Dear Guru: Can I Use Cellulose Insulation?

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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:

My recommendation would be to use fiberglass insulation.

For the walls, use BIBS (read more about BIBS here: 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:

4 thoughts on “Dear Guru: Can I Use Cellulose Insulation?

  1. On my 42×63 2 story pole building ( heated first floor ) I have trusses 9’ oc standard roof purloins 2’ oc I was wondering if I could use cardboard up against steel roofing for venting air flow of the humps in the steel roof panels ( std steel w/ 1” humps not standing seam ) then install heavy plastic on bottom of purlins and fill cavity w/ cellulose blown insulation. Would this work correctly for ventilation of steel and insulate correctly. Combination of being cheap/frugal and I have free heavy cardboard from washers/dryers/ refrigs to fit between purlins. Greatly appreciate your opinions. Thank you

    1. admin Post author

      Thank you for your kind words. I will surmise suggested placement of plastic on bottom of purlins means you do not have a method of controlling condensation from underside of roof steel. Short of taking the roof steel off and installing a thermal break (not recommended), your only real solution is two inches of closed cell spray foam directly to underside of steel roofing. Your idea would not be adequate for proper ventilation or condensation control.

  2. I have a 36’ x 56’ x 16’ pole barn with 2’ on center trusses and 6/12 pitch roof. I had a metal ceiling installed and currently have no insulation in the attic. I was thinking of doing a blown in cellulose insulation of 12” which should be an R38 rating. Do I have to be concerned with any of the cellulose materials possibly having corrosive properties to my steel ceiling ? Also I had 1.5” solid foam board panels installed in the walls when the barn was constructed. Do I need to be concerned about condensation anywhere ? I may leave it this way and I live in a Northern Climate Region. I have a hanging unit heater and will just kick it on from time to time when I use it in the winter but not too often.

    1. Do not use cellulose – chemicals in it can corrode your steel ceiling. Use Granulated rockwool (best) or fiberglass. You may need to mechanically dehumidify your building in order to prevent condensation.


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