Building new 36'x60' Pole Barn - Advice on venting and insulation?

[captainehh]

I am mid way through framing a 36x60' pole barn outiside of Portland, OR. Link to plans below. I will be finishing the loft space eventually, basically making it an insulated and air sealed 12'x60'x8' six-sided box. The plans call for a continous ridge vent, which I will be installing as part of the corrugated metal roof.

View attachment 517065

My questions are:

1) When I finish the loft space out, how will the rest of the barn vent? The finished loft will basically block off the ridge vent to the rest of the barn, and then the ridge vent will only vent the 'attic space'. Correct? I plan to install bird blocking in the eves of the main roof, but what should I install on the uphill side of the roof to allow convection to do its job and passively vent the space?

2) How should I install the metal roof? My plan is to install directly on the stick framed rafters and put batt insulation snug on underside of metal roof using twine (mostly for noise and hopefully to retain a little heat in the winter). Condensation is an issue on our climate. Will this work, or do I also need to install a vapor barrier under the metal roof?

I will be insulating the concrete slab. Barn will be used for automative/tractor/living and hobby space.

Thoughts? What am I missing?

Thank you!

 

[mx842]

I am mid way through framing a 36x60' pole barn outiside of Portland, OR. Link to plans below. I will be finishing the loft space eventually, basically making it an insulated and air sealed 12'x60'x8' six-sided box. The plans call for a continous ridge vent, which I will be installing as part of the corrugated metal roof.

View attachment 517065

My questions are:

1) When I finish the loft space out, how will the rest of the barn vent? The finished loft will basically block off the ridge vent to the rest of the barn, and then the ridge vent will only vent the 'attic space'. Correct? I plan to install bird blocking in the eves of the main roof, but what should I install on the uphill side of the roof to allow convection to do its job and passively vent the space?

2) How should I install the metal roof? My plan is to install directly on the stick framed rafters and put batt insulation snug on underside of metal roof using twine (mostly for noise and hopefully to retain a little heat in the winter). Condensation is an issue on our climate. Will this work, or do I also need to install a vapor barrier under the metal roof?

I will be insulating the concrete slab. Barn will be used for automative/tractor/living and hobby space.

Thoughts? What am I missing?

Thank you!

The building should vent just fine. You will need to add 2x4 perlins to the roof to screw the metal roofing to. You would have nothing to screw the metal to just using the truss. Start at the bottom of the truss with the perlins all the way across with about 3/4 of an inch overhang on each end. Then add the next line and the next on 2 foot centers until you get to the top. Depending on the numbers yo may have to add an extra line at the top for your ridge cap to screw to. Though you should be able to do the math and space the perlins so that the last row comes out where it needs to be a couple inches one way or another wont make that much difference. The roofing manufacturer can help you with how far to space your perlins and proper screw locations. Don't skimp on the screws and don't over or under compress the seal rings on the screws.

Applying that foil faced bubble wrap under the roof metal will help but is not necessary once the building gets sealed up. If it was an uninsulated building it would help with condensation forming on the roof panels and dripping down to the floor but if you are insulation the inside of the building once its all buttoned up you wont have a problem. OH!!!!!..... and don't put your insulation snug up against any of the roof or siding in the building. There needs to be an air space between the two. This air space will keep condensation in check if your insulation is installed properly it is more likely to form on the outside than on the inside of the panel.

 

[EddieWalker]

My questions are:

1) When I finish the loft space out, how will the rest of the barn vent? The finished loft will basically block off the ridge vent to the rest of the barn, and then the ridge vent will only vent the 'attic space'. Correct? I plan to install bird blocking in the eves of the main roof, but what should I install on the uphill side of the roof to allow convection to do its job and passively vent the space?

2) How should I install the metal roof? My plan is to install directly on the stick framed rafters and put batt insulation snug on underside of metal roof using twine (mostly for noise and hopefully to retain a little heat in the winter). Condensation is an issue on our climate. Will this work, or do I also need to install a vapor barrier under the metal roof?

I will be insulating the concrete slab. Barn will be used for automative/tractor/living and hobby space.

Thoughts? What am I missing?

Thank you!

1. Talk to your metal roof supplier. They make a flashing that kind of looks like an upside down F. The metal roofing goes into the flashing so air can flow under the metal, and up, and out of the flashing, but still keep water out.

2. First, you need purlins going across your rafters to attach the metal. Most metal requires this every four feet. Your metal supplier will tell you for sure what they require. It does vary according to metal thickness, style of metal roof, and your local weather. How far apart are your rafters? If 24 inches, you can get away with just about anything for purlins, but I would go with 2x4's on the flat if it was me.

Fiberglass insulation directly under a metal roof is going to get soaked over time from condensation. You absolutely need some kind of vapor barrier between the metal and the fiberglass. Your metal supplier will probably have some sort of bubble type, plastic rolls of insulation that goes under the metal. This will stop all condensation issues because the moisture will drop onto the plastic and drain down out of the building, or just sit there until it evaporates and goes away.

I would not block the underside of the metal at the eaves. The more air flow you get through there, the dryer it will remain, and the longer everything will last.

 

[thepumpguysc]

I'm experiencing the SAME THING.. I bought a metal building, had it installed & started looking for insulation options.. there are NO clear-cut instructions.. IF you wanna build a deck, no problem, thousands of plans.. your wanna run electric to your yard, no problem, thousands of plans.. you wanna insulate a metal building?? NOTHING..
The MAIN opinion is put the roll covered insulation on BEFORE the skin..
I ended up talking to EVERYONE that has a metal building in my area of SC.. I ended up measuring between the studs & outside metal.. I have
2 1/4" so I bought 2" 4x8 foil faced PLY foam board.. cut it to width & wedged it between the metal studs w/ the foil towards the OUTSIDE of the building to reflect the heat back out..
I haven't done the ceiling/roof yet because I need some scaffolding to get up there.. I'm going to use 2x4 "nailers" across the rafters to hold the 1/2" plywood covering..

 

[captainehh]

1. Talk to your metal roof supplier. They make a flashing that kind of looks like an upside down F. The metal roofing goes into the flashing so air can flow under the metal, and up, and out of the flashing, but still keep water out.

2. First, you need purlins going across your rafters to attach the metal. Most metal requires this every four feet. Your metal supplier will tell you for sure what they require. It does vary according to metal thickness, style of metal roof, and your local weather. How far apart are your rafters? If 24 inches, you can get away with just about anything for purlins, but I would go with 2x4's on the flat if it was me.

Fiberglass insulation directly under a metal roof is going to get soaked over time from condensation. You absolutely need some kind of vapor barrier between the metal and the fiberglass. Your metal supplier will probably have some sort of bubble type, plastic rolls of insulation that goes under the metal. This will stop all condensation issues because the moisture will drop onto the plastic and drain down out of the building, or just sit there until it evaporates and goes away.

I would not block the underside of the metal at the eaves. The more air flow you get through there, the dryer it will remain, and the longer everything will last.

Thanks Eddie Walker and mx842 for the great replies. Yes, the barn is built with perlins as well, so no problems there in terms of securing the roof. Sorry, I should have been more clear.

Eddie Walker, you nailed it. I chatted with the metal supplier today and indeed, there is a vent flashing the tucks under the siding on the uphill side of roof, roofing goes over top of flashing, and the flashing still allows for venting of the space down below. And yes, they concurred that I should install a vapor barrier underneath the roof.

Good stuff. I'm glad I asked these questions before it was too late!

Thanks again.

 

[Texasmark]

How I have it done: On the roof insulation, install rolled bubble wrap (specific insulation for the purpose, to name one) vertically from eave, across the peak on down the other side to the eave, which includes aluminum foil, and contains adhesive to seal seams. Then put your sheating (roofing) on top of that. Is a pain for the installers, especially on windy days, but that's what it takes as far as I'm concerned. That's the way I did my last 2 shops; one was built in '81, the other in '05 and nar a drop of condensation on anything inside over the years. Your purlins will sweat on the underside and this allows the moisture to run off the building and not into the building. On batts, you are relying on the vapor barrier to be your moisture barrier and may not do the job.

Some folks don't agree on roofs sweating. That's a moot point. As long as a surface is below the dew point, the moisture in the air will condense on it; just ask your cold can of soda.....ok so you put it in an insulated sleeve (aka the roof tin has a layer of insulation under it). Pull the pop out of the sleeve.....it's wet.

My buildings were erected with professional crews from Morton and BCI buildings as a reference. I put roof insulation in the spec and they provided it.

Continuous ridge vent: Perfect.

On what to do after finishing out the loft, install wall fans high up on the wall in the lower section, preferably on the lee side of the prevailing wind in the summer when the air is hot and can contain more moisture.

You can www how many CFM to vent per hour per weather condition. Figure the cubic feet of the area to be ventilated and ventilate accordingly. Get the fans with jalousie shutters that open and close as a function of air flow. That way when you fan is off you don't have (much of) a hole in the wall.

 

[sdef]

I'm experiencing the SAME THING.. I bought a metal building, had it installed & started looking for insulation options.. there are NO clear-cut instructions.. IF you wanna build a deck, no problem, thousands of plans.. your wanna run electric to your yard, no problem, thousands of plans.. you wanna insulate a metal building?? NOTHING..
The MAIN opinion is put the roll covered insulation on BEFORE the skin..
I ended up talking to EVERYONE that has a metal building in my area of SC.. I ended up measuring between the studs & outside metal.. I have
2 1/4" so I bought 2" 4x8 foil faced PLY foam board.. cut it to width & wedged it between the metal studs w/ the foil towards the OUTSIDE of the building to reflect the heat back out..
I haven't done the ceiling/roof yet because I need some scaffolding to get up there.. I'm going to use 2x4 "nailers" across the rafters to hold the 1/2" plywood covering..

Hoover buildings recently completed a 40 x 40 x 12 for me with a roll type insulation I have never seen before and must be designed for this type of building. It is a fiberglass blanket sealed in a moderate thickness, pliable, plastic, attached before the metal skin and works very well so far in the heat.

 

[mx842]

Hoover buildings recently completed a 40 x 40 x 12 for me with a roll type insulation I have never seen before and must be designed for this type of building. It is a fiberglass blanket sealed in a moderate thickness, pliable, plastic, attached before the metal skin and works very well so far in the heat.

View attachment 518482View attachment 518483View attachment 518484

What did that insulation cost out where you live? I looked at that same stuff when I did mine but it was really expensive. I came out better by adding 2x4's on the inside.......sorta like a stick built wall then went with R-15 wall insulation. Any way you go about it the insulation part of the job is going to be one of the highest cost points in the building.

You have a nice clean looking building going on there really looks good. The only drawback with that insulation is after a few years the outside layer will start to get brittle and is pretty easy to tear or punch a hole in. The stuff you used may not be the same stuff I see in a lot of buildings around here though. Anyway, you have a great looking building going on there. What's that copper looking tubing in the last pic?