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Radiant In-Floor Heating: Choosing the Best Flooring
You wake up on a cold winter morning, step out of bed, and the first thing you feel beneath your bare feet is a toasty,
warm floor. Sound like a dream? With an in-floor radiant heating system, this dream can be your reality.
The Benefits of In-Floor Radiant Heat
Conventional heating systems force heat through the air. This can be an effective way to heat the air within a room.
But because heat rises, forced-air heating systems often fall short in maintaining consistent warmth underfoot. With
hot air settling closet to the ceiling, homes that use forced-air heat are also prone to drafts and cold spots.
With a radiant heating system installed under a floor, heat is emitted throughout the floor’s surface, evenly dispersing
the warmth throughout the room. Not only does this greatly improve a room’s overall warmth and comfort, it also
boosts energy efficiency, which can equate to significant savings on home heating bills. Homes that use radiant
heating systems also tend to be cleaner and have better air quality than those that use forced-air heat. This is because
airborne particles such as dust, dirt, and mold spores are not blown through the air. What’s more, radiant heat is
invisible. There are no radiators, ducts, grills, or registers to take away from your interior design. And it’s quiet –
eliminating the rumbling, clicking, and whistling sounds commonly heard with forced-air heating.
With all these benefits, in-floor radiant heat has become a popular heating option for homeowners in recent years –
and today’s systems are more affordable and reliable than ever. Following is a brief overview as well as some things to
consider when purchasing flooring for use over radiant heat.
Types of Radiant Heating Systems
There are two basic types of radiant heating systems: electric or hot water (called hydronic).
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Electric radiant heat typically uses loops of resistance wire cable and mesh mats to transfer heat under floors.
These systems, which are often installed in a single room such as bathroom, are generally controlled with dual sensing
thermostats that combine input from a floor sensor with a room thermostat. When the floors dip below or rise above a
predetermined temperature, heat flow is cycled on and off. A few of these systems can control voltage in relation to
room temperature, and some systems include self-regulating elements to further control heat output.
Hydronic radiant heating systems, which are the most popular and cost-effective way to heat an entire house,
work by pumping hot water from a boiler or water heater through loops of polyethylene tubing under the installed
flooring. With this system, you can control the water temperature, as well as the volume of water, and the duration of
the water flow per pulse.
Installing Radiant Heating Systems
There are several ways to install in-floor radiant heating systems.
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For installations involving a home renovation, it’s common to install the radiant heat tubing directly under a
wood subfloor from below. In this case, traditional fiberglass or a bubble/foil product is often used for added
insulation.
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Radiant heat tubing can also be installed within a plywood underlayment system – either directly over an existing
wood subfloor or over an existing concrete slab. For installations over concrete slabs, it’s recommended to
include traditional closed-cell foam insulation manufactured for use in damp locations.
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For new construction, radiant heat tubing can also be embedded within the concrete slab itself during the
pouring of the concrete.
What Flooring Works Best with Radiant Heat?
With proper installation, many flooring materials can be successfully used over radiant heat – with a few caveats.
Solid Hardwoods
Generally, solid woods are not recommended for use with radiant heat, as solid wood is a natural material that tends
to expand and contract when exposed to high moisture levels and extreme temperature fluctuations. Dry heat directly
under the flooring can cause solid woods to quickly dry out and contract, leading to cupping issues or large gaps
between boards. For this reason, many manufacturers’ warranties for solid woods do not cover installations over
radiant heat. However, if you have your heart set on a traditional solid ¾ inch thick solid wood floor, here are a few
recommendations:
Select a quarter-sawn wood: When boards are cut from the log, they are cut in one of two ways: quarter sawn, in
which the direction of the grain runs vertically, or plain sawn, in which the direction of the grains is horizontal. When
exposed to temperature changes, plain-sawn woods will expand from side to side, which is more likely to produce
cupping and gaps. In contrast, quarter-sawn woods expand from top to bottom – effectively reducing this issue. One
drawback: many quarter-sawn woods are not pre-finished at the factory.
Choose narrower boards: The more narrow the board, the more seams there will be within the flooring, which
will help take up any possible movement.
Consider the species: Solid White Oak, which is known for its stability, can be used successfully over radiant heat.
While some woods such as Maple, Brazilian Cherry, and Pecan are not recommended for use with radiant heat. To be
sure you make the best choice, discuss your flooring options with your flooring retailer.
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Go with a professional installation: Installation of solid ¾ inch floors generally involves nailing or stapling the
wood, which runs the risk of puncturing radiant heat tubing below. Therefore, it’s a good idea to use a professional
installer who has experience with these types of installations.
Engineered Hardwoods
Engineered woods are the better choice for hardwood flooring installations over radiant heat. With engineered woods,
thin plies of wood are arranged so that wood grains run in opposite directions. This cross-ply construction makes the
planks much more dimensionally stable (less movement) and better able to withstand moisture and temperature
fluctuations than solid woods. In addition, most engineered woods can be floated making them ideal for installation
over concrete or most any flat and secure subfloor. While most manufacturers of engineered floating floors cover
installations over radiant heating systems in their warranties, typically installations must be performed according to
the manufacturer’s specifications.
A non-floating installation is also possible, but special care should be taken when stapling or nailing the flooring to
avoid puncturing the radiant heat tubing. If considering a glue-down installation, keep in mind that flooring should
not be glued over a lightweight concrete or directly to any exposed piping, as this may cause damage to the radiant
heat tubes. In these cases, it’s recommended to first install a 3/8 inch plywood underlayment.
Other Considerations for Wood Flooring Installations
To further minimize the potential for gaps and cupping, before installing any wood floor, it is important to store the
wood in the room where it will be installed for at least 4 to 7 days prior to installation. The radiant heat system should
run during this time, and the room’s relative humidity level should be between 30% - 50%, or within the
manufacturer’s recommendation. This will help acclimate the wood to the moisture content in the air.
When installing the flooring, leave the proper expansion gap around the perimeter and at all fixed objects. Once floors
are installed, raise the heat gradually, allowing the wood to further adjust. The subfloor’s surface temperature should
never exceed 80°F.
Laminate Flooring
Laminate flooring works well over radiant heat due to its thin, dense construction. With an image layer on top and a
dense center core, laminates offer excellent stability. But not all laminates are created equal. Since laminates are often
comprised of many layers, it’s important that the layers are well bonded and that the flooring is deemed suitable for
use with radiant heat. High temperatures can also dry out and distort laminate floors, so surface temperature of the
subfloor should be maintained at or under 80°F. Many laminate manufacturer’s warranties cover installation over
radiant heat. However, failure to follow the manufacturer’s specific installation guidelines may void the warranty.
Porcelain, Stone, and Ceramic Tile
Porcelain, stone, and ceramic tile are perfect flooring choices for use over radiant heating systems. These materials
are excellent heat conductors, do not expand and contract with heat, and are resistant to warping or cracking. If
possible, consider using crack isolation membranes for tile. This allows the flooring to expand and contract separately
from the heating system.
Vinyl and LVT
Vinyl flooring can be very conducive to radiant heating systems. Some vinyl products have specific temperature limits,
so it’s always best to follow the manufacturer’s recommendations,. Quality is also key when selecting vinyl flooring, as
low-quality floors may discolor or emit a strong odor when heated.
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Many high-end luxury vinyl tile (LVT) products can be successfully used over radiant heat. For LVT installations, the
initial floor temperature should not exceed 70°F for 24 hours prior to and 48 hours after installation. Thereafter, the
temperature can be gradually increased to the desired setting, up to a maximum of 85°F.
Carpet
Many carpet styles are well suited for radiant heat, though there is enormous variation among carpet padding in the
ability to conduct heat. Generally, the thicker and more plush the padding, the less thermally effective it will be.
Carpet with thin padding helps maximize heat transfer and thus works best.
Find Out More
If you are considering installing a radiant heating system in your home, it’s always best to consult with your heating
professional on which flooring materials will work best with a specific system. In addition, you should always check
the flooring manufacturer’s warranty to ensure the flooring you choose is recommended for use with radiant heat. To
find out more about flooring that works well with radiant heat, contact your local flooring retailer.
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