Geothermal heating and cooling is possible through the use of heat pump technology. Heat pumps move heat from one location to another. Examples of heat pumps include:
- Air conditioning condensers
- Portable and window air conditioners
- Air source heat pumps
- Heat pump or hybrid water heaters
- Pool heaters
Heat pumps are not a new technology. Although relatively unknown, geothermal heat pumps have been used for building heating and cooling since the 1940s. In fact, one of the nation’s most documented geothermal system is located in Winchester, Massachusetts.
Our YouTube channel is chock-full of information about geothermal heating and cooling in New England. Our Geothermal 101 video is a great place to start!
How long does it take to install a geothermal system?
Retrofits can be expected to take 6 to 8 weeks from start to finish. Installations in new construction typically take longer due to the coordination and scheduling with other contractors. Each stage of a geothermal installation can be expected to take the following lengths of time:
- Permitting and Design – 2 to 3 Weeks
- Drilling – 3 to 5 Days
- Trenching Between Boring and House – 1 to 2 Days
- Piping Connections – 2 to 5 Days
- Duct Modification or Installation – 1 to 2 Weeks
- Electrical Connections – 2 to 3 Days
- Thermostat Set-up, Zoning Control Programming and Start-up – 1 Day
How is a geothermal ground loop installed?
Although EnergySmart Alternatives has experience installing horizontal ground loops, almost all of our installations are vertical closed loop systems.
There is a common misconception that horizontal trenching is always the cheapest method of installation. In New England, where bedrock is close to the ground surface and there are many rocks (and boulders!), trenching can be difficult and unpredictable. In ideal situations, an experienced excavator can trench 100 to 150 feet per day. The time required to excavate can easily be doubled when difficult conditions arise. If a lot of rocks are present, it may be necessary to line the trench with sand or clean soil in order to protect the pipe from abrasion. Although we take great care to compact the soil after back-filling the trenches, there can be significant settling of the area over time.
Vertical drilling is very predictable. Bedrock (ledge) is not a problem – it is actually preferable for its heat transfer properties. The drill rig is the same equipment that is utilized to install drinking water or irrigation wells. An experienced driller will be able to drill 200 to 300 feet per day or more. The borings are finished three to four feet below the ground surface so there is no evidence of the boring once the area is back-filled. There is no visible well head. Our on-line photo albums have a lot of great pictures showing the drilling equipment used for vertical drilling.
To see how the pipe is installed into a vertical boring, please see our video from a geothermal installation in Winchester, MA.
Do I need a backup heating system?
No! A properly designed geothermal system will provide all of your heating and cooling needs. There is no need to have fossil fuels for heating whatsoever. In many cases, our clients prefer to remove their fuel oil tanks, boilers and/or furnaces. Imagine finally being rid of unsightly tanks and condensers!
How do geothermal heat pumps work?
Geothermal heating and cooling takes advantage of the constant temperature of the earth. In the summer, heat is extracted from the building and is discharged into the ground. In the winter, heat is extracted from the ground and discharged into the building. The heat is concentrated through the use of a heat pump. Unlike air source heat pumps that work against highly variable air temperatures, geothermal heat pumps both heat and cool using a constant earth temperature.
In New England, the ground temperature is approximately 55 F degrees year round at depths greater than 10 feet below the surface. Typically, for vertical geothermal installations, the borings are 300 to 600 feet deep. For horizontal installations, the trenches are 6 to 8 feet deep and hundreds of feet long. Even in horizontal installations, the ground temperature at this shallower depth offers enough stability to adequately heat and cool your home year-round.
Heat pumps can also be used in other applications to move heat from one location to another. For example, many industrial processing or manufacturing facilities have excess heat in one area that is discharged outdoors while other areas of the building will utilize fossil fuels for heat. Through the use of heat pumps, heat can be moved from one location to another thus minimizing the utilization of fossil fuels for heating. Excess heat in one location can be moved to heat another room or building or can be used to produce hot water for process wash water or snow melting.
The table below demonstrates the temperature differences that an air source heat pump and a geothermal heat pump must overcome. Although both technologies are technically heat pumps, the geothermal system experiences a much smaller temperature difference (delta T) than the air source heat pump. The geothermal system, in effect, has less work to do to achieve the desired indoor air temperature than the air source system.
What do geothermal pumps look like?
There are three main types of geothermal heat pumps:
Package Geothermal Units
Package units, or water-to-air geothermal heat pumps, are not unlike traditional forced hot air furnaces. The compressor is in the bottom of the cabinet and the air handler is on top. The duct work is attached to the cabinet similar to a traditional forced air system.
Split Geothermal Units
Split units work in a similar fashion to package units except that the cabinet is split into two components: 1) the compressor and 2) the air handler. They are connected to each other with a refrigerant line that is run from the heat pump location to the location of the air handler. These types of systems are usually used when it is not possible to get duct work from the basement up to the attic. We install these often in 2 and 3 story homes.
The photo depicts a package unit on the left and a split unit on the right. Above the split unit is an energy recovery ventilator. Please visit our Facebook page to see more photos of a geothermal package unit and a split unit that were installed in the same house. Our YouTube Channel also has a video of geothermal heat pump installation with a package and a split unit.
Hydronic Geothermal Units
Hydronic units, or water-to-water geothermal heat pumps, can behave as a boiler in the winter and as a chiller in the summer. Hydronic units look similar to split units and usually have one or two water storage tanks connected to them. These storage tanks, that have a volume of 85 gallons to 120 gallons are used to hold water that is pumped to air handlers that are located elsewhere in the building. In the winter, these tanks hold hot water at a temperature usually between 110F and 125F. In the summer, they hold water at temperatures usually between 45F and 65F.
Geothermal in New Construction
Construction is the ideal time to install a geothermal system for the following reasons:
- The 30% federal tax credit can be applied to the installation.
- With the available credits, the installation can sometimes be cheaper than high-efficiency ‘conventional’ heating and cooling systems. If more expensive, the incremental price difference pays for itself in only a few years.
- Landscape repair is not an issue since landscaping is usually done when construction is complete.
- Eliminate the need to install a gas line, oil tank or propane tanks for heating.
Watch this video to learn a little about a new construction project that we completed in Lexington, Massachusetts.
Please also check out our many photo albums to see many more examples of geothermal systems we have installed at new construction projects.
What are the Benefits of Switching to Geothermal?
Geothermal systems pay for themselves
- A rapid return on investment (ROI) can be expected.
- When financed, positive cash flow can be realized immediately. Operating costs plus the loan payments can be less than what you were paying for oil, gas, or propane.
- No more oil, gas, or propane bills for heating.
- In areas without natural gas service, installing a geothermal system can be cheaper than bringing gas service to the house.
Geothermal systems improve indoor air quality
- No carbon monoxide risk because there is no combustion.
- Fossil fuels are eliminated for heating. Gas and oil vapors are gone.
- Superior dehumidification during air conditioning season.
- Humidification can be added for dry winter months.
- High-grade and hospital-grade filtration systems available for those with pets, allergies, or health issues.
- Energy recovery ventilators can be integrated to conserve energy while providing fresh air.
Geothermal systems are good for the environment
- No more burning of fossil fuels for heating.
- Reduce your home’s carbon footprint by 30% to 50%.
- Eliminate the risk of an oil spill on your property.
- Minimize your contribution to the urban heat island effect by dissipating heat deep below the ground surface in the summer.
- Reduce vehicular traffic as a result of less oil deliveries to your neighborhood.
- Can be integrated with other renewable technologies like solar PV panels or solar hot water collectors.
Geothermal can improve your lifestyle
- Gain financial freedom by eliminating fossil fuel price volatility from your life.
- Be more comfortable more often by maintaining a constant temperature in your home year round. Goodbye 10 degree setbacks!
- Pay one less bill. Heating is now on your electricity bill.
- Service and maintain only one piece of equipment. One unit does both heating and cooling.
- Brag to your friends about how low your heating bill is with your new state of the art geothermal system.
- Geothermal is the only cost effective alternative to oil or propane when gas service is not available.
- Reclaim your backyard by disconnecting and removing your noisy outdoor air conditioner.
- Have better control over your home by using programmable thermostats and integrating with home automation.