New Barn Build - Insulation help needed

[WNY Tony]

Hi All,

I have recently built a pole barn, incorporating a lot of knowledge that I have learned from this site, so first off, thank you! Here are the basic details of the barn:

30x48 barn, 8/12 pitch roof with attic trusses
10' eave height, vinyl siding, shingle roof, OSB under both the roof and siding.
Intent will be that the front 30x30 area will be vehicle storage/general barn area, and the rear 18x30 will be a wood shop. At this point, I have run a 100 amp sub-panel to the barn and a frost-free hydrant from my house.

My initial intent was to just insulate and heat the back portion of the barn where I will do wood-working (heating as in 50ish degrees, just enough to make it reasonable to work in. Some of my friends tell me that I will regret not insulating/heating the rest of the barn as well, which has me thinking.

I have a question, I am looking to start doing some insulation work, and need some ideas on which method will be better for the ceiling/roof insulation. I have 18" overhangs with vented soffits, and a ridge vent. Either option will include rafter vents that allow air to get from the soffits to the ridge. I included a picture as I probably won't be able to get all of the description and jargon correct.

Option 1 would be to run R-19 the entire length of the truss rafter from soffit to ridge (the rafter portion of my trusses is 2x8, which would leave space for an air gap between the insulation and the roof deck).

Option 2 would be to run R30 insulation along the ceiling on either side of the attic space, then run r-19 up the knee walls in the attic, and then up to the ridge.

The ceiling is going to be white painted steel paneling.

Any and all feedback will be greatly appreciated!!

 

[Jimmies63]

I'm in your 'hood and just built a barn. It's in the garage gallery. 40x72. Shop is 28x40 and heated. The rest is unheated. Workshop and cold storage. Sound familiar?

Initial build had r30 in the shop ceiling with ridge vent and soffit vents. The walls I was going to do in r12. The roof went in. As we were building the interior, the r12 fiberglass was looking expensive. Had a guy come to do sprayed foam for the walls. About the same as pink - actually likely more in the end with labor. Foam guy said we should have just sprayed the whole thing. I asked about venting the roof. He said I didn't need it with foam. Foam on the inside of the roof deck prevents any heat or condensation getting to the building. No need to vent.

As it stands, the foam in the walls is awesome. Building is super tight. The new radiant tube (50,000 btu) is awesome but we have only had 32 degrees so far.

Depending on what the gas bill looks like this winter, the plan is to spray-foam the storage side next year and put in another tube heater. Spray foam was about $2/sq ft. Will be a little more for the roof deck. Worth every penny in so many ways.

Thus, whatever you do, just spray foam it and you won't regret it. Never look back. Stage it if you have too. It isn't whether you do all or some, I think it is a 'how much foam can you afford'. I paid to insulate a 40x12 interior wall while I see what the gas cost is. I am stuck with an r30 glass attic over 28'. The wall may go to waste and I may regret it, but I'll never regret the foam.

If i do do the other side, it will be all foam.

 

[theoldwizard1]

Option 2 would be to run R30 insulation along the ceiling on either side of the attic space, then run r-19 up the knee walls in the attic, and then up to the ridge.

Option 2. Someday you will want that attic space to be on the "warm" side of the insulation !

 

[jives]

Option 3 is insulate only the ceiling of the garage/workshop and leave the entire attic
uninsulated. It is storage only, so why heat it? I'm guessing you have pull down attic
stairs? You will rarely, if ever, use this as work space, so let it get blazin' hot in the
summer and freezing in the winter. If, one day, you do decide on turning it into work
space or living space (probably illegal without a lot of modifications), then you will still
want the floor insulated.

 

[WNY Tony]

Thanks for the suggestions so far.

I have a question I can't seem to find an answer for. I personally don't want to have to keep the barn heated when I am not using it, but I am concerned about moisture/condensation build up during the winter/spring and having things rust on me. Is this a valid concern, or will my stuff remain OK? Forgive my ignorance, I have never had a detached unheated building before. The drainage around the building is excellent, good overhangs, and sandy soil that drains well. I intend to install a ceiling so that the ridge vent only draws air from teh vented soffits. If rust isn't a concern in an unheated space, then my plan would change to simply insulate the back room and the ceiling over it, and put an electric garage heater in there for the times that I plan to use the space.

I appreciate any knowledge on this question.

 

[Tazzie]

I also vote for spray foam it will seal the building very well. Also if you have not poured cement yet put 4x8x2" sheets of foam under the cement. Good luck with the build.

 

[Jimmies63]

I also vote for spray foam it will seal the building very well. Also if you have not poured cement yet put 4x8x2" sheets of foam under the cement. Good luck with the build.

Absolutely. I balked. Regretting it now and will forever.

 

[Jimmies63]

Thanks for the suggestions so far.

I have a question I can't seem to find an answer for. I personally don't want to have to keep the barn heated when I am not using it, but I am concerned about moisture/condensation build up during the winter/spring and having things rust on me. Is this a valid concern, or will my stuff remain OK? Forgive my ignorance, I have never had a detached unheated building before. The drainage around the building is excellent, good overhangs, and sandy soil that drains well. I intend to install a ceiling so that the ridge vent only draws air from teh vented soffits. If rust isn't a concern in an unheated space, then my plan would change to simply insulate the back room and the ceiling over it, and put an electric garage heater in there for the times that I plan to use the space.

I appreciate any knowledge on this question.

As I understand it, if there is no moisture getting into the building - generally through the slab on poorly draining soil, then the only moisture getting in is the air you breath. Put down 10mil plastic under the slab and that problem is solved accept for the general air you breath. My neighbor has a barn full of rare old cars, I/2 shop 1/2 left cold. 0 moisture/rust issues in 12 or more years. I followed his lead on my build, but I had to watch the guys putting in the floor. I had to argue with them constantly to put down the plastic. If I wasn't there, they might not have. If I could go back 3 months, I would have had a layer of insulation laid down under the slab too.

The air in general will only condense and turn to water when dew point is high, temps drop and the sun heats up your roof later on. Even that is only parts of the year. If you have a wood sheathed roof, it will absorb and release the moisture through your ridge vent. If you have a metal roof like me, get Dripstop! on it and it won't rain inside.

Now, all that works in vacant space or insulated space when you have a vapor barrier on the warm side of the wall.

All that changes when you spray foam. Spray foam on the inside of your roof, the inside of the roof never heats up, never generates moisture to have to vent. On the inside of the room, the foam acts as it's own vapor barrier and nothing moves or condenses inside the room. Humidity and moisture come and go as you open and close the door. Nothing will rust out any faster than anything in your home.

This foam stuff really is like magic. I'm a convert. Wish I believed it to begin with then I wouldn't have put pink in my shop ceiling.

 

[sevensandeights]

I have a 40x60 stick built with attic trusses, vented soffit/ridge vent and white steel interior ceiling. I put R19 batts in the walls. For the attic, I had cellulose blown in (R30 or 38)outside of the knee walls. R19 batts up the knee walls and over the top of the attic ceiling.

Also, I paid an insulation contractor to do this - I think it was about $3k 3 years ago. My cost for materials was close to that so it was a no brainer to pay them to do the work.

 

[WNY Tony]

Well, this is encouraging. I am happy to hear that I may not need to condition the 'garage' portion of my barn in order to keep things from rusting. I will be sure to put down foam insulation and a vapor barrier before the slab is poured (won't be until next year at this point).

As for the spray foam insulation, it sounds like it is the real deal based on what everyone says. I just struggle with the cost of the spray for a given r-value. I understand it helps seal things up tight, but would this be overkill if I am only looking to heat this occasionally, and only to 50-60 degrees? Also, the barn has Tyvek on the exterior under the vinyl siding, which I figured would have helped tighten things up already. I bought r13 kraft faced fiberglass batts on sale last week thinking that was the direction I was headed, but could always return them.

Sevensandeights, your setup sounds exactly like what I was thinking about in option 1, which sounds great. I guess I am getting gun-shy about the potential energy bills to condition the whole space like that.

So many options!!!!

 

[Tazzie]

You need to do what fits your budget. I had 3" of spray foam on the celling and 1" on the walls to seal the building up then framed between the post with 2x4s and added r13 fiberglass. Also plastic 2" foam then more plastic under the cement. I run a radiant tube heater and works very well for me. I keep the barn 40 degrees all winter then bump it up when out there. Cost me apx $40 a month I am in Michigan. Hope this helps