Flooring Trends: Hydronic Radiant Floor Heating
Radiant heating has been around for centuries, but today’s modern applications have a much more involved design and installation process which can be more expensive for the client upfront, says Scott Menzie, owner of Air Craft Heating and Air Conditioning in Boulder County, Colo.
Kevin Gerrity, owner of Solutions Heating, Radiant and Plumbing Inc., in Sandwich, Mass., adds that when a contractor is unsure about a product, it can be harder to sell. However, once a contractor understands the inner workings of a radiant floor system, the benefits will outweigh the complexities, and the system can add substantial value to a home.
According to Menzie, the process begins when either a boiler or a geothermal system heats water that is then pumped through tubing underneath the floor’s surface. The heat generated from the hot water will then rise and warm the floor above.
There are three different ways to install hydronic radiant floor systems. While each method may go by a different name depending on a contractor’s training, the process is the same.
- A Dry Below (dry meaning without concrete slurry) has tubing installed underneath the subfloor from the room below. Metal plates are then installed as the tubing goes in. Before a subcontractor finishes the drywall from the lower room, enough insulation must be placed below the tubing to prevent heat from escaping.
- In Dry Above, the tubing is installed directly at the subfloor. The tubing is fit into place through recessed plywood forms, and remains below the floor level.
- Both experts agree the most efficient method is Infloor Radiant. The tubing is installed above the subfloor with gypsum concrete poured over it, making the tubing part of the floor. The flooring material is then placed on top.
“[Infloor radiant] gains efficiency because you can use a lower water temperature since there aren’t as many layers to go through,” Menzie says. In addition, he says that this method also produces an even surface temperature and a larger thermal mass because it is set in concrete.
Conveniently, radiant floor heating works with any type of flooring material, but Menzie says solid surfaces produce a better heat transfer. Regardless of the flooring material you choose, it is imperative to have the right amount of insulation underneath the tubing.
“The key is to have at least three times as much insulation below the radiant tubing as you have above it, so heat will go up rather than down,” Menzie says.
In order to implement a radiant floor heating system, contractors must first consider the home’s design and solar gain potential because they can affect the process, says Gerrity. These factors can then decipher the complexity of the design.
“We look at the structure of the home—how it was built, the insulation and how its built to prevent heat load or loss,” he says. His company employs the use of software to help calculate heat loss. “We design systems around those calculations, and they tell us how much energy we will need to heat the home on the coldest day of the year.”
The next step is to talk to your customer about what they want out of their heating system, how they will be using each room and how warm they want their home when it’s 10 degrees outside—so you can design the system accordingly.
Most systems are installed basic, with one thermostat to control an entire floor. Since it doesn’t factor solar gain, if one room on the floor is sunny then the rest of the floor goes cool. When the sun goes down, the radiant flooring can take six to eight hours to kick in.
“Radiant flooring isn’t hot all the time, unless you design it that way,” Gerrity says. He recommends separating parts or rooms of the home into “zones” depending on solar gain potential and the client’s usage.
“An ideal radiant flooring system has no thermostats,” he adds. “An intelligent control system will cause the heating system to react to what is needed. Instead of turning up the thermostat when you feel cold, the sensors will take the outside and inside temperatures into account and adjust accordingly.”