to the builder or customer would be really great. If it's not too much trouble.

Fiberglass insulation should really be banned. We have much better options (like Roxul), and have for a long while now. I am still deciding how to insulate my next build here on the frigid/scalding hot Canadian prairies. People should maybe shrink their house size a bit (and their corresponding egos) and spend the money on efficiency instead. It's 2022 for crying out loud and we're still building 1950s homes 🙄. Contractors generally lie because it benefits them financially. Always remember 'qui bono" in every decision in life...who benefits?

The closed cell stuff is way better but I am going to throw shade on the statement from the 2007 article that claims it is only 5% more. No way. How about 300% more? Getting bids for my new house now and that is what I'm seeing. Still planning on using CC foam. Over time the cost will make sense.

This assessment Badly needs a do over. Looking at Spray Foam VS Fiber Glass Batt is NOT the same as looking at Flash and Batt because of the Thermal Layering effects of the two together. Its not a 1 plus 1 sum but a much more than the sum of the two separate parts. You haven't addressed the physics and proven benefits of thermal layering. Any outdoors enthusiast quickly realizes your error in that the layering affect has the advantage of giving more thermal protection than simply adding up the value of the separate layers and can be vastly superior to just the one type of insulation that is the same thickness of the two combined. Energy has a relative hard time transferring between different materials. Also once you put on the spray foam the ability of air to move through the fiberglass is significantly reduced. So if the problem is air flow moving through fiberglass you have addressed the problem of air moving through fiberglass insulation. Importantly, your anecdotal stories from "old' spray foamers observations was totally proven worthless by the very scientific documents you presented at the first. Take the R value of one inch of foam and times it by the true installed value and then compare it to 12 inches of Fiberglass times by the installed value, and put them side by side. 1 inch closed cell foam is R 7. 12inches of Fiberglass has an r value of 2.9-3.8 per INCH so lets use 3 for easy math so 12 inches times 3 equals and R value of 36. But it performs at 50% efficiency (at its worst) so you have half the R value of 36 or a functional installed value of 18. Or nearly 3 times the thermal protection level of one inch of foam. (a closer comparison is 3.8 times 12, times .72 efficiency or 32.8 4.67 times better than one inch of foam) Given that you couldnt mentally conceptualize that instantly and use the most basic level of critical thinking makes your whole presentation questionable if not simply discountable. You show incredible weakness in your integrity using facts to prove one point and wild hearsay for another with the facts right there presented by you. Then you need to address other issues, such as rock wool has a slightly higher R value than fiber glass. Does rock wool have the same issue of air flow? We dont know as you failed to address it. Neither fiberglass nor rock wool burn and importantly don't release DEADLY fumes when they burned like spray insulation does. Also neither off gasses fumes whose affects are still being questioned like foam does. This desperately needs a do over that honestly looks at Flash Batt NOT spray foam compared to fiberglass.

I love all your advice , my neighbor is a spray foam applicator , only one on our area . There so busy with commercial and large products they won’t even give me a bid on spray foam for a house remodel , I’m thinking I’m gonna have to DIY

I really like your videos, and am going to keep watching 'cause you are real awesome.. you even find real studies.. my question is more of rigid polyurethane foam.. tell me if its better to use spray foam or rigit PUR foam.. just like u said with SIP, i would like to know if i can use PUR as a sandwich with aluminium foil and shingles on top or even as steel sheets (steel roofing).. thanks for your time.. the roofing insulation value has to be a minimum of r-38.. i am from europe and the ristrictions are very hard.. i want to insulate on top of the roof, not really eager to do it between the trusses, mostly because of these hard restrictions and far less thermal bridging. Sorry for so much questions..

The only thing that bothers me is encasing electrical and data in the foam. Putting them in conduit can’t be that much more expensive. Other than that, I agree closed cell should be the norm.

I will tell the more I can get to the client information they are at awww Always the same y did the builder not tell me this they should at least Give the the option in a nut shell contracter wants to get the job and He'll be lower in price and he will move to the next one and home owners Think they got the best house on the block (outside maybe) And home owners stuck pay big heating bills if you take a 20 yr Mortgage the extra $5000 more for foam way out way $18 a month Extra on mortgage payment and save a minimum 30% on heating & cooling Keep up the info it will be a greener world

Make sure after ya'll research this video you lookup a few videos about ERVs. You will need one.

Thank You!!! Very informative!!! What about flashing #2 foam then filling with open cell? Would there be any value in that?

Pay the spray man a little more and get it done right the first time.. He is already on site ready to work..

Do you know of a YT channel called Marshall Remodel. He just put up a video regarding his issue with spray foam insulation and his bat insulation topping it soaking wet. He was actually able to wring the water out. What is your take on the cause of that?

By using zip R3 vs using zip R6 followed by 2 to 3 inches of spray foam, do you think you would notice a difference in the thermal bridging between the two options using FLIR cameras? Thank you for all the great information and education on your product.

sounds like codes need to be revised to be fair with spray foam

The flash and batt technique with closed cell foam + rockwool is by far the best solution. You hit all the R values you possibly need and the sound insulation is top notch. Using fiberglass batts is just ridiculous...

2" spray foam for air barrier and moisture sealing , 3-4" rockwool for sound deadening 👍👍

Main reason to use foam and batt is for sound isolation.

I use 2inch foam board on the outside of the frame. Rockwool between the studs.

Fiberglass insulation is junk. The builders I know that flash and Bat use Rockwool.......

I can’t help but wonder if someone were build a home in a cold weather climate. Frame, electrical and drywall the attic ceiling and exterior walls before sheating the exterior of the walls then spray close cell foam from the outside creating a vapor barrier/insulation cocoon tight up against the interior of the walls and ceiling. A small air gap on the exterior of the walls would aid in a path for moisture to dissipate and the back side of all outlets and ceiling mounted light fixtures would essentially prevent any air leaks. I’m curious if your thoughts if this would be a better way to build a house?

Very interesting to say the least. Sure wish this wasn't so expensive, maybe the prices will come down in the future as more people are doing it. I had 2" of closed cell sprayed on the outside of my metal roof. Amazed at what it did! After that, with 2x6 rafters, I added a 2x2 under the rafters. Then 1 1/2" pink foam board under that. Then blown insulation filling the cavity. That made another huge difference. I think not having ventilation between the underside of the roof and the blown insulation is a big help. This leads me to ask: Would having an air gap between the spray foam and the drywall cause the spray foam to be less efficient than if there were no drywall and the heat were able to get directly to the foam? If so, would fiberglass help this? My thoughts go to 2x6 walls with 2" of spray foam and R13 to fill the air gap. Or would it be better to just use 2x4s and an air gap between the foam and the drywall?

can you foam over poly? (rim joist lip would have poly/tuck tape from below)

Excuse me if I am wrong but these studies are all talking about fiberglass batts and they are by themselves, not with any other closed cell foam. I am about to have my 2x6 exterior walls insulated with 1" closed cell and filled in with "net and blow" fiberglass. Does the blow in fiberglass react better when cold? Also are there any studies where the fiberglass is monitored when paired with the closed cell foam? Thank you for your time, I enjoy the videos!!

Although there's no question that closed-cell spray foam is a superior insulation material over fiberglass batts, the point you are making in this video is incorrect, and your argument is flawed. The reasons for the 28%, or more, loss in insulation value with commonly installed fiberglass batts is either poor framing, gaps in framing members, and poor siding material installations, among other poor construction practices; all of which result in air infiltration in the wall cavity, which is the main reason for poor fiberglass batt insulation performance. Without air infiltration, fiberglass batts perform close to their rated R value. Therefore, when fiberglass is added to a wall cavity with sufficient depth for the fiberglass batt, such in a 2x6 wall cavity, over say 2" of spray foam, the resulting R value is simply the sum of the foam R value plus the rated fiberglass R value, since air infiltration has been eliminated with the use of spray foam. To conclude, flash and batt (2" spray foam & fiberglass batts) is a very sound investment and maximizes R-value at the lowest cost, when installed correctly.

What about Flash and Batt Rockwool? Seems like Rockwool would perform better. You say you don't like flash and batt, but you only address one type of insulation.

Thanks @SprayJones what if I'm doing a retro fit and pulling insulation out of the wall? Is it gonna hurt to put foam in and then back fill with the insulation you can fit instead of throwing it out?

I wouldn't ever suggest using Batts after u spray, just spray it at right depth and enjoy saving money rest of your life.. idk how that makes sense..rofl..also u pay a good chunk just to have truck show up.. so putting right depth instead of spray and batt.. ur not winning

What, what about using it for sound insulation of Rock wool? Insulation has had studies that show it basically amplifies some frequencies. I want to use 2 inches of foam and the rest of rock wool for this reason.

Would not recommend this video. You can not use data that separates the two products individually and say that they wouldn't work as a combo product. You have admitted that in the convection test fiberglass has a high R value. If you take out the air movement and moisture. So it would stand that if you get rid of those two factors using spray foam you no longer have a low end product you are actually using it in an ideal condition. It's like saying a sponge won't soak up ice fast however if the ice is melted it works really well. Still like some of the information, the logic just needs fine tuning.

Great information! Just purchased a new home that is 100% closed cell foam in exterior walls (full 3") and roof structure (over 7"). At first, I was skeptical about its effectiveness particularly in the roof area above the attic. But after this year's extended snow, ice and sub-freezing conditions in Texas, I am now convinced that fiberglass insulation is "old world" technology essentially like hiring a cave man with a club to bring home dinner!

Have some questions about spray foam, vapor barrier, and building a home inside metal grain bins.

We are building a Barndo with 3” closed cell on all walls and 5 1/2” open cell on the ceilings what’s your opinion please?

The only reason that I can think of to add batt to foam is to concede to building code and inspectors.... not for actual performance. Its like a government tax to pay, not to keep the heat in.

Hi, thank you for making these great videos. I was wondering if you have a video in the works comparing dense pack cellulose and the cellulose overall with spray foam? Thank you

What if the walls are 2x8, I feel like I should be filling the “void”

Would adding batt insulation help with sound deadening though?

I agree that the lets say 2 inches of closed cell foam is a far superior product . The way you present the studies though is misleading. You are using studies with just one type insulation where air movement is likely the major reason for the different findings besides the installation details. The fiberglass doesn't have much air movement to hurt is performance as much once the foam has sealed the structure well. If you want a real answer ask the lab to do a test under the same conditions with foam and fiberglass. I suspect the fiberglass would perform at over half its rating under those conditions. That of course doesnt mean its cost effective to add fiberglass to foam vs just a little more foam or adding open cell foam on top of the closed cell. I can see if a home has say 2x12 rafters and currently has fiberglass batts say r 30 that they may want to remove the glass and spray 2 inches of closed cell then replace the fiberglass rather than discard it. Whatever it adds might be better than nothing. Lets not forget there are other products like mineral wool that may be denser etc and not allow as much air movement that could be added also. Even double and triple pane gas filled windows have convection currents within them with the warmer das rising and cooler gas falling. Some windows actually have "invisible" baffles in them to help control this movement. I personally would much prefer all foam but you are comparing data that is not comparable in the way you are citing the data except for the initial decline in fiberglass r value new and from quality of installation.

Depends on what zone you are in, I disagree with some of this in real hot environments with metal roofs.

So...Owens-Corning cheated BIG TIME?

I have seen exactly what your talking about. My Dad overstuffed the cavity because he insisted that the fiberglass was never good enough. (in the days before spray foam and R13 walls)

Another banger video! Do spray foam here in Michigan, my boss is as well educated as you and I learn alot through him but get that extra learning from you spray Jones! Thanks sir

Great vid! Marshall Remodel and Little Mountain Life just found water in the fiberglass insulation. Hope you all can find a solution for those of us in the planning stage. Especially when you consider all the other diy home builders without a YT channel having the same problem.

I would install Rockwool instead of fiberglass. Sound proofing qualities is the only reason and it does have better insulation qualities and drying qualities in case moisture does reach it from inside the home. I personally would not use open cell due to it acting as a sponge if moisture is actually able to reach it. Spend the extra few hundred bucks and just go closed cell. Structural integrity, vapor/air barrier is included with the installation due to its chemical makeup.

If the batt is Rock Wool that can be compressed it will work better than fiberglass

How would closed cell spray foam do in a small bunkie that isn't heated all winter? We are planing to build a small bunkie and wood stove for heat and camp in the winter but the majority of the time there will be no heat. would that be any issues as it's super sealed?

hello! looking into insulating a custom built cold box. We're thinking about doing a flash and batt with 2" of closed cell and mineral wool insulation to get some extra r value. We have 2x6 walls and a 2x8 ceiling and floor. Can you see any problems with combining the two products? thinking that the closed cell will stop all air leakage... I'm comparing the assembly to a cooling driven climate, where the outside air (the rest of the commercial space) is warmer and more humid... the sprayfoam should do a good job of keeping whatever little vapor out of the cold box walls? thanks also for the content, we don't use sprayfoam much, but appreciate that it can be a really useful product. your videos are super insightful and well made!

Nothing about rockwool?

Thank you for these videos. Been through about a dozen of them and have enjoyed.

What is the best way to insulate a read iron shop that was built with no insulate thanks I live in Joliet mt . Thanks 😊

Flash and batt does not make any sense with fiberglass insulation. Using your spray foam 100% for your "minimim code" (making sure you meet your vapor rating as well) then filling the rest with Roxul for the fire and sound absorbsion would be the only way (in my opinion) that flash and batt makes sense. Houses are not properly air sealed and being very leaky wall cavities adding spray foam seals those up which is an added benefit that plays a massive part in the effectiveness

This is believable for fiberglass, but what about dense pack cellulose? It doesn't allow circulation currents like fiberglass. Also the results at 10:35 seem completely misleading. You're comparing attic temperatures for 2 completely different insulation methods. The spray foam was sprayed on the underside of the roof, but the fiberglass was sitting on the attic floor. OF COURSE the attic will be hotter for the fiberglass system, the fiberglass was on the attic floor, the attic wasn't even insulated!

When I managed and Insulation company, I always hated when people and or architects recommended flashing batt wall assemblies. Here in Virginia we don’t require a poly moisture barrier, but the big issue with the flashing bat was calculating where the dewpoint would fall in the wall assembly nine times out of 10 the dewpoint would fall within the bat portion of the insulation, which within caused condensation on the surface of the foam And or the bat insulation. It was always an uphill battle to get either of the homeowner, builder, architect to change the assembly specs for the wall. I had a personal friend whose house was gutted by a fire, when he rebuilt it I convinced him to spray foam the entire house. His average electric bills before the rebuild were around $200 per month post rebuild, the spray, foam and energy, efficient, lightbulbs and appliances. Average electric bill was $85 footprint same number of rooms same exact finish square footage. That shows the power and efficiency of spray foam. Also, his house is dead silent inside.

This is believable for fiberglass, but what about dense pack cellulose? Also, the results at 10:35 seem completely misleading. They are comparing two complete different insulation methods. The foam is insulating the roof underside, but the fiberglass is insulating the attic FLOOR, so OF COURSE the attic temps will vary more with the fiberglass, in that system the fiberglass is on the attic floor, the attic isn't even insulated!

So fiberglass batts are 💩, we can all agree on that. What about combining a nominal 2" of closed cell with a fill type insulation, such as cellulose or blown rockwool / fiberglass? I think that would ameliorate the massive loss of effective r value due to poor installation and the many other pitfalls of batt insulation, but still reduce overall cost vs 5 inches of spray?

What about batt and flash? I don’t pretend to understand the science but could you not have 3/12 inches of rock wool first in a 2x6 wall cavity first then have 2 inches of closed cell over it? Wouldn’t this give you the benefit of having a better STC wall for sound proofing and having the benefits of closed cell and it’s Vapor retardation properties? So is the flash and batt a problem for moisture developing in the batt side?

Here’s a new one: joists at 3.7in cc SF, concrete wall at 2.5in (R15) cc from top to 1 foot off the slab. (6 ft total). Then reused FB (only if dry and in good shape )at no cost overlayed entire wall down to bottom slab. No poly. Why no spray foam on bottom foot? Because it’s always dry, never cold and save some money. SF now is very expensive and a budget is even more required. Im in zone 5/6

Fire resistant insulation

You said it your self. The batts performs poorly when air is leaking. But what happens when you seal that up. I know it Said it didn’t matter if you had tyvex or siding on it, but what about a product that is better? Zip system sheathing could solve that problem and have the batt do it’s job. And vice versa your spray foam by sealing the back of the osb and stacking the batt in. We just have to eliminate that air movement. So I believe that method still holds true because spray foam is expensive and our walls still need to have high r-values. You couldn’t have just one inch and call it done.

My garage ceiling is accessible via a hatch. No vapor barrier over the drywall. Garage is heated. Insulation tech stated 2 inches of closed foam and then blown insulation will ensure airtight (no poly placed). Plus, keep heat in my garage/workshop. This video is saying I don't need blown insulation if 2 inches of foam is placed. But the company is stating a fire retardant needs to be sprayed over it, if there is no blown cellulose on top. What's your thoughts? I'm in southern Ontario

Comes across pretty biased from the get go. I wish there had been more analysis on pro and con, now just feels like a SPF guy pushing his product (no different from the FG guys with all the safety issue "research" on SPF)

Ok so 4 inches of spray foam will equal what in R value in an attic floor ( vented attic). Would it suffice in Maine winter? Thank you for your time. Trying to understand but it's a bit difficult form me

Great information I have an odd question, what’s your thoughts on closed cell inside of a cargo van that’s going to be used to live in in all climates ? Thanks

Depending on the climate you are in, you could be condensing moisture on the surface of the closed cell foam and soaking the fluffy stuff. Closed cell should be applied such that the inner surface is above a condensation point in the wall.

Geeeze, came across your vid's, had 15min to kill. you hooked me for 4hrs. your the master.

The biggest reason why so many people stick with bat and the loose insulation instead of getting the spray foam insulation is due to safety and expense. Spray foam is extremely more expensive as it requires actual knowledge to install it correctly. Too many people have found cheaper installers only to have the spray foam installed incorrectly which then makes their entire house completely toxic to live in until the foam is removed and aired out.

If you can afford it, go with 4" of spray foam. If you want to combine go with closed cell and rockwool combo.

Really interesting the R value loss with fiberglass. Do you have any reports that where done with wet blown cellulose insulation? and blown in cellulose insulation and there rated and actual R Values. Just curious how they perform as well. Obviously the spray foam is the best.

I've got a pole building house I'm putting up 2 inch's of rigid xps foam which is closed cell foam. Then r23 mineral wool in front of that

What if you were to use the rock wool insulation

Let’s face it, the building inspector won’t let you do what you suggest. You can try to fight city hall but it’s easier to put in the batts.