Mould keeps coming
back when the moisture source is still there.

An R-value tells you how well a material or building system resists heat flow. A higher R-value means greater resistance, but only under the stated conditions that may not be the actual condition of your shed once it is installed.

Thermal bridging is when heat finds a shortcut around your insulation, and it’s a major issue in metal sheds. Steel is highly conductive, so the frame and fixings give heat an easy path straight past the insulation. If those bridges aren’t addressed, they can seriously reduce how well it works. Even screws alone can reduce the performance of some insulation materials by up to 40%.

Insulation needs to keep doing its job through the conditions your shed experiences over time. Dust, moisture, compression and physical damage can affect different products in different ways. How the installed system holds up matters as much as how it performs when new.

A product’s R-value only measures its resistance to heat flow. It says nothing about how well the product stops hot or cold air getting in or out. In sheds and commercial buildings, stopping that air can be the most critical job an insulation product does.

When insulation is left exposed, its fire rating matters. Products react to fire in different ways, and some resist the spread of flame and smoke better than others. In commercial settings, the use of the building determines the group rating its internal linings must meet. If the insulation is covered by a lining, its own fire performance usually matters far less.

Existing wiring in a shed needs to be taken into account when choosing insulation. In some cases the wiring must be run through conduit, because the insulation may not be chemically compatible with the cable sheathing. Cables that are fully covered by insulation may also need to be de-rated, so check with the manufacturer and speak to a licensed electrician if in doubt.

Believe it or not, some shed insulation products expressly state that they’re not suitable for farm or rural buildings, especially where animals are present. Reflective insulation can also lose effectiveness in dusty, dirty settings, because dust building up on the surface reduces how much heat it reflects. In rural buildings it may need cleaning about every 12 months.

Installation requirements can change the scope of the job. Batts, for example, can’t be left as an exposed lining, so this guide assesses their performance as part of a lined stud wall system. Other types need ventilated cavities to perform. It’s important to understand these requirements before you buy, so you can be sure the product suits your building.

Warranty length and warranty coverage are different things. Unfortunately, in many cases the actual performance of a product isn’t covered by its warranty. Many warranties only cover products that are defective before installation, and some offer no warranty once the product is installed. That’s why suitability matters. If the manufacturer won’t stand behind a product for the way you plan to use it, it is because the results you are assuming you will get once installed are simply not a reality.