Pipe insulation is an inexpensive, energy-saving measure

In conducting energy audits of greenhouse operations, I’ve frequently observed uninsulated hot-water system piping.

These are in areas where heat is not needed or where better heat control could be obtained if piping was insulated. It’s surprising how much heat an uninsulated pipe gives off.

I know one grower with two large boilers heating a gutter-connected greenhouse. He told me that before insulating the supply/return pipes in his boiler room, he frequently had to leave the windows and doors open or it would get too hot in the room to work. Once the pipes were insulated, extra heat had to be added to the room to make it comfortable.

Heat loss from pipes depends on several factors, including the diameter and length of the pipe, the water temperature inside the pipe, the air temperature surrounding the pipe and the length of time the pipe is carrying hot water. Adding insulation slows the heat loss and lowers the fuel bill.

Estimating your savings
Table 1 provides the approximate annual savings from insulating a linear foot of different diameter pipe with 1-inch of fiberglass or foam. It assumes 2,000 hours of annual use, typical of a greenhouse heating system in a northern climate.

To use the table, select a pipe diameter and multiply the length of pipe by the savings given in the table. For example, a grower can save $372 a year by insulating 100 feet of 2-inch diameter heating system pipe carrying 180°F water if the boiler is fired with natural gas costing $1.05 per therm. The savings from the pipe insulation = 100 feet × $3.72 per linear foot = $372.

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Insulation installation
The time it takes to install pipe insulation depends on the material and access to put it on. Average time varies between 250 feet per day for smaller size pipe to 80 feet per day for larger size pipe.