Preventing Damage to Mechanical Insulation on Below-Ambient Systems

Steve Fisher

October 1, 2014

While all mechanical insulation is susceptible to damage, some applications or areas of an application are more vulnerable than others and need to be treated differently. Damaged insulation will reduce the performance of the mechanical system being insulated; to prevent this, steps should be taken to protect the integrity of the mechanical system. On a system operating in below-ambient temperatures, water vapor
condensation and moisture is usually a concern. Even a small area of damaged insulation can cause degradation of the insulation in other areas, resulting in a failure of the system or process due to moisture ingress. Preventing the damage from occurring in the first place is the best way to protect a system during the design and construction stage and reduce expensive repair costs later, during the operational

On a hot system, damaged insulation results in loss of energy; the daily cost resulting from this damage can be estimated by calculation. On a system that operates at below-ambient temperatures—specifically where condensation control is the primary performance parameter—damaged insulation in a small area can result in major degradation of the complete system and a total failure, resulting in costly
repairs and lost energy.

Start at the Beginning

The case for preventing damage to insulation starts at the design stage. The first step in preventing damage is specifying a suitable type of insulation, and when needed, the accompanying jacket system. This involves knowing the design considerations for the mechanical system being insulated and the environmental conditions. The insulation system must be able to withstand the temperature cycles of the mechanical
system being insulated and the mechanical abuse it may see. For most outdoor applications and materials, a protective jacket is recommended to achieve the normal life expectancy of the system.

It should be noted that some jacketing systems are stronger than others and thus, are less susceptible to damage. Traditional jackets are either metal, such as sheet aluminum and stainless steel, or sheet plastic, such as PVC. Each option has its strong points. Metal provides excellent UV resistance and zero permeance; however, due to the difficulty of sealing metal jacketing, it is normally not used as a vapor
retarder. While not a vapor barrier or vapor retarder, PVC provides easier installation, is light weight and dent resistant, but must be continuously sealed at all lap and butt joints to provide some resistance to water vapor intrusion.

Some laminate jackets have a combination of these traits and also incorporate aluminum foil with a thickness of at least 1 mil—providing zero permeance as well as dent resistance, and have seams sealed with a pressure-sensitive adhesive. These jackets can also be lightweight, flexible, and are easy to install. Some insulation materials have factory or fabrication-facility applied laminate jacketing for
faster installation and adherence to the insulation under environmentally controlled factory conditions. If you apply this type of jacket to a material that provides a permeability of less than 0.1 perm/inch and a sheet or film vapor retarder on the outside surface, you have extra security against water vapor intrusion. In outdoor applications, a vapor retarder must also be suitable for outdoor exposure unless
covered by a protective jacketing suitable for outdoor conditions. For example, vapor retarders that meet ASTM C1136 are only suitable for either indoor use or outdoor use with weather protection, but those that meet C1775 are suitable for weather exposure (i.e., sun, precipitation, wind, and humidity). Knowledge of industry standards and proper material selection during the design stage will go a long way toward
preventing insulation damage.

Insulation jacket systems with double-closure mechanisms, (i.e., that incorporate a seal on the seam and an overlap tape) have seams that are less susceptible to damage than a single-closure system. Specifying jacket systems with redundant sealing systems reduces the risk of any damage to the insulation, and are also less susceptible to installation error than single-closure systems.

Avoid Damaging New Materials

After the correct material is selected, proper shipping and storage are essential to help prevent damage to the insulation. Damage to insulation can occur during shipping, storage, or fabrication of the materials. Damaged insulation should never be installed on a job, especially on an application that operates at below-ambient temperatures and is susceptible to condensation issues. All insulation materials
should be stored at the job site in a clean, dry area. No wet or contaminated insulation should be installed, as wet insulation may create major issues with mold/mildew down the road. Insulation boxes should also be stacked neatly in a dry location in order to prevent crushing the boxes and damaging the insulation.

Installation and Maintenance

The product should not be installed until the building is closed in (meaning the roof, walls, windows, and doors are installed), thus limiting the possibility that it may become wet due to outside weather conditions. In addition, the operating system should not be turned on until the building has been conditioned to a stabilized dew point temperature. It is also important that the general and mechanical
contractors schedule the work to be done in a sequence that avoids damage to the insulation after it is installed. Other trades coming in after the insulation is installed can easily damage the insulation, resulting in the need for repairs. To prevent damage, make sure that systems are designed with enough room for the insulation without crushing or damaging it when the other trades do their work.

All systems, including insulation, need periodic inspection and maintenance. If it is known that little maintenance will be available after the insulation is installed, design the system with that in mind by providing a more damage-resistant jacket system. A damage-resistant system—such as those with coatings that are available for outdoor applications—or a stronger jacket, such as a metal, PVC, or
laminate jacket that meets ASTM C1775, can be specified. However, when it is discovered that repairs are needed, these should be made as soon as possible, especially on a system that operates at below-ambient temperatures—including duct work.

In summary, great caution should be taken to prevent damage to insulation, especially on a system that operates at below-ambient temperatures where condensation is an issue. Prevention should start at the design stage and continue through the installation and maintenance stages of the application. Failure can result on a system that operates at below-ambient temperatures if there is not ongoing inspection,
maintenance, and repair of the insulation system. This type of failure can be costly and cause potential health and safety issues. Specifying the proper equipment, ensuring proper conditions, and enacting a maintenance program are all crucial to preventing damage and protecting the integrity of a mechanical system.