Armacell technical experts are often asked when it is appropriate to switch from single-layer insulation to multi-layered insulation on a mechanical system. We advise that for demanding HVAC, refrigeration, and plumbing conditions, like a cold line in a hot operating environment, the proper elastomeric insulation thickness must be installed to prevent condensation, save energy, minimize heat loss / gain, and comply with local energy codes. When insulation thickness must be greater than the available products, it is necessary to multilayer or “nest” the insulation to obtain the desired thickness.

When installing a layered insulation system, the first layer of ArmaFlex® insulation should be installed with the joints and longitudinal seams under compression and be properly sealed with ArmaFlex 520 adhesive to avoid insulation failure. The second layer of ArmaFlex insulation should have the longitudinal and end joints staggered, then sealed with ArmaFlex 520 adhesive.  

Our layering chart, also known as a “sleeving” or “nesting” chart, offers the best fit for installing an additional layer. This chart explains which insulation ID size fits over an initial layer of ArmaFlex with a given ID and wall size. To use the chart, first select the ID from the far left column and then the wall thickness under the “Nesting Size” label. The intersection of the ID row with the wall thickness column is the ID size that will fit over the first layer. The wall thickness should be chosen to provide the total required thickness of the insulation system.

For example, if a 2" iron pipe (IPS) requires 3" of insulation and 2" thick insulation is chosen as the bottom layer, the ID for the top layer (from the chart) would be 6" IPS and the wall would be 1" (2" bottom layer + 1" top = 3" total).

ArmaFlex Insulation Size

Please note that there are some sizes that are too large to layer with pipe insulation. These sizes are indicated by “Sheet” on the nesting chart and sheet or roll insulation must be used for the top layer. Please also be aware that layering insulation above its maximum rated thickness for flame and smoke invalidates the flame and smoke ratings. Therefore, do not layer insulation above the rated thickness if a flame and smoke rating is required.