Jordan Garrow is getting ready to build a new house in New York State, on the cusp between Climate Zones 5 and 6, and he’s planning to heat and cool it with a ground-source heat pump. His contractor wants to install a horizontal “slinky loop” heat exchanger, one of several possible options, and Garrow is seeking a second opinion.
A heat load calculation for the house specifies a 4-ton system (one with a capacity of 48,000 Btu/hour), but the contractor wants the heat exchange loops designed as if they were serving a 6-ton system.
“His plan is to do a 6-ton horizontal slinky loop field with a 4-ton heat pump,” Garrow writes in Q&A post at GreenBuildingAdvisor. “He claims that an oversized slinky loop field performs the best. However, I’ve heard bad things about slinky loops, and slinky is the only kind of loop they do.”
It doesn’t seem either efficient or cost-effective to overbuild the field, since that represents a major part of the system’s cost. He’s sought another quote for a horizontal loop using straight lines, as well as a vertical closed-loop heat exchanger, which would be placed in a well. But the local geology is something of a concern.
“I’m worried about the vertical [method] since there is a lot of shale in my area,” he adds, “and I’m not sure how deep the wells could go.”
As a point of reference, the 2,500-square-foot house will have 2×6 walls with fiberglass batt insulation plus R-10 of rigid foam insulation installed over that. In the attic, he’s planning on 18 inches of blown-in cellulose.
How should Garrow proceed? That’s the topic for this Q&A Spotlight.
Oversized slinky option may not be a bad idea
The contractor may have a…