Critique My insulation plan....

[HunterDan]

Here for a little critiqueing of my plan going forward. I'm getting ready to start wiring the barn, and plan to move right onto insulation when I'm done.

The barns 40x48x16 and I plan to atleast heat (maybe a/c) eventually. I would love to do spray foam, but for a building this size, it's just out of the question for me. I'm also nervous about fiberglass batts getting moisture in them from the metal siding. I'd like to find 4-8' wide batts, but that is seeming to be a challenge as well. So here's what I've pretty much decided on, please let me know if I should do something different.

I'm gonna put down a layer of 1/4" fan fold foam ins against my outside purlins, to keep my mind from worrying about the Fiberglass touching the metal, and to keep any air infiltration to a minimum. I have a rodent guard that my outside metal sits on, and have spray foamed any gaps where I can see daylight.

If I can't find wide insulation rolls, I'm then gonna stud out in between my posts with 2x4 on 24" centers. (I was gonna do 2x6 but feel I don't need to as its not bearing any load, and all I need it for it to staple the batts to, correct?)

On top of that, I'll then put a 6 mil (I guess? Gotta look more into that yet) vapor barrier and cover it all with either Osb, or I may do 4' metal wainscoat then white pine pieces above that (depending how fancy I decide to go, also $$)


Does this seem like a solid plan?

 

[bikesandcars]

I've done the math for my 40x60 and am at the same stage, spray foam really isn't that bad if you have to pay someone either way. Spray foam averages $2 sq foot for 2.1" r14. 2" xps 4 x 8 sheets are $1 sq ft R10, 3" $1.25. R19 batts around $.70

You are right about wanting to stop air. What the r values for fiberglass batts assume is dead air space. They do not block air movement well.

Foam blocks air, provides a thermal break, and also has a much higher perm value than plastic (varies per thickness)...I.e it will breathe.

From inside out: wall covering, plastic vapor barrier, unfaced batts, xps, outer wall is a great system for cold climates.

I'm doing spray foam because if I add up the cost of labor (mine or theirs) and the benefits, it is superior. I work full time and foam board or batt costs need to count labor. Spray foam is a phone call and a check to a stable legit R14, not using spray foam requires a system that is labor intensive

If I wanted to use just batts I would have the contractor Tyvek the outside wall between purlins and steel properly taping joints. That's probably best bang for the buck to pure insulation, disregarding other benefits of solidifying the structure

Sent from my XT1585 using Tapatalk

 

[HunterDan]

My bigger concern with the spray foam is having to change panels down the road. With 3" of foam stuck to them, it cannot be easy?

 

[bikesandcars]

I'm going through same issue.... Spray foam direct on panels or not. I talked to installer and they do both ways...on panels or over a barrier you put on the inside of purlins...or could do on Tyvek inside or outside of purlins(if you thought ahead)

1/4 fan fold is relatively cheap, not much more than tyvek, I might put that in quick without tape and spray on top

Sent from my XT1585 using Tapatalk

 

[HunterDan]

Yea if I went spry foAm I'd have to have it sprayed onto tyvek or fanfold, but will it stick?

 

[bikesandcars]

My installer said yes to Tyvek or xps, no issues, but I would verify that with your guy. I have no idea about how different types of spray foam or applications could change the situation.

Sent from my XT1585 using Tapatalk

 

[HunterDan]

I talked to one of the local companies, he said they won't spray against 1/4 as its to "flimsy"

Said they will spray against 3/4-1" foam board or 7/16 Osb.

Just so happens I've got a ton of Osb around, if I nail that to the inside of my exterior purlins, then have them spray to that, am I inviting any type of moisture problems between the osb and metal exterior? Or will the spray foam act as my moisture barrier and all will be ok?

 

[bikesandcars]

Spray foam acts as a vapor retarder, you should be good!

Check out the perm values

If really worried about moisture you could put plastic between the inside purlins and the inside wall, depending also on your wall covering.

Sent from my XT1585 using Tapatalk

 

[bikesandcars]

The more I think about it, the combo of OSB and spray foam should really solidify the structure, I like it and OSB is not very expensive.

Sent from my XT1585 using Tapatalk

 

[HunterDan]

Yea I'm thinking the same thing. Last winter I got 80 sheets of 7/16 for 5$/sheet off Craigslist. Was gonna use that as my wall covering, but may be putting tHat in to be sprayed.

I'm gonna have to sit down and really do some math and decide which way to go, wether it be

- fanfold xps, 8' wide batts, vapor barrier, interior horizontal purlins then my wall covering

- fanfold, stud out between my posts with 2x4, use 24" wide batts, vapor barrier then wall covering

Or

- Osb against exterior purlins, 3" closed cell, interior horizontal purlins, wall covering

 

[bikesandcars]

I settled OSB. Love how it's going to stiffen everything up. I live by a highway and I hope it will reduce noise too. Gives a solid surface for spray foam with the rough side in. Also somewhat protects against insects.

http://www.garagejournal.com/forum/showthread.php?t=343706

Sent from my XT1585 using Tapatalk