Pole Barn Insulation Question

[jynx]

K, building a pole barn.

28x40, vented ridge and vented soffits. Metal to be attached to the wood roof purlins. Purlins 2' on center.

Generally to help prevent it from raining inside you need to insulate along the roof. Typically this is done with a foil backed type roll out material to help give the thermal break. I am wondering if some 1" pink foam board or some do it yourself spray foam insulation would do the same or better.

Plan to install a ceiling of some sort eventually but may be a little bit so trying to decide the best way to beat this. Trusses should go up this weekend and metal will follow soon after so trying to get an idea of the best way to mitigate the condensation issues.

Anyone been thru this or have any thoughts?

Thanks

 

[Helipilot]

I would suggest using 4" or 6" white vinyl backed fiberglass. Comes in 8' widths and rolls about 20' long. Rolls on from the ridge down the roof and then again from the eve down to the foundation. Vinyl side in and just apply your metal over the insulation and fasten down as usual. Works great and really lightens up the shop as well. I have it in my pre-engineered metal shop. Works great. Good luck!

 

[jynx]

Do you have any kind of foil backed vapor barrier? I been doing some reading and seems that is pretty standard for most structures similar to mine? My main concern is keeping the condensation at bay.

 

[FJ40-GARAGE]

Pictures would help.
As mentioned you will, depending on the weather and humidity, have condensation at the inner side of the metal roof.
Usually and when i write usually i mean by german standards, you first of all put a foil on top of the rafters to prevent condensing water dripping down, then you put a counter batten along the rafters to create some air space. On these counter battens you put your horizontal battens where you fix metal roofing. That way you have ventilation by airflow below the metal roof what means less heat up in summer and less condensation in winter.
If you like to use insulation you put that between the rafters and put a vapor barrier below it, to the side of the heated room.

 

[jynx]

This is what I am describing.

Trusses, roof purlins, then the foil backed bubble insulation then metal directly over the foil/bubble insulation.

I will have a continuous ridge vent and the soffit is vented so I will get airflow from eve to ridge. I plan to eventually put up a ceiling and insulate above that as well, but for now the building will likely be open and I want to avoid/reduce condensation on the inside of the metal.

 

[FJ40-GARAGE]

Red= Metal roof
Black= Foil
Yellow=Insulation

 

[Delancy]

Bubble wrap is a radiant barrier, not a vapor barrier, hence the U not R factor, and the same U results may be achieved with Galvalume or white roof.

Not saying a bad idea, but metal roofing inherently does not trap heat like other forms of roofing, so a nominal gain, especially where the thermal conductivity properties of the sub frame, wood, are nil.

If the environmental conditions are right, especially with the venting described that's inviting moisture in, bubble wrap nor a blanket insulation with a vapor barrier will guarantee consensation not to form, and I've seen it rain from both.

I'd think you'd be better to open the ridge later, when finishing out the interior and insulating above. Unless the contractor has specified otherwise, most "ridge vents" for metal roofs are accomplished with a vented closure strip sandwiched between the flat ridge cap and panels, so a fairly simple task to remove the ridge, cut itch back, then replace solid foam closures with vented.

 

[jynx]

Ok, so I am finally got the building assembled and closed up and with winter just around the corner I want to get some insulation in the walls. Building is metal skin screwed to wood substructure. I did end up putting the bubble foil radiant barrier under the roof panels and the roof is vented with the closure strip as noted above.

So for the walls I am planning to build them out with 2x4 framing and then skin it with something. So can I just get some fiberglass and put it in there, and if so does it need to be paper or vinyl backed? Do I need something between the Batts and metal exterior panels? Would a DIY closed cell foam kit 1" thick on the metal then batt atop that be a good combo?

I also know most heat is lost up, so a ceiling is a must. Again, regardless of covering, what should go above. Batt, rigid foam, or something else? Given how things are put together, want to avoid blown in or loose stuff.

Also, not looking to maintain 50° in the summer or 90° in the dead of winter, just keep things comfortable for wrenching, smoking cigars and generally hiding out.