What Is a Radiant Heating System?
Most modern heat distribution systems, such as radiators and forced-air ducts, are convective – by circulating heated air through a finite space, they warm the entire volume to a desired temperature. Cooking ovens work on this basic principle as well.
By contrast, radiant heating systems deliver heat through a building’s floors or walls, warming adjacent air only indirectly. When installed only in flooring, systems may simply be referred to as “underfloor” or “floor” heating systems.
Radiant heating systems are most effective as indoor heat sources, either in a localized area (such as a bathroom) or an entire dwelling. However, some businesses (often restaurants or entertainment venues) and upscale homes use radiant heat to warm patios and other outdoor spaces.
Hydronic (Water) Radiant Heat
Hydronic radiant heat is the more efficient and popular form of radiant heat in widespread use. Hydronic systems feature corrosion-resistant polyethylene tubes that meet at the home’s boiler and circulate hot water throughout the structure. The boiler itself is controlled by the home’s thermostat, but newer systems typically have zoning valves that control water flow to each room, allowing heat to be reduced or shut off in seldom-used spaces without affecting other parts of the house.
Advantages of Radiant Heating Systems
1. Potential for Lower Utility Bills
Radiant heating systems – particularly hydronic systems – often lower utility bills relative to sources of heat, such as forced air and steam. Typically, hydronic floor heating systems are up to 30% more efficient than forced-air systems.
Water conducts heat more effectively than air, which quickly loses heat without a constant source. That means less energy is required to maintain water at a particular temperature over time.
Hydronic systems also deliver heat directly to solid surfaces that are even better than water at conducting heat, such as wood or tile flooring and wall paneling. Since heat transfer between the heated water and solid surfaces is more efficient than, say, heat transfer between steam and air or an electric radiator and the air, the water supply of a hydronic system can be maintained at a lower temperature than other heat distribution media.
2. No Ductwork
Radiant heating systems don’t require ductwork to function properly. And if your home doesn’t have a central air conditioning system, it doesn’t need ducts at all.
Homeowners without ducts have one less piece of infrastructure to maintain – and one less budgetary line item to worry about. High-quality duct cleaning services can cost $300 to $500, and are recommended once every other year for homes with heavily used HVAC systems.
Even if you do have a central air conditioning system, you probably don’t need to use it all year long. Ducts that aren’t used for much of the year wear more slowly and don’t require heavy maintenance.
3. More Floor Space/No Registers or Vents
Aside from the boiler and possibly zoning valves, radiant heating systems don’t have any visible components. Most other commonly used heat distribution systems have registers, vents, baseboards, radiators, or other visible components that take up floor space in a home’s living area and reduce the amount of square footage available for decorations, furniture, storage, and other usage.
These system components also require varying degrees of maintenance and cleaning – particularly registers and baseboards, which are magnets for dust and pet hair.
4. Better Indoor Air Quality
Forced-air heating systems continuously circulate air through a home’s ducts and registers, quickly distributing pet dander, dust, mold spores, and other allergens throughout the structure. By contrast, radiant heating systems don’t circulate air at all, and thus don’t keep allergens airborne as long as forced-air systems. That means better indoor air quality – a particularly important consideration for adults and children with allergies, asthma, and other conditions that can be exacerbated by indoor pollution.
5. Uniform Vertical Heat Distribution
Most heating systems deliver heat into a room from a focused point, such as a forced-air vent or steam radiator, or a single side, such as a baseboard radiator. The adjacent area is typically the warmest place in the room.
However, as the heated air or steam enters the room, it almost immediately begins to rise towards the ceiling, and only falls after losing much of its heat. That makes the air near the floor noticeably colder – 20 degrees or more – than the air at head level, five or six feet above the ground. The result: cold feet and hot heads. This effect is more pronounced in homes without excellent insulation and when it’s very cold outside.
By contrast, radiant heating systems slowly heat rooms from the floors up, from the walls in, or both. The heated surfaces warm adjacent air at a relatively low temperature, transferring heat to other parts of the room at a uniform rate. This means less noticeable temperature contrasts within rooms, little to no vertical temperature stratification, and more comfortable rooms overall.