Radiant heating was used in the form of radiators in many older homes during the last century, and steam heating was proven to be highly efficient, although the technology of the time was not without risks.
Today, we find a return to using radiant floor heating as a way to keep those toes nice and warm on a cold winter day.
What is Hydronic Radiant Floor Heating?
There are three major types of radiant floor heating systems. The original (and largely abandoned in the West) method was used most notably in Turkish baths and consisted of a raised floor to allow hot air underneath, keeping the floor nice and warm.
While the true origin of radiant floor heating is unknown, Primitive Technology proves it was possible with even stone age methods. While this form of heating may still be found in some historic buildings, it is rarely (if ever) used in modern construction.
The second is a more modern solution and uses a series of electric cables installed between the floor and subfloor. Electric radiant floor heating works well in a small space, but (as you can imagine) becomes prohibitively expensive when used throughout an entire house unless you’re generating most of your power off-the-grid.
The final method, hydronic floor heating, uses the same basic principles of traditional radiator heating. This provides a cost-effective heating solution that gives a more consistent result than modern forced-air HVAC systems, although it isn’t perfect.
Related: Indirect Water Heaters: How They Work and Why You’d Want One
How Does Hydronic Radiant Floor Heating Work?
Hydronic floor heating takes advantage of the flexibility found in PEX tubing. Uncut lengths snake through the room, with the beginning and end attached to a manifold.
Because the floor will be sealed, there can be no joints in the tubing. Each loop of the tube is set approximately nine inches apart, then held in place with specially shaped staples.
The sub-floor and tubing is covered by concrete, gypcrete, or dry-tamped mortar, providing a solid seal.
These materials hold heat, allowing it to radiate evenly whether the system is running or not. In most cases, the floor is finished using ceramic floor tiles, as these also hold heat well.
Heading from the room to the system itself, the manifold helps keep the water evenly distributing between lengths of PEX tubing (see also ‘Should PEX Piping Be Insulated?‘) and helps vent the system. At the other end of the system is a dedicated boiler or water heater, with a circulating pump pulling water into the system and returning it to the bottom of the boiler to reheat.
As the water generally only loses about ten degrees, a running system maintains heat quite efficiently.
Advantages of a Hydronic System
There are quite a few things to love about radiant floor heating systems. Because the heat radiates from the floor itself, there are no vents to place furniture around and the furniture itself can pick up a bit of the warmth.
Unlike forced air systems, they won’t spread allergens around the room and heat evenly, eliminating cold spots.
Best of all, these silent systems tend to be between 10 and 30 percent more energy efficient than standard HVAC systems and will continue to keep the house warm for hours after a power outage.
Disadvantages of a Hydronic System
These systems are not without their flaws. The biggest problem is that you’re more restricted on floor coverings. Carpets can actually block the heat, for example. You will also have a longer wait time when the system is first turned on and can increase the humidity of your rooms near the floor.
The biggest headaches, however, happen during installation. You will need a contractor who’s trained to install the system due to its special requirements.
They can also get very complicated if you’re installing into an existing floor. Any repairs will likewise be rather complicated and potentially expensive, although any necessary repairs to the submerged portions are very rare.
Hydronic vs Electric
Hydronic systems tend to be cheaper to install and run than electric. They used a closed system, making the cost of running the boiler and pump your only real fees.
Compare this to an electric system, which needs to pump electricity throughout the system.
Hydronic vs Forced Air
Forced air systems require a furnace and duct work to be run throughout your home. Even with modern systems, this can lead to cold spots and the ducts need regular cleaning to reduce the spread of allergens.
The modular nature of duct work can also lead to heat loss and less overall efficiency. Because a hydronic system has its parts embedded and uses a smaller heating unit, most of these problems are eliminated.
See Also: 10 Important Innovations in Water Heater History
How Much does Hydronic Radiant Floor Heating Cost?
Installing and running a hydronic radiant floor heating system (see also ‘Which Is The Better Option For Your Home: Radiant Heat Or Forced Air?‘) is a very different experience than adding forced air systems. As such, planning out your expenses isn’t quite as predictable.
We’ve broken down many of the details so you can get a better idea of the cost. Please note that some materials, local rates, and other factors may result in higher or lower fees, especially for installation.
Cost to Install
Adding one of these systems is best done during a major renovation or new construction to avoid having to rip up an existing floor. Removal of an existing floor will vary greatly in cost depending upon the material and room size.
In some cases, you will also need to add extra support for the sub-floor to withstand the heavier weight of your filler material.
Hydronic systems tend to be cheaper to install than their electric counterparts, beginning at $6 per square foot (as opposed to $8 for electric). Larger areas will generally be cheaper to install than smaller, as space restrictions can compound the task.
As such, a smaller room may cost $9 or more per square foot, while extremely large areas could cost as little as $5 per square foot. The exact cost per square foot will thus be a combination of system type and project size.
One other factor that will affect the cost of installation comes in the form of temperature zones. Some rooms are more lived-in than others, and these will often need a higher average temperature than less frequented areas of the house. Such zones can require more complex systems, adding to the general cost.
In all, you can expect to pay anywhere from $6,000 to $14,000 to install a hydronic radiant floor heating system. This includes the system itself and the cost for a dedicated water heater or boiler (generally $360 to $1,000 for a 50 gallon water heater or approximately $6,000 for a boiler).
Cost to Operate
Thanks to the invention of the programmable thermostat, running a hydronic system can be much cheaper to operate than a traditional HVAC system. You can set the system to run during off-peak hours to reduce your electric bill and the floor will continue to radiate heat long after the system shuts off.
Radiant systems can also usually be run at six to eight degrees cooler than forced air (see also ‘How To Tell If Forced Air Heating Is Gas Or Electric‘), as hot air rises and the latter usually pushes the hot air in at the top of the room, reducing its effectiveness.
As water is more efficient at retaining heat, the system needs far less energy to reheat the recirculated water than a furnace does to reheat returning air. This results in energy savings of up to 30 percent.
These savings will only get better as solar heating systems continue to improve, promising to eventually replace the need for using grid power entirely in these systems.
Radiant floor heating, especially hydronic systems, can offer a lot of options, but also have some restrictions. Planning ahead will save a lot of time and effort when adding one of these systems to your home.
Best Places to Install
You will ideally want to install the system during construction or renovation, but it can also be important to consider whether you wish to do your entire house or just one or two rooms. Larger rooms where your family spends most of its time are the most ideal.
The most common areas to warrant coverage are bathrooms, uncarpeted bedrooms and living rooms, hallways, or kitchens (in a busy household). Some say that bathrooms should only be done when installing a full-house system, but there’s nothing better than stepping on a warm tile floor after waking up on a chilly winter morning.
You will also need to think carefully if you plan to add a cooling system. Radiant cooling should be installed in the ceiling, so you may want to further restrict partial installations to account for this fact.
Remember, a radiant floor heating system can be used to augment or replace an existing HVAC system, but it’s far more complicated than swapping out a furnace, so plan any partial coverage carefully.
Best Flooring for Radiant Heat
The type of flooring you use will have a major effect on the efficiency of your new radiant floor heating system. Thankfully, you have a few options.
Porcelain or Ceramic Tile
Tile is perhaps the most popular solution, boasting a high heat conduction rate and the ability to continue radiating stored heat in addition to what’s held in the underlying surface.
Right alongside tile are natural stone. Stone tiles work very similar to ceramic and work well in conjunction with the material beneath.
Laminate floors are also an excellent match, although you will want to pay attention to any heating restrictions by the manufacturer, since water damage from below can ruin laminate easily. As most manufacturers have a limit as high as 85 degrees Fahrenheit, it’s pretty hard to hit those restrictions.
Wood flooring suffers from reduced efficiency, but can still be used. It’s best to go with engineered wood flooring, as the underlying plywood is less likely to warp. Solid hardwood should be quarter-sawn for improved flexibility and to accommodate any thermal expansion.
In both cases, the floor will take longer to warm up and won’t hold the heat nearly as well as with other materials.
Worst Flooring for Radiant Heating
Conversely, we have several types of flooring that can negate the effectiveness of your new heating system.
The biggest culprit is carpeting, which is designed to absorb heat but has terrible conductivity.
Similarly, concrete actually defeats itself when used as the main floor covering. Radiant systems rely upon layered flooring to help distribute and store heat. Without a higher layer of different material, the concrete loses most of its efficiency.
While not commonly used, rubber flooring is another terrible choice, as it will give off an unpleasant odor due to the heat.