Thermal-efficiency problems caused by moisture and condensation often can be prevented by choosing the right insulation system.

Water is the number one enemy of any insulation system, particularly in processes that operate below ambient temperatures. Just 4 percent moisture in a below-ambient insulation system can reduce the insulation’s thermal efficiency by 70 percent and cause many other problems. For example, the moisture can migrate toward the substrate and condense or even freeze. This condensation can cause equipment to run harder and thereby consume more energy and increase operating costs. It also can cause corrosion on pipes and equipment, and it can help promote mold and mildew growth.

Fortunately, most moisture problems can be prevented by choosing the right insulation system. Following are eight basic tips to keep in mind when evaluating insulation systems.

1. Choose Closed-Cell Insulation

Moisture is a natural phenomenon in below-ambient operations. Picture a cold glass of iced tea in the summer. Moisture from the air around the glass (ambient air) condenses in small beads of water against the colder glass surface. The same thing happens with cold pipes and equipment. A closed-cell, non-fibrous, non-wicking insulation makes it more difficult for moisture in the form of vapor or liquid to pass through the insulation toward the colder surface.

On an improperly insulated pipe, moisture can migrate toward the substrate and condense or freeze.

2. Choose Rigid Insulation

Unlike fibrous and elastomeric insulation, which can be compressed easily, rigid insulation provides support, strength and durability. Rigid insulation also can bear the weight of the pipe, allowing continuous insulation to be used in the support areas. Historically, these areas have been weak points in the insulation system and often a place of failure.

3. Compare Thermal Conductivity (K-Factor) at Operating Temperature

Research the k-factor of the insulation you are considering at the operating temperature of your system. In general, the lower the k-factor, the better the insulation’s performance. However, do not base your decision solely on the printed k-factor because the published rating may not reflect the temperature your system is going to experience. Ask the insulation manufacturer to provide k-factor information that is relative to your application.

4. Request Thickness Calculations

Many insulation manufacturers can run a thickness calculation based on the following information from your application:
  • Operating temperature.
  • Ambient temperature.
  • Relative humidity.
  • Cladding type.
  • Your reasons for insulating.
The manufacturer then will provide a suggested insulation thickness for the product. Keep in mind that in most cases, the dimension provided will be the minimum thickness required to insulate your system. This means that if any of your process parameters change, your system could fail. It is always helpful to increase the thickness to add a safety factor. Work with the manufacturer on the thickness calculation, and base the conditions on a worst-case scenario.

Make sure that you build redundancy into your insulation system. The mechanical jacket protects the vapor-retarding jacket, which, in turn, protects the insulation system.

5. Choose a Quality Vapor-Retarding Jacket

Vapor-retarding jackets are available in many different materials. They add a second line of defense against moisture (in the form of vapor or liquid) penetrating the insulation and reaching the pipe. Look for a retarding jacket that does not contain paper. Paper-type vapor-retarding jackets can be subject to mold growth if the conditions are favorable.

6. Choose an Appropriate Mechanical Jacket (Cladding)

Carefully look at the conditions to which your system is going to be exposed. Weather, maintenance, vandalism and other forms of “mechanical abuse” can wreak havoc on your system. Cladding is a “security blanket” that protects the other components of your insulation system. Mechanical jackets are available in aluminum, stainless steel, PVC and laminated membranes. While a system located indoors often can use PVC or membranes, outdoor applications most likely will require more durable aluminum or stainless steel.

7. Eliminate Tacks and Staples

Tacks and staples should not be used on any below-ambient insulation system. The holes that they put into the system allow moisture (liquid or vapor) to enter the system. Instead, look for alternative methods of fastening such as high-strength adhesives and sealants.

Nonrigid insulation can fail due to mechanical abuse.

8. Maximize Your Investment

In addition to the previous steps, make sure that you build redundancy into your insulation system. The mechanical jacket protects the vapor-retarding jacket, which, in turn, protects the insulation system. All of these components work together in harmony to keep out moisture.

Finally, make sure to maintain your system properly. Failures happen for a variety of reasons. The easiest way to protect your investment and avoid system failures - in addition to choosing and installing the correct materials at the correct thickness - is by implementing a sound preventive maintenance program. Holes, gaps and other problems need to be reconciled immediately to prevent moisture from getting into your insulation system.

Because insulation is one of the last items installed on a process cooling system, its importance often is discounted when a project runs into budget constraints. However, using the wrong insulation can jeopardize operating costs, production costs and equipment life. A properly insulated system can save you money and will continue its return on investment for years to come.