Another insulation question!

[Rocker4x4]

So I've researched as much as I can and still cannot figure out what I want to do. So I'm posting this to get the latest feedback, as a lot of the info I dug up on here were old post. This is on a 40x72 2x6 framed garage, 14' metal walls. One insulation company said they would just spray 7-8" of cellulose on walls and be done with it. The other I had come out said they would be very concerned with condensation with the metal walls using cellulose. Their suggestion is a bit more pricey, but does sound very good. 1.5-2" of closed spray foam, then 6" bats over top. Seals everything up well and higher R value. Also no need to worry on the condensation issue. He did make a comment, there are lots of people that just do Cellulose because it is cheaper and have no issues. He would do it anyway I wanted, just wants to make sure I know some of risk with cellulose and metal walls. What are your thoughts on this?? Thanks
Location is SE Indiana

 

[Rocker4x4]

If they were to blow wet cellulose on the walls, would I put plastic 6mil before inside metal liner panels?? If I used batts, I deff would be using plastic before liner panels. Or is the wet cellulose a bad idea all together against metal, inside or out??? With jst 6" bats, no spray foam, it would leave an air gap between metal and insulation. I know Morton has done it this way for years so it must work. My only concern with just using batts is the low R value

 

[Rocker4x4]

Darn, I sure hoped for little more help from this site! Maybe cuase no one really knows for sure, or everyone has own opinion. Like ford vs chevy vs dodge!! Amazing after all the people I've talked to, even with insulation guys, they all have different ideas. The one thing I am not liking is spray foam against the metal. Even though all the insulation guys said that's what they do it, I don't agree. Morton is old school, they've been in the game a long time, there is a reason they don't agree with it. I did find some 1/2 foam board I thought about using it in between studs, then ether spray foam against that or use cellulose! But the other bad thing I hear about foam is that it is more flammable than cellulose! This it more of a metal fab shop than anything, last thing I want to worry about is insulation fire b/c a hot spark got behind the wall!! Even if cellulose is lower R, But is more flame retardant, That's a plus to me, I'll just have to cut more wood to feed the OWB!! This is nerve racking, I thought this was the easy part, just get it insulated, and move on..

 

[DC73]

A layer of spray foam with batts over the top is a good way to go. The spray foam air seals and the batts are cheaper than going spray foam all the way. This method is often called "flash and batt" if you want to do some more research.

Any discussion of using plastic as a vapor barrier makes me nervous. It's too easy to trap moisture inside a wall if the details aren't perfect. Most building scientists are leaning away from true vapor barriers and instead recommending vapor retarders in some applications. Whether you need them or not is highly climate specific.

Recommend you visit these two sites and do some research:

GreenBuildingAdvisor.com

BuildingScience.com

The Q&A forum on GBA is frequented by building scientist types who can set you on the right path.

DC

 

[Gixx]

might try posting in the "heating/cooling" section of the site. Seems like a lot more insulation type threads over there...

 

[theoldwizard1]

I like #2. How are the batts going to be held up ?

Fill in your location in your profile.

 

[jrsavoie]

I have always been big on high density spray foam insulation. I plan on having my shop sprayed. I would go thicker on the spray foam. I'm not big on batting in the shop area as in the country we can have mice problems.

I'm thinking 2 to 3" of spray foam and a 1 1/2" gap to the inside steel covering. Or maybe foam filled steel panels for the interior.

 

[mg283680]

With the steel inside, why not go with the cellulose, then a plastic sheet over the studs before the steel? I'm thinking the bottom should be open so condensation can drain.
Seems like the closed cell spray foam and 4" (not 6") of fiberglass is a good way to go.

 

[Rocker4x4]

might try posting in the "heating/cooling" section of the site. Seems like a lot more insulation type threads over there

I know, new guy here and noticed that after posting this.

I'm very leery about spraying foam directly on metal. I know the insulation guys say they do this all the time, but it worries me. Also they said they would rather do open cell foam vs closed!! To me its like when there is undercoat sprayed on a truck frame, it makes it worse by trapping the moisture and rusting. Regardless to what I do, I pretty sure I will place this 1/2" foam board before the sheet metal. Also this is a 2x6 2' on center framed building, so if I flash/batt, the batt would be pretty easy as well. I really leaning toward the cellulose. To me that sounds like best bang for buck on my application.??

 

[DC73]

Also they said they would rather do open cell foam vs closed!!

Definitely run this by the experts on the GBA Q&A forum. There's no problem with spraying foam on your metal but closed cell vs open cell is very climate dependent and when using flash/batt, the thickness and type of spray foam has to be considered to avoid condensation issues between the foam and the batt insulation.

DC

 

[speed bump]

The humidity and temperature differential will play a large role in what you can get away with. 1.5-2" of foam is typically enough down to really cold to prevent condensation in the wall up to a pretty high delta. That is also a pretty common insulation technique for pole barns and steel buildings.

If I understand the building design properly there are 2x6 walls with steel panels? Fastened directly to the studs. If that is the case I would probably go one of two ways. First is expensive but worth it If you plan on keeping the place forever or use it a lot. That would be to spray foam and batt. If you don't use it much I would pull the panels, place a foil backed thin insulation layer and then reinstall the panels. After that cellulose.

 

[Rocker4x4]

2x6 walls with 2x4 girts. then the metal. So that's why I was thinking the 1/2 foam board to the 2x4 girts. that would leave 1.5" air space between the metal. Spray foam in the area is running about .50 a 1/2" per square foot. the building is 40x72 14' walls. so 3" thick of spray foam would add up. not saying I wouldn't do it, but for one if it would be worth the energy savings, and two, spend that kind of money to have my metal rust out early