A Comparison of Mechanical Insulation Materials

Insulation materials are different in their make-up and composition. These differences result in different ratings when one compares the materials side by side. Some do better with Flame and Smoke while other perform better with water vapor transmission or water absorption. Some perform better on cold systems while others do better on hot systems. There is no "perfect" insulation material that is why it is important to understand key characteristics associated with each insulation material.

The two major types of insulation are cellular and fibrous. Armacell makes the insulation types bolded below.

Cellular  (Closed Cell)

  • Polyethylene (PE)

  • Elastomeric "Rubber" (EL)

  • Polystyrene

  • Polyisocyanurate

Fibrous  (Open Cell)

  • Mineral Wool
  • Fiberglass

Characteristics: Cellular v. Fibrous

Cellular Insulation/Closed-Cell

Fibrous Insulation

Has a non-interconnected cellular structure

Has a non-connecting, random structure of small strands of glass or mineral

Cells have sealed walls which inhibit moisture migration or wicking inside the insulation

The intertwined strands have no walls, creating a porous blanket that allows for moisture migration or wicking inside the insulation

Has the vapor retarder built-in

Requires a separate vapor retarder

Has a uniform structure which cannot be compromised by surface punctures or tears

The vapor barrier jacket can fail the moment it's punctured or torn. Care must be taken during and after installation to avoid damaging the vapor retarder

Armacell products are closed-cell insulation

Fiberglass is an open-cell insulation

A note about closed-cell spray foam – If you Google “closed-cell foam insulation” you may also see spray foam insulation listed. This compound is formed when liquid polyurethane or isocyanate are mixed with a foaming agent. When applied it can expand to 30-60 times its original size filling gaps completely. There is an open-cell, less dense version and a closed-cell version that is water resistant and holds its structure. While these can be excellent insulators, spray foam is usually used in walls or ceilings and rarely for insulating mechanical equipment because it cannot be removed for maintenance. Therefore, we won’t use it in our comparisons of products.

Key Performance Characteristics for Mechanical Insulation

A measure of a material's ability to transfer heat through conduction (aka “Thermal Conductivity”). Usually reported with a “mean” temperature (the higher the temperature, the higher the k-factor). The lower the k-factor, the higher the R-value, and the better the insulation.
The measure of apparent thermal conductivity, thus describing the rate that heat energy is transferred through a material or assembly. The higher the R-value, the lower the k-factor, and the better the insulation.
Water Vapor Transmission Rate
The measure of the passage of water vapor through a substance.
Water Absorption
The measure of water absorption/retention as water vapor passes through the insulation.
Flame and Smoke
Measure of the flame spread index and smoke development of an insulation product.

Key Performance Characteristics for Common Insulation Materials

If you are an Armacell distributor, an insulation installer or mechanical engineer and you want to learn more about mechanical insulation and mechanical systems, please visit our e-learning platform Armacell Academy.