The PBG answers questions about insulation, snow loads, and best choice for condensation.
DEAR POLE BARN GURU: I am wanting to finish the interior of my pole barn and have an cathedral like ceiling. If I were to follow the trusses up to the peak with foam board Insulation and use 2x4s spanning between the trusses for support would there be enough air flo between 2x4s and metel to prevent condensation? If not is there a way. I have a ridge vent along peak and soffit vents on both sides of 1ft eves. Thanks for taking the time to answer. TIM in PORTAGE
DEAR TIM: To begin with, I will surmise you have either a rather typical Midwest style post frame (pole barn) building with trusses spaced every four feet on top of “truss carriers” (headers) or a building with single trusses widely spaced somewhere from seven to 10 feet on center.
You have a couple of choices – if you are going to utilize the existing intake (soffit vents) and exhaust (ridge vents) then a minimum of one inch of clear airflow must exist above the insulation. The high ribs of the roof steel will not provide adequate ventilation and there is really no way to create it after the fact. An alternative would be to seal the vents and use closed cell spray foam on the underside of the roof system. The closed cell foam should take care of any condensation concerns from the underside of the roof steel and it provides approximately an R 7 insulation value per every inch of thickness.
DEAR POLE BARN GURU: Can your building be designed to handle a 40# snow load? 24 x 30. JIM in WISCONSIN RAPIDS
DEAR JIM: Any snow load is very possible to be designed for, even those at high altitude snow ski resorts (including this one: https://www.hansenpolebuildings.com/2014/04/2014-winter-olympics/). Besides the snow loads in excess of 200 pounds per square foot at ski resorts, I’ve also provided post frame buildings in places like Glacier National Park, where the snow is so deep the park roads close for months in the winter.
DEAR POLE BARN GURU: I am planning on a 24x48x12 steel truss pole barn for vehicle/toy storage. Would you recommend a radiant bubble material under the metal to keep the inside of the barn for becoming a convection oven sitting in the hot Florida sun? Best wishes, JOHN in FLORIDA
DEAR JOHN: My first choice would be closed cell spray foam. While it is going to be more expensive, you will save greatly in labor as opposed to using a radiant reflective barrier. Radiant Reflective Barrier, installed correctly, might give you the performance you are seeking. If you do go with the barrier, single cell will perform pretty much as well as single cell. Buy six foot wide rolls with a tab. The tabs should have a pull strip over adhesive, which eliminates the need for taping seams. The six foot wide rolls mean fewer pieces to handle and overlaps to seal.