An Overview of Pipe Insulation for Plumbing Designers
Many long years ago, I put myself through college (B.S. in mechanical engineering) by installing pipe insulation. I spent several years with insulation manufacturers doing pipe insulation testing, product development and technical service.
The changes in the pipe insulation industry have been few and far between. A couple of notes:
Many ChoicesToday we have many choices for pipe insulation:
For plumbing applications, the most popular products are:
Insulation manufacturers publish the limitation of their product. Included in the literature is the upper and lower temperature limits of the insulation. Most consulting engineers do not approach the upper and lower limits of insulation. It is common to see material specified that has a 25°F higher or lower limit than the system for which it is designed.
It is important for insulation to be properly specified. If not, there could be a failure of the insulation. The most common types of pipe insulation failures are due to:
Most plumbing pipe insulation applications are for pipe temperatures between 50°F and 180°F. Foam insulation is one of the most popular products for cold water; and glass fiber insulation is the most popular for hot water. The thickness depends upon the energy savings required for the installation. It is also important to check with the local energy code for minimum thickness or R-values.
The successful performance of the insulation will depend upon the correct adhesions and jackets. Duct tape is never a suitable product for installing pipe insulation. Duct tape is prone to failure, resulting in the insulation falling off the pipe.
There are many excellent listed tapes on the market for attaching pipe insulation. Self-sealing laps are also excellent for sealing and fastening pipe insulation and/or the jackets. The concerns for abuse include:
JacketsFlexible foam pipe insulation does not require a jacket. However, if the pipe insulation is outdoors, it must have a coating as recommended by the insulation manufacturer.
With glass fiber pipe insulation, almost every application requires a jacket. Many manufacturers supply coverings that are all service jackets. Because ASJ has a paper exterior, the paper surface may have mold growth after being wet. Glass fiber insulation manufacturers provide plastic jackets that are resistant to mold growth. Aluminum jacket 16 mil (.016”) in 3-ft.-wide rolls is available to cover insulation for abuse protection and weather resistance. Preformed aluminum ells and tees are also available for a complete packaged system.
For many years there have been various color PVC jacket systems available from manufacturers. Where you need the ultimate jacket for chemical, abuse and fire resistance, stainless-steel jackets also are available.
Green and Other ColorsGlass fiber is made from sand, limestone, recycled beer bottles, etc. This gives the manufacturers the ability to advertise their products as green. Historically flexible (elastomeric) foam insulations have only been available in grey and black. Now, at least one manufacturer is selling white flexible foam pipe insulation.
Up-to-Date SpecificationsBe sure that your specifications for insulation are up to date. This is an area that is often ignored by engineers, yet it is extremely important for having the proper installation.
Underground InsulationWhen you need to insulate a pipe in direct burial, be sure to specify insulation that is designed for burial. It is also important to determine whether the underground insulation will be located below the water table. Engineers should be conservative with determining the water table for insulation below grade. Cellular glass is an excellent material for underground installations. There are also manufactured piping products specifically designed for such installations.
HangersHangers can ruin a good pipe insulation job. You must provide adequate space for the thickness of the insulation. Specify hangers with a saddle whenever possible so the insulation is not crushed at the hanger.
Finally, there are many special applications of pipe insulation that, if not carefully specified and installed, can be very costly.
Tips to Stay Out of Trouble When Specifying Pipe InsulationMuch of my consulting practice is troubleshooting insulation failures; frequently for insurance companies, contractors and lawyers. Here are some tips to help you stay out of trouble (and out of court).
The insulation should be installed by a professional mechanical insulation contractor, preferably a member of the National Insulation Association. Presently, I am consulting for an owner where the pipe insulation contractor’s workmanship was poor, which is rather unusual. Apparantly the insulator was lax in workmanship because he felt that no one would see the pipes, which were hidden behind plastered walls and ceilings. In the hot humid climate, condensation occurred on the pipes then dripped and stained the plaster, making quite a mess.
Insulate 100% of the piping in an attic. Case in point…In a hot attic of a south Texas nursing home, the domestic hot water pipe was poorly insulated (i.e., open gaps, bare fittings, etc.). The net result was hot water leaving the water heater at 115°F, but arriving at the patients’ lavs at 125°F and hotter. The state code mandatory maximum water temperature was 115°F. The nursing home manager nearly lost her license.
Make sure the roof above the attic is also insulated. Case in point...In a Maine nursing home, the water pipes were poorly insulated in the cold attic. The problem became a freezing/bursting issue. However, a quality pipe insulation job (continuous, with no pipe visible), combined with an insulated roof above the attic, solved the problem.
Do not use solvent-based adhesives in conjunction with styrene insulation. If this occurs, polystyrene insulation may melt.
Be aware that some adhesive solvents may also damage PVC jackets. A few years ago I was involved in a case where adhesive used to attach PVC jackets to the pipe insulation caused the PVC to wrinkle. It was not a pretty picture.
Never use an attachment device that reduces the insulation thickness. Instead, use tapes and adhesives made specifically for attaching pipe insulation. Many are available.
Never attach soft (foam) pipe insulation with wire or a plastic tie. It looks very unprofessional.