Efficient comfort with propane in-floor heat

Served by energy-efficient, propane-fueled boilers and 'combi' units, in-floor radiant heat is a cozy way to keep your homeowners warm and comfortable.

Sharon O'Malley
Staff Writer

Homeowners in cool climates are warming up to a heating system that works from the floor up.

In-floor radiant heating, still a niche product in home heating, is growing in popularity, notes Michael Willburn, president of Infloor Heating Systems, a radiant heating system supplier in Buena Vista, Colo., where forced-air heat is prevalent.

Still, Wilburn says, "When it comes to comfort, there's really no comparison between a radiant-floor home and a forced-air home. With radiant, you get a very even temperature."

Most often fueled by a propane or natural gas boiler, an in-floor radiant heating system combines underfloor tubing with heated water. Typically, the tubes, or loops, are embedded in a concrete slab, which retains the heat and radiates it up into the room.

<br>In an in-floor radiant heating system, tubes of hot water heat a concrete slab beneath the floor.

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<br>The heat exchanger in a modulating condensing boiler transfers heat to the water, which can be used in an in-floor radiant heating system.

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It distributes the heat evenly over the entire surface of the floor, warming everything in its path, including people and furniture, without creating cold spots in the room. Unlike a forced-air heating system, which typically warms the air near its ceiling-height registers more than anywhere else in the room, radiant energy transfers heat to people and objects upon contact.

That means air eight feet above the floor doesn't need heating, Wilburn says. "If your feet are warm and your head is warm, you stay warmer," he says. "We don't have to heat unlivable space. We heat where the homeowner lives, and that makes it a comfortable environment."

It also saves energy and lowers homeowners' heating bills. Because the entire floor surface evenly radiates heat, the room will feel warmer than with forced-air heat, even at a lower temperature. Plus, the boiler that fuels the in-floor system can operate at a lower temperature than it would for a forced-air or baseboard heater, explains Eric Ashley, product marketing supervisor for Navien, a manufacturer of boilers and water heaters. The U.S. Department of Energy estimates that radiant floor heating uses 15 to 20 percent less fuel than a forced hot-air system.

We don't have to heat unlivable space. We heat where the homeowner lives, and that makes it a comfortable environment.

And because an in-floor system can be zoned so every room or group of rooms can be controlled by a separate thermostat, homeowners save energy by directing more heat to the rooms they use the most often.

New propane and natural gas boilers, which can achieve efficiency levels of up to 98 percent annual fuel utilization efficiency (AFUE), deserve a lot of credit for the energy savings, notes Tracy Young, product management specialist for Rinnai, a manufacturer of water heaters and boilers. Indeed, manufacturers agree, although a gas-fueled in-floor heating loop costs more to install than an electric system, its operating cost will be lower for the life of the product, except in areas with unusually low electric rates.

System efficiency

Heating specialists and manufacturers urge contractors who install the systems to get the proper training, saying do-it-yourselfers and handymen should consult with a pro who has experience with installing in-floor radiant systems. The project requires a detailed pre-installation plan for placement and spacing of the tubing.

Other advice:

  • Consider pairing the in-floor system with a condensing modulating boiler for energy efficiencies of 93 percent or more. The propane or natural gas boiler extracts additional heat from combustion waste gas and automatically "modulates" the fuel output to adjust to the water temperature, so the indoor heat goes down when the outdoor temperature rises and up when it dips.
  • Another smart pairing: Connect a traditional boiler to an indirect tank so the home uses a single source to heat water for the in-floor system and water for drinking and bathing. Several manufacturers have elevated that pairing into a "combi" boiler, a single unit that passes water through at 180 degrees and heats water for domestic use and for the radiant heating system.
  • Consult with an engineer if the homeowner wants to retrofit a second- or third-story floor with in-floor radiant heat. Most in-floor systems are in an earth-level floor, but it is possible to suspend the tubing between the joists underneath an upstairs subfloor. Still, you will need to determine how much weight the floor can carry and what kind of insulation is needed.
  • While the price of an in-floor system has eased over the years, the up-front costs for the loops and installation are higher than for forced-air or baseboard heating. Explaining the energy-efficiency benefits of an in-floor hydronic system to homeowners can help them understand how it will lower their utility bills over the life of the system.
  • Choose a floor covering that will not prevent heat from radiating through it. Ceramic tile is a typical choice, but laminates, thin carpets, and wood can also work. Follow manufacturers' guidelines for using various flooring materials with the systems to ensure that the heat doesn't ruin the flooring product and that the flooring doesn't impede the heat.
  • In-floor radiant heat is touted as most cost-effective in cooler climates with long heating seasons. In warm regions where air conditioning is more prevalent than heat, the up-front costs might outweigh the system's benefits, manufacturers and contractors say.
  • The underfloor tubing can be used to cool a house, but it's not a common form of air conditioning.

Read more about radiant floor heating in these articles:

How a historical renovation revived a rustic ranch
Efficient comfort with propane in-floor heat
8 Propane Product Picks for 2013


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