ASHRAE Issues Updated Standard 90.1 and Handbook Chapter on Mechanical Insulation

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®

February 1, 2014

ASHRAE, founded in 1894 (and formerly known as the American Society of Heating, Refrigerating, and Air Conditioning Engineers), is one of the largest engineering groups in North America, with more than 54,000 members worldwide. The group and its members focus on building systems, energy efficiency, indoor air quality, refrigeration, and sustainability within the industry. ASHRAE’s mission is to advance the arts and sciences of heating, ventilating, air conditioning, and refrigerating through research, standards writing, publishing, and continuing education.

ASHRAE Publications
The well-known Standard 90.1—which contains standards for the energy-efficient design of high-rise residential, commercial, and institutional buildings—as well as Standard 55—on thermal comfort standards in buildings—are periodically revised. In recent years, Standard 90.1 has been revised every 3 years and is referenced by its year of issue: 90.1-2004, 90.1-2007, 90.1-2010, and 90.1-2013. Standard 90.1 was first published in the mid-70s. ASHRAE publishes 4 Handbook volumes: Fundamentals, Refrigeration, HVAC Applications, and HVAC Systems and Equipment. Each volume is updated every 4 years. The ASHRAE Handbook—Fundamentals was published in 2001; 2005; 2009; and, most recently, in June 2013. The ASHRAE Handbook—Refrigeration was published in 1998; 2002; 2006; and, most recently, in 2010. The 2014 edition has been approved and is being type-set for printing and distribution in June 2014. There are many other ASHRAE publications, such as copies of technical papers presented at the semi-annual meetings. They also publish many books; 2 examples are The ASHRAE Guide for Buildings in Hot and Humid Climates and the ASHRAE Green Guide: The Design, Construction, and Operation of Sustainable Buildings.

ASHRAE Standard 90.1-2013
ASHRAE recently released the latest edition of Standard 90.1, entitled Energy Standard for Buildings Except Low-Rise Residential Buildings. This standard addresses high-rise residential, commercial, and institutional buildings (i.e., not single-family residences or low-rise apartments). It has sections on minimum requirements for the building envelope, fenestration (i.e., windows and doors), service water heating, power, lighting, and HVAC (including mechanical insulation). A major goal of issuing periodic revisions to Standard 90.1 is to make improvements in reducing building energy use. Hence, the 2013 edition, if followed for a new building design, will result in at least 50% less energy use, by design, than the 2004 edition (with the 2007 and 2010 editions each successively leading to less energy use than the previous edition). This is done by requiring, among other considerations, greater roof and wall R-values; greater use of triple-glazed windows; more reflective window glass; more tightly sealed envelopes; more efficient HVAC equipment; greater use of heat exchangers for ventilation; better control over fresh air ventilation dampers and fans; more energy-efficient lighting (with controls to turn lights off when not needed); and, of course, greater mechanical insulation thicknesses and R-values.

Minimum required insulation thicknesses and R-values for pipe, equipment, and ducts were increased in the 2010 edition over the 2007 edition, but there are no changes in this area in the 2013 edition over the 2010 edition. While this may seem to be an oversight on the part of Standard Projects Committee 90.1, it may instead reflect the requirements in the HVAC section for greater use of lower temperature hot water systems for space heating (i.e., most hot water heating systems operate with a maximum supply water temperature of about 180°F in the coldest weather, and that adjusts downward in milder weather by using electronic controls). In addition, old-style steam heating systems—that often have operating temperatures up to 380°F—are being replaced in both old and new buildings with hot water distribution systems, even if steam is sent to the building from a central steam plant (as is often done at colleges, universities, and hospitals). ASHRAE 90.1-2010 requires insulation with a certain K-factor performance to be applied at a thickness of 5 inches on pipes with an operating temperature greater than 350° F, and a diameter greater than 3/4 inch NPS. In these circumstances, meeting this requirement with mineral fiber insulation requires a double layer.

2013 ASHRAE Handbook—Fundamentals, Chapter 23
Chapter 23 in the ASHRAE Handbook—Fundamentals covers “Insulation for Mechanical Systems.” The 2005 version was the first ASHRAE Handbook—Fundamentals edition with a chapter on this subject, so the 2013 edition is only the second revision of that original chapter. The following is a list of major changes to that chapter in the 2013 edition:

  • Recommended minimum pipe insulation thicknesses, for both hot and chilled pipes, were increased to match those in Standard 90.1-2010.
  • The section called “Condensation Control” was rewritten to better explain how to accomplish the following in regard to chilled water (CHW) pipe:
    • Calculate pipe insulation thickness to minimize surface condensation in unconditioned spaces such as mechanical rooms and central chiller plants, and
    • Minimize moisture intrusion problems in the insulation on those pipes.
  • The section on “Corrosion Under Insulation” (CUI) was updated to explain how to minimize CUI problems and includes recommendations for the use of weather barrier jacketing on outdoor systems.
  • The updated “Materials and Systems” section now recommends the use of lower permeance insulation systems on CHW pipe and equipment systems, and use of appropriate weather protection on outdoor systems.
  • The subsection on vapor retarders now urges caution when using traditional All Service Jacket (ASJ) on CHW systems in unconditioned spaces, particularly when the building is located in a region with a hot and humid climate. In the same subsection, there are new recommendations to use appropriate vapor retarders on CHW pipes.
  • The “Installation” section added advice on the design of factory-insulated pipe supports. The section also includes new information advising designers and building owners to pay particular attention to pipe components in mechanical rooms (such as valves, flanges, strainers, etc.) that need to be insulated along with the pipes. They also need regular maintenance, since that insulation is often stripped by mechanical maintenance personnel.
  • The updated edition includes findings of Research Project RP-1356 on a method of testing CHW pipe insulation and the increased thermal conductivity of pipe insulation with a condensed water content.

2014 ASHRAE Handbook—Refrigeration, Chapter 10
ASHRAE’s TC 10.3 – Refrigeration Piping, Controls, and Accessories has responsibility for the chapter in the 2014 ASHRAE Handbook—Refrigeration entitled “Insulation Systems for Refrigerant Piping,” with a scope that it “is a guide to specifying insulation systems for refrigeration piping, fittings, and vessels operated at temperatures ranging from 35 to -100°F. It does not deal with HVAC systems or applications such as chilled-water systems.” The 2014 Handbook is not yet published, but all revisions have already been approved. The major changes that were approved by TC 10.3 are:

  • An increased emphasis on the need for the vapor retarder system to be continuous
  • Explanation that water entering an insulation system can bring with it a near-inexhaustible supply of corrosive contaminants from the ambient environment, which can exacerbate corrosion.
  • Changes to all the insulation thickness tables to:
    1. Determine all insulation thicknesses using the current state-of-the-art calculation methodology (ASTM C680-10).
    2. Use the latest thermal conductivity curves from the appropriate ASTM material standard for each insulation material.
    3. Maintain the same design criteria used in the 2010 Handbook—Refrigeration (i.e., condensation control and 8 Btu/hr-ft² heat flux limit).
    4. Continue the practice of not including any safety factor in the condensation control calculations.
    5. Use the correct emittance for aluminum jacketing of 0.1, as specified in ASTM C1729-13, Standard Specification for Aluminum Jacketing for Insulation, instead of the 0.4 value used in the past.
    6. Maintain the same design conditions used in the 2010 Handbook, except for changes in relative humidity and jacket emittance.
    7. Minimize the changes from the 2010 Handbook to insulation thicknesses in the tables, since the insulation thicknesses in the current tables have proven to be acceptable in the field. To accomplish this goal for the outdoor condition tables, the design relative humidity was increased until the overall insulation thickness changes to the tables were minimized. This occurred at a relative humidity of 94%, not the 90% previously used. For the indoor tables, the heat gain portion of the design criteria controls the required thickness, so increasing the relative humidity would have no impact. Since the 8 Btu/hr-ft² heat gain limit is firmly set in the industry, it was deemed inappropriate to modify this design criteria. The insulation thicknesses in the indoor tables were therefore allowed to deviate based on only goals 1-4 above.

ASHRAE Research Related to Mechanical Insulation
ASHRAE sponsors a large number of research projects on HVAC-related topics, one of which is ASHRAE Research Project RP-1356 (mentioned in the ASHRAE Handbook Fundamentals section). Dr. Lorenzo Cremaschi, of Oklahoma State University (OSU), gave a presentation on this project at the National Insulation Association’s (NIA’s) 2013 Annual Convention. That project is complete and will be featured in an upcoming issue of Insulation Outlook. The full report is also available for purchase from ASHRAE’s online bookstore for $30. Another project—RP-1550, conducted by David Yarbrough—addresses the thermal performance of thermal insulating coatings. That project was also recently completed and is going to be featured in an upcoming issue of Insulation Outlook. The full report is available for purchase through ASHRAE for $30. In this project, 3 commercially available coatings were tested using an ASTM C335 hot pipe test apparatus.

Finally, OSU is currently conducting another research project, RP-1646, using the same test facility it developed as part of RP-1356 (i.e., an environmental chamber with 2 identical chilled thermal test pipes, 1 pipe being used for moisture condensation test samples, and the other for thermal measurements). OSU is testing 6 different insulation systems for thermal and moisture performance. The pipe temperature for these tests is 38°F, located in an environmental chamber held constant at 90°F and 83% relative humidity. Additional test conditions include:

  1. Flexible elastomeric insulation with all joints glued together and no separate vapor retarder jacket;
  2. Cellular glass insulation with all joints sealed and no separate vapor retarder jacket;
  3. Fiberglass jacketed with standard ASJ and sealed with standard taped butt and lap joints;
  4. Same system as number 3, with the addition of solvent sealed PVC jacket;
  5. Polyisocyanurate insulation covered with PVDC film, with taped butt and lap joints; and
  6. Phenolic foam insulation covered with a very low permeance vapor retarder jacket and tape, with a pressure-sensitive adhesive, which both meet ASTM C1136, Type IX.

Since each system must be tested for 2 months’ duration, progress is slow. The first couple of tests had to be repeated due to irregularities that were discovered. Hence, this research project may not be complete, with a test report reviewed and approved by TC 1.8, until late in 2014 or early 2015. When completed, each system will have been characterized by a tested system vapor permeance and a relationship, for the insulation material, between condensed water content and thermal conductivity at a below-ambient temperature.

What Does ASHRAE Do?
Among other matters at the society-wide meetings, the Technical Committees (TCs) meet to discuss their objectives and projects. Three such groups are: TC 1.8 – Mechanical Systems Insulation, TC 10.3 – Refrigerant Piping, and TC 1.12 – Moisture Management in Buildings. The TCs are responsible for certain chapters in ASHRAE’s 4-volume Handbook; and they sponsor research, technical sessions, seminars, and forums at the society-wide meetings. There are also a number of Special Project Committees, many of which write standards.