Pros/Cons of insulating underground sked 80 PVC for chilled water

[rkessler]

My Church is debating whether or not to insulate the schedule 80 PVC underground piping that will replace an old run of iron piping. We are debating reducing the up front cost by omitting the insulation. I am interested in any info in the net R value loss between insulated and non insulated schedule 80 PVC pipe. Also perhaps some hard money numbers for approx 50 yards of supply and 50 yards of return piping. (Cost savings over 1 year between insulated and non-insulated). Figure avg earth temperature of approx 85 degrees. Thanks for any advice or opinions.

 

[CESSNA1]

RKESSLER: It depends on several factors, If the pipe is near the surface you may have warm soil. If you go down to near the frost line the soil the year round temperature is relatively constant. The estimation is fairly simple. Obtain the "R" value for the pipe, The chilled water temperature (usually around 40 deg F), and the soil temperature.
Obtain the wall area of the pipe =
3.141.59 * pipe outside circumference(ft) * length(ft)

Obtain the pipe wall thickness(inches)

Obtain the "R" (BTU-IN/hr-ft^2-DEG f) value for the
insulated and uninsulated pipe.

Estimate the temperature difference between the chilled
water and soil. Probably about 45 Deg F near the surface
and about 15 Deg F near the frost line.

Once the units are identical the calculation is

Q = R * Area * Temp Diff / t

Regards
Dave