Tag Archives: fire resistant barrier

Plastic Vapor Barrier, PermaColumn, and a Fire Resistant Barrier

This Wednesday the Pole Barn Guru answers reader questions about use of 6 mil plastic vapor barrier in Michigan, if Hansen provides the option of a precast concrete pier to keep columns out of the ground, build heights, and “if anything needed between interior PVC panels, closed cell spray foam and the exterior metal siding.”

DEAR POLE BARN GURU: I have a pole barn that I am planning on insulating. The trusses are 2 foot on center and it has a shingled roof, the outside of the pole barn is steel. I live in Michigan and I was wondering if it is a good idea to put 6 mil plastic on the bottom of trusses before I hang steel on the ceiling. I will be blowing in insulation up there later. KAL in HUDSONVILLE

DEAR KAL: You are in Climate Zone 5A, so a ceiling vapor barrier is not required by Code. Building scientist and founding principal of Building Science Corporation Joe Lstiburek states, “Plastic vapor barriers should only be installed in vented attics in climates with more than 8,000 heating degree days.” (More on degree days here: https://www.hansenpolebuildings.com/2022/11/what-is-degree-day/).

I would only recommend you installing a vapor barrier above your steel ceiling if you were to be considering blowing in cellulose insulation. Why cellulose? https://www.hansenpolebuildings.com/2022/10/cellulose-post-frame-attic-insulation/


DEAR POLE BARN GURU: Do you deal with post frame designs that: 1) use the precast column to keep wood out of the ground? 2) Deal with designs that are 20′ eave height to accommodate 2 story interiors. JONATHAN in ZANESVILLE

DEAR JONATHAN: We have had several clients provide their own pre-cast Permacolumns and they can be incorporated into our engineered designs. There is, however, a less costly option to explore: https://www.hansenpolebuildings.com/2018/04/perma-column-price-advantage/

We can engineer and provide up to 40 foot tall walls and three stories without needing fire suppression sprinklers, so 20 feet eave heights are not a problem.


DEAR POLE BARN GURU: Hello, my question, which I can’t seem to find a straight answer anywhere online. Is anything needed between interior PVC panels, closed cell spray foam and the exterior metal siding? The pole barn is located in southern Indiana. It’s used as a shop and being heated occasionally with a wood stove. BENJAMIN in INDIANA

DEAR BENJAMIN: As your PVC and closed cell spray foam are both flammable, I would use an intumescent fire proof paint on interior face of closed cell spray foam, then fill balance of wall cavity (if any) with rockwool batts. As an alternative to intumescent paint, you could place sheetrock between wall framing and PVC panels (panels will lay much smoother).