This week the Pole Barn Guru answers questions about vapor barrier, a solution for skylights, and how to reduce frost heave.
DEAR POLE BARN GURU: Vapor barrier under roof metal or under trusses with insulation on top?
I find never-ending opinions about where to place vapor barrier in a post frame building.
If the space is to be insulated would it not be better to put nothing directly under the roof metal and put a vapor barrier on the ceiling with insulation above that?
Everyone says to put on single or double bubble before putting down roof metal but if I do that how do I insulate the ceiling because then I will have a vapor barrier above the insulation. DAVID in KIRKWOOD
DEAR DAVID: Vapor barrier under roof steel if you are creating a dead attic space. It is essential to prevent warm moist air from within your attic from reaching underside of roof steel. My preference would be to use roof steel with Dripstop (https://www.hansenpolebuildings.com/2017/03/integral-condensation-control/) or Condenstop (https://www.hansenpolebuildings.com/2014/07/condenstop/) applied.
Do not place a vapor barrier between ceiling sheetrock and attic insulation. Do properly ventilate your dead attic space as Code requires (https://www.hansenpolebuildings.com/2018/03/adequate-eave-ridge-ventilation/).
DEAR POLE BARN GURU: I have a pole shed 1972? with skylights that need replacing where do I find . DAVE in COLFAX
DEAR DAVE: One of my previous questioners had a similar issue, you might want to read here: https://www.hansenpolebuildings.com/2018/08/sky-lights-leaking/.
DEAR POLE BARN GURU: What do you recommend for creating a frost wall around a post frame (posts in the ground) structure. The posts are dug down below frost level, so the footings are protected. But if the interior floor is a slab poured on grade, what is the best way to protect this slab from frost heave?
Thank you, CHRIS in NEW HOLLAND
DEAR CHRIS: Good to hear from you! (side note – Chris is a personal friend of mine) There is a relatively simple solution for this – do the post frame version of a shallow frost protected foundation: https://www.hansenpolebuildings.com/2017/09/post-frame-frost-walls/.