Thermal Insulation Standards: ASTM C16

There have been a surprising number of changes to mechanical insulation standards in the past 2 years. Learn which ones apply to which materials and what you need to know before you start your next project. NIA also offers a specification chart at

Gordon H. Hart

Gordon H. Hart, P.E., is a consulting engineer for Artek Engineering, LLC. He has over 35 years of experience working in the thermal insulation industry. He is an active member of ASTM committees, including Committees C16 on thermal insulation and F25 on marine technology, ASHRAE's Technical Committee on Insulation for Mechanical Systems, and the National Insulation Association's Technical Information Committee. He received his BSE degree from Princeton University. and his MSE degree from Purdue University, both in mechanical engineering. He is a registered professional engineer. He can be reached at gordon.hart®

March 1, 2022

ASTM Committee C16 on Thermal Insulation met virtually in October 2021. The following includes a C16 overview, scope, individual subcommittee scopes, and a summary of some of the activities by task groups reviewing and/or writing standards related to mechanical insulation. You can learn more about ASTM C16 by going to, clicking on “Get Involved,” and then “Technical Committees,” then “Technical Committees Full List,” and finally selecting “C16” from the hundred-plus ASTM committees.

By policy, each ASTM standard must either be reapproved as is or revised and approved within 8 years. If not, the standard is automatically dropped from the Book of Standards. Therefore, some standards that may have previously been referenced by specifications are no longer published. In all specifications, the number of the ASTM standards should be followed by the year of most recent approval or reapproval. For example, “ASTM C612” is insufficient. A specification should read, “ASTM C612-19” to differentiate it from an earlier version.

Committee C16 Overview

ASTM Committee C16 on Thermal Insulation was formed in 1938. Prior to the pandemic, C16 would meet twice a year in person, usually in April and October, with approximately 150 members attending more than 3 days of technical meetings capped by a discussion on relevant topics in the thermal insulation industry. The committee, with current membership of 400+ people, has jurisdiction of about 134 standards, published in the Annual Book of ASTM Standards. These standards continue to play a preeminent role in all aspects of thermal insulation, including products, systems, and associated coatings and coverings, excluding refractories.

Committee C16 Scope

The scope of the Committee C16 is given on the ASTM website as follows: “The scope of the committee shall be the development of standards, promotion of knowledge, and stimulation of research pertaining to thermal insulation materials, products, systems, and associated coatings and coverings, but not including insulating refractories. These activities shall be coordinated with those of other ASTM committees and national and international organizations having similar interest.”

C16 develops and maintains standards that are specifications for insulation and accessory materials, practices for mandatory activities such as installation, test methods for conducting particular tests (such as thermal tests), and guides for activities that are not mandatory. While C16 is always working actively to develop new standards, occasionally it votes to remove an older standard that is no longer being used.

Development of New C16 Standards

To develop a new standard, a task group is formed, which operates under the jurisdiction of a particular subcommittee and must meet at least once to discuss the new standard (it normally meets several times, when working on a new standard). The Task Group Chair must get a unique Work Item number from ASTM. Once a new draft standard has been developed, it must first be sent out for at least one subcommittee ballot. If Negative votes are received, they must be resolved at this early stage, usually by making revisions to the draft standard. With all Negatives so considered, the draft standard is ready to be sent to C16 and the sponsoring subcommittee for what is known as a “concurrent” ballot. At this stage, any Negatives must either be incorporated into a revised draft, or the Negative must be found non-persuasive by both the subcommittee and the main committee in formal voting held at actual meetings (normally, with everyone meeting in person; but, in the past 2 years, virtually). Once Negatives have either been incorporated into a new draft, which must be approved by a concurrent ballot, or been found to be non-persuasive, the draft standard is ready for a society ballot (i.e., one consisting of all ASTM members as well as outsiders, when interested). Normally, this last step is a formality, but it must nevertheless be followed.

C16 Membership

As of October 2021, ASTM Committee C16 had 427 members. For voting purposes, members are designated as Producers, Users, General Interest, or Consumers, based on their employer. Of the 427 members, 244 are formally classified as voters, and 183 are classified as non-voters. Each company (or other institution) can only have one voting member on C16 and only one voting member on each subcommittee (although it can have as many members as it wants on both), and the number of Producer voting members must be less than or equal to the sum of the number of Users, General Interest, and Consumer members. Producers are those companies that manufacture and/or sell insulation products covered by C16. Users typically work for engineering companies or for a company that purchases and uses insulation materials. General Interest members can include people who work for laboratories that test thermal insulation materials, colleges and/or universities, or government agencies. Consumers are anyone who is not included in the previous categories.

C16 Subcommittee Scopes and Current Development Work

The following are scopes of C16 subcommittees, followed by summaries of standards they are responsible for, in addition to recent activities on individual standards relating to mechanical insulation materials and systems. These are organized by the subcommittee associated with each standard. Note that although subcommittee meetings and the C16 main committee meeting are held on specified dates in the spring and fall, task group meetings can be held anytime, particularly in a virtual format. In some cases, with particularly active task groups, there may be several virtual meetings held in a 6-month period. Since the pandemic started 2 years ago, the active use of virtual meetings has actually increased participation on some task groups.

C16 has not met in person since October 2019. The committee missed the spring 2020 meeting altogether because the pandemic shutdown occurred within 3 weeks of the scheduled meeting time and ASTM did not have adequate time to set up virtual meetings. By autumn 2020, ASTM sponsored the first virtual C16 meeting, which occurred next in the spring of 2021, and the autumn of 2021. C16 is scheduled to meet in person in Seattle during the last week of April 2022.

C16.20 Homogeneous Inorganic Thermal Insulation Materials. On its website, ASTM gives the C16.20 Subcommittee scope as follows: “Develop and maintain standard test methods, definitions and nomenclature, recommended practices, classifications and specifications for all homogeneous inorganic thermal insulation materials under C16, except those assigned to subcommittee C16.21 and C16.23.”

This scope includes inorganic mechanical insulation materials such as calcium silicate pipe and block (C533), molded perlite pipe and block (C610), cellular glass pipe and block (C552), mineral fiber pipe (C547), mineral fiber boards (C612), calcium silicate structural insulating board (C656), and microporous insulation (C1676). This subcommittee also oversees the Practice for Inner and Outer Diameters of Thermal Insulation for Nominal Sizes of Pipe and Tubing (C585). Very recently, this subcommittee developed
a new Specification for Cellular Glass Insulation Used in Building and Roof Applications (C1902), removing this type of cellular glass—used for building envelope applications—from C552, the specification for pipe and block insulation used in mechanical applications.

C16.20 also oversees a couple of standards related to limiting stress-corrosion cracking of austenitic stainless steel. One is titled “Specification for Thermal Insulation for Use on Austenitic Stainless Steel (C795)” and the other is “Practice for Handling Thermal Insulation Materials for Use in Contact with Austenitic Stainless Steel (C929).” Finally, there is a task group actively working to develop a new Specification for Layered, Glass Fiber Felt Pipe and Board Insulation, a relatively new, commercially available mechanical insulation product.

C16.21 Reflective Insulation. On its website, ASTM gives the C16.21 Subcommittee scope as follows: “Develop and maintain product specifications, practices, nomenclature and test methods that are unique to thermal insulation which depend primarily on low IR emittance (heat reflectivity) for their effectiveness. Jurisdiction of this Subcommittee shall include material or assemblies consisting of one or more low-emittance materials applied, mounted or unmounted, with or without substrates such as paper, fibrous insulation, foam sheet, or plastic bubble pack.”

For the most part, there are no mechanical insulation products covered by this subcommittee.

C16.22 Organic and Nonhomogeneous Inorganic Thermal Insulations. On its website, ASTM gives the C16.22 Subcommittee scope as follows: “Develop and maintain standard test methods, definitions and nomenclature, recommended practices, classifications and specifications for all organic and non-homogeneous inorganic thermal insulation materials under C16, except those assigned to subcommittee C16.21 and C16.23.”

This scope includes mechanical insulation materials such as polystyrene, both expanded and extruded (C578), poly-isocyanurate (C591), phenolic foam (C1126), melamine foam (C1410), flexible elastomeric sheet and tube (C534), polyolefin (C1427), and polyimide (C1482 and C1594). Note that while Subcommittee C16.22 has oversight over a specification for spray-applied polyurethane insulation (C1029), it applies primarily to building envelopes and does not include low temperature-based performance data needed for a mechanical insulation specification. It is hoped that ASTM C16 fills that gap soon, since spray-applied polyurethane foam insulation is widely used as a mechanical insulation product, sometimes for cryogenic applications.

There are several ballots on the above specifications being held now. These are on C208 (one ballot), C578 (two ballots), C591 (one ballot), C728 (one ballot), and C1534 (one ballot).

C16.23 Blanket and Loose Fill Insulation. On its website, ASTM gives the C16.23 Subcommittee scope as follows: “Develop and maintain product specifications; recommended practices and test methods (when not under the jurisdiction of a methods subcommittee) for all thermal insulation materials under C16, except those assigned to subcommittee C16.20, C16.21, and C16.22.”

This scope includes mechanical insulation materials such as mineral fiber blankets (C553), metal mesh-covered mineral fiber blankets (C592), fiber glass duct wrap (C1290), spray-applied mineral fiber insulation (C1014), glass fiber felt insulation (C1086), high-temperature fiber blanket insulation (C892), pneumatically applied high-temperature fiber insulation (C1685), and flexible aerogel (C1728). During the current ballot, there are revisions proposed to two of these specifications: C592 and C1728.

C16.30 Thermal Measurements (Including Calculation Methods). On its website, ASTM gives the C16.30 Subcommittee scope as follows: “Develop and maintain test methods and recommended practices relating to the transfer of energy within and through thermal insulating materials and systems.”

This scope includes well-known test methods such as Heat Flow Meter Methods (C518) and Guarded Hot Plate Thermal Test Method (C177—which can be used for high-temperature testing and, with modifications, for cryogenic thermal testing, both of flat samples). Test Method for Steady-State Heat Transfer Properties of Pipe Insulation (C335), by contrast, is used to test pipe insulation for heat transfer from a hot pipe (i.e., operating at above-ambient temperatures). This subcommittee’s scope also includes Practice for Computer Method, Heat Gain or Loss (C680) for calculating heat loss/gain through thermal insulation in either flat or pipe configurations. C16.30 also includes some lesser-known test methods such as Total Hemispheric Emittance (C835) and Surface Burn Potential (C1057), as well as lesser-known calculation methodologies such as Practice for Estimating Heat Loss from Valves (C1129).

C16.31 Chemical and Physical Properties. On its website, ASTM gives the C16.31 Subcommittee scope as follows: “Develop and maintain test methods and practices related to chemical and selected physical properties of thermal insulating materials.”

This scope includes test methods such as Practice for Estimating the Maximum Use Temperature of Thermal Insulations (C447), Practice for Conditioning of Thermal Insulating Materials (C870), and Practice for Mixing Thermal Insulating Cement Samples (C163). Other methods within this subcommittee have lengthy, detailed names, to include the Test Method for Covering Capacity and Volume Change Upon Drying of Thermal Insulating Cement (C166); Test Method for Linear Shrinkage of Preformed High-Temperature Thermal Insulation Subjected to Soaking Heat (C356); Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel (C692); Test Methods for Chemical Analysis of Thermal Insulation Materials for Leachable Chloride, Fluoride, Silicate, and Sodium Ions (C871); and Practice for Quantitative Accelerated Laboratory Evaluation of Extraction Solutions Containing Ions Leached from Thermal Insulation on Aqueous Corrosion of Metals (C1617). There are active task groups that support the updating of each of these test methods and practices, which are then referenced by various material specifications, as necessary.

C16.32 Mechanical Properties. On its website, ASTM gives the C16.32 Subcommittee scope as follows: “Develop and maintain test methods and practices related to selected mechanical and physical properties of thermal insulation and associated materials.”

This scope oversees test methods commonly referenced in insulation material specifications, such as Test Method for Measuring Compressive Properties of Thermal Insulations (C165), Test Methods for Breaking Load and Flexural Properties of Block-Type Thermal Insulation (C203), Test Method for Density and Dimensions of Preformed Pipe-Covering-Type Thermal Insulation (C302), and Test Method for Measuring Non-Fibrous Content of Man-Made Rock and Slag Mineral Fiber Insulation (C1335).

C16.33 Insulation Finishes and Moisture. On its website, ASTM gives the C16.33 Subcommittee scope as follows: “Develop and maintain material specifications, test methods, recommended practices and classification systems: 1. applicable to coatings, coverings, adhesives and sealants used in association with thermal insulations; and 2. involving the transfer of vapor through thermal insulation and associated materials; 3. involving the accumulation of moisture in thermal insulating materials and systems.”

This scope includes well-known test methods, practices, and specifications used for finishes and moisture protection materials, such as the widely used Test Methods for Water Vapor Transmission (E96), Practice for Determining Properties of Jacketing Materials (C921), Practice for Selection of Vapor Retarders (C755), Test Methods for Mastics and Coatings (C461), and Specification for Selection of Low Permeance Vapor Retarders (C1136). There are also new standards, less well known, including Test Method for Elevated Temperature and Humidity Resistance of Vapor Retarders (C1258) and Specifications for Adhesives for Duct Insulation (C916). A task group is currently working on a proposed new standard titled, “Test Method for Water Retention of Rigid Thermal Insulation Materials after Immersion and Exposure to Drying Conditions.” This does not yet have an ASTM number designation, but it hopefully will soon. Finally, specifically for mechanical insulation, there is a Task Group working on a new standard to be titled, “Practice for Preparation and Reporting of Results for Water Vapor Transmission Property Testing of Preformed Pipe Insulation.” This practice is currently out for a C16 Main Committee ballot.

C16.40 Insulation Systems. On its website, ASTM gives the C16.40 Subcommittee scope as follows: “The development and maintenance of performance specifications and standard practices for thermal insulation systems. The systems include all the individual components combined in a manner to provide an effective control of heat transfer and moisture transmission within the insulation systems under the operational and environmental conditions of its intended use. Such components, if part of the system, will include the thermal insulation, supports, securements and protective coverings.”

Over the past 12 or so years, this subcommittee has introduced several new specifications for protective jacketing materials. This includes those for aluminum jacketing (C1729), for stainless-steel jacketing (C1767), for laminate protective jacketing and tape (C1775), and for Flexible Protective Jackets Made of Modified Asphalt/Butyl Rubber (C1916). The last one, C1916, is very new, just approved in November 2021. Note that it includes both jacketing materials that are used on exterior insulated duct, pipe, and equipment as well as materials used on insulated direct burial pipe and equipment. There is also a task group continuing work on a new specification for PVC jacketing (the draft document was out for
C16 ballot as of this writing) and another task group actively working on a new specification for Glass Reinforced Plastic (GRP) jacketing.

There are also some relatively new standards pertaining to mechanical insulation systems, such as Practice for Fabrication of Cellular Glass Pipe and Tubing Insulation (C1639), Guide for Installation of Flexible Closed Cell Preformed Insulation in Tube and Sheet Form (C1710), and Practice for Installation of Aluminum and Stainless-Steel Jacketing over Thermal Insulation on Pipe and Rigid Tubing (C1879). There is another fairly new Specification for Fabrication of Flexible Removable and Reusable Blanket Insulation for Hot Service (C1695), as well as a fairly new Practice for Preparation of Specimens and Reporting of Results for Permeance Testing of Pressure Sensitive Adhesive Sealed Joints in Insulation Vapor Retarders (C1809). Finally, the decades-old Specification for Prefabricated Reflective Insulation Systems for Equipment and Pipe Operating at Temperatures above Ambient Air (C667) has recently been transferred from Subcommittee C16.21 on Reflective Insulation to Subcommittee C16.40, since it is a specification for an insulation system that is more suitable to C16.40.

Subcommittee C16.94—Terminology. This subcommittee only has one standard to address, C168, which contains a number of insulation term definitions. C168 is revised frequently, due to the need to add additional definitions pertaining to C16 standards. Some of these terms are standard in the English language, such as “jacket,” but have a more specific meaning when applied to thermal insulation on pipe and equipment. For example, in the case of “jacket,” it is defined in C168 as “a covering installed over insulation. DISCUSSION—A facing is a type of jacket. Jacket (as related to insulation jacketing).” Likewise, the word “blanket” is also a standard English word, usually with a meaning that is unrelated to thermal insulation. C168, however, defines “blanket” in the following manner: “…flexible insulation product, supplied rolled or flat.”

The general practice is to define a word, within a particular standard, that is only used in that particular standard. However, when a word needs to be used in more than one standard, it will usually be moved to C168, at least when a C168 ballot to do so is successful.


This article summarizes the scopes of the ASTM Committee C16 subcommittees and provides an update on C16 activities. While sometimes it may appear that not much changes in the construction industry, when viewed over a dozen or so years, a great deal has changed. This is reflected in updates to existing ASTM standards as well as new ASTM standards. As a recognized industry standards body, ASTM contributes to raising the bar for the construction industry, establishing standards for thermal insulation that are used across the insulation industry. Since ASTM C16 was started in 1938 (84 years ago), it has worked continuously to improve both the thermal insulation industry and the construction industry.

Note on the 2021 Book of Standards: Every November, ASTM publishes and releases a new Book of Standards, Volume 04.06, “Thermal Insulation; Environmental Acoustics.” This includes all existing standards as well as any new or revised standards that were approved between July of the previous year and July of the current year. The 2021 Book of Standards is now available. In addition, and perhaps more importantly, each standard is available online and can be individually purchased from ASTM. C16 members receive all the C16 standards as part of their membership and can purchase other standards, produced by other committees, at a discounted price.