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Community and Q&A

How to insulate a steel building?

Vinny Rucinski, Jr. | Posted in General Questions on

As way of introduction I live in Fair hill MD on an acre lot.I consider myself to be a handyman and not afraid to do most of all the renovations to this gem in the rough!

I have no experience working on steel buildings and would like to do this job right the first time. I would like to know the best way to insulate a steel building. I bought my house 4 years ago and now getting around to setting up my woodshop in this pre existing steel building. The building itself is on a concrete pad. The steel building was added to the back of a wooden garage which the neighbors told me was cut in half and move to this site on flatbed trucks. Therefore the steel building itself is has only 3 sides steel. I have read a good deal online about insulating steel buildings. The more I read, the info becomes more conflicted depending on which manufacturer is selling what product eg. foam, bubble wrap types, fiberglass, etc. I will include some pictures for clarification.

Thanks for any help you can give me,


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  1. GBA Editor
    Martin Holladay | | #1

    This type of building can be tricky to insulate.

    1. You don't really want the insulation to touch any of your metal panels.

    2. If you choose to install a fluffy insulation like fiberglass batts, you need to have an air barrier (for example, OSB with taped seams or housewrap with taped seams) on the exterior side of the fluffy insulation. Ideally, there is an air gap between this air barrier and the steel panels.

    3. If you choose to install spray foam, you don't really want to spray the foam directly against the steel panels, because you may need to remove a few panels in the future due to panel rust or remodeling.

    There are several options. If I were doing this work, I would start by installing plywood, OSB, or 4x8 pieces of rigid foam on the interior side of your 2x4 purlins, so that there is a 1.5-inch gap between the steel panels and this new air barrier. I would carefully tape the seams of these 4x8 sheets with high quality European tape.

    Once your exterior air barrier is established, you can install framing or insulation in whatever manner you prefer.

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