Many of the Faith Communities that we visit during the Green Audit are in the market for a new boiler or furnace. We often come across gigantic mechanical beasts that suck up huge amounts of Natural Gas every heating season. In many cases, I am asked about geothermal and whether or not it would make sense in a given situation. I hope to shed some light on that question here.
First, the basics:
In a nutshell, geothermal systems, or ground source heat pumps, use the constant heat and cool from the earth, to heat and cool your home or building. It circulates a liquid (usually anti-freeze), through either closed vertical or horizontal loops in the ground, in order to extract the suns energy that is stored in the Earth. The liquid then runs through a compressor, very much like what your refrigerator has, to extract that energy for heating and cooling purposes. It is then distributed through your building via air ducts or radiant heat.
Basically, geothermal systems are highly efficient electrically powered HVAC units. They can be 4-5 times more efficient than electric heating and can be more than twice as efficient as a typical air conditioner. When combining the two, you are looking at big energy savings.
So why aren’t these systems used in every building across the continent?
- They are costly: While the hardware that sits in your basement is comparable in cost to a high efficiency gas furnace, the installation of the loop system can triple the installation costs over a conventional furnace.
- You need space: Horizontal loops are cheaper to install than vertical loops, and horizontal loops require more land. That is why in general, you see more geothermal units installed in the country. Consider that a 1 tonne heat pump unit requires about 1000 sq. ft. of land for its loops. A large house may require a 6 tonne unit and therefore require 6000 sq. ft. of land. So you can see how space can be an issue when considering a 20,000 sq. ft. building.
- Real-life performance: There seems to be an ongoing debate on how efficient the systems actually are and whether or not the advertised efficiency ratings actually reflect real-life performance. I won’t attempt to explain the issues here but you can read about it, and other concerns at the following link: http://www.greenbuildingadvisor.com/blogs/dept/musings/are-affordable-ground-source-heat-pumps-horizon
1. The price of electricity is projected to rise considerably in the coming years. You must factor this into the long term cost of operation.
2. Systems generally come with an auxiliary electric heating coil. This ensures that even on the coldest days or if your equipment malfunctions, your building will still have enough heat. If a system is undersized, or you have an extremely cold winter, then your electricity bill will sky rocket if this coil is used regularly.
3. Many units come with a domestic hot water assist. So if you use a lot of domestic hot water, the unit can supplement the energy required for this purpose.
4. In terms of GHG emissions, what is the electricity mix in your province? Quebec, BC and Manitoba rely mostly on hydro power, so converting to geothermal would makes sense in terms of lowering your carbon footprint. But it would not make as much sense in Alberta, Nova Scotia or Saskatchewan, where fossil fuels are used extensively to produce electricity.
Province GHG/kWh (kg)
New Brunswick 0.46
Nova Scotia 0.79
Will it work for your faith community?
If you have a small rural faith building, then I would say yes, it is worth it to look into it. If you have a larger building, or are located in the city, then it is unlikely that the installation costs and annual savings will beat that of a more conventional high efficiency NG system.
– David Patterson