What is the best heating and cooling system for your home?
Comparing ground source, air source and dual energy.
In Wilden we have tested all of these systems either in our townhomes or the homes we built for research. We have collected data on energy efficiency, cost recovery and carbon footprint over many years. Homeowners in Wilden have given us an abundance of feedback. There is no one-system-fits-all solution, but there are findings that will help with your decision process.
Lessons learned from the largest geothermal community in British Columbia
In the early 2000s Wilden started a partnership with Kelowna’s geothermal contractor GeoTility. In collaboration they founded TerraSource which offered geothermal heating and cooling for a monthly “loop fee”. Home owners were able to access ground source heating without having to invest in the drilling upfront. Hundreds of homes were provided with this service, which turned Wilden into the largest geothermal community in British Columbia.
Ground source heat pumps are recognised throughout the world as the most energy efficient heating and cooling system. They show an efficiency of 300-500%, which means the energy put into the system is tripled, quadrupled or even quintupled by the output. As a comparison, a conventional gas furnace is only 98% efficient, hardly putting out the energy that it uses. Geothermal systems are also the quietest mechanical system available. On the downside: the initial investment into drilling and equipment is high compared to a gas furnace or air source heat pump.
Despite its high performance, “Geo” became increasingly unpopular from the year 2011, when the cost for electricity began to climb and the cost for gas dropped drastically. The power bills for running the pumps through the winter were very high. In 2018 the gap maxed out, gas was at its lowest and electricity at its highest rate.
Meanwhile in Wilden, most of the homes that had been built with geothermal systems had been re-sold. The new owners were frustrated with the operating cost. Many of them made their frustration public on the “Neighbours of Wilden” Facebook group. Some home owners switched to a gas furnace. Only those residents with strong environmental motivation remained determined to stick with the renewable energy source from the ground.
After 2018, with gas prices coming back up and carbon tax taking its influence, rates evened out. Today both rates, electricity and gas, are equally high, and it is more important than ever to save energy.
Thinking Envelope First
Over the years we learned, that the essential ingredient for energy efficiency in a home is not the HVAC system, it is the home envelope. Each dollar spent on airtight, well-insulated walls, basement, roof and windows pays back in energy savings faster than any mechanical system ever could. Your heat pump can be downsized and you will need much less power to maintain a comfortable temperature in your living space.
Getting your air exchange per hour (ACH) down to 1 instead of the currently required 2.5 can save you up to 60% of mechanical energy, because the heat or cold generated will not escape through the shell as easily.
For those who have bought a house with a geothermal heat pump and are not happy about the operating cost, there are two things to consider: Always look at the whole year when checking your power bills. Geo uses very little energy to cool your space in summer. Also, before putting your money into a gas furnace, double check if you could upgrade your windows, roof or walls instead. It is a given that gas prices will not come down.
Dual or Single Energy Source?
Still, even with the best envelope, heating and cooling are expensive and they are carbon emitters. They should be planned diligently.
When we build townhomes in Wilden, the main factor when deciding which type of heat pump to use is how much space we have around the units. For duplex units we typically go with an air source heat pump, which sits outside the house and uses the outside temperature for heating and cooling. Since the energy use of this type of heat pump can get intense when the temperature is below zero, a gas furnace is installed as a back-up.
This dual energy system has become very popular among our residents, because it keeps them independent from one single energy source. Those who are conscious about their carbon footprint choose Renewable Natural Gas for the back-up, a certified carbon-neutral energy source provided by FortisBC through the gas lines.
When we are working with fourplex buildings or even denser developments, we go geothermal. Since it is so efficient and our building envelopes surpass the current code requirements, we do not need a gas backup for heating to be affordable. Being independent from fossil fuels also aligns with our goal to keep new development carbon neutral going forward.
For those building a new home in Wilden, please talk to your Wilden builder about your energy efficiency goals and tap into their expertise. Also, please follow the Wilden Living Lab, our research and learning project for sustainable home building.
Wilden is the largest master-planned community in the Okanagan Valley, located only ten minutes north of downtown Kelowna.
The roughly 1,500 acres are developed by a local family who’s primary goal is to promote sustainability and carbon neutrality in residential living.