Welcome to Ask the Pole Barn Guru – where you can ask questions about building topics, with answers posted on Mondays.  With many questions to answer, please be patient to watch for yours to come up on a future Monday segment.  If you want a quick answer, please be sure to answer with a “reply-able” email address.

Email all questions to: PoleBarnGuru@HansenPoleBuildings.com

DEAR POLE BARN GURU: I am finishing a 36x40x14 pole building. The roof is asphalt shingles on osb and the siding is typical metal (.026 I think). I want to use dense pack cellulose blow in in the walls which will be covered with OSB and painted. There is no plastic or vapor barrier, just metal on the 2×4 frame members. Do I need to install plastic or housewrap with the insulation? Can I staple housewrap to the inside framing to hold the blow in insulation until I install the OSB wall sheathing?

I had a metal ceiling installed when they built it but no insulation exists.

I want to use blow in R38 for the ceiling and cellulose seems to be ok to use but I have read that it may corrode the metal.

Please give me your recommendations to insulate my pole barn. Thank you. CELLULOSED IN CRAWFORDSVILLE

DEAR CELLULOSED: The issues with cellulose insulation appear to be if it is or gets wet. There are two sides to the argument.

Side A (it is no problem) says: “There have always been concerns about insulation causing corrosion when in direct contact with metal building components such as sweaty pipes, electrical wires or metal boxes, etc. Consequently, ASTM standards for every insulation material contain testing which specifically addresses these concerns. In addition, in 1979, the CPSC promulgated a law, which regulated the fire and corrosive characteristics of cellulose insulation. A statement of compliance with these requirements is required on every bag of cellulose insulation. The types of metal tested with all insulation materials are copper, aluminum, steel, and additionally in Canada, galvanized steel. Our test requires placing soaking-wet cellulose insulation with an imbedded .003-inch thick metal coupon inside a humidity chamber under conditions that are ideal for promoting corrosion. After 14 days, the metal coupons are removed, cleaned, and examined under a light to detect the smallest pinhole. In all, there are two coupons of each metal and all must be free of even one pinhole. This is a very strict test!”

Side B can be read about at: https://www.chemaxx.com/cellulose.html

My recommendation would be to use fiberglass insulation. https://www.hansenpolebuildings.com/blog/2012/02/fiberglass-insulation-2/

For the walls, use BIBS (read more about BIBS here: www.hansenpolebuildings.com/blog/2011/11/bibs/). A vapor barrier should be installed on the inside face of any wall insulation, before the interior finish is applied (whether osb, drywall or steel liner). Housewrap is NOT a vapor barrier, and should not be installed on the climate controlled side of insulation.

DEAR POLE BARN GURU: I am having a local contractor build a pole barn cabin with a steel roof and vinyl siding. They do use bubble under the roof girts. I am having them use 2×10 for a vaulted ceiling so I can finish a loft. I want to insulate between the 2×10’s -24 on center. Just wanted to know how to best insulate between these and put a tongue and groove ceiling in. MASSILLON MARK

DEAR MASSILLON: My answer will assume your roof purlins are being installed the length of your building, rather than from eave to ridge (like rafters). On top of the purlins, install 2×4, laid flat (3-1/2” face towards the purlins) running from eave to ridge. Then install the reflective insulation. Next place 2×4 laid flat the same direction as the purlins, then the roof steel. Make certain to adequately ventilate the eave and the ridge. The insulation between the purlins should be unfaced, and no more than 9-1/4” thick.

Before you blow insulation into the attic space, make sure you have adequate attic ventilation. While this article is written with steel roofing in mind, the same ventilation requirements and solutions apply: https://www.hansenpolebuildings.com/blog/2012/08/ventilation-blows/