Help a newb insulate a new shop

[stm317]

Hello all! I've been lurking here for awhile now as my project has progressed and it's been super informative, so thanks for sharing all of your knowledge! Anyway, I have a 32' X 48' metal pole barn that I need to finish out, and could use some advise from you all.

Location: Central Indiana, so 4 seasons and temps from -20 up to 100+ aren't out of the question. Humidity in the summer is also very present.

Building: Metal shell with wooden framing. Metal roof. The walls have a vapor barrier (Tyvek) under the metal, and the roof has a moisture barrier to keep the metal from sweating and dripping down inside. Scissor trusses are spaced 48 on center and are currently open, but will probably have metal hung on the underside to act as a ceiling. There is no venting of any kind (no gable vents, ridge vents, or soffit vents).

Now ideally, I'd have it all foamed to the proper thickness, but that's not in the budget right now, so I'm looking for a middle ground I guess. At the moment I'm leaning towards doing about an inch of spray foam on the underside of the roof to seal it up well (and provide about R6 insulation), and then using blown-in cellulose on top of the ceiling to achieve the remaining R value that I need.

Does this seem like it might work well enough, or is it a recipe for disaster to have 2 types of insulation, separated by an air gap? How does having no venting affect things? Should I skip the foam completely and just do it all with cellulose on top of the ceiling?

 

[stm317]

So, maybe some pics would help clarify the situation a bit. Here's the building before the floor was done.
https://scontent-ort2-1.**.fbcdn.net/v/t1.0-9/18839050_10108298912275208_8296920578996540141_n.jpg?oh=8ff5cef49d0a563bba04000afeb26021&oe=5A24122C

https://scontent-ort2-1.**.fbcdn.net/v/t31.0-8/18814746_10102893929823504_1136363322416181122_o.jpg?oh=58bb6120a654a72838abbc28500e6e96&oe=5A2E9B56

And here's the inside as it currently stands. I'd like to get this thing insulated in the next couple of months before it gets cold.
https://scontent-ort2-1.**.fbcdn.net/v/t31.0-8/20507295_10103055840767674_4959884492121106213_o.jpg?oh=b1db97167dc128817e41e75015c71a87&oe=5A38446C

Any suggestions for insulating the ceiling?
Anyone willing to share their results after foaming a roof?
Any Midwesterners have other suggestions?

 

[hake]

So, maybe some pics would help clarify the situation a bit. Here's the building before the floor was done.
https://scontent-ort2-1.**.fbcdn.net/v/t1.0-9/18839050_10108298912275208_8296920578996540141_n.jpg?oh=8ff5cef49d0a563bba04000afeb26021&oe=5A24122C

https://scontent-ort2-1.**.fbcdn.net/v/t31.0-8/18814746_10102893929823504_1136363322416181122_o.jpg?oh=58bb6120a654a72838abbc28500e6e96&oe=5A2E9B56

And here's the inside as it currently stands. I'd like to get this thing insulated in the next couple of months before it gets cold.
https://scontent-ort2-1.**.fbcdn.net/v/t31.0-8/20507295_10103055840767674_4959884492121106213_o.jpg?oh=b1db97167dc128817e41e75015c71a87&oe=5A38446C

Any suggestions for insulating the ceiling?
Anyone willing to share their results after foaming a roof?
Any Midwesterners have other suggestions?

Nice building, another member on here foamed their entire building. What size is your building including the height? Who built it? I'm in KY looking for something very similar. If you don't care, how much did the building cost? I am hoping to build a 36x48 for 13k.


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[ptgarcia]

That's a handsome building!

 

[earlybirds]

I am in the midst of insulating my 30x40x12 pole barn. It is not heated all the time, only when I'm working in there. I like the open truss look because I have air lines, air hose and trouble light cord reels, and 3 ceiling fans ABOVE the bottom chord of the trusses.

I used 2 inch thick sheets of thermally faced polyiso insulation(R13)screwed to the bottom of the roof purlins. I had to buy a 48 sheet bundle at Menards. This was enough to do the entire roof and both gable ends down to the 12 foot height in my building. I do have soffit and ridge vents for air flow between the insulation and the metal roofing.

For the walls, I'm using 2 layers of 1-1/2 inch pink foam sheets(R15). One layer between the wall girts, then another layer over the girts, then covered with 5/8 inch plywood for the interior wall covering.

Living in Iowa, we have about the same temperature range that you mentioned. I could tell a HUGE increase in comfort just getting the roof and gable ends insulated last winter.

I am currently using a 125,000 BTU torpedo heater for temporary heat, but have plans to add a natural gas line and install a hanging furnace vented to the outside.

Insulating and finishing the interior walls will be this winter's project.

 

[rattle_snake]

IMHO, ventilation is step 1. Once the attic is enclosed, the air in the attic space will produce moisture and no where for it to go, regardless of insulation location(s).

It would be OK to do both roof deck and ceiling insulation. Mine is like that as I have a foam roof (1" close cell on top/outside of decking), and blow in at ceiling.
Sealing the roof deck is up to you, but not needed if you do blow in on ceiling.

The roof metal will sweat less without the foam, as attic temp would stay closer to outside.

 

[stm317]

Nice building, another member on here foamed their entire building. What size is your building including the height? Who built it? I'm in KY looking for something very similar. If you don't care, how much did the building cost? I am hoping to build a 36x48 for 13k.

Thanks. The building is 32x48x10. It was built by a local barn builder who did a couple of buildings for family members. I got the idea for the building from a kit sold at Menards though. I think that kit was price around $15k for material, not including any grading, concrete or labor to put it up. My estimates were all similar in price to the kit, plus labor of course. I'd be pretty surprised if you could do a larger building for less, but stranger things have probably occurred.

 

[stm317]

That's a handsome building!

Thank you!

I am in the midst of insulating my 30x40x12 pole barn. It is not heated all the time, only when I'm working in there. I like the open truss look because I have air lines, air hose and trouble light cord reels, and 3 ceiling fans ABOVE the bottom chord of the trusses.

I used 2 inch thick sheets of thermally faced polyiso insulation(R13)screwed to the bottom of the roof purlins. I had to buy a 48 sheet bundle at Menards. This was enough to do the entire roof and both gable ends down to the 12 foot height in my building. I do have soffit and ridge vents for air flow between the insulation and the metal roofing.

For the walls, I'm using 2 layers of 1-1/2 inch pink foam sheets(R15). One layer between the wall girts, then another layer over the girts, then covered with 5/8 inch plywood for the interior wall covering.

Living in Iowa, we have about the same temperature range that you mentioned. I could tell a HUGE increase in comfort just getting the roof and gable ends insulated last winter.

I am currently using a 125,000 BTU torpedo heater for temporary heat, but have plans to add a natural gas line and install a hanging furnace vented to the outside.

Insulating and finishing the interior walls will be this winter's project.

R13 seems pretty low for a ceiling in Iowa. Most places that I've seen suggest at least R50 for zone 5. I'm sure it's better than nothing though. Id like to get a higher R value personally.

IMHO, ventilation is step 1. Once the attic is enclosed, the air in the attic space will produce moisture and no where for it to go, regardless of insulation location(s).

It would be OK to do both roof deck and ceiling insulation. Mine is like that as I have a foam roof (1" close cell on top/outside of decking), and blow in at ceiling.
Sealing the roof deck is up to you, but not needed if you do blow in on ceiling.

The roof metal will sweat less without the foam, as attic temp would stay closer to outside.

Gable vents may be an option. There is a barrier installed between the underside of the roof metal and the framing, so I'm not too concerned about condensation forming on the roof panels, as long as it stays on top of the barrier. Moisture developing underneath that barrier, on insulation however would become an issue.

To me, it's almost like the debate between a vented vs non vented crawl space. In that case, vents will allow some air flow, but they can also allow more humidity in than having no vents would. Because of that, Vented crawl spaces are against code around here now, and sealing the vents and treating the crawl as conditioned space works much better. Can we learn similar things with an attic though? Hmmmm. I'm off to go do more reading.

 

[Black Oak]

I agree with rattle snake, in that how you are venting is critical. A plan before you start might have helped. What is the material under the roof metal? I'm not sure you can spray foam against radiant bubble or vinyl enclosed fiberglass. Rigid foam panels are a good option , foam in a can on the seams, then batts. Tyvek with spray foam on it is no longer "breathable".Do lots of research, that is a great shop.

 

[DC73]

You definitely don't have to vent the roof but the details must be correct to avoid issues. But, you do need enough foam insulation under the roof to prevent condensation from forming. There are charts to help determine how thick that layer of insulation needs to be and is very climate dependent. I'm guessing most of the experts would prefer to see the remaining insulation under the roof deck as well instead of on the ceiling. I could be wrong about that. I would recommend you visit the Q&A forum at GreenBuildingAdvisors and post your question. They have building science gurus who frequent that forum and can set you on the right path. Post back here what they say - I'd be interested in knowing if your approach is valid.

Good luck,

DC

 

[matt_i]

Normally I would say i think its a bad idea to put blown/loose insulation on top of a sloped roof, especially metal. But you don't have any soffit vents to block.

I also think by sealing + insulating the attic you are going to create a "microclimate" which is going to be very slow to change states of temp and humidity relative to the outdoors. The typical worrysome condition would be where you have humid air trapped in the building (all open, no insulation) and the roof goes cold via rainstorm or nightfall and then you can get the sweating/dripping. So the sealing is actually going to be good.

The only thing I would change about your plan is to ditch the torpedo heater and jump up the use of the vented fuelgas heater to the top of the priority list. The torpedo puts a tremendous humidity input into the space and eventually that is going to diffuse into the sealed attic space. Bottom line, my free opinion is: keep the attic dry, it will stay dry.

 

[stm317]

You definitely don't have to vent the roof but the details must be correct to avoid issues. But, you do need enough foam insulation under the roof to prevent condensation from forming. There are charts to help determine how thick that layer of insulation needs to be and is very climate dependent. I'm guessing most of the experts would prefer to see the remaining insulation under the roof deck as well instead of on the ceiling. I could be wrong about that. I would recommend you visit the Q&A forum at GreenBuildingAdvisors and post your question. They have building science gurus who frequent that forum and can set you on the right path. Post back here what they say - I'd be interested in knowing if your approach is valid.

Good luck,

DC

I've read a few threads over there while researching. They seem to know their stuff. I might pose the question to them as well. Thanks for the suggestion.

Normally I would say i think its a bad idea to put blown/loose insulation on top of a sloped roof, especially metal. But you don't have any soffit vents to block.

I also think by sealing + insulating the attic you are going to create a "microclimate" which is going to be very slow to change states of temp and humidity relative to the outdoors. The typical worrysome condition would be where you have humid air trapped in the building (all open, no insulation) and the roof goes cold via rainstorm or nightfall and then you can get the sweating/dripping. So the sealing is actually going to be good.

The only thing I would change about your plan is to ditch the torpedo heater and jump up the use of the vented fuelgas heater to the top of the priority list. The torpedo puts a tremendous humidity input into the space and eventually that is going to diffuse into the sealed attic space. Bottom line, my free opinion is: keep the attic dry, it will stay dry.

Thank you for the input. I wish there were more of a consensus on if it might work or not, even if everyone thought it was a terrible idea. Every garage is different however, and the thermodynamics involved aren't simple so I understand and appreciate the different suggestions.

I do want to clarify, that I have no plans to use a torpedo here. When it eventually gets heat, it will be a suspended natural gas heater that vents to the outside.

 

[C91x]

I am in the midst of insulating my 30x40x12 pole barn. It is not heated all the time, only when I'm working in there. I like the open truss look because I have air lines, air hose and trouble light cord reels, and 3 ceiling fans ABOVE the bottom chord of the trusses.

I used 2 inch thick sheets of thermally faced polyiso insulation(R13)screwed to the bottom of the roof purlins. I had to buy a 48 sheet bundle at Menards. This was enough to do the entire roof and both gable ends down to the 12 foot height in my building. I do have soffit and ridge vents for air flow between the insulation and the metal roofing.

For the walls, I'm using 2 layers of 1-1/2 inch pink foam sheets(R15). One layer between the wall girts, then another layer over the girts, then covered with 5/8 inch plywood for the interior wall covering.

Living in Iowa, we have about the same temperature range that you mentioned. I could tell a HUGE increase in comfort just getting the roof and gable ends insulated last winter.

I am currently using a 125,000 BTU torpedo heater for temporary heat, but have plans to add a natural gas line and install a hanging furnace vented to the outside.

Insulating and finishing the interior walls will be this winter's project.

Do you have a picture of this?