Insulation questions

[NetWareHead]

How do you get batt insulation to stay in the stud bays? Is it just held up by friction or are their supports/anchors etc... that are used to retain it? This is 2x4 construction in walls (old school construction where most of the studs are actually 4 inches, except for a few odd ones that have been ripped down to other dimensions.

Considered spray foam insulation but I only have 2 rooms to do and it may not be cost effective to get a crew in here.

Faced or unfaced batt insulation?

Saw in home depot rolls of plastic sheeting in various thickness that can serve as a vapor barrier. When I removed drywall when gutting, the rooms that were redone in more modern times had plastic sheeting. I've seen opinions go both ways regarding whether or not I need vapor barrier. Abut the only think agreeable I've found is the barrier should be installed on the interior side of the wall. What do you guys say?

I have a few windows to insulate around so thinking about picking up a few cans of spray insulation to fill in the holes and gaps between window casings and framework.

House is in NH and Im insulating exterior walls. One wall has a stairwell on its other side which is not heated so I'm treating that like an exterior wall. Thanks...

 

[Blain]

Insulation supports.
Faced on "exterior walls". Face side towards heated/cooled space. Plastic sheeting can be used with unfaced insulation as a vapor barrier.
You don't want water vapor to go through the insulation and condense inside exterior walls. Water vapor should exit up and out through the attic space.
Expanding foam comes in high or low expansion types, depending on how large a gap needs to be filled.

 

[Greenman]

Depends on the insulation. Faced batt's have a lip on them you staple through. Unfaced batts are friction fit, you stuff them in and they hang there.
Vapor barrier will be up to local code. We don't ever use one around here, but I think it's required in the frozen wastelands where of you live.

For spray foam, Great Stuff makes a handy little spray gun and cans of foam that attach to it. Cheaper than the little cans, and you don't have to use it all at once.

 

[NetWareHead]

Sounds like I can use either one of the other? Do I use a faced insulation and the paper serves as vapor barrier? Or should I use plastic sheeting? Logic seems to dictate the plastic would block more air movement while the paper is more permeable.

 

[3chordcharlie]

Sounds like I can use either one of the other? Do I use a faced insulation and the paper serves as vapor barrier? Or should I use plastic sheeting? Logic seems to dictate the plastic would block more air movement while the paper is more permeable.

Honestly I think either is OK as long as it can breath to at least one side. I would assume the vapor barrier should be on the side with the greater temperature/moisture gradient potential although this might be a matter of some debate. For my area:

100F (90%) ---> 70F (50%) in summer
-10F (N/A%) ---> 70F (40%) in winter

By code vapor barrier goes on the interior side in my area. Some people disagree with this, but if you open a wall it is ALWAYS fine unless it has had a leak, regardless of faced batts, vapor barrier (taped or un-taped) or even significant holes in the barrier. Uni-insulated walls are almost always perfect inside, unless exposed to persistent leaking / trapped water.

 

[DrPizza]

Sounds like I can use either one of the other? Do I use a faced insulation and the paper serves as vapor barrier? Or should I use plastic sheeting? Logic seems to dictate the plastic would block more air movement while the paper is more permeable.

The paper is treated so that it's not permeable. At least, the brands I've purchased. I suppose it depends on code, but given a choice, I think I'd go with unfaced & sheet plastic as the vapor barrier. I *hate* putting up insulation. The paper always seems to have wrinkles and folds in it that makes it a pain in the neck. While it would probably cost marginally more to do the plastic, a lot fewer staples would likely be used.

IIRC, I've seen on a video that they recommended a bead of caulk at the top of the wall and floor - that seals off the wall so that you're not just funneling any air to the floor or ceiling.

 

[gbeirn]

Buy paper faced R-what ever value you want, cut to size of opening, place in between studs, flip out tab along stud and staple in place.

 

[Greenman]

The paper is treated so that it's not permeable. At least, the brands I've purchased. I suppose it depends on code, but given a choice, I think I'd go with unfaced & sheet plastic as the vapor barrier. I *hate* putting up insulation. The paper always seems to have wrinkles and folds in it that makes it a pain in the neck. While it would probably cost marginally more to do the plastic, a lot fewer staples would likely be used.

IIRC, I've seen on a video that they recommended a bead of caulk at the top of the wall and floor - that seals off the wall so that you're not just funneling any air to the floor or ceiling.

I'd say you're right on point.
The bead of caulking behind the drywall is to stop air movement, I don't think it would be needed with a plastic vapor barrier, as there really isn't anywhere for the air to go.

 

[paperfist]

The paper is treated so that it's not permeable. At least, the brands I've purchased. I suppose it depends on code, but given a choice, I think I'd go with unfaced & sheet plastic as the vapor barrier. I *hate* putting up insulation. The paper always seems to have wrinkles and folds in it that makes it a pain in the neck. While it would probably cost marginally more to do the plastic, a lot fewer staples would likely be used.

IIRC, I've seen on a video that they recommended a bead of caulk at the top of the wall and floor - that seals off the wall so that you're not just funneling any air to the floor or ceiling.

Yeah but after you're done man handling and cursing batt insulation the paper ends up all torn up and ripped and thus permeable

Get some ROXUL insulation, it will stand up on it's own.

And if you insulate the outside you don't want a vapor barrier their if you put one inside.

 

[DrPizza]

Yeah but after you're done man handling and cursing batt insulation the paper ends up all torn up and ripped and thus permeable

Get some ROXUL insulation, it will stand up on it's own.

And if you insulate the outside you don't want a vapor barrier their if you put one inside.

That's so true about the faced batts. And, it's such a pain when working around electrical boxes (outlets, switches), to cut the paper. Ditto wires running horizontally between studs, since they're centered from front to back. If you jam the insulation over the front of them, you lose R-value. If you squish the insulation and tuck it behind, you lose R-value. Properly, you split the batt in half (thickness wise) and tuck half behind, and the other half in front. If you're putting up faced batts, you (or at least, I) want each cavity to be one piece so you don't have tons of cuts (tears until you change the utility blade again, and again.) But, with unfaced batts, you can piece it in, no problem, so you're not fighting with an 8 foot section to tuck several feet behind a wire.

Here's a good video on what I mean: https://www.youtube.com/watch?v=fJbJbKyX8Xs

 

[paperfist]

That's so true about the faced batts. And, it's such a pain when working around electrical boxes (outlets, switches), to cut the paper. Ditto wires running horizontally between studs, since they're centered from front to back. If you jam the insulation over the front of them, you lose R-value. If you squish the insulation and tuck it behind, you lose R-value. Properly, you split the batt in half (thickness wise) and tuck half behind, and the other half in front. If you're putting up faced batts, you (or at least, I) want each cavity to be one piece so you don't have tons of cuts (tears until you change the utility blade again, and again.) But, with unfaced batts, you can piece it in, no problem, so you're not fighting with an 8 foot section to tuck several feet behind a wire.

Here's a good video on what I mean: https://www.youtube.com/watch?v=fJbJbKyX8Xs

Yeah that's another reason why I hate the pink fiberglass insulation. You end up hacking it so much that it's useless. Not to mention it's basically an air filter.

I'm not sure which insulation you are referring to though that can be split in half? The only kind I've used like that is the ROXUL which I believe to be wool. I put it in my ceilings for noise reduction when I renovate a room each year and the stuff is so dense it stays up there on its own without falling down. It's so easy to work with, I use a big kitchen knife to trim it to fit the cavities and it's like cutting plywood without the need for a circular saw.

My walls are all spray foamed. Just have 1 room left to do. Amazing stuff, it's pricey but the pay back is pretty fast if you have a home like mine with no insulation and nothing but air leaks.

 

[monkeydelmagico]

How do you get batt insulation to stay in the stud bays? Is it just held up by friction or are their supports/anchors etc... that are used to retain it? This is 2x4 construction in walls (old school construction where most of the studs are actually 4 inches, except for a few odd ones that have been ripped down to other dimensions.

Considered spray foam insulation but I only have 2 rooms to do and it may not be cost effective to get a crew in here.

Faced or unfaced batt insulation?

Faced. Staple gun. Scissors. A pair of gloves and some duct tape to seal the gloves to your long sleeve shirt.

Saw in home depot rolls of plastic sheeting in various thickness that can serve as a vapor barrier. When I removed drywall when gutting, the rooms that were redone in more modern times had plastic sheeting. I've seen opinions go both ways regarding whether or not I need vapor barrier. Abut the only think agreeable I've found is the barrier should be installed on the interior side of the wall. What do you guys say?

I think it's a bad idea. Plastic is for fairly specific builds and can cause alot of problems if done badly. I've been told to avoid it in our location (northeast). Here is a bit of proof but certainly not exhaustive research http://nationalfiber.com/docs/Cellul...rriers0909.pdf

I have a few windows to insulate around so thinking about picking up a few cans of spray insulation to fill in the holes and gaps between window casings and framework.

Make sure yo use the non-expanding type around windows otherwise it could cause some bowing/buckling.

 

[NetWareHead]

I think it's a bad idea. Plastic is for fairly specific builds and can cause alot of problems if done badly. I've been told to avoid it in our location (northeast). Here is a bit of proof but certainly not exhaustive research http://nationalfiber.com/docs/Cellul...rriers0909.pdf

The link did not display correctly, cant get it out of your post. Mind reposting?

 

[monkeydelmagico]

http://nationalfiber.com/docs/CelluloseInsulationMoistureAndVaporBarriers0909.pdf

 

[NoCreativity]

If you end up using ROXUL or rock wool type insulation, invest in a cheapo electric knife. Cuts through those batts like a warm knife through butter.

Go to ROXUL and whatever the pink panther company is to get some useful info on working with each product (unfaced and faced respectively).

 

[NetWareHead]

If you end up using ROXUL or rock wool type insulation, invest in a cheapo electric knife. Cuts through those batts like a warm knife through butter.

Also, youtube insulation installation. Go to ROXUL and whatever the pink panther company is to get some useful info on working with each product.

Ive been seeing alot of roxul insulation in my research. You guys like it better than the typical pink stuff?

Also, an electric knife? You mean like an electric knife for carving a turkey?

 

[NoCreativity]

Ive been seeing alot of roxul insulation in my research. You guys like it better than the typical pink stuff?

Also, an electric knife? You mean like an electric knife for carving a turkey?

Exactly. I did the ROXUL sound insulation in my house. Started out with a bread knife like they recommend and it was okay but I switched to the electric based on a coworkers recommendation and I was cutting pieces in half the time.

I haven't worked with the pink stuff so I can't compare but the ROXUL was pretty easy to work with.

 

[Red Squirrel]

I would not bother with faced, it creates too many air seams. Not even sure if it's code anymore tbh. I guess the drywall will compress it, but still, I prefer plastic with the least seams as possible, with vapour barrier tape for seams (not duct tape). Make sure you tape in places that have studs so the drywall presses against it. You can even put a bead of acoustic sealent at edges, it's a mucky caulk like substance that never dries. Creates a good seal. Messy to work with though. If you do get it on something, rubbing alcohol works great.

For electrical boxes there are foam inserts that go around and then you tape the vapour barrier to it. The drywall will press seal it.

Insulation and vapour barrier both play an important role in the thermal value of the home, you want the least amount of air leakage as possible, since insulation just acts as a filter when there is an air leak. Foam is different though it acts as vapour barrier too. When pulling up insulation, if you notice lot of black, it's often a good sign of air leakage. Typical around wiring boxes.

And yeah Roxul is considered better than fibreglass now. The pink stuff is not bad though, the Roxul is just better.

 

[Humpy]

Insulation and vapour barrier both play an important role in the thermal value of the home, you want the least amount of air leakage as possible, since insulation just acts as a filter when there is an air leak. Foam is different though it acts as vapour barrier too. When pulling up insulation, if you notice lot of black, it's often a good sign of air leakage. Typical around wiring boxes.

What good does plastic sheeting on the interior of a wall do as far as an air infiltration barrier?

Acting as a vapor barrier, how does plastic sheeting improve thermal properties?

 

[Red Squirrel]

What good does plastic sheeting on the interior of a wall do as far as an air infiltration barrier?

Acting as a vapor barrier, how does plastic sheeting improve thermal properties?

Sorry meant on the interrior side of outside walls. Would not bother for actual partition walls unless you are trying to seal a room from the rest. Ex: When I do my server room I'll vapour barrier and seal it, and it will have it's own HVAC. I'm doing it mostly for a safety reason (UPS battery hydrogen) as well as a dust mitigation reason. (air will keep going through hepa filters).

As far as thermal properties it stops air flow. On an outside wall if you have insulation but no vapour barrier, air can still travel through the drywall or any other cracks or seams in the construction, even the tyvec, The tyvec is a general protective shield in case water gets behind the outside face like the siding or brick but not actually a full barrier, you don't want a full air barrier on that side of the wall, only on the conditioned side.

 

[Howard]

Ive been seeing alot of roxul insulation in my research. You guys like it better than the typical pink stuff?

Also, an electric knife? You mean like an electric knife for carving a turkey?

It rocks (no pun intended). Holds up way better to water and is much easier on your body.

 

[3chordcharlie]

It rocks (no pun intended). Holds up way better to water and is much easier on your body.

Definitely. Also it is much easier to get a good installation because rock wool has some structure to it. I do hope "they" don't come along in 10 years and tell us rock wool is poison.

 

[paperfist]

Ive been seeing alot of roxul insulation in my research. You guys like it better than the typical pink stuff?

Also, an electric knife? You mean like an electric knife for carving a turkey?

Pink insulation is basically an air filter. When I ripped out my upstairs walls the stuff was black with all the air movement coming off the wood through the insulation and past the leaks in the drywall. I can only imagine how diminished it's R value was after it was saturated with soils.

I don't think the big box stores carry Roxsul. If you were able to see it side by side you wouldn't even hesitate in using it.

 

[Howard]

Pink insulation is basically an air filter. When I ripped out my upstairs walls the stuff was black with all the air movement coming off the wood through the insulation and past the leaks in the drywall. I can only imagine how diminished it's R value was after it was saturated with soils.

I don't think the big box stores carry Roxsul. If you were able to see it side by side you wouldn't even hesitate in using it.

What was wrong with your air barrier, that there was so much flow through the insulation?

 

[Blain]

I do hope "they" don't come along in 10 years and tell us rock wool is poison.

Mineral Wool / Rockwool has been around for a very long time and has been studied for safety issues in the US and Europe.
Asbestos insulation is a totally different story.