SAND AS INSULATION

This technical bulletin has been revised and the version on the screen is superseded by the new version found at Revised Sand as Insulation

ASHRAE 90.1-2010, Table 6.8.3A “Minimum Pipe Insulation Thickness Heating and Hot Water Systems” lists the required insulation conductivity for piping carrying hot water heating and domestic hot water systems. Some of the data from that table have been summarized below:

Fluid Temp. (°F)	Conductivity	Pipe or Tube Size
		<1	1 to <1½	1½ to <4	4 to <8	>8
141 °F – 200 °F	0.25 – 0.29	1.5	1.5	2.0	2.0	2.0
105 °F – 140 °F	0.22 – 0.28	1.0	1.0	1.5	1.5	1.5

For example, a 1-1/2″ pipe carrying 140oF domestic hot water would need to have an insulation with a K-Value of 0.22 – 0.28 with a minimum thickness of 1 1/2″.

For pipe buried underground the code allows a reduction in the amount of insulation by 1.5″, but not to thicknesses less than 1″.

Dry coarse grained sand may be used as a substitute for the insulation required by code in a buried pipe situation. The thermal conductivity, K, of coarse dry sand varies between 0.15 – 0.25 W/mK. Converting to Imperial units = 1.7 Btu.in/ft2.oF.hr. R-value is the reciprocal of conductivity therefore, the R-value of coarse dry sand = 0.58 ft2.oF.hr/Btu.in.

1 inch of fiberglass insulation with a conductivity of 0.27 has an R-value of 3.70. Conversely, 6″ of dry coarse sand has an R-value of 3.46; 12″ would have an R-value of 6.92.

In addition, some provisions need to be made to keep the insulating sand as dry as possible. Saturated sand has a thermal conductivity in the range of 2-4 W/m-K which causes the sand layer thickness to go astronomical. In areas where it is anticipated that the sand may become wet, provide a layer of 4-6 mil HDPE in the trench first, under the sand to wrap/enclose the sand after the pipe is laid.

Thus it can be shown that sand is a good replacement for fiberglass pipe insulation in underground, direct buried applications. It’s easier to install and costs less.