Radiant heat isn’t a new concept – it’s the same heat you feel from the sun. It’s also the same kind of heat that warms you from a fireplace, woodstove, boiler-powered radiator or portable electric heater. But in our continuous search for better ways to heat our homes, there’s quite a bit of buzz about radiant heat, both because of the even comfort it provides, as well as the fact that it can be efficient and non-polluting.
Let’s have a look at how you might work radiant heat into your new home or redo, or add it to your existing home.
What Is Radiant Heat?
Radiant heat involves heat transfer through electromagnetic infrared waves. For instance, with a portable heater, coils are heated by the power of electricity, and the heat is transferred to the individual experiencing the heat. This is in contrast to how a furnace works by heating air and distributing it into a home, or a heat pump, which moves heat from the outdoors by means of refrigerant to the indoors.
Heat pumps in a cooler climate such as ours must default at lower temperatures to auxiliary heating sources, which may make them inefficient, while the inefficiencies of forced air furnaces are well known: air blasts out of the registers at a temperature of 120 degrees, quickly rises to the top of room, then as it loses heat, it drop down on the home’s occupants. The room’s air becomes stratified so that your feet may be freezing while you’re breathing stuffy air. The cycling of the furnace may also increase discomfort. For instance, you set the furnace for 68 degrees, it turns on and quickly warms up the room and then turns off, leaving the occupants to feel chilled until it comes back on.
With radiant floor heating, the heat is spread out more evenly. Warm air will still rise, but when it emits from the floor, it tends to keep the cooler air at ceiling level.
Some of the most popular types of heating are floor heating, ceiling or wall panels and baseboard heating.
Radiant Floor Heating
Radiant floor heating heats by means of three different media: air, electricity and hot water. The types of installation for these three are divided into “wet installations,” either in a large-mass slab floor made of concrete, or lightweight concrete over a wooden subfloor, or “dry installations,” where the radiant floor tubing is sandwiched between layers of plywood, or the tubing is attached under the subfloor or finished floor.
Air-heated radiant floors are not considered cost effective in residential buildings, so are not often found.
Electric radiant floors may feature electric cables installed in the floor, or else conductive plastic mats mounted below a floor covering (tile, perhaps) in the subfloor. Given that electricity is fairly expensive, this heating method is usually only cost effective when installed in a thick concrete floor or if the utility company offers cheaper off-peak rates, say, during the night. The radiant system can heat up the floor and house sufficiently overnight that the house, if well insulated, may hold on to the heat for eight to 10 hours so that you can turn the system off.
Hydronic floors are the preferred method of radiant heating, especially in cooler climates. They work by pumping water heated by a boiler through tubes in the floor. Zoning valves or thermostats regulate the temperature.
As to the installations, whether you opt for dry or wet will depend on the kind of foundation you have. A couple of examples of wet installations: cables or tubes might be installed in a thick concrete slab floor, or a layer of concrete or gypsum might be installed on top of a subfloor, and the cable or tubing placed in that layer. Homeowners should consult an engineer to make sure their floor has sufficient carrying capacity for the latter. Although concrete slabs are good for storing heat, they have slow response time, so it’s really not practical to try to save on costs by turning the heat down at night.
So-called dry floors, in which cables or tubing are run through an air space under the floor, are growing in popularity, although they offer some challenges. They are fast and easy to build, but heating air requires more electricity than heating concrete. Typically, tubing or cables are suspended beneath the subfloor between joists, Reflective insulation under the tubing directs the heat upwards. Another type of installation is to insert tubing or cables between two layers of a subfloor above the floor. Aluminum diffusers are then installed to spread heat more evenly.
Ceramic tile is the best material for the floor covering, as it is a good heat conductor and also helps store it. Carpet, vinyl, linoleum or wood will work, but make the system less efficient because they tend to insulate the heat.
Radiant Wall or Ceiling Panels
Radiant wall heating was quite popular in the 1950s and 1960s, but as the cost of electricity rose, it became less so. More efficient hydronically-powered wall and ceiling panels are now available, the water that circulates in them being heated by gas or oil. While this type of wall panel is less common than the electric types, as there are concerns about leaking water, interest in them is growing. They are easily installed in the lower 4-foot section of the wall and may be extended by as much as 8 feet upward if you have high ceilings. Insulation should be installed behind them.
Ceiling panels should be installed in ceilings that are 8- to 12-feet high and should be insulated. A side benefit of hydronic ceiling panels is that in summer, cool water can be pumped through them, which will help cool your home.
Electric wall or ceiling panels are made of aluminum, and radiate heat generated by electricity. As with any type of electric heating, these can be expensive to operate. It makes most sense to install panels in a room where it’s prohibitive to extend ductwork or else where the homeowner wants auxiliary heat. The benefit of this type of heating is that the room reaches a comfortable temperature quickly. Some homeowners prefer ceiling-mounted panels because they warm the heads and shoulders of the room’s occupants.
Radiant Baseboard Heating
You may not think of baseboard heating as a type of radiant heating, but it is. This is an easy-to-install option and may be more affordable for the whole house or even for that hard-to-heat room than other types of radiant heating. The baseboard units are available either as electric or hydronic units.
Electric baseboard heaters are installed beneath windows, where the cool air enters and falls into a vent in the unit. The cool air is warmed by heated metal fins, and then rises to heat the room. Be aware that though relatively inexpensive to purchase and install, they can run up your electric bill, and should probably be used as a supplement to a central heating system: turn down the furnace or boiler at night, and turn on the baseboard heating in the rooms that need it. Most often, electric baseboard heaters are hardwired into the home’s electric system; portable units do exist, however.
Hydronic baseboard heaters use electricity to heat a liquid, either water or oil, that circulates through tubing, giving off heat as it circulates. This type of baseboard heater is more efficient than the electric kind, because it takes the liquid longer to cool down than it does for the metal fins to lose heat. Usually a home that runs exclusively on baseboard heat has a hydronic system, because it is less expensive to run than the electric kind. The main drawback with these systems is that air can intrude into the lines, requiring bleeding of the pipes. Hydronic systems also take longer to heat up than the electric kind.
Other Pros and Cons
As you can see from the discussion above, one of the main drawbacks of some types of radiant heat, particularly radiant floors, is the cost of installation, and for electric-powered radiant heat in particular, the cost of operation. The low cost of natural gas right now is a consideration, but as we all know, gas prices historically fluctuate. Having at least one room with radiant heat could provide the homeowner with an advantage when and if gas prices go up again. Because radiant floor heating is even and comfortable, it may over time compensate for installation costs by allowing the homeowner to dial back on the thermostat.
Another benefit of radiant heat in general is that it is quiet: no burst of noise when the heat is “on.” What’s more, it doesn’t recirculate allergens and other irritants in the air supply the way a central system does. Further, you don’t need to be concerned about maintaining ductwork.
For more information on radiant heating systems, contact us at Roberts Heating and Air Conditioning, Inc. We’ve been serving Northbrook, Glenview, Evanston and the surrounding area since 1979.