Introduction

The National Insulation Association (NIA) originally developed this guide to design of mechanical insulation for commercial and industrial applications through the National Institute of Building Sciences’ (NIBS’) National Mechanical Insulation Committee. The Design Guide is intended to be a comprehensive educational resource to assist specifiers and users of mechanical insulation in the design and specification of mechanical insulation systems for a wide range of applications.

Background

Mechanical insulation systems are defined as the materials and components used to insulate piping, equipment, vessels, ducts, and other types of mechanical items. Although important to facility operations and manufacturing processes, mechanical insulation is often overlooked and undervalued. National standards, universal energy policies, or generally accepted recommendations as to what should be insulated, what insulation systems are acceptable for a specific use, and application best practices do not currently exist. As a result, the value of mechanical insulation is not being realized to its potential for energy conservation, reducing our dependency on foreign energy sources, improving our environment by reducing greenhouse gas emissions, improving our global competitiveness, and providing a safer work environment for personnel and process.

Insulation is applied, but it is rarely engineered. With the best intentions, but not necessarily thorough knowledge, many specifications have evolved over the years primarily based on modification of old documents. This practice—combined with the lack of educational and awareness programs on the value of having a properly engineered, installed, and maintained mechanical insulation system—has led to the underutilization of mechanical insulation in energy conservation, emission reduction, process and productivity improvement, life-cycle cost reduction, personnel and life safety, workplace improvements, and a host of other applications.

NIA's Mechanical Insulation Design Guide Objective

The overall objective of the NIA Design Guide is to identify, develop, and disseminate information related to mechanical insulation in commercial and industrial applications by examining current policies, procedures, and practices; identifying research or testing needs; developing recommendations utilizing the best science and information available; providing education and awareness programs as to the merits and value of properly designed, installed, and maintained insulation systems; and to establish a roadmap to implement improvements in insulation system design and selection, and establish application best practices.

The Design Guide is continually updated as deemed necessary and appropriate by the NIA to reflect current and state-of-the-art information.

Mechanical Insulation Market Definitions

MECHANICAL INSULATION encompasses all thermal, acoustical, and personnel safety requirements in:

• Mechanical piping and equipment, hot and cold, applications;
• Heating, Venting & Air Conditioning (HVAC) applications; and
• Refrigeration and other low-temperature piping and equipment applications.

Mechanical insulation in the BUILDING SECTOR is defined to include systems used in education, health care, institutional, retail and wholesale, office, food processing, light manufacturing, and similar types of applications. This sector is often referred to as the commercial sector.

Mechanical insulation in the INDUSTRIAL SECTOR is defined to include systems used in power, petrochemical, chemical, pulp and paper, refining, gas processing, brewery, heavy manufacturing, and similar types of applications.

Scope of the Design Guide

The scope of the Design Guide includes the design, specification, installation, and maintenance of insulation systems for use within the markets defined above. Specialized insulated air-handling products (flex-duct, duct liner, and duct board products) are not considered to be mechanical insulation in the context of this guide and are not addressed.

The Design Guide is an evolving, web-based resource intended to provide architects, engineers, facility managers, project managers, etc. with design guidance, criteria, and technology for mechanical insulation systems. The guide is continually updated with new information and is structured as a "vertical portal," enabling users to access increasingly specific information as they navigate deeper into the site.

Using the NIA Mechanical Insulation Design Guide

As the name implies, the Design Guide is primarily intended to assist designers, specifiers, facility owners, and users of mechanical insulation systems. The engineering design process is generally divided into phases, such as:

1. Identify the need or define the problem.
2. Gather pertinent information.
3. Identify possible solutions.
4. Analyze and select a solution.
5. Communicate the solution.

For an insulation design project, these phases could be expanded and restated as follows:

1. Identify the design objectives. (Why insulate?)
2. Identify what is to be insulated. (What?)
3. Identify the location and appropriate ambient design conditions. (Where?)
4. Identify the materials and systems available. (How?)
5. Analyze and determine acceptable solutions. (How to? How much?)
6. Write the specification.
7. Inspect what you expect.

For insulation, the design process boils down to developing answers to six basic questions:

Why? What? Where? How? How to? How much?

Examples of problems that can arise in the insulation design process, as well as how to use the Mechanical Insulation Design Guide, can be viewed below.

The Mechanical Insulation Design Guide is organized to help develop answers to the six basic questions. The guide is divided into six sections, as follows:

1. Design Objectives (Why, What, and Where?)
   This section is aimed at first answering the question Why? It includes a discussion of each of the potential design objectives for mechanical insulation systems. It also contains a discussion of some of the design considerations (What and Where?) that must be addressed when designing or selecting an insulation system. An insulation system can be designed for specific objectives, like energy conservation or condensation control, or multiple objectives. To select the right insulation system, you need to evaluate the objective(s) for the finished system.
2. Materials and Systems (How?)
   In most cases, there are multiple types of mechanical insulation materials from which to choose from for any given application. This section discusses each of the respective material categories and provides resource information to testing methods, as well as links to manufacturers of the various materials. Note: The NIA is the only trade organization focused solely on the mechanical insulation industry. For more information, and for a list of NIA members, including manufacturers, please visit www.insulation.org.
3. Installation (How to?)
   The installation section provides best practice information related to various mechanical insulation applications and describes a variety of field/job site working conditions that need to be considered during the installation phase. Both new construction and maintenance applications are discussed.
4. Design Data (How much?)
   This section provides useful equations, data, and design examples. These data are intended to assist with analysis of insulation systems. The section also includes discussion and links to available software tools for use in analysis of mechanical insulation problems.
5. Specifications
   This section provides information on mechanical insulation specifications and the important role they play in the overall design process. Too often, mechanical insulation specifications are developed by “dusting off” the specification from a previous project. This often results in confusion, delays, and increased cost. Good specifications should communicate the design objectives, materials, thicknesses, finishes, securements, and other systems requirements.
6. Resources
   The section contains a listing and contact information for the various resources utilized in the development of this guide and additional resource requirements.

Design Problem Examples

The following examples are intended to illustrate the insulation system design process as well as the use of the Mechanical Insulation Design Guide.

Example 1

A light-manufacturing facility near Midway Airport in Chicago is expanding. 150 psig steam will be required for several of the new processes, and multiple natural gas-fired boilers will be installed to provide the required steam. These boilers will also serve as the energy source for space heating in the plant and in the adjacent office area. The new boilers will be located in an existing boiler house, remote to the main plant. The main steam line is NPS 8 steel and will be located in overhead pipe racks adjacent to a pedestrian walkway. Total length of the outdoor run is 150 ft. The task is to design the insulation system for the NPS 8 line.

Step 1: Identify the design objectives. (Why?)
Design objectives and considerations are discussed in the Design Objectives section of the Design Guide. After reviewing this section, it is determined that the project has multiple design objectives. First, operating costs are a concern, as the energy costs are expected to be a significant portion of the unit costs of the manufactured product. In addition, the overhead pipe rack will include a pedestrian walkway. Personnel protection will therefore be important. Abuse resistance will be a design consideration due to the proximity of the steam line to the pedestrian walkway.

Step 2: Identify what is to be insulated. (What?)
The main piping run will be steel piping and will be oriented primarily horizontally. The steam pressure in this line will be controlled to a set point of 150 psig. The temperature of this saturated steam will be 366°F. It is understood that the steam line will operate year round (8,760 hrs./yr.).

Step 3: Identify the location and appropriate ambient conditions. (Where?)
The 8 NPS steel piping runs outdoors between the boiler house and the main plant. After reviewing the Resources section of the Design Guide, we recognize that design weather data for the Chicago area is available from the ASHRAE Handbook—Fundamentals. Annual average weather data is available via the National Climatic Data Center website. For energy calculations, we will use the average annual temperature and wind speed at Midway Airport (51°F and 10 mph). For personnel protection, we will use the ASHRAE 0.4% summer design temperature of 92.3°F and 0 mph wind speed.

Step 4: Identify the materials and systems available. (How?)
Candidate insulation materials and systems are reviewed in the Materials and Systems section. After entering the operating temperature of 366°F into the Performance Property Guide (Table 1), we see there are 17 available insulation materials that satisfy the operating temperature requirement of 366°F. Selecting the material types that pertain to pipe insulations, we identify the following candidate materials:

• Cellular Glass (ASTM C552)
• Mineral Fiber Pipe (ASTM C Type I Fiberglass)
• Mineral Fiber Pipe (ASTM C547 Types II – V Mineral Wool)
• Polyimide (ASTM C1482)
• Calcium Silicate (ASTM C533)
• Expanded Perlite (ASTM C610)
• Flexible Aerogel (ASTM C1728 Type III, Grade A)
• Microporous (ASTM C1676 Type II, Grade 2B)

Referring again to Table 1, these insulation materials differ in several key properties (e.g., density, thermal conductivity, and compressive resistance), but all would meet the thermal requirements for the project.

For jacketing/finishing systems, we note that the location is outdoors, so weather protection is required. We also note that abuse resistance is a consideration for the design for the piping located in the pipe rack. Possible jacketing materials include metal, UV-stabilized PVC jacket, synthetic rubber laminates, and multi-ply laminates. Since low water vapor permeance is not a consideration for this project, we will specify aluminum jacketing.

Step 5: Analyze and determine acceptable solutions. (How to? How much?)
After reviewing the Design Data section of the Design Guide, we utilize the North American Insulation Manufacturers Association (NAIMA) 3E Plus® software to analyze the candidate systems to estimate the surface temperatures and heat losses. For these calculations, we assume horizontal pipe and a jacket emittance of 0.1 (corresponding to weathered aluminum). Starting with the personnel protection objective (with a maximum surface temperature criterion of 140°F) at the summer design condition of 92.3°F and 0 mph wind speed, we calculate the required thicknesses for each of the candidate materials.

Table 1. Thickness Required for Personnel Protection NPS 8 Piping

Material	Thickness, in.	Surface Temp., °F	Heat Loss, Btu/(h·ft)
Cellular Glass	2½	135	130
Polyimide	2½	138	143
Fiberglass	2	133	114
Mineral Wool	2	132	109
Calcium Silicate	2½	133	122
Expanded Perlite	2½	137	141
Flexible Aerogel	1	137	111
Microporous	1½	128	90

Based on these results, we conclude that approximately 1 to 2-½inches of insulation will be required to keep the temperature of the outer surface of the insulation system at or below 140°F.

The next step is to analyze the candidate insulation systems with respect to operating costs. Using the Cost of Energy function in 3E Plus, and using the expected cost of natural gas of $3/MCF with a boiler efficiency of 75%, we generate the following table:

Table 2. Annual Cost of Lost Energy, $/ft/yr.

Thickness	Cellular Glass	Polyimide	Mineral Fiber (Fiberglass)	Mineral Fiber (Mineral Wool)	Calcium Silicate	Expanded Perlite	Flexible Aerogel	Microporous
Bare	118.41	118.41	118.41	118.41	118.41	118.41	118.41	118.41
1"	11.49	12.46	8.22	7.88	10.99	12.68	4.78	5.37
2"	6.66	7.21	4.69	4.50	6.40	7.45	2.70	3.05
3"	4.75	5.14	3.33	3.20	4.57	5.34
4"	3.89	4.20	2.72	2.61	3.75	4.38
5"	3.35	3.62	2.34	2.25	3.23	3.78
6"	2.98	3.22	2.08	1.99	2.87	3.36

Reviewing these data, it appears that some operating cost savings are available by going beyond the 2 to 2-½" thicknesses required for personnel protection. For example, the operating cost for 2“ of mineral wool is $4.50/ft/yr., compared to $3.20/ft/yr. for 3” thickness. Using the default cost data from the Economic Thickness section of 3E Plus, with a labor rate of $80/hr., a discount rate of 5%, and an estimated life of 10 years, we determine that a thickness of 2-½” of Mineral Wool insulation (single layer) minimizes the life-cycle cost of the insulation system. A similar calculation using fiber glass pipe insulation also yields an economic thickness of 2-½” These results, however, are dependent on the installed costs of the insulation material and could vary from the default values.

At this point, we recognize that the operating cost estimates for several of the candidates are sufficiently close to warrant additional analysis. Using the links in the Materials and Systems section, we can reference product data sheets for specific insulations to refine the analysis. The additional design consideration of abuse resistance may warrant review of additional product properties (e.g., compressive resistance). After this review, we can prepare the specification around several of the best candidates and competitively bid the project.

Step 6. Write the specification.
The final step is to communicate the design intent utilizing the specification (How To?). We may have access to one or more guide specifications (e.g., Deltek MasterSpec®, Process Industry Practices, UFGS 23 07 00) that could be utilized. Insulation manufacturers may also have guide specifications.

Example 2

A standby diesel-powered generator set is to be installed to provide backup power for a large hospital complex in Charlotte, North Carolina. The generator set is located in an unconditioned but ventilated detached building on the hospital grounds. Exhaust gases will be piped out of the building but will pass near high-traffic walkways accessible to maintenance personnel. The generator set will be run periodically for testing and maintenance, but it is designed to run continuously if needed. The exhaust gases are estimated to be about 1,000°F under full load conditions. Exhaust piping is NPS 12 steel.

Step 1: Identify the design objectives. (Why?)
Design objective are discussed in Section 1 of the guide. The design objective here is personnel protection. Since we are dealing with exhaust gases ducted outside the building, energy conservation is not a concern. The insulation system will be designed to keep the surface temperature below 140°F at worst-case conditions. Since the exhaust piping will be near a high-traffic area, abuse resistance is another design consideration.

Step 2: Identify what is to be insulated. (What?)
The 12 NPS steel piping in the generator building has both horizontal and vertical runs. The temperature of the exhaust gases in this piping will vary, depending on the load on the generator set. For the purpose of this example, we will assume full load conditions (1,000°F).

Step 3: Identify the location and appropriate ambient conditions. (Where?)
The exhaust piping is located in the stand-alone generator building. This building is unconditioned during the summer months. Ventilation in the form of exhaust fans is provided. The thermal conditions in the generator building will vary with the outdoor weather and internal loading.

For outdoor conditions, design weather data (ASHRAE Handbook—Fundamentals) shows four values for the outdoor design dry-bulb temperature for Charlotte (Table 3).

Table 3. Design Cooling Temperatures for Charlotte, North Carolina

Level	Design Dry-bulb Temperature, °F
Mean of Annual Extremes	97.0
0.4%	93.9
1%	91.5
2%	89.2

The 0.4%, 1%, and 2% levels represent the annual cumulative frequency of occurrence. In other words, we could expect, based on the 30-year weather record examined, that the outdoor dry-bulb temperature would exceed the 1% level 1% of the time (i.e., 88 hours per year). The exhaust piping, however, is not located outdoors. Conditions indoors may be warmer (particularly if the generator set is running at full load). How much warmer is difficult to determine, but it seems prudent to select an indoor design temperature of 95°F for this example.

Since the generator building would be ventilated during equipment operation, air movement around potions of the exhaust piping could be significant. However, since this is a personnel protection design, we will assume no air movement.

Step 4: Identify the materials and systems available. (How?)
Materials and systems are reviewed in Section 2 of the Design Guide. Referring to Table 1, there are five insulation products currently available that satisfy the operating temperature of 1,000°F:

• Calcium Silicate Pipe (ASTM C533 Type I)
• Mineral Fiber Pipe (ASTM C547 Types II-V)
• Expanded Perlite Pipe (ASTM C610)
• Flexible Aerogel (ASTM C1728 Type III, Grade A)
• Microporous (ASTM C1676 Type II, Grade 2B)

Referring again to Table 1, these insulation materials differ in several key properties (e.g., density, thermal conductivity, and compressive resistance), but all three would meet the thermal and physical requirements for the project.

For jacketing/finishing systems, we note that the location is indoors, so weather protection is not required. We also note that this is an above-ambient application, so a vapor retarder is not required. Referring to Section 1 of the Design Guide, we note that personnel protection applications should utilize a high emittance surface to minimize surface temperatures. We also note that abuse resistance is a consideration for this design. We therefore identify painted metal as a candidate jacketing material.

Step 5: Analyze and determine acceptable solutions. (How to? How much?)
Utilizing 3E Plus, we analyze the five candidate systems to estimate the necessary personnel protection thickness, assuming horizontal pipe (Table 4).

Table 4. Personnel Protection Thicknesses of Five Insulation Options

Calcium Silicate ASTM C533-04	Mineral Fiber ASTM C547-06	Expanded Perlite ASTM C610-05	Microporous ASTM C1676	Flexible Aerogel ASTM C1728
5½"	5½"	6"	2½"	3"

At this point, we could reference product data sheets for specific insulation products to refine the analysis. Alternatively, we could prepare the specification around several choices and competitively bid the project.

Step 6 Write the specification.
The final step is to communicate the design intent utilizing the specification (How To?). We may have access to one or more guide specifications (e.g., Deltek MasterSpec, Process Industry Practices, UFGS 23 07 00) that could be utilized. Insulation manufacturers may also have guide specifications.