When Jomol and her husband Saiju decided to build their dream home in Lexington, MA, fossil fuel heating was out of the question. They contacted several geothermal contractors before deciding on EnergySmart Alternatives, located only a few miles away. We met with their builder in July 2011 do discuss the components of a geothermal heating and cooling system and to see how we might fit into the construction team. When construction began in the fall, we began the permitting and design process, electing for a closed loop vertical boring system connected to two geothermal heat pumps.
We found this new home to be an ideal candidate for geothermal because:
- The homeowners are eligible for the 30% Federal Tax Credit for the geothermal installation.
- Many components of the geothermal system are similar to those required for a conventional heating and cooling system. These components would have been needed anyway, making the geothermal system nominally more expensive than the conventional system.
- The installation of all underground structures was done at the same time, minimizing risk of damage to the geothermal ground loop, electrical, water, cable or sewer lines.
Drilling consisted of two 6 inch diameter borings – one for each heat pump. Pipes were installed into each of the borings and sealed in place with geothermal grout. Four pipes were brought into the mechanical room through 2.5-inch cores through the concrete foundation approximately 4-feet below finished grade. Two 1.25” diameter pipes were connected to each geothermal heat pump.
The geothermal heat pump system takes the place of a fossil fuel furnace and outdoor air conditioning condensers. Any ductwork in unconditioned space was sealed and insulated according to the Stretch Code.
The geothermal hot-water assist feature has been activated to pre-heat water before it enters the gas on-demand water heater. It is estimated that this feature will produce approximately 50% of the family’s hot water needs over the course of one year.
A zoning controller was provided such that the basement can be zoned separately from the main floor. Three programmable EnergyStar heat pump thermostats with LED displays will control temperature on three floors, plus the basement. A power meter has been provided to monitor electricity use by the geothermal heat pumps in real time. An energy recovery ventilator (ERV) was integrated with the ductwork to bring fresh air into the home with minimal energy loss.
Benefits to installing a geothermal system in new construction:
- Nominally more expensive than installing a conventional heating and cooling system with similar features when taking into account the expected lifespan of the system and the available incentives;
- Same piece of equipment provides heating and cooling;
- Hot water-assist feature provides 50% of hot water needs for very little cost;
- Highly efficient heating and cooling;
- No combustion for heating thus eliminating carbon monoxide risk;
- Adjustable fan speed allows for superior dehumidification in the summer