Pole Barn Insulation?!?

[RJLiath]

Hello all. Sorry to start a new thread for this but I've searched the forums and I can't seem to find what I need to know. I'm building a pole barn in NW Florida (it's a "kit" barn with engineered metal trusses 12' o.c. with 2 x 6 purlins running horizontally like a ladder and a plain galvalume metal roof) and I could use some advice. Some details: 30 x 72 x 12. I will stick build 2 x 4 walls with T1-11 wood siding. The floor is 4000 psi with fiber and 6 mil plastic underneath. There will be 6 roll up doors (would prefer insulated garage type doors if I can find some that follow the roof pitch and maintain head room. I won't be in there all the time as of now, but I'm trying to "future proof" it so I need to make it comfortable enough to work in all the time now rather than wish for it later. It will be mostly shop but it will have some man cave attributes, so should I build it like a shop or like a house? I'm in Florida so I have extreme humidity and temperatures to plan for. There will only be a ceiling in 3 bays. (There are 6 "bays". only the first and last 2 bays will have a ceiling. the rest will be open to the roof to have some head room for lifts, etc).
So my big questions are:
1. Is the ridge vent necessary or even functional in this application? With the purlins the way they are, (horizontal like a ladder) am I getting any air flow to the ridge? If I decide on closed cell spray foam, could I just spray right over the vent to seal it and use powered gable vents instead?
2. If spray foam proves too expensive, can I use kraft or vinyl faced glass in between the purlins (leaving an air gap between the fiberglass and the metal)? If so, could I first hang a radiant barrier foil (letting it sag and create an air gap of course) then the glass, creating a kind of insulation sandwich?
3. If I can manage the foam, shouldn't there be a gap between the metal and the spray? You hear it both ways on that. Some (most) think foam is the be-all end-all solution and say spray it floor to ceiling and everything in between. Some say to leave an air gap between the foam (any insulation, really) and the metal, which makes sense to me but will it matter in my instance with those crazy purlins?
4. House wrap or no?
5. Whatever insulation I choose, what should I do in the eaves? It seems like vented soffit would be a waste, but it would still need to be insulated, right? Where will the moisture go?
I'll have a million more questions I'm sure but in the meantime I've got to go dunk my head and cool my overheated brain!
Thanks in advance. This is my first post and I've learned a lot from you guys. Hoping for some insight from all the experience collected here.

 

[RJLiath]

Any advice at all?

 

[Flathead Red]

Where in NW Florida are you? I am in Navarre, near Pensacola

Red


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[SALIV8]

There's a bunch of posts on this subject. Try the search at top cause I've seem some very clever ideas...

 

[RJLiath]

I'm in Chipley. About 40 or 50 miles north of Panama City.

 

[RJLiath]

I've searched quite a bit, but I can't seem to find any info specific to my situation. It sounds like most pole barns on these forums are of the standard truss type. It's the horizontal purlins that are messing me up.

 

[Hornman]

Am I correct in assuming that picture 2 shows the completed full kit?

 

[rodm1]

This is old school way of doing it 60's. On my barn they installed the purlins and girts then nailed Black fiber board (R3.5) to the purlins and girts. Toped it with the steel panels. Roof leaks makes the board sag but on the walls its ok. Foam panels I here brake down and start to loosen and make noise on windy days.

Personally if you are using exposed screw panels for the roof you can expect leaks and plan your insulation accordingly. On the walls I think the fiber board is fine or use the stuff they use on houses then wrap it with house wrap.

 

[Hornman]

You didn't specifically mention HVAC, but with all the talk about insulation, man cave, and Gulf Coast I guess A/C is a given. In Florida the goal is to keep heat out not in. That metal roof will have to receive some serious attention. I would run furring strips perpendicular to the purlins and staple radiant barrier to the furring. That will still allow air flow under the metal roofing. Use that ridge vent to help keep the heat out. Gulf Coast ceiling insulation recommendation is R-42. Extruded polystyrene or ridgid urethane might be the easiest way to achieve that. If you use rigid or spray foam you will have to cover it for fire protection. That is a lot of work on scaffolding and ladders.

If I ever build another house it will have either 2 x6 or double 2 x 4 wall framing with 2 lb closed cell spray in foam. Housewrap required. Hardiplank siding for the garage.

Much of the year you should be able to open the rollup doors on the ends of the building to get flow through ventilation.

 

[RJLiath]

Thanks for the input. HVAC may well be in the cards sometime down the road, so I'd better seal it properly now. So you're saying the ridge vent is functional and I should keep it open? And if I use spray foam I'll need to finish the walls inside? I haven't even priced the foam yet. I guess I'm scared to find out what it'll cost. I was hoping I could get creative with the roof and use regular batt insulation in the walls.

 

[Bruhntune]

Hello guys , glad it see some it in the same boat as I'm in .
I live in SE Alabama about 50 miles from you I'm also building a 40x84x12 pole barn with a heated and cooled man cave,and shop on one end,the rest open doors two on the rear and three in front the for air flow on nice days.we added some of the foambacked 1/4 inch insulation under the tin for a start. Am also wondering what to do about the walls and have a million other questions as well .Am planning on using metal on the walls same as the top. I have been reading everyone's post and looking at info for about 2 months and feel I have learned a lot. Best of luck with your barn and thanks in advance for any advice .

 

[Bruhntune]

 

[Bruhntune]

 

[kippieland]

IMO spray foam is expensive for a shop. Spray foam does a great job at preventing water vapor in, but insulates the same as others. I like the pink/blue foam boards, since it keeps water vapor out as well. Still pricey but cheaper and just as effective as spray foam. Both are used more for preventing heat meeting cold air in cold climate areas. When I moved the Western part of Washington from the Eastern (where it is cold) part, it cracked me up how nobody has heard of spray foam. If you do use spray foam, you should finish the walls with something, I have heard its very flammable. Good luck.