Horizontal loops are popular for a few reasons:
They are generally considered to be cheaper to install. This is not necessarily true.
Their performance is considered to be just as good as vertical boreholes. Wrong.
They can be squished closer together as in slinky loops. Dead wrong.
They can be economically installed at the time of construction since an excavator is already there. A maybe.
Drawbacks to Horizontal Loops:
Horizontal loops are always installed in the overburden layer of your
soil/property. This means the thermal conductivity of the soil ranges
from barely ok to abysmal. See the chart below.
rock and dirt TC chart
We see from this chart that an average sand/clay/whatever horizontal overburden has a TC value of 0.5 whereas rock has a value of 1.5 to 2. This simple arithmetic alone should pretty much discredit anyone doing horizontal loops.
Any horizontal loop shallower than 20 ft still shows a seasonal swing whereas a borehole never does.
And here comes the last straw for cooling dominant systems… the heat dumped into a cooling dominant loop causes the soil to dry out and lose most all TC it may have had (unless you made provisions to irrigate it). I have measured cooling loops at 123 deg F !!! A heating dominant loop on the other hand, sucking heat out of the ground, actually attracts moisture.
Horizontal Loops require a lot more space than you realize.
Regardless of what someone may claim, the laws of physics still supercede advertising claims. A responsibly designed horizontal loop actually requires approx twice the square footage of the home. I recently consulted on a project where the contractor for a 70 ton system for a 26,000 sq ft home decided to pile slinky loops on top of slinky loops in a deep pit. It should have been spread out over more than 2 acres.
Ever think of subdividing your property with a geo loop spread all over it?
Vertical Loops
Boreholes can be more versatile than commonly thought. 10 years ago TheGeoGuy installed a 5+ ton system for a 5,200 sq ft home with a single 600 ft borehole using double U-tubes in the driveway right next to the mech room. A very tidy low cost installation. Maximizing the value of a borehole (on top of the TC improvement) is where the savings in vertical loops occur.
1 hole maintaining 40 deg F loop temp for 10 years! That’s the way to save.
