Outside of tropical climates, every dwelling requires a reliable source of artificial heat. Depending on the type of dwelling, geographical location, and the property owner’s budget, heating systems take different forms: forced-air ducts connected to heat pumps or central furnaces, steam radiators connected to boiler units, electric baseboards, and electric space heaters that plug directly into wall sockets, to name several.
When the weather is cool, heat is a nonnegotiable expense, no matter what type of system you have. However, there are many ways to reduce your heating bills, such as installing a programmable thermostat or bulking up your home’s insulation.
If you’re willing and able to shoulder a significant upfront cost, one of the best ways to reduce your heating expenses (and carbon footprint) is to replace an older, inefficient system with a newer, greener one. Homeowners and landlords looking to improve efficiency and lower costs often turn to radiant heat, an ancient indoor heating method that’s gaining favor with cost- and eco-conscious property owners.
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.
Humans have understood and employed the principle of radiant heat for thousands of years. The Romans used an early form of radiant heat in public buildings as early as the 1st century B.C., though their approach (known as hypocaust) was prohibitively costly for private property owners. Archaeological evidence suggests that similar systems were invented independently in Pakistan and the Caucasus as early as the 4th century B.C.
Today, radiant heating systems come in two basic forms.
Electric Radiant Heat
Electric radiant heating systems feature loops of charged cable (resistance wire) that generate heat either continuously or during the evening and overnight hours. Some systems run cables directly into a layer of material, such as concrete or gypsum, between the sub-floor and the floor’s visible layer. Others affix cables to heat-amplifying conductive panels, typically made of plastic or metal, in an air pocket between floor layers. The intensity of the charge (and generated heat) reflects the thermostat setting.
In both cases, electric heating makes the most practical sense with hard floor coverings, such as tile and concrete. Because generated heat diffuses faster in softer, less conductive surfaces, it’s not ideal for heavily carpeted rooms.
The cost of electric radiant heat depends on local electricity rates and the system’s workload. Relative to forced-air and baseboard systems, it’s typically not cost-effective for whole-house heating in colder climates or areas with high electricity costs.
However, even in high-cost, high-demand areas, it’s often useful for delivering supplemental heat in specific applications – for instance, heating bathroom floors overnight and in the morning. It can also be cost-effective where local utilities charge lower rates for power consumed during off-hours, usually overnight and in the early morning.
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.
As with electric heating systems, hydronic systems can either run directly through flooring material (wet systems) or heat an insulated air layer beneath the floor (dry systems). Wet hydronic systems can be operated at lower water temperatures (often just 75 to 100 degrees, compared to 120 degrees or higher for dry systems), potentially reducing heating costs. However, dry systems are usually cheaper and faster to install.
It’s worth mentioning that some radiant heating systems use air instead of electrically heated panels or hydronic pipes. However, air-heated floors and walls are intrinsically less efficient than electric or hydronic systems, so these systems are rarely used in residential applications.
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. According to Bob Vila, 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. According to Angie’s List, 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.
Disadvantages of Radiant Heating Systems
1. Substantial Upfront Cost
Though they’re often more cost-effective in the long run and may eventually pay for themselves through lower utility bills, radiant heating systems cost a lot to install.
According to This Old House, a hydronic floor heating system costs anywhere from $6 to $15 per square foot to install, depending on the location, system type, and layout of the home. To completely heat a 1,500 square foot house, that equates to an investment of $9,000 to $22,500. That’s about 50% higher than the cost of a forced-air system for a similarly sized house.
2. Risk of Leaks in Hydronic Systems
Hydronic heating systems use flexible, corrosion-resistant polyethylene pipes that last longer than copper pipes (which corrode over time) under normal circumstances. Hydronic systems are also completely closed, meaning you shouldn’t need to add or remove water – a process that can introduce oxygen in a corrosive, gaseous form.
However, there’s still a small risk of leakage in any hydronic heating system. As in traditional plumbing systems, even a small leak can have big effects, particularly if it’s not detected for some time. Your homeowners insurance policy is likely to cover initial cleanup and repair costs, but possibly not secondary issues, such as mold growth.
3. Risk of Fire in Electric Systems
All electric heat sources, including space heater and baseboards, present some level of fire risk. Electric radiant floor heating systems are no different. In fact, the risk of fire can be greater with these systems, particularly where sub-floor wiring isn’t properly insulated or conductive panels come into contact with flammable debris, such as wood scraps or dust.
Though your homeowners insurance policy may cover some or all of the cleanup, repair, and replacement costs associated with a heating system fire, a serious fire could render your home temporarily uninhabitable or even result in a total loss. If you have an electric radiant heating system anywhere in your house, make sure you have a working fire extinguisher on hand.
4. Difficult to Access for Repairs
Since the bulk of the typical radiant heating system is located in the walls or under floors, even basic diagnostic or repair work can be costly and inconvenient. Some other heat sources, such as forced-air duct systems and electric baseboards, are easier to access and less resource-intensive to repair.
What to Consider Before Purchasing a Radiant Heating System
A radiant heating system represents a significant investment in the future of your home. Evaluate these factors as you consider whether it makes good financial and practical sense for you.
1. Type of Existing System
Some heating systems are costly or inconvenient to remove. For instance, if your home has a central heating system that uses the same ducts as your central air conditioning unit, it may simply be more convenient to continue using that system (and replace the central heating unit when the time comes).
Likewise, space constraints may render it impractical or impossible to install a modern boiler (for hydronic heat) alongside an old-fashioned furnace that delivers forced-air heat through ducts and registers. Removing that old furnace and sealing the system could add thousands to the cost of your project, if it’s possible at all.
2. Age and Condition of Existing System
If you recently installed a new, non-radiant heating system in your home, shouldering the cost and inconvenience of replacing it doesn’t make sense. Likewise, it’s rare for homeowners to budget for a heating system replacement after moving into a home (especially a new construction home) with a recently updated or even perfectly functional heating system.
If the idea of radiant heat strongly appeals to you, at least wait until you have a good sense of your annual heating costs – probably several winters – to determine whether replacing a fully functional non-radiant system makes financial sense.
3. Current Heating Costs
Because one of the top benefits of a radiant heating system is the possibility of substantially reduced utility bills, your current heating costs must be a key (perhaps the key) consideration.
If you live in a mild climate and don’t use heat for most of the year, a whole-house radiant system likely won’t ever pay for itself. A localized electric system, perhaps in the bathroom or on the porch, is probably all you need.
If you live in a cold climate and shell out $300 or $400 per winter month for forced-air heat, a hydronic system that reduces your heat expenditures by 30% could pay for itself within five to eight years.
4. Risk of Fire or Leak
Both electric and hydronic radiant heating systems come with safety risks – fire and water leakage, respectively. Even localized leaks and fires threaten your home’s structure and contents. Depending on their scale, such events can be highly inconvenient, even forcing you to relocate until the damage has been repaired.
If you’re no longer carrying a mortgage and have allowed your homeowners insurance policy to lapse, fire or water damage can be financially catastrophic as well. A family friend of ours recently settled a $20,000-plus repair bill – mostly covered by insurance – for a fire that damaged part of his basement. Without insurance, that bill would have been a major hardship.
Due to hefty installation costs, whole-house radiant heating systems are often a better deal for the next homeowner – the person who buys from the person who installed the system. The buyer gets all the benefits of radiant heat – lower utility bills, better indoor air quality – without the upfront cost (though the system’s cost may be reflected in the home’s selling price). If you’re in the market for a new home, pay close attention to what’s under the floors.
Does your home have a radiant heating system? Would you buy a house with one or install one yourself?