Insulation Systems: The Value of Insulation and Maintenance

The information below is excerpted from the online Mechanical Insulation Design Guide, a free resource to help engineers, specifiers, insulation contractors, and others understand how to design and maintain all types of insulation systems. The guide leads you through pre-project design questions and considerations, offers an overview of available materials, provides eight free calculators to assist with your project’s design and installation, and assists you through the entire project to the creation of a maintenance plan. NIA’s goal is to improve the quality of all insulation systems nationwide, and we urge you to make use of all of these free resources.

February 1, 2021

Insulation systems have many surprising benefits and will continue to save your company money for years…if you take care of them and do not allow them to deteriorate. Like all mechanical insulation systems, they require periodic inspection and maintenance. While inspection and maintenance are the responsibility of the facility owner, the fact is that many insulation systems are frequently ignored. With time, insulation systems can be damaged for a variety of reasons, and if they are not repaired or replaced, they can become ineffective or—worse yet—contribute to the degradation of the mechanical system.

Failure to perform inspections and timely and proper maintenance carries a number of risks. On above-ambient (hot) systems, damaged or missing insulation results in loss of insulation efficiency, which may translate to significant economic losses over time. In addition, increased energy consumption, increases in carbon emissions, and occupational and/or process safety concerns may result.

Mitigating Corrosion under Insulation

Corrosion under insulation (CUI) is at the top of the list of concerns resulting from lack of inspection and improper maintenance. In the mechanical insulation industry, CUI is a phrase that has been used for many years, and it almost sounds as though insulation causes corrosion, or corrosion is to be expected. Insulation does not cause corrosion; moisture causes corrosion.

If moisture enters into an insulation system—whether indoor or outdoor, and for above- or below-ambient applications—it has many potential consequences in addition to compromising the effectiveness of the insulation system, of which, CUI is most notable. Some corrosion engineers have suggested leaving off the insulation, but this not only does not solve the problem, it introduces a lot more problems. Without insulation you would not have corrosion under insulation but you would probably still have corrosion occurring. And your systems would be deprived of the many benefits that insulation provides, including protecting personnel from hot or cold pipes/equipment, maintaining process temperature, extending expensive equipment life, and saving energy (and therefore dollars). In addition, it is possible that manufacturing and/or the delivery processes for air, gases, or products would need to be redesigned—or even potentially eliminated—if insulation were not used.

To combat the misperception that insulation causes CUI, the industry should consider refining the phrase to mitigating corrosion under insulation (MCUI) and not just CUI.
In addition to increased rates of corrosion, on below-ambient (cold) systems, damaged vapor retarders or other areas of potential water/vapor ingress will lead to increased water vapor intrusion, which again can reduce insulation effectiveness, and increase the potential for mold growth. If an inspection reveals missing or damaged insulation, repairs should be scheduled as soon as possible. This is particularly true for cold systems, where water vapor intrusion can rapidly spread.

Inspection and Maintenance

Inspection and maintenance of mechanical insulation systems normally come down to a facility owner either understanding the value of being proactive in having a meaningful and ongoing maintenance program or being reactive as the need or requirement presents itself. Some owners employ a combination of both approaches, which also can vary from year to year. With either approach, identifying the inspection scope and schedule are really one and the same for maintenance or previously installed mechanical insulation systems. However, there are several topics that should be considered in the decision process.

  • Is the insulated system considered critical? In other words, could damaged insulation
    potentially lead to an explosion or release of potentially hazardous material? As an example, on an ammonia refrigeration system, damaged insulation could result in CUI, which could result in the release of ammonia.
  • Could damaged insulation lead to the development of CUI?
  • Is temperature control of the contents critical in the process or for quality-control purposes? This is more critical on some systems, such as those for food processing; but in some cases, the purpose of the insulation is to control temperature drops or increases, so temperature could be considered critical.
  • Is freeze protection considered critical? This is not only important in the northern
    states, as freezes do happen in the southern states. When freezing occurs, companies spend a lot of money for immediate, short-term protection—a particularly costly expense when compared to what they could have spent had they considered (and accounted for) the potential condition in advance.
  • What is the age and/or condition of the insulation system? Older systems, especially those installed before 1973, could be problematic because of asbestos. In addition, though, a general rule is the older an insulation system is, the higher probability
    it may not be performing as expected.
  • Does the damaged insulation potentially contain contaminants that could be problematic? This includes not only contaminants from the atmosphere but also potentially those from leaks in the piping or equipment.
  • Is the environment impacting the life and/or performance of the insulation system?
    In other words, are there conditions now present that may be impacting the system?
    For example, has a unit been erected that releases contaminants or that has changed the surrounding atmosphere? Another example could be a recent weather event like a flood or hailstorm.

There may be other questions that should be added to this list, as every facility/plant and situation is different.

Determining inspection intervals depends on many variables as well as each facility owner’s view of priorities. As an example, indoor, above-ambient applications may be inspected annually, unless they are exposed to moisture and the operating temperature is conducive to the development of corrosion. For outdoor, above- and below-ambient applications, however, a continual inspection approach should be implemented. At a minimum, inspection should include checking for signs of cracking, distortion, damage, or corrosion; evidence of hot spots on high-temperature systems; and condensation, mold, and/or ice buildup on low-temperature systems.

If the insulation system is being repaired due to damage that has been incurred, it is recommended that substrate inspection be conducted at that time rather than penetrating an intact, performing insulation system in that same general area at a later time for inspection.

Physical penetration of any intact and operating insulation system should be viewed as destructive and avoided if possible. Forms of noninvasive inspection should be investigated before proceeding with any procedure that requires penetration of the insulation system.

Consideration should be given to the need to penetrate the system for substrate inspection in the insulation system design phase, including the potential use of inspection ports, drains, or vents; and identification of the location of inspection points.

The respective facility owner and/or insulation system design engineer may have specific repair and replacement recommendations. In addition, the insulation, vapor retarder, protective covering, and system component manufacturers should be contacted for their repair and replacement recommendations.

Risk Assessment

There are multiple risks associated with not maintaining a mechanical insulation system in a timely and effective manner. Those risks, the severity of the risks, and the view of potential consequences will vary, depending on the use/service temperature of the operating system on which the insulation is installed, the surrounding environment, ambient conditions, the extent of any damage to the insulation system, the insulation system design, the quality of the installation, the timeline for correcting any damage, and other occurrences that may be unique to the area in question.

The degree of risk tolerance and determining what is an immediate or higher risk compared to a longer-term risk need to be decided by the facility owner. The following list depicts the types of risks that could occur. They may not apply to all situations and may occur separately or simultaneously.

  • Air-quality contamination;
  • Increase in energy costs and energy consumption;
  • Increase in greenhouse gas emissions;
  • Loss of process/production quality and increase in costs;
  • Occurrence of CUI or risk of corrosion;
  • Development of condensation or ice, depending on the service temperature;
  • Development of mold or mildew (concerns for occupational safety and air-quality contamination);
  • Decrease in personnel safety;
  • Decrease in personnel productivity;
  • Loss of time spent on other projects;
  • Decline in facility appearance;
  • Decrease in the life and operational efficiency of equipment;
  • Increase in life-cycle cost;
  • Failure to obtain sustainability objectives; and
  • Failure to obtain return on investment estimates.

Each company has its own description and level of risk tolerance; however, the risks associated with failing to establish, implement, and maintain a timely and proper mechanical insulation maintenance program are real and should not be overlooked
or underestimated.

Maintenance Checklist

The checklist below is provided as a simple guide for individuals evaluating the condition of an installed mechanical insulation system. It is not intended to be all inclusive or to serve as a stand-alone document that would allow anyone, regardless of experience level, to function as an inspector of mechanical insulation systems. Note that the listed items do not appear in order of importance or priority.

  • Damage to or wearing of the outer protective jacketing/finish of the insulation system (damage could be caused by mechanical abuse, negligence, or weather; or it could simply occur over time);
  • Damaged or missing vapor retarder;
  • Vapor stops (dam) that appear not to be functioning correctly and/or are damaged;
  • Areas subject to water infiltration;
  • Evidence of potential corrosion;
  • Unsealed protrusions or damaged sealants around protrusions;
  • Damaged, missing, or wet insulation;
  • Places where insulation has been removed and not replaced, or replaced incorrectly;
  • Insulation supports that are failing or appear not to be working correctly;
  • Ice, mold, and/or mildew on/in the insulation system;
  • Condensation;
  • Discoloration of the insulation system (other than by dirt);
  • “Fish mouthing” of the outer jacketing seams;
  • Flashing that appears not to be working correctly or is damaged;
  • Missing—or loosening of—insulation system securements;
  • Expansion or contraction joints that appear not to be working;
  • Noise/acoustical areas of concern;
  • Inspection ports not installed or maintained correctly;
  • Exposed mastic reinforcement or cracking;
  • Sagging or pulling away of the insulation system;
  • “Hot spots” in the insulation system (thermal leakage);
  • Appearance of moisture on the insulation system;
  • Joints in the insulation that appear to be opening;
  • Expansion or contraction joints that appear to be functioning incorrectly;
  • Insulation system being used in an environment or service that is different from its original design; and/or
  • General condition of the insulation system(s) is lacking.

Checking for all of the occurrences listed is a good start for a maintenance plan. Upon observing any of the conditions listed, a maintenance request/action plan should be implemented to assess the degree of damage; and the affected area of the insulation system should be repaired or replaced to prevent further damage and avoid further risk.

Of the overall cost of industrial and commercial new construction and facility maintenance, mechanical insulation represents a very small amount. However, the impact of improper design, installation, and/or maintenance can be substantial. In more cases than not, mechanical insulation is typically taken for granted during the design phase, not normally inspected during the construction phase, and not focused on in the maintenance phase. That combination will ultimately yield negative results for the facility owner and others in the decision and construction chain.

Decisions regarding the need for and type(s) of mechanical insulation, as well as allocating the investment, are made during the design and construction phases of a facility. Without timely inspection and proper maintenance of insulation systems, a facility owner may not only realize lower than expected return on investment but also create a much greater need for additional investment and experience potential operational disruptions.

This content has been reproduced from NIA’s Mechanical Insulation Design Guide which will be available at in the first quarter of 2021.