By / Steve Clayman
Let’s go back about ten years and revisit a serious concern numerous people in the mechanical insulation industry were having. The topic de jour was uninsulated plastic piping. It was such a concern that companies such as Owens Corning and Nomaco spent time and money running tests to verify (or disprove) the plastic pipe manufacturers’ claims that the wall thickness of plastic pipe provided sufficient R-value to the extent that pipe insulation could be reduced in thickness or eliminated entirely. National Insulation Association (NIA) also became involved, as did TIAC.
Suffice it to say, the plastic pipe manufacturers revised their respective approaches to this issue from a technical perspective, but not necessarily from a marketing perspective. Perhaps this latter statement is a bit strong. A more accurate approach would be to say the plastic pipe manufacturers haven’t undone the misconception they created that insulation isn’t required. As we approach 2022, uninsulated plastic pipe remains a subject of concern. After ten years, why is this still a problem?
Background
Let’s take a brief look at what has so far been published:
Nomaco Insulation (now owned by Armacell)
“Insulating Plastic Piping in Plumbing and Hydronic Heating Applications,” June 5, 2012, by Shawn Dunahue, technical sales manager.
Dunahue states, “There are two main reasons mechanical pipe insulation is installed on plumbing and hydronic heating systems operating at 200 degrees F: condensation control and energy conservation.” He goes on to illustrate, as an example, a three-storey hotel with a total 6,150 linear feet of ½” to 2” PEX pipe. Other details include a hot water circulation system at 140 degrees F and an RH of 50%. The ambient temperature is 72 degrees F. Insulate or not?
Despite what the manufacturers’ literature intimates, the prevailing code requires 1” thickness of pipe insulation. Who was there to make sure this happened?
Owens-Corning
“K-Value Calculations & Heat Loss”, June 20, 2011.
Owens Corning referenced ASTM C335, “Standard Test Method for Steady-State Heat Transfer of Pipe Insulation”. The test results showed:
- Aquatherm:
- Test temperature: 150 degrees F
- R-value: 0.64
- Aquatherm + Owens Corning pipe:
- Test temperature: 149.98 degrees F
- R-value: 5.07
The report concludes:
- “Hot water with a temperature of 140 degrees F travelling in a 1” diameter non-insulated plastic pipe, will lose 34.26 BTU/hr across one foot of travel in a building at 70 degrees F.”
- “If the 1” plastic pipe above is insulated with 1” thick fiberglass, in the same hot water and building conditions, the energy loss across one foot is 7.95 BTU/hr.”
National Insulation Association
“Insulation for Plastic Piping: How Much is Needed?” Insulation Outlook, September 1, 2012, by Christopher P. Crall.
This detailed nine-page report (available online at insulation.org/io/articles/insulation-for-plastic-piping-how-much-is-needed) offers an in-depth rationale for insulating and not insulating plastic piping. The conclusions centre on energy conservation and condensation control and how pipe insulation, regardless of the type of pipe wall material, is beneficial short and long-term.
TIAC
TIAC Fact Bulletin No. 1: “Pipe Insulation and Plastic Piping” in addition to several presentations on the topic.
A synopsis of where the calculations lead to while underscoring the importance of pipe insulation for energy and water conservation, condensation control, and personnel protection.
Aquatherm
Aquatherm Technical Bulletin 201208A-AQTTB, “Piping Condensation and Aquatherm,” August 15, 2012.
Quoting from the report (emphasis is Aquatherm’s):
“But even Aquatherm piping cannot be guaranteed not to sweatwhen exposed to the proper conditions.”
“It is, therefore, the position of Aquatherm that all piping installations where cold or chilled water is to be carried or where the surface temperature of the piping is expected to be below the ambient temperature, shall be insulated per code.”
IPEX AquaRise
According to the manufacturer, the stated R-value is listed in the table below. Keep in mind the following as you scrutinize the information:
- The Coefficient of Thermal Conductivity listed for AquaRise is 0.95 BTU/hr/sq2/oF/in. Note the “per inch”. The R-value is therefore 1.05 per inch. Let’s say the wall thickness is 1/8”, making the actual R-value, 0.13. By comparison, 1” of fibreglass pipe insulation would have an R-value of 4.3.
- There isn’t a referenced test method.
Thermal Conductivity
Compared to traditional metal materials, the thermal conductivity of thermoplastics is low, thus giving excellent insulating properties. Therefore, the potential for condensation forming on the pipe exterior is greatly reduced with AquaRise versus metallic piping. Conversely, most metal piping products require insulation to limit condensation. Should insulation be specified by the designer, the rigit nature of AquaRise allows for easy installation.
Note: To maximize system efficiency for hot water recirculation systems, it is recommended that AquaRise or any other pipe should be insulated.
Coefficients of Thermal Conductivity
| Material | BTU/hr/ft2/°F/in | W/m/°K |
| AquaRise | 0.95 | 0.137 |
| Carbon Steel | 360 | 51.922 |
| Aluminum | 1,000 | 144.23 |
| Copper | 2,700 | 389.42 |
ASHRAE 90.1
Table 6.8.3A Minimum Pipe Insulation Thickness – Heating and Hot Water Systems (Footnote “e”)
Table 6.8.3B Minimum Pipe Insulation Thickness – Cooling Systems (Footnote “d”)
Both footnotes say exactly the same thing: that an allowance for the non-steel insulating value of the piping wall thickness is permitted. Then there are very specific caveats, including that any consideration in this regard has to be documented (calculated) and approved by the consultant.
National Energy Code for Buildings (NECB) – 2015
Table 5.2.5.3. Minimum Thickness of Piping Insulation
The approach NECB takes is different from that of ASHRAE 90.1:
- There is no recognition of the claimed R-value put forward by the plastic pipe manufacturers. Therefore, the insulating value of plastic pipe is treated no differently than that of copper or steel.
- Uninsulated piping is permitted if the operating temperature is between 16 degrees C (61F) and 41 degrees C (106F) and the area the piping goes through is conditioned space. Conditioned space is a heated or cooled area suitable for human habitation. For example, if the conditioned space is at 22 degrees C (72F), the Delta-T isn’t great enough to justify the cost of insulating these lines. There is still heat loss, or gain, regardless. The consultant is obligated to weigh these facts and factor in the possibility of below ambient conditions. NECB reflects the minimum allowable approach.
I’ll conclude by asking a question: if the prevalence of uninsulated plastic piping is negatively impacting the mechanical insulation industry and goes against the energy conservation mantra, is there at least one person in the Canadian industry who can assemble the details in a science-based presentation and take this to the very people responsible for allowing uninsulated plastic piping to continue in the marketplace? ▪
