Right Vs Wrong: Installing Insulation Batts In Exterior Walls - Part Two 

Good Insulation Tips: 1. Cut to proper length and width. 2. Use foam insulation to electrical boxes. 3. Cut insulation to fit any shape properly. Basically, don’t over stuff insulation and keep cold air out.

Tyg Rahof it seems like that many of contractors goal, just do stuff as fast as you can. I believe our house was never inspected after being built 27 years ago. Even as a DIY is see stuff done incorrectly or not at all. Can you guess why I watched this video...that’s right some of our insulation was Improperly installed.

You’re welcome! We are happy to help!

As shown in the first video, the batt should be just wide enough that it sticks in the wall cavity but is not noticeably compressed. You can leave the backing wider if you are stapling to the studs by cutting the insulation separate from the backing or use unbacked batts and install a separate vapor barrier if needed. Note that normally interior walls are not insulated as both sides of the wall are likely to be close in temperature. However this can be done for sound insulation or other reasons, such as an unheated space.

Vapor barrier?

opinionatorX Interior walls normally do not have insulation, unless you specify it (in which case it's normally done for sound dampening, not thermal reasons) but high utility bills and the label 'newly renovated' can be a sign of bigger problems (I've seen people cover up rot holes that lead straight outside) I know your post was from a year ago, and I'm no expert (apprentice electrician). this is just from personal experience.

Looked more like stud thermal bridging to me. What you'd be better doing is put rigid external (usually foam) insulation boards on the outside, which is what stricter energy efficiency standards have been moving towards. R 4-6 studs are murdering the average insulation value of the entire wall, and it has a higher impact the better your between-stud insulation. (because those studs have a bigger impact if you're using R-30 insulation compared to R-10 insulation).

Hi Bernard, we are glad you found the video helpful! We have a few different batt knives and utility knives we would recommend. You can find them all listed here: www.idi-insulation.com/product-type/parts-tools/. Hope this helps!

Tyvek is not a vapor barrier. Vapor barrier goes on the warm side of the wall, so this varies by climate zone.

Brian Hall as long as you prime first, your friendly painter

Matt, there are a couple of items in your question and statement I would like to give some information on. Regarding the garage walls, if you are doing this yourself, you can attempt to fill that walls of the garage with blown-in insulation, but what about air sealing and how would you know if you got everything? If you open the wall you can do a good job, except for the fact that it's a lot of work. If you drill holes and fill it, you might get it all, and then again you may not, but then there is that air sealing thing. Certainly adding any insulation to the exterior wall will be good, but if you are trying to help the room above the garage, then you may want to consider getting to the rim joist or where the bedroom floor/garage ceiling meets the outside wall. This is one of the most common leakage areas for home and areas for energy losses as well as big comfort issues. If you can address both areas, I would. If not, my first line of defense would be this area and then the garage walls.

vapor retarder backing, not water barrier. and yes goes to the inside.

vapor barrier to the warm side...inside if normally the enclosure is being heated more than cooled. E.g. if the lows are 30, house is 70, and highs are lower than 110, vapor barrier inside. If lows are 50, house is 75, and highs are 100, vapor barrier to the outside, or maybe no vapor barrier.

Yes, I am also guilty. Kinda makes me feel bad. Maybe I can do better in the future. Yes, I think I can! I will do better! I will be the best! Then I will make my own video! Watch out world!

The rigid foam is normally installed as a solid layer, not between studs. If you did both and sealed well the r values would be additive. However, doubling the R-value cuts the heat loss in half (theoretically, not at the gaps as evidenced in the video.) So adding 3.2 to 13 is a 25% increase, cutting the heat loss by approximately 10%. However, the biggest benefit would probably be the seal, since the solid layer would have few gaps, except at the outlets, which should be given special attention. Let's say that in the leaky spots your effective r-value is only 3.2 instead of 13. Here you would be reducing the heat loss in half. Spray foam is a more expensive treatment, and the studs would still only have an r-value of 4.38. BTW, on the heat map, you can see the studs, so if the color shift is greater in the flawed areas than it is for the studs, your effective insulation in those places is lower than R-4! However, the insulation might still be cutting the heat loss to some extent, since even r-1 would still mean cutting the heat loss in half compared to an uninsulated barrier. Of course the wall itself has some r value. Composite siding is r-1, cement board (hardie) is r-3, tyvek house wrap is r-5, tar paper is r-0. Spray foam is often recommended in situations where moisture is a problem, for instance the condensation in tiny homes. Spray foam has closed cells and so moisture does not penetrate. The same is true for rigid foam panels.

@@SteveSpinella One thing I noticed in this video, the stud bays are all spray foamed at the edges and corners before batts put in. That takes a good bit of time and attention to detail, (I know because I've been doing it for a 12x16 shed, and almost every time I go to spray foam the next stretch of wall, I find there have been spots I missed before, usually the 3.5" crack at the top or bottom of the stud joining a top/bottom plate). I'm sprayfoaming canned sprayfoam beads in ALL cracks, joints, and also the holes where wiring was run through, and doing mineral wool batt insulation. Going to skip vapor barrier given I'm in a Zone 3 hot-humid climate and it's only going to be a semi-conditioned space. For those "small areas", what I've done is I just spray foamed the full volume of any cavity less than 4" wide with lots of canned spray foam rather than try cutting and installing a batt to a uniformly small width. Same with the odd corners (I believe it's called a California corner) where there's the thickness of a 2x4 wide, the width of a 2x4 deep, in a corner, that would be difficult installing insulation in that corner. I foamed out those corners until they overflowed, and then I handsawed the excess at right angles to the stud, making just a square cavity. It's taking a lot of time and attention to detail, but my time is my own.

@@LackeysLack Sounds like you enjoy spraying cans of foam! Unless you're planning to turn that shed into a refrigerator, you might be doing a bit of overkill in your climate zone. I think the most common issue where you are is usually mold rather than insulation--especially with sheds. Enjoy your shed!

@@SteveSpinella It didn't take much, only 4 large cans with a spraygun.

Yes, it matters. The "furry" side should be pointed towards the warm side of the house. For people in the south, say Florida or Texas, the warm side is the OUTSIDE of the home, so the "furry" side should be pointed towards the OUTSIDE of the home. (You shouldn't see the furry side) For people up north, say New York Minnesota or even Canada, the warm side is the INSIDE of the home. So the "furry" side should be pointed towards the INSIDE of the home. (You should see the furry side)

@@NuttedInYoMom just another example of something i've been doing wrong...thanks

@@NuttedInYoMom That's backwards. The paper side is the vapor barrier that goes toward the warm side of the wall. The furry, non-papered side goes toward the colder side of the wall. Paper in (fuzzy out) in colder climates, paper out (fuzzy in) in warmer climates.

Mitch, Thank you so much for your question. Unfortunately, it is one that could only be answered by testing a specific wall because it depend on the air tightness of the assembly and some other factors. No doubt the fastest form of thermal transfer is convection, but it is possible that even different cavities in a wall could have different ratios.

@@IDIDistributors Thanks for answering. Yeah, I was more just wondering about typical scenarios like the blue areas showing up on your thermal images. It sounds like you're saying it's mostly convective. Interesting.

Right!

Me? Making a premium dog house.

i did too, but it was my kids play house.

15 itches

Insulation is generally priced by volume, so R13, which is generally 3.5" thick, would be priced by square feet of coverage, and typically comes in 15" widths for 14.5" cavities between studs and 23" widths for 22.5" cavities. A smaller roll might be around $20 for 40 sq ft, or about .50 per sq ft.