Guide to Radiant Floor Heating Systems

Imagine stepping from a warm bed or shower to a warm floor when it’s cold outside. That’s the magic of radiant floor heating. 

Radiant floor heating systems keep you warm directly through infrared radiation. It’s a much more efficient and comfortable heating method compared to forced air systems, and with no cold spots or drafts, room temperature will feel much more consistent. Learn more about how electric, water-based, and air floor heating work in this guide. 

History of Radiant Floor Heating

Many people assume that radiant floor heating is a fairly new concept, but it’s actually one of the oldest ways to heat a home. Floor heating goes as far back as 5,000 BC. in China and Korea. The ancient Romans perfected the system around the third century BC. 

Roman floor heating worked by assembling layers of tile and concrete, and an extra layer of tile was raised on pillars so hot air could circulate more freely. This system disappeared with Rome, however, and wasn’t revived until around the 17th century in Europe, when Sir John Stone used heated water in pipes for greenhouses and commercial spaces. Sir Stone’s invention led to some of the first research into how radiant heat transfer worked.

Radiant heating first came to America during the Civil War, when hot air warmed hospital tents using a mechanism resembling the oldest Chinese systems. In 1907, it was discovered that small hot water pipes could be embedded in concrete or plaster, but this technique wasn’t widely used until Frank Lloyd Wright started adopting it for his buildings.

What Are the Benefits of Radiant Floor Heating?

Radiant floor heating systems offer a number of advantages, including:

• Even heat distribution: The heat radiates from the floor, creating a consistent temperature throughout the room.
• Energy efficiency: Radiant systems can be more efficient than forced air, potentially lowering your energy bills.
• Improved air quality: Without blowing air through ducts, fewer allergens will enter your spaces.
• Silent operation: There’s no noise from fans or air rushing through vents.
• Design flexibility: The system works with various flooring types and doesn’t require visible radiators or vents.

The Basic Components of a Radiant Heating System

Depending on the type of system you choose, there are only a few key components you need to make the system operational.

For hydronic systems, all that’s necessary is a water heater or boiler, the in-floor pipes, which are usually made of PEX tubing, and the plumbing manifold, including any required valves and fittings, which runs the hot water from the boiler to the floor.

For electric systems, you’ll need a heated floor mat, which is wired to your home’s electric panel, and in all systems, you’ll need a thermostat for radiant heat to control the system and the heat. 

Types of Radiant Floor Heating Systems

There are two basic styles of installing radiant floor heating—wet and dry installations. With wet systems, the tubing and wires are embedded in concrete or other material that can transmit heat. Dry systems have tubing in a cavity below the floor. Both systems can use either water or electricity to heat the floor.

Beyond installation types, there are three different styles of heating systems, each with its own attributes.

Air-Heated Radiant Underfloor Heating Systems

Air-heated systems are descendants of the oldest systems used in China, Korea, and Rome. They’re a little less energy efficient than the other types and are, therefore, less common for homes. You may see them used in large commercial or industrial settings.

Rather than pumping air directly beneath the floor, with these systems, the heated air is circulated through a series of tubes resembling water pipes. Since air is lighter and easier to push through the tubes, you can get warmth quickly.

Air-heated systems must be wet installed for best results, so they’re closed. The heaters are housed in boxes that make access for repairs easy.

Electric Radiant Floor Heating System

In an electric radiant floor heating system, wires, cables, and sometimes mats are installed either wet or dry beneath the flooring. The wires are directly connected to your home’s electrical system, and the floor is controlled by a thermostat. A heat-conducting plastic layer helps to transfer the heat from the cables to the floor above.

For small spaces, mats embedded with the wires can be laid in a thin layer of mortar, with the mats cut to fit the area. In larger spaces, the wires themselves are usually looped about 3 inches apart throughout the space, also embedded in a thin layer of mortar.

You can install an electric radiant floor heating system under any type of flooring without issues, and the cables won’t end up raising the floor like a thicker system can. However, it will also be more expensive. According to Angi, you can expect to pay around $19,000 to $36,000 for a whole-home system.

Hydronic Radiant Floor Heating System

Hydronic systems use water heated in a boiler and piping beneath the floor to warm your home. The system is completely closed and can be installed either wet or dry. The materials are also commonly available, so it’s a perfect candidate if you’re looking to retrofit.

This type of system can be installed beneath any type of flooring, and you can route the pipes as a loop or make a larger network. It uses less energy than a traditional furnace, and since water keeps heat very well, you may not have to turn your thermostat as high. That could save you up to 30% on electric bills over time.

The cost to install a hydronic system is among the lowest of the three types. According to Angi, a whole-home system costs between $19,000 and $48,000. That’s about $10 per square foot for dry installations and $14 a foot for wet installations. This doesn’t include the cost of the finished flooring for a dry installation or the concrete for a wet installation.

Types of Hydronic Floor Heating Systems

There are two different subtypes of hydronic radiant floor heating installations: open-loop and closed-loop.

In an open-loop system, the water gets pulled from a source like a well, heated, and pumped once through the system before being discarded.

In a closed-loop system, a heat exchanger constantly heats the water, which runs in a loop through the floor. Since the water is fully contained, there’s less contamination risk. 

Key Components of a Hydronic Radiant Floor Heating System

The most basic components of a hydronic heating system include the following:

• Heat source: You can use a natural gas or propane-powered water heater, boiler, geothermal heat pump, solar water heater, or tankless system.
• Tubing: The tubing is almost always PEX, a flexible material that doesn’t crack, corrode, or break over time.
• Liquid medium: Most people choose water, but in a closed system, you can also use glycol or a mixture of water and antifreeze—just in case your system is at risk of freezing in cold temperatures.
• Heat exchanger: A heat exchanger is a must-have for closed-loop systems.
• Pump: A pump is necessary to keep the water circulating through the tubes.
• Thermostat: A thermostat controls the heat source, just like any other heating system.

There are few problems with most hydronic systems, and the most common are associated with the valves and the circulator pumps. They do need to be repaired or replaced on occasion. Another common issue is airlock, which is what happens when air gets introduced into the system and prevents the water from circulating. Allowing the air to escape at specific valves can help fix this issue.