For the HVAC system in their lakeside Minnesota dream home, Justin Isaacson’s clients had straightforward goals: the best comfort, the best efficiency, and the best overall bang for their buck.
Isaacson, owner of Ike’s Heating and Cooling in Nevis, Minnesota, knew one solution could meet all three of those goals because it’s a system he specializes in designing and installing. The 8,000-square-foot home uses hybrid heating anchored by geothermal and a propane furnace and boiler. “This system is going to provide comfort and efficiency that would be unparalleled by any other system,” Isaacson says. “It will be year-round comfort.”
In our latest round of Tech & Trend videos, Isaacson describes why geothermal and propane hybrid systems are a smart choice to enhance comfort and energy efficiency, especially in climates with temperature extremes such as Minnesota. And he offers perspective on how to optimize the design and installation of these systems to achieve your client’s goals. Check out the videos below, and read on to see why Isaacson’s heating installations almost never go all-electric.
Hybrid heating with geothermal and propane
Geothermal heating and cooling are growing in popularity in Isaacson’s northern Minnesota market, with about 50 percent of his clients installing ground-source heat pumps. The growth is driven by federal tax credits and rebates from local power companies, as well as homeowners’ desire to lower their energy consumption and carbon footprint. Geothermal systems use underground loops to transfer heat to or from the ground, improving their efficiency.
But like all heat pumps, geothermal systems are more efficient at milder temperatures. “Probably the greatest downfall of geothermal would be the fact that in the extreme cold, it is going to have trouble keeping up with the heat loss from the building,” Isaacson says. And in his climate, the temperatures can drop as low as 65 degrees below 0 Fahrenheit. “And so that’s where the propane system comes in well, to complement the geo,” he says.
At his project on the south side of Leech Lake near Walker, Minnesota, for instance, the heating system includes a water-to-water geothermal system, a propane furnace, and a propane combi boiler. The geothermal system and boiler charge a buffer tank and distribute heated or chilled solution to different zones around the house as they call for heat or cooling. The propane furnace kicks in if the geothermal system goes down or can’t keep up with the heat demand. It also qualifies the home for a dual-fuel discount from the electric utility. The entire hybrid system, including the propane units, is eligible for a 30 percent federal tax credit.
The supplemental propane systems are critical not only for comfort but for the overall cost of the geothermal system, which Isaacson can size smaller knowing he doesn’t need it to meet peak heating demands. “If we were to design that geothermal system to meet the 95-degree design temperature or even further a 100 or 125 degrees, which sometimes that design temperature reaches that amount in Minnesota, you would have such a large geothermal system that it would basically cost itself out of the installation,” Isaacson says. “I mean, it wouldn’t be feasible. So not only the amount of wells that have to be put into the ground but also the size and tonnage of the geo unit would just be ridiculous.”
With a more sensibly sized geothermal unit, clients can achieve a faster return on investment, as well as higher levels of comfort when the propane systems kick in. “The propane furnace is going to have a delta-T or change in temperature about double of what the geothermal heat pump would be,” Isaacson says. “So the air blowing on your skin instead of being 95 degrees will be 130 degrees, which is going to feel much more comfortable.”
Balancing hybrid heating for comfort and efficiency
In addition to using propane furnaces and boilers in hybrid heating systems, experienced pros can tune their installations to optimize homeowner comfort. Isaacson uses several characteristics to dictate when the supplemental propane heat kicks in. One is to simply set it to come on when the outside air reaches a set temperature. A second is when the power utility has a period of peak demand, requiring homes with dual-fuel electrical rates to shed the load of their geothermal system and switch to propane. A third is run time: When the geothermal has been running for a preset period, perhaps 30 or 120 minutes, the system defaults to the gas furnace or boiler.
The latter point is a smart solution in vacation homes, where an owner might keep their Wi-Fi thermostat set at 60 degrees during the week and then dial it up to 70 when they’re driving up for the weekend. “That geothermal isn’t meant to recover several degrees,” Isaacson says. “That’s where the propane is going to kick in and bring it up to temperature and get the people the comfort they desire.”
Isaacson also uses zoned systems to optimize comfort and efficiency. Zoned controls allow the owners to keep less-used spaces at a lower temperature to conserve energy while keeping occupied spaces at a more comfortable setting. Hydronic systems, such as the one he installed on the Leech Lake project, can be zoned more easily than forced-air systems, he says. Each zone has a thermostat that communicates with the main control unit when it has a call for heat or cooling. The system’s buffer tank is charged by the propane boiler and geothermal system to maintain the necessary water temperature.
The northern Minnesota market is filled with trees, lakes, and beautiful rolling countryside, making it a huge draw for clients to build their retirement dream homes. But the remote area has no access to natural gas, making propane a vital energy source. Going all-electric, Isaacson says, simply wouldn’t be feasible.
“A house this size would consume copious amounts of electricity to maintain the building temperature,” he says. “And then also the kilowatt per-hour rate would actually be so exorbitant that it wouldn’t be feasible to heat a home this size. I mean, it would be thousands of dollars a month versus hundreds of dollars a month to heat a home like this using electricity only.”
So it’s little surprise that 95 percent of Isaacson’s projects include some form of propane heating. With comfort, efficiency, and economics in his favor, it’s only natural he’s become a trusted area expert on optimizing home heating with hybrid propane and geothermal systems.