What is a closed loop system?

A closed loop system uses a continuous loop of buried polyethylene pipe. The pipe is connected to the indoor heat pump to form a sealed underground loop through which an environmentally friendly antifreeze-and-water solution is circulated. A closed loop system constantly recirculates its heat-transferring solution in pressurized pipe, unlike an open loop system that consumes water from a well. Most closed loops are trenched horizontally in areas adjacent to the building. However, where adequate land is not available, loops are vertically bored. Any area near a home or business with appropriate soil conditions and adequate square footage will work.