Heated Concrete Floors: A Homeowner's Guide

A radiant floor heating system doesn't just leave you with warm toes when you walk around on a cold winter morning. It can actually heat your whole room or home, depending on where you install the floor. In fact, using radiant heating in your concrete flooring offers many benefits over a traditional forced-air heating system.

Radiant flooring heating systems heat a space from the floor up as air warmed near the floor naturally rises and fills the rest of the room. There are two types of radiant floor heating available: electric and hydronic (hot water).

Electric radiant floors are constructed of either cables or mats that are embedded into a concrete floor (a wet installation) or wire mesh mats mounted on top of the subfloor, covered in an insulating material and then topped with flooring such as tile, laminate or certain hardwoods (a dry installation). Because electricity can be so expensive, electric radiant floors are generally only cost effective when installed directly below the flooring or in something of significant thermal mass, like a concrete slab, which retains heat well.

Hydronic radiant floors are more expensive to install because they involve more complex systems that involve laying PEX, or flexible plastic tubing, across the floor and then connecting the tubes to water pumps that push the water through a boiler or water heater, which will heat the water according to the temperature set on the connected thermostat. These can also be laid installed through wet or dry methods.

While the upfront cost of such systems is more expensive than electric radiant flooring systems, they take less electricity, and water heaters and boilers can be powered by cheaper energy sources such as solar, gas, wood or oil.

There are many reasons to choose a radiant heating system over other heating systems, including reduced allergens, increased energy efficiency and reduced maintenance. When you're deciding whether a heated concrete floor is right for your home, there are some advantages to consider:

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• ​Increased efficiency:​ Energy.gov
  notes that radiant heating is far more energy efficient than baseboard heating
  and as much as 25 percent more efficient than forced-air systems because there is no heat loss through air ducts.
  Depending on the system, homeowners can even limit their heating system's use
  to cover only the rooms or heating zones where it will be needed.
  Whereas these systems can lose efficiency when topped with an insulating floor
  covering like carpet, concrete floors help ensure the heat source operates at
  maximum efficiency.
• ​Cost effective:​ Naturally, that reduced energy use doesn't
  just mean heated concrete floors are good for the environment. It also
  translates into reduced heating costs. Similarly, the lack of necessary
  maintenance can save you money if you have an electric system.
• ​Little to no​ ​maintenance:​ While hydronic systems have boilers, water heaters and pumps that need to be serviced, the floor itself will require no maintenance because there are no moving parts. As for electric radiant flooring, there is actually no maintenance required, and as a result, many companies
  selling electric radiant heating systems offer lengthy warranties.
• ​Allergen-free:​ Whereas forced-air systems can push allergens
  through the air, radiant heating does not circulate the air at all. Moreover,
  radiant floor heating also prevents the air from becoming dry like many other
  heating methods, preventing dried-out airways that make colds and allergy
  attacks feel worse.
• ​More even temperatures:​ When using other heating systems,
  you'll likely notice that the heat is mostly concentrated by the heating
  source, leaving the rest of the room cooler. With a radiant heat system, the
  floor heats up evenly, and because heat travels upward, the entire room will have a consistent, even temperature.

While having a heating system built right into your concrete floor offers many benefits, there are also downsides to using radiant heating systems. Some of the biggest problems with radiant heating include:

• ​High installation costs:​ Because the process is so
  complicated — requiring coordination between the heating specialist and the
  contractor installing the concrete — radiant floor heating system installation
  can be rather pricey, with hydronic systems having a higher upfront cost since
  they are more complex. While increased energy efficiency means these systems should have a relatively low operating cost over their lifetimes, they do require a substantial initial investment.
• ​Difficult repairs:​ While it's rare for radiant heating
  systems to experience problems, if they do have issues, it can be difficult to
  identify why. Systems installed in concrete floors will require breaking
  the floor open for repairs. This means you'll not only have to factor in repair
  costs for the heating system but also for your floor as well.
• ​Slow to heat:​ Electric radiant floor heating systems can
  take an hour to heat a room, and hydronic
  systems can sometimes take hours to heat. That being said, heated concrete
  floors stay warm for a long period, so it's possible to take advantage of time-of-use
  billing programs by heating up the home during off hours and turning the power
  off during peak rate times.

There are two basic ways to install radiant flooring in a home: wet and dry installations. These methods are largely similar whether they involve electric or hydronic systems. Wet installations are installed in a concrete slab, whereas dry installations are placed on top of a subfloor and covered in an insulating material, and another flooring surface is then laid on top of the heating equipment.

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If you want to have a concrete floor fitted with a radiant heating system, you must use a wet installation method. Unfortunately, it is impractical if not impossible to retrofit an existing concrete slab to accommodate a radiant heating system. While new, ultra-thin heating systems have made it possible to install electric or hydronic heating elements in a thin layer of new concrete or gypsum installed on a concrete or wood subfloor, this concrete layer will not work as a floor, and you will need to top it with tile, linoleum or radiant-flooring-approved hardwood. In other words, if you want concrete heated flooring, you'll need to install it while building a new home.

With wet installations in new homes, first a compacted aggregate base will be laid, which will be topped by a vapor barrier, and then insulation and a layer of rebar or wire mesh will be installed to provide support. Next, the PEX tubes, electric coils or mats will be installed. The heating specialist will then use air pressure to check the system for leaks if it is a hydronic system. If working with an electric system, they will test the current. A final layer of concrete will then be laid above the tubes or coils, and once the concrete has fully cured, the system will be connected and powered up.

Dry floor installations involve laying hydronic PEX tubes, loose electric cables or a mat fitted with electric cables below the finished flooring. There are multiple ways to perform a dry install depending on whether or not you have access to the floor joists and the type of system with which you are working. Sometimes, the cables or PEX tubes can be secured directly to the bottom of a wood subfloor from below the floor, and then the spaces below can be filled with insulating material. Other times, they may be laid on top of a wooden or concrete subfloor and then covered in a thin layer of cement or gypsum.

For a hydronic system, you can purchase a grooved board system fitted with slots for PEX tubing and then cover the whole floor with an aluminum heat transfer plate. Thin electric mat systems fitted with built-in aluminum insulation can be installed directly on a concrete subfloor that has been covered with an insulating underlayment, and flooring can be installed directly above.

While tile is the most popular flooring used above radiant heating systems, almost any flooring can be laid on a dry installation except for those that are wet by nature, such as concrete. It is also best to avoid those that are insulating, such as carpet. Good alternatives include linoleum, vinyl, engineered hardwood or select hardwoods that have been specifically approved for use with radiant flooring.

Whether working with a dry or wet installation method, hydronic systems must be connected to a boiler or water heater, a heat exchanger, a heat sensor and a thermostat, whereas electric systems must be connected to a power source, a heat sensor and a thermostat.

While most electricians can handle installing an electric radiant floor heating system, hydronic systems require heating specialists with experience handling heating, electrical and plumbing work. It may be difficult to find someone in a remote area who is qualified to install or work on a hydronic system, but you can start by searching online for "hydronic radiant heating" followed by your city name.

Make sure a pro can handle doing a wet or dry installation for a hydronic or electric system depending on your needs, and always check reviews before setting up an appointment. Also, be sure to ask about the following:

• ​Sourcing the system:​ No single company manufactures
  all parts for a hydronic system, so a qualified installer should know where to
  acquire all necessary parts.
• ​Multiple heating zones:​ These allow you to fine tune the
  amount of heat used in different rooms around your house, maximizing your
  comfort and energy efficiency simultaneously. Find an expert comfortable with this.
• ​Outdoor reset control:​ This slowly raises and lowers the volume
  of water in the PEX tubing based on outside temperatures. Anyone qualified to
  install hydronic systems should be familiar with setting this up.
• ​Schedule availability:​ Because wet installation requires
  both the heating contractor and concrete installer to work together, it's
  important to ensure both contractors will be available around the same period
  of time.

While the first step to ensuring your radiant flooring is installed properly is making sure you have a qualified professional, there are some other things you should keep in mind to ensure you end up with a heated concrete floor with which you're happy.

• ​Get a good water heater:​ If you're working with a hydronic
  system, you'll either need a boiler or a water heater. While some people assume
  a boiler would be better because they operate at higher temperatures, water
  heaters are far more affordable up front and can actually save money in the
  long run. In fact, because boilers are designed to provide boiling hot water for radiators, they can actually be damaged by cold water and must be fitted with special components to work with lower-temperature water, which is required for radiant heating systems. Water heaters are designed to work with cooler water and can be operated at lower temperatures as needed,
  saving energy. There aren't water heaters designed precisely for hydronic heating systems, and not all water heaters are up to the task, so be sure to look for a system that
  has long-lasting materials, a high-enough BTU rating to keep your home warm (consult
  with your heating professional) and a high efficiency rating.
• ​Insulate your slab:​ Always insist that your installer use
  insulation underneath and around the perimeter when installing a new slab.
  That's because the cold ground and air can steal heat from the slab. In fact,
  an insulated slab will retain 70 percent more heat than an uninsulated one.
• ​Inspect the work:​ Before the final layer of concrete is
  poured, always review the heating system. Verify the coils will end up no more
  than 2 inches below the concrete surface, or the heat will not properly penetrate
  your floor. If using a hydronic system, ensure there are no leaks.

Because of the increased difficulty involved with installing hydronic systems, the installation of these will generally be a little more than electric systems, with the installation and materials of hydronic systems averaging around $13 per square foot, and installation of electric systems coming in at around $11 per square foot. Overall, the cost for a heated concrete floor will come out to between $15 and $30 per square foot depending on which heating system you use and how much embellishment you add to the concrete flooring (with options such as etching, staining and polishing).

Hydronic systems will also require a hot water source, so if your system cannot be hooked up to an existing water heater or boiler, a new one will need to be installed, which can cost an extra $770 to $1,450 for a water heater or $3,500 to $7,700 for a boiler.