If Justin Isaacson had a nickel for every time he encountered a mechanical room that was too small for the heating and water-heating equipment, he’d be a rich man.

That’s one reason Isaacson has become a big fan of propane-fueled combi boilers. These innovative systems can provide both space heating and nonstop domestic hot water for a home in one small, wall-mounted piece of equipment, replacing two systems that would typically take up much more space. And they also happen to be one of the most energy-efficient and adaptable heating options on the market.

In our latest Tech & Trend video, Isaacson, owner of Ike’s Heating & Cooling in Nevis, Minnesota, explains why combi boilers are an ideal fit in both new-construction and oil-replacement scenarios. Check out the video below, and read on to see how technology innovations are making combi boilers more reliable than ever.

Combi boiler size and efficiency

From a builder or mechanical contractor’s perspective, a combi boiler has a small footprint and dual-purpose functionality that makes it ideal for projects with space constraints. “Typically with these homes, the mechanical room is just a small fraction of the home,” says Isaacson, who works on residential and commercial buildings throughout a region filled with rustic, lakeside vacation homes.

At about 14 inches wide, 2 feet tall, and 80 pounds, combi boilers can be neatly tucked away to free up space for other equipment. And they can be vented with a two-pipe, sealed-combustion system using affordable PVC venting, venting either vertically or horizontally through a side wall.

But while the combi boiler’s compact design is appealing, it’s the energy efficiency and endless supply of hot water that homeowners typically find most appealing, Isaacson says. “When I explain to my clients that they’re going to have an endless supply of hot water, they kind of look at me with surprise,” he says. “‘How is that even possible?’” Some of his clients with large vacation homes might have 10 or 12 people in the house at a time. “And everybody wants to take a shower,” he says.

Like tankless water heaters, combi boilers heat water on demand when the flow switch is activated, so they don’t have to keep a tank of water hot like a conventional water heater. They’re also condensing, which means they can achieve efficiency levels of 95 percent by extracting additional heat energy out of the flue gas. And in a remote, rural region with limited access to natural gas, propane-fueled water heating is a more cost-effective option than going with electricity. “With the general service rate for the electricity, you’re going to be paying quite a bit more to produce that hot water,” Isaacson says.

Combi boilers with geothermal

For a new home project on Leech Lake in Minnesota, Justin Isaacson, owner of Ike’s Heating & Cooling, specified a heating system that includes both geothermal heating and a propane combi boiler.

As an expert in geothermal/propane hybrid heating systems, Isaacson also appreciates combi boilers’ adaptability to a range of heating systems. For a project under construction on Minnesota’s Leech Lake, for instance, Isaacson specified a propane-fueled combi boiler that can kick in when the geothermal system can’t keep up with the heat load of the building or in the event of load management from the power utility.

“They’re so versatile that we can use them for in-floor heat, we can use them for hot-water baseboard heat, we can use them for a fan coil that is in an air handler,” Isaacson says. “So they’re very adaptable.” Using outdoor reset, the units can modulate the hot-water temperature to achieve the greatest efficiency for the building’s heating needs.

Replacing heating oil

Isaacson is also seeing propane combi boilers as a popular replacement option for systems fueled by heating oil.

“A lot of homes in this area, in Walker in particular, have fuel-oil furnaces and hot-water heaters,” Isaacson says. “The fuel-oil efficiency at best is 80 percent, and they’re very dirty. It’s very maintenance-intensive.” To avoid rapidly declining efficiency or equipment failures, homeowners with oil equipment need to perform annual maintenance. Propane, he says, is much cleaner. “The efficiency and maintenance required is minimal compared to the oil alternative.”

That’s especially true in modern propane combi boilers, which use a heated solution containing water, antifreeze, and a corrosion inhibitor in a sealed circuit for space heating. The domestic hot water is then indirectly heated in the heat exchanger. The setup avoids the sediment and calcification buildup on the heat exchanger typically associated with on-demand water heaters.

Many of Isaacson’s projects include multiple types of heating, all of which a propane combi boiler can accommodate. With its energy efficiency, space savings, and adaptability, it’s become an invaluable component in Isaacson’s diverse array of projects.