Another Insulation Dilemma........

Gents, so i am at the point whilst waiting for concrete that I need to get cracking on insulation, in order to start sheathing before it gets too cold here in TN.

I have been kicking around a few ideas for insulation, I don't need it to hold heat in like my house, however I would like a little something more than bare metal inside the walls.

I am planning on sheathing with sanded plywood in order to hang things up in any place that I choose once the building is complete. i am also planning on running all of my electrical in exposed conduit on the walls in order to facilitate changes in the future if I see fit.

The builders did not insulate the walls with the double bubble insulation on the exterior and recommends that I use rolled batts in between the studs in order to insulate.

My issue with this is that I am already planning on rolling out the red carpet for mice and other pests as I live in the woods. I have seen rodents turn rolled fiberglass insulation into 5 star resorts before and would like to avoid that scenario.

Spray foam is out of the question as it costs $1000 more than my concrete quote on the low end. So that leaves me with foam board insulation.

I was considering 1 of 2 options.

1. Using GAF POLYISO 0.5" thick foam board insulation between the studs and securing it to the metal with liquid nails then sealing up the gaps and cracks with DIY spray foam. I have heard great things about this product, based on its minimal thickness it provides an R-value of 3.6 at its 0.5" thickness which is pretty good for its size.

2. Using the same product, but sheathing the entire interior of the building, taping the joints and then sheathing over the insulation board with sanded plywood. That would leave a 6" gap between the metal and the insulation board to allow air flow, however I wonder if this will be too much airflow and eventually cause moisture to build up in between the walls.

I would really prefer to not use rolled fiberglass due to previous rodent experiences, however I would consider it if anyone has better suggestions on how to manage critters getting in the walls.

Would either of these options be better than the other or would both of them be about the same as not insulating at all? Like I said, I realize that the R-value of 3.6 isn't that much, but I will have a wood stove in the building for the winter and potentially an AC unit for the summer eventually.

The biggest reason for wanting to use this product is because I already have about 1500 square feet on hand from a previous siding project.

As you can see by the pictures below, the building has been studded out horizontally between the posts.

Thanks!

Insulation also keeps out summer heat and noise. If it were my shop, I'd use either a Roxul Comfortbatt, or your local mineral wool equivalent. Critters don't like it. Then sheet with your polyiso and tape the seams, and your have around R16. I would add insulation of some sort between those headers at the top of the poles. I have had to deal with bee hives in areas like that in one of our old hay barns. My dad is allergic to been stings and I'm not, sadly removal couldn't involve fire.

I agree with North Run Grader above. To me insulating to an "r" 3.6 is not insulating (worth the effort). You can however, put up your ridgid in layers if you want to stay with foam. Your (horiz) framing detail should help with your mice worries and you should be able to control them with proper bottom edge & corner "closure" made with metal. I'd go as far a filling at every 9" V in the siding between the wood. Once those little bas..rds get in….. It would be tedious, but a little time with sone metal snips and some coil, you could shut them off.

Here's my plan for an exact building as yours near Louisville KY. I too am planning to run my studs horizontally on 24" centers. I am going to stuff stainless steel wool into all of the openings in the metal. There is also a rodent stop type trim that is put on the bottom that helps too. I'll try and find a pic and post it. I'm going to foam the corners and gaps that I can't easily put insulation. Then I'm putting r19 in the walls. I have my trusses on 4' centers and I plan on hanging tin on the ceiling and blowing in r38-40. Just need more time and money, but don't we all.

Ohmthis said:

Here's my plan for an exact building as yours near Louisville KY. I too am planning to run my studs horizontally on 24" centers. I am going to stuff stainless steel wool into all of the openings in the metal. There is also a rodent stop type trim that is put on the bottom that helps too. I'll try and find a pic and post it. I'm going to foam the corners and gaps that I can't easily put insulation. Then I'm putting r19 in the walls. I have my trusses on 4' centers and I plan on hanging tin on the ceiling and blowing in r38-40. Just need more time and money, but don't we all.

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That is the exact plan for my ceiling as well, however everything is done is stages.

The walls are the first issue.

So all in all, the best way to tackle this will be to actually put some batts in between the studs and then fix and tape the seams of the GAF PolyIso over all of the framing and the put the walls up.

Would foam work inside the gaps between the metal and framing to help keep the mice out?

After looking at it, I have the rat guard boards installed at the base already, however there are a few places that those SOBs might be able to get in. hence why i am asking about the foam.

Who knows, they might eat it.

North Run Grader said:

Insulation also keeps out summer heat and noise. If it were my shop, I'd use either a Roxul Comfortbatt, or your local mineral wool equivalent. Critters don't like it. Then sheet with your polyiso and tape the seams, and your have around R16. I would add insulation of some sort between those headers at the top of the poles. I have had to deal with bee hives in areas like that in one of our old hay barns. My dad is allergic to been stings and I'm not, sadly removal couldn't involve fire.

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Holy $50 bucks for a 4' section of that Roxul Comfortbatt.........

That will end up running around 10K for the size building that I have.

At least that is what Lowes.com has the price listed as.

The more I think about it, I may just consider using the standard Owens Corning faced R-19 between the studs. That will be around another $400 bucks.

In order to keep the mice out and keep them from destroying that, I guess the key will be to seal up the bottom and top prior to finishing the building so that they can't get into the walls. Foam comes to mind as the easiest, but I may have to go the route that was previously mentioned with cutting metal, at least on the top and bottom.

So, if I were to go this route.........based on where I live..........(Middle Tennessee), would I need to install the facing of the insulation towards the metal or towards the interior of the building?

Or would I use unfaced rolled fiberglass?

Then which direction would I install the GAF PolyISO over the framing? Foil side towards the interior or faced side towards the interior?

Thanks guys. This is helping a lot!

rigid foam on the bottom foot or two, R-19 batts for the rest.

OR

Box the foot of the wall with steel rain gutter as a rat barrier, insulate it all with fiberglass. or downspout. or commercial build-out metal studs.

eta looking at your pictures, forget all that. Tack in metal mesh along the bottom seam where the tin skin hits your bottom 2x6, then cover it in spray foam to seal all the bottom holes and bind it all together. Then stuff it with R-19 and sheath as you go.

Gotcha, so which side would I put the facing of the insulation? Is it going to conflict with the PolyIso board over all of the framing and trap moisture in?

I have heard negative reviews about a vapor barrier here in Tennessee so, I am thinking that I am going to pass on that.

Rats will live in the foam just as well as batts. AMHIK

I'd do what ever is cheapest. But don't forget to take care of air leaks.

ddawg16 said:

Rats will live in the foam just as well as batts. AMHIK

I'd do what ever is cheapest. But don't forget to take care of air leaks.

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Touche.........

Putting the PolyIso foam board over all of the framing should help manage any air leaks inside of the building. Just need to decide which product will work the best for my climate.

How big is your shop? I can't calculate the scale from the 2 pictures. I'm amazed that Roxul costs that much down there, I usually pay $40 - 49 a bundle up here. I would check out Roxul.com directly and use their calculator and find a local dealer with a better price. A quick Google search pulls all the main manufacturersite when you search "mineral wool insulation". I'd invest more research into it. Even treated blown cellulose has way better insect and rodent repellance then plain fiberglass. I just don't like fiberglass if there are any available options close to to the same price.

Roxul is sold in multiple sheets of 4' length. I think it's like 12 4' lengths or $40 for 48'. I've used Roxul, fiberglass & cellulose around my house. The fiberglass was the best performing for temperature insulation. Roxul helps with sound. Cellulose was easiest on already closed up cavities. Since yours is open go with fiberglass. The paper or moisture barrier side goes toward the hot side. So if it's cold in the winter the paper goes to the inside. If it's hot outside like you live in Florida then paper goes on the outside. If it's both then you go inside because moisture is more prevalent in cold winters.

Ihateclevernames said:

Putting the PolyIso foam board over all of the framing should help manage any air leaks inside of the building. Just need to decide which product will work the best for my climate.

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When I priced polyiso last summer the cheapest I found in my area was a fiberglass faced product from Valutherm at my local Menards.

I believe wet pack cellulose has additives which make it fire and rodent resistant but I don't know if it can be sprayed right up against the steel. It is said to do a good job of air sealing. Not as good as closed cell foam but is usually much cheaper, assuming you have installers in your area.

cbracer said:

Roxul is sold in multiple sheets of 4' length. I think it's like 12 4' lengths or $40 for 48'. I've used Roxul, fiberglass & cellulose around my house. The fiberglass was the best performing for temperature insulation. Roxul helps with sound. Cellulose was easiest on already closed up cavities. Since yours is open go with fiberglass. The paper or moisture barrier side goes toward the hot side. So if it's cold in the winter the paper goes to the inside. If it's hot outside like you live in Florida then paper goes on the outside. If it's both then you go inside because moisture is more prevalent in cold winters.

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I see.

Starting to make sense now. Based on this option, if I were to use the PolyIso foam over it, will that conflict with having the paper side of the insulation facing out?

I really like the idea of having continuous insulation inside the shop, just need to make sure that putting the PolyIso foam on the framing on the interior is not going to compound issues inside of the walls since is will basically act as a vapor barrier, which they do not recommend in middle TN.

Or am I missing something and does that foam actually breathe a little bit?

And I must have been wrong about the Roxul, it didn't specify that it has multiple sheets in the package.......Lowes.com error.

The shop is 36' x 45'

As far as sealing up the bottom of the metal, that is what rat guard trim does.. On my new (under construction) building I used 1" rigid foam that is foil faced. It is between the the frame and the metal on all sides and the roof.

you didn't say if the spray foam quote was for a contractor to do it or you, so just in case I thought I'd throw this link in for you. Might be worth looking into. They aren't the only company and I have no experience with them.

https://www.sprayfoamkit.com/spray-foam-insulation/best-spray-foam-insulation.html

Thanks for the link, but I have been doing some research on the DIY spray foam kits and have seen marginal reviews at best. I would hate to drop that kind of money on something that may not work the way I need it to.

So, after all of this discussion..........

I realized that I should just ask my builder as he has been building these in the area for over 20 years and has one of the best reputations around based on his construction techniques.

He said skip the foam board, and just put R-19 in between the studs and then add a vapor barrier.

Done.

I am going to get started on it tonight and begin sheathing as I go as well in order to keep any critters out that may decide to get in there.

Great stuff makes a foam that you need to be using for your fill in. It's got a chemical in it that makes the foam so bitter that mice and others will not touch it. Home depot has it but you may have to ask to find it. When I found it over at the concrete isle instead of insulation isle with all the other Great Stuff.

Milton Shaw said:

Great stuff makes a foam that you need to be using for your fill in. It's got a chemical in it that makes the foam so bitter that mice and others will not touch it. Home depot has it but you may have to ask to find it. When I found it over at the concrete isle instead of insulation isle with all the other Great Stuff.

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I think your talking about the one in the green can right? I think it says pest blocker or something like that. I have already gotten started on a few areas with the regular stuff and totally forgot about that. I will pick some up today and press on with it. At the very least, I will really emphasize using that on the top and bottom.

A little off topic, but I know that you should not have 2 moisture barriers so, wouldn't the metal be considered a MB? I had never thought of this until this thread.

jack stand said:

A little off topic, but I know that you should not have 2 moisture barriers so, wouldn't the metal be considered a MB? I had never thought of this until this thread.

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If the metal is a continuous piece and sealed, then in some ways yes but the top and bottom likely aren't completely sealed? So moisture would still be able to get out. I think he'd be fine with or without a moisture barrier since he said it's not required where he lives in TN.

Exactly what I was thinking as well. Being that the top will actually be open and allow the air to rise to the ceiling, it should dissipate with no issues.

Hopefully.......