Steel Building Insulation

Roof and wall insulation get discussed as one item and behave as two. The roof is where temperature differences are largest, where warm interior air collects, and where any condensation that forms will end up dripping onto whatever is below. The walls are more forgiving thermally but carry more interruptions — doors, windows, framed openings — and each interruption is a place where an insulation system stops and has to be detailed back together.

Systems also differ by location. Therm-All describes banded liner systems as suitable for roofs and walls in both new construction and retrofit, while long tab banded systems are described as designed for metal building roofs only. So a proposal that names one product for the whole building is either using a system rated for both, or has not been thought through. Ask which.

The practical consequence for a buyer is that it is entirely reasonable — and often sensible — to insulate the roof to a higher standard than the walls, or to insulate a conditioned office area differently from an adjoining unheated store. Say what each part of the building is for before the quote is written.

Therm-All classifies metal building insulation into three primary categories: fibreglass, continuous insulation systems, and insulated metal panels. Most quotes you receive will be one of these, or a combination.

Condensation is the reason insulation arguments get heated. Therm-All describes it as occurring when warm, moist air meets cold surfaces — framing members, windows and accessories, or a colder region inside the envelope once moisture has passed the vapour retarder — and notes that trapped moisture can corrode metal components and degrade the insulation's thermal performance.

Two things follow from that description, and both are buyer decisions rather than installer details. First, insulation reduces the temperature difference between the metal and the interior air, which reduces the potential for condensation to form. Second, the vapour retarder is doing separate work: Therm-All calls it the first and last line of defence against condensation, and stresses that selection and installation both matter.

Installation is where a specified system quietly becomes a different system. Butler's parts documentation lists skipping vapour retarder protection where insulation runs around girts among the common mistakes it sees in metal buildings. A vapour retarder that is torn, cut around an opening and never repaired, or simply stopped short at the eave is not the product that was priced. If your building will be heated, humid, or used for anything that puts moisture into the air, treat the vapour retarder detailing as a line item you are entitled to ask about.

Whether your specific building needs a vapour retarder of a particular permeance, and how the assembly should be detailed, is a design question for the supplier's engineering and your design professional. It varies by climate, use and assembly, and this page does not answer it.

Insulation is one of the few components of a steel building with a genuine regulatory floor. Commercial energy codes set minimum requirements, and Therm-All's guide is explicit that the majority of metal buildings in the U.S. are conditioned spaces expected to comply with the minimum insulation requirements in the governing commercial energy code, while semi-heated buildings are treated differently.

What those minima are for your building is not something a national guide can tell you. Requirements depend on the code edition your jurisdiction has adopted, the climate zone, the building's use classification and the assembly type. The Department of Energy's Building Energy Codes Program publishes which codes states have adopted, and ASHRAE Standard 90.1 is one of the reference standards commercial energy codes are written against. Those are the right places to start, and your local authority having jurisdiction is the place that decides.

For a buyer, the useful move is not to learn the code. It is to ask the supplier one question in writing: which energy code and climate zone was this quote's insulation package designed to, and who is confirming that with the authority having jurisdiction. If two quotes answer that question differently, you have found the reason the prices differ.

The single most useful thing you can bring to an insulation conversation is an honest description of what will happen inside the building, for the next decade rather than the next month. A cold store, a heated workshop, an unheated equipment barn and a building with an office in one corner are four different insulation problems even at identical dimensions.

Beyond temperature, Therm-All notes benefits that matter in specific uses: sound absorption in recreational facilities and buildings holding loud equipment, and the finished interior appearance an exposed vapour retarder gives, which it notes may allow for reduced lighting loads. If any of those apply to you, they belong in the brief, because they change which system is the sensible one rather than merely how much of it you buy.

It is also worth being explicit about future use. Retrofitting insulation into an occupied metal building is possible — banded liner systems are described as suitable for retrofit — but it is disruptive and it is rarely cheaper than doing it during erection. If there is a realistic chance the building becomes conditioned later, price both now.

Insulation is a common source of apparent price differences between otherwise similar building quotes, because the scope can legitimately be drawn in several places. One quote may carry a single laminated layer in roof and walls; another a banded liner system in the roof only; a third may exclude insulation entirely and expect it to be bought and installed separately.

Ask for the insulation to be broken out as its own line rather than absorbed into the building package. Once it is separate, the comparison becomes tractable: same system type, same locations, same vapour retarder, same installation responsibility. Any remaining difference is then a real difference rather than an accounting one.

Also confirm who installs it. Insulation supplied but not installed is a common and perfectly legitimate scope, and an equally common source of surprise cost when the erector's quote arrives assuming somebody else was doing it.