#BeTheChange: Residential Geothermal Heating & Cooling SystemsView Profile
Construction of a new home or cottage on an empty lot is akin to starting a new painting with a blank canvas. We are fully immersed in this process with a new build and there are hundreds of decisions to make from paint colors, selection of cabinet knobs to the choice of a heating and cooling system. It is also an opportunity to be impactful in a meaningful way.
Conventional home heating systems typically include natural gas, propane, or electricity (some places still use coal or heating oil). These conventional systems are hydrocarbon based and cheap from an installation and operating basis but a drag on our planet. There are other options out there, one of which is a geothermal based system.
The word “geothermal” is a combination of two Greek words, Geo and thermal, which means the “Earth” and “heat,” respectively. Therefore, geothermal energy is the energy that comes from the constant and higher temperatures within the Earth’s core. As our cave-dwelling ancestors discovered long ago, if you go far enough underground, the Earth’s temperature stays at a constant 6 to 11°C below the frost line, regardless of air temperature. These systems can make use of that constant temperature year-round, no matter how hot or cold it gets outside.
Geothermal energy can be used for heating and cooling in modern residential homes. There are three types of heating and cooling systems currently in use: vertical closed loop systems, horizontal closed loop systems and open loop systems. Each type operates by basic refrigeration principles.
In a vertical closed loop system, refrigerant and water are pumped through pipes drilled into the earth. On the way, the liquid in the pipe is either heated or cooled by the earth (depending on the season). It is then compressed by the heat pump once inside the home. This compression raises the temperature to whatever indoor temperature the home is set to.
Vertical closed loop systems are the most common type of geothermal exchange system. Horizontal closed loop systems run that same refrigerant through pipes buried horizontally in a grid. These are typically laid 6 to 10 feet underground. That requires a sizeable amount of space (at least 5000 ft. sq.). If you have the space, horizontal ground loops are generally more cost-effective since you don’t need a drilling rig to install them.
The major benefits of residential geothermal systems can be summarized as:
- They can act as furnaces or air conditioners and can pre-heat a hot water tank all as one system.
- They’re responsible for fewer greenhouse gas emissions than more traditional sources of heating and cooling.
- Since geothermal exchange systems transfer, rather than generate, heat, they’ll always be more efficient than traditional fossil-fuel burning systems.
- In addition to being efficient, geothermal systems also have the advantage of being very long-lived. Heat pumps have an average life span of 25 years, while the ground loop systems typically last over 50 years.
- Once installed, they’re very inexpensive to run since you are only operating a heat pump and compressor (no furnace burning fuel and no separate air conditioning unit sucking electricity).
So why don’t more people install geothermal systems? The simple answer is installation cost. The cost of installing the pipes by excavating to place horizontal pipes or drilling to place vertical pipes can easily reach $20,000 – $30,000. There will eventually be a return from reduced operating costs but the timeline for this can be 20 years or more (though costs of propane have recently risen ~300%).
But there are times when you should just do it anyway!
Considering that our building lot has bedrock at the surface, our only feasible choice was a vertical loop system which added even more to the cost for drilling in rock. To calculate the proper length of pipe needed, we engaged a mechanical engineering specialist to prepare heat / loss calculations based on our plans. The result was the need for 4 x 150-foot-deep holes and at least a 3.5-ton ground source heat pump unit.
The build is in progress and the holes have been drilled. During drilling, they encountered a void at the 50-foot depth and subsequently had to change their plans and place 13 x 45-foot-deep holes. The result is the same length of pipe in contact with the earth.
We are excited about the completion of our venture later this summer and doing our little bit for our precious planet. There are still more decisions to make…is wind or solar power an option? How many planter boxes can we fit? Do we go with an electric sauna or wood burning? Wood burning of course! More sustainable and better-quality steam/heat.
At RVA, we believe that climate action not only relies on what our organization does, but on the individual choices we make each and every day. Our #BeTheChange stories seek to inform, challenge, and inspire people to learn about the impacts of climate change, and empower them to take make responsible choices at home and at work. By increasing climate literacy and promoting a culture of sustainability within our firm and beyond, we can help drive collective action at the scale required to facilitate the transition to a low-carbon future.