A Contractor’s Perspective: Mechanical Insulation 101

Alec J. Rexroat

February 1, 2010

To avoid costly problems, an owner, engineer, and/or architect should check some basic things on their mechanical insulation systems during construction. While no article can educate everyone on the nuances of mechanical insulation, the basic information in this article is important for facility owners, architects, and engineers to understand. This article is meant for the majority of Insulation Outlook readers who are owners, operators, architects, and engineers. It is not directed at mechanical insulation contractor readers, who already know what makes a mechanical insulation installation live up to its potential.

Lesson 1: The Specification

If the community where the facility is being constructed has an energy code, be sure the mechanical insulation specification meets or exceeds that code. Many, but not all, specifications adhere to ASHRAE 90.1 2007. Make sure the specification for mechanical insulation takes the current environment into consideration. The next standard will undoubtedly have stricter energy efficiency requirements, so if you go cheap now, you may pay dearly later.

There are a few items that the owner should consider for a properly functioning facility:

  • All domestic hot and cold water pipe systems should be properly insulated.
    • Hot water systems should be insulated from the hot water heater or storage tank to the branch leading to the faucet. Every foot of uninsulated hot water pipe translates into dollars out the window for the building owner. The lack of insulation on a 140-degree pipe system can become very expensive (see Lesson 2).
    • Failure to insulate domestic cold water systems can lead to condensation on the pipes, causing unsafe conditions for walking and mold growth that can be very expensive to eradicate.
  • On heating systems, all heating hot water supply and return piping, steam and condensate piping, and process heating system piping should be properly insulated, including valves, strainers, and fittings. This will help reduce greenhouse gas emissions by allowing the system to work efficiently.
  • Proper insulation of cooling systems will also have an environmental impact. Proper insulation on below-ambient cooling pipes will reduce the possibility of mold growth and lessen the chances of condensation problems, as well as increase equipment efficiency.
  • Proper mechanical insulation on ventilation systems should be included in the specification. This should include the supply and, in many cases, the return duct systems.

Lesson 2: “Value Engineering”

Did the mechanical insulation for this facility get “value engineered,” or is someone trying to convince you to “value engineer” your insulation specification? Value engineering, when it comes to mechanical insulation, almost always means compromising the insulation thickness, changing the materials (a cheaper substitute), or eliminating the insulation on some services or portion of services.

Value engineering is used to get the initial building cost at or below the number placed on the facility during the design stage. The problem with value engineering mechanical insulation is that the cost to operate the building will increase as mechanical insulation is eliminated or reduced. When mechanical insulation is reduced, the equipment within a facility works harder, thus increasing operating costs and decreasing the life of the equipment.

The process is almost never done with the long-term ramifications of building operation in mind. A case in point: a building owner or architect allows the specification for a 180-degree hot water heating system to be decreased from 1½-in. thick fiberglass material to 1 in. thick. There would be a small savings in material cost. But the CO2, NOx, and CE emissions go up 32 percent each, while the heat loss for the system goes up 32 percent. The cost per foot per year also goes up 32 percent. These numbers are just for reducing the insulation thickness; imagine the impact if parts of the system are not insulated at all.

Another example: a building owner or architect allows the specification for a 140-degree domestic water system to decrease from 1 1/2-in. thick fiberglass to 1 in. thick. The CO2, NOx, and CE emissions go up 28 percent, and the heat loss for the system goes up 28 percent. The cost per foot per year goes up 28 percent. Again, imagine the impact if the system is not insulated at all due to value engineering.

Mechanical insulation on domestic water systems is a frequent victim of value engineering. If your facility’s mechanical insulation was value engineered, you may be paying for something you are not getting, and you will be paying for it for years to come. If some form of the current cap-and-trade legislation comes to fruition, you may well be paying for your increased carbon footprint with higher taxes as well.

Lesson 3: Mechanical Pipe, Duct, and Equipment Installation

The proper installation of the mechanical services is critical to the proper installation of mechanical insulation. From the mechanical perspective, if the fluid in the pipes gets to where it should, the air in the ducts gets to the diffusers, the toilets flush, and the faucets work, it’s all good. But if the pipes were installed too close together for the insulation to be installed properly, it can become a big problem.

If the pipe or conduit has been installed using the sheet metal duct as a support system, it may require that the conduit and/or pipe be insulated with the duct. A simple rule of thumb is that the outside edge of parallel pipes that require insulation should be at least double the insulation thickness plus 1/2 in. apart. If a duct system requires insulation, the electrician, fitter, plumber, cable installer, or any other trade should not use the duct as a support system, and the duct should be installed with enough clearance to insulate around the entire duct. If pipes, ducts, or equipment requires insulation, the items should be installed with enough clearance to allow proper installation of the insulation.

Lesson 4: Materials

Make sure the proper insulation material is installed on each mechanical service. Many materials look alike but are not alike. Make sure the labels are on the materials and that the proper thicknesses are on the jobsite ready for installation. This can be accomplished by a quick walk through of the facility. All major insulation manufacturers label their materials properly, and you should be able to see the labels at a glance.

Lesson 5: Weather

Never force the mechanical insulation contractor to install material prior to establishing a dry building. If insulation materials are installed before the roof or windows are on the building, moisture may damage the insulation. Wet insulation will support mold growth and be less effective.

If you force the insulation contractor to install material before the building is ready, you are taking a risk. High-rise buildings frequently require insulation to begin on the lower floors while the upper floors are still under construction. There are no windows or roof on the building, but the schedule requires completion on a certain date, so the pressure is on to insulate now. Rain, snow, and ice can enter the upper floors and melt down onto the materials installed on the lower floors. This is a problem you don’t want. You will forget the accelerated schedule long before you solve the problem of wet and damaged insulation.

In the industrial sector, material must often be installed in inclement weather; however, in most cases the materials are protected immediately after application.

Lesson 6: The Little Gaps

Look for little transgressions that can become big problems later. One example is not properly butting the insulation materials to one another as the materials are installed. A small gap between insulation sections may seem like a little thing, but it can compromise materials and become very expensive. If the gap is on a cold pipe system, it can allow condensation to form on the pipe at the opening. The condensation can form a moist area on the insulation or on the ceiling where mold can grow. The dripping condensation can also lead to unsafe conditions on the floor, where the moisture can collect and cause a slipping hazard.

On the hot side of things, the small gap is not as noticeable. But it allows heat loss for the life of the building (see Lesson 2). That heat loss translates to dollars out the window for the facility owner.

Make sure the mechanical insulation is installed with properly butted joints and vapor barriers. Duct systems can have the same types of problems too. If mechanical insulation does not look clean and sharp when it is finished, it probably has not been installed properly.

Lesson 7: Vapor Barriers

Vapor barriers are extremely important when insulating cold systems. Improperly installed vapor barriers can cost significantly when the failures become apparent. Most pipe insulation materials are furnished with factory-applied vapor barriers from the manufacturer.

Many vapor barrier system failures occur at irregular surfaces. Cold insulation systems require vapor barrier mastic to seal the fittings, valves, strainers, valve stems, etc. Make sure that small appurtenances are insulated to avoid condensation that can creep back into the main, causing possible mold problems and dripping.

Ask to look at the mastic containers to ensure that the product is a vapor barrier material. When the wrong mastic is used, the costs can be very high: removing the old materials and replacing them with the correct materials, as well as removal and replacement of portions of the ceilings and walls. It can be very expensive. Make sure it is done right the first time.

Lesson 8: Pipe Supports

Pipes must be supported by hanger systems installed by the pipe fitting contractor. There are many types of support systems, but all require some insulation between or over the pipe and hanger.

When walking through the facility, pay particular attention to the pipe support systems on all services. Most specifications require some insulation protection at the pipe supports. There are many different systems to alleviate this pipe support problem:

  • Insulation support saddles are designed to spread the weight of the pipe over a larger area at the hanger.
  • Wood plugs can be inserted between the insulation support saddle and the pipe.
  • Special treated wood saddles, half the diameter of the pipe, can be used between the pipe hanger and the insulation.
  • Heavy density materials can be installed at each pipe support to protect the insulation.
  • Special insulation protection systems that will support the pipe at the proper level while performing the insulation function are manufactured by several companies.

If there is no insulation protection saddle at the support, chances are good that the insulation will be crushed when liquid is placed in the pipes. The crushing will decrease the value of the insulation and may cause breaks in the vapor barrier, which will allow failure in the future.

The softer insulation materials usually require some sort of insert between the pipe and the protection saddle to spread the weight of the pipe over a large area. If the insulation is showing signs of crushing, the chances are very good the inserts have not been installed.

Large bore pipe sizes almost always require some sort of protection to ensure that the insulation is not crushed. Insulation protection inserts are manufactured to size to address this problem.

Copper pipes are frequently clamped directly to a unistrut hanger. The insulation can be field fabricated to go around and over most of the unistrut, but not the portion that is in direct contact with the unistrut itself. That portion is destined to fail. There are many manufacturers of special hangers that allow proper spacing at the unistrut to allow insulation.

Lesson 9: Flashings

One of the most important parts of an outdoor installation is the weather protection. Many facilities use various gauges of metal products to protect the mechanical insulation from snow, rain, wind, ice, and abuse. If the protection fails, water may enter the insulation system and begin the process of corrosion under the insulation, as well as cause the material to stop performing as specified.

Failure points can be found in many places on outdoor systems. The lap of the jacketing on straight pipes should be facing down at four o’clock or eight o’clock. On risers, the lap should be away from the direction of the prevailing wind. All joints should be overlapped by at least 3 in. to ensure that no moisture can be driven into the system. On risers, the circumferential lap from the piece of jacket above should be over the jacket below to ensure water will flow away from the insulation system. Valve bodies, elbows, tees, and other areas where irregular insulation is used should be properly flashed so the water will run away from the system, not into it. The edge may be cleaner if the jacket is run up and over the down side of the elbow cover, but the moisture will run down and into the insulation system if this practice is used.

Common sense should dictate how flashings are done. If water will run into the system, it is done wrong. Caulking should be used at all appurtenances to keep moisture out of the system. Insulated systems should not be used as a platform or ladder to access higher areas. When people stand on weatherproofed material, they can destroy the protection and allow moisture to enter the system. There are many new weatherproofing materials on the market that not only provide weather protection but also act as a vapor barrier, and they are gaining wide acceptance.

Lesson 10: The Clean, Safe Job

Every project should be kept as clean as possible. The floors should be kept clean of insulation scraps, lap backings, empty boxes, materials not being used, and other items that can create a danger to the insulator or other tradespeople. Protective coverings should be placed under areas where mastic is being applied to avoid splattering. Protective equipment should be worn by all tradespeople at all times on the project site. Ladders should be inspected and used only if in good order. All OSHA rules and regulations should be adhered to at all times on the project site.

The safe job is a topic that could take an entire issue of Outlook to cover. Follow OSHA regulations, and remember: a dirty job is trouble waiting to happen.


So there you have it: the top 10 basics of mechanical insulation. There are many more lessons, and all of the above could be expounded on in much greater detail. To learn more about mechanical insulation installation, check out the Mechanical Insulation Design Guide at www.wbdg.org/midg or search the National Insulation Association’s technical articles database at www.insulation.org/articles/. Another great reference for any person responsible for mechanical insulation is the Midwest Insulation Contractors Association (MICA) National Commercial and Industrial Insulation Standards Manual (available at www.insulation.org/products).