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With the industry’s focus on improved indoor environmental quality (IEQ) and high-performance building design, more homeowners and building owners are requesting the addition of radiant heating and/or cooling to bring greater comfort, efficiency, and sustainability to their projects.

While radiant heating and cooling has been around for decades in North America, it is still a bit of a niche in the industry. Knowing the installation methods is just a portion of the key points to know when designing and installing a system.

Hence, it is important to take a radiant training course from a respected radiant system manufacturer before you get started on a job. It is also advisable to have the manufacturer’s design team create your first few radiant designs to help ensure the system will function as intended. It is nearly impossible to fix a bad design once the installation is complete, so starting off with a good design is paramount.

PROPER INSTALLATION IS KEY: It’s important to take a radiant training course from a respected radiant system manufacturer before starting a job. (Courtesy of Uponor)

Understanding the different installation methods for radiant heating and/or cooling will help provide guidance when you’re ready to begin the design process with a radiant design professional or after you have completed training.

Refer to these nine different installation methods to gain a high-level overview of the applications and how they can best meet a project's needs.

Staple Down

The staple-down method is one of the more common installation practices for new construction in both residential and commercial applications. It incorporates either metal staples for wood subfloors or plastic staples for foam insulation on a concrete slab. To install, use a special radiant piping stapler tool to fasten the flexible plastic radiant pipe (called PEX) to the surface. The staples go around the outside of the pipe (not through it) and then adhere to the surface. After the pipe is completely fastened, pour a lightweight gypsum concrete over the piping to create a smooth, solid surface for the flooring.

Tie Down

Use the tie-down method for residential or commercial installations on or below grade. This method requires a compacted base material such as dirt, sand, or gravel, with a wire mesh or rebar grid placed over the ground. Wire ties affix the PEX pipe to the wire mesh or rebar (typically every three feet) to ensure the pipe stays in place as the concrete is poured over the pipe and wire mesh or rebar grid system. It is important to note that when doing this type of installation, there can be under-slab heat loss that can hinder system performance, so under-slab insulation is typically necessary to ensure heat is not lost to the ground.

Pex Rails

PEX rails are long pieces of plastic, nylon, or metal that feature “channels” to hold the PEX pipe at a consistent spacing distance. Typically used in structural and non-structural concrete slab applications (either residential or commercial), PEX rails can be fastened to almost any surface, including wood, foam board insulation, and concrete. PEX rails help to ensure an even spacing for the layout pattern and can add efficiencies to projects compared with the time it takes to manually staple or tie down the pipe.

Aluminum Plates

Aluminum is an excellent conductor of heat, so using aluminum heat-transfer plates is an effective way to install a high-performing radiant system when concrete overpour on the surface of the floor is not an option. Typically used in residential applications, the plates fasten to the underside of the subfloor between the joists and feature a channel down the middle where the piping locks into place. A “stamped” aluminum heat-transfer plate features the tubing channel on the face (or top) of the plate that fastens to the subfloor, so the pipe must be installed first and then the plate is fastened to the underside of the subfloor. An “extruded” aluminum heat-transfer plate has the channel on the underside of the plate, so the plate can first be fastened to the subfloor and then the pipe can be installed. Note that after installation, it is important to add a minimum of R-11 fiberglass insulation into the joist bay snug against the plates to prevent downward heat loss.

Knobbed Mats

Knobbed mats are becoming a more widely used option for residential radiant due to their ease of use. The mats come preformed with knobs throughout the surface, which make it easy to “snap” the pipe into place. Simply adhere the mats to the concrete slab or wood subfloor and press the pipe between the knobs (either by foot or by hand). After the pipe is installed, it is then covered with a lightweight gypsum concrete to create a smooth, solid surface for the flooring. The mats are available with or without insulation and can accommodate various pipe sizes, depending on the product and application.

Wood Panels

With typical thicknesses of only a half inch, wood radiant panels are an ideal solution for residential remodel and retrofit applications. The panels simply fasten to the plywood subfloor and feature a groove down the center for the piping placement. An aluminum sheet on the bottom of the panel increases the heat transferability. This method offers several advantages in addition to the minimal increase in floor height, including no moisture from concrete overpours and increased BTU output potential over joist heating.

Foam Panels

Designed for residential new construction and remodels, these panels feature a lightweight XPS foam laminated with aluminum around the entire surface to provide exceptional heat-transfer capability. Designed for use with 5/16" PEX pipe, the panels feature a low, 5/8" profile to minimize construction in remodel projects as well as 6" on-center pipe spacing to accurately meet residential radiant application needs. The natural moisture resistance of the XPS foam eliminates the need to caulk edges or panel grooves for increased installation efficiencies and also eliminates the need to insulate in the joist space below the subfloor, saving labor time and materials costs.

Joist Clips

This method is most appropriate for “floor conditioning” or “floor warming,” which does not actually provide heat into the space. The clips simply fasten to the underside of the subfloor between the joists and suspend the PEX from the subfloor. Like aluminum plates, it is important to add fiberglass insulation after the piping is installed. However, unlike aluminum plates — where the insulation must be snug against the plate — in joist clip installations, there must be an inch gap between the PEX pipe and the insulation. This creates an air gap below the subfloor that will enable the heat to better transfer to the floor.

Rollout Mats

For large commercial applications, some manufacturers offer a custom-designed, prefabricated, pre-pressurized network of PEX piping all rolled up as a mat. These radiant mats can be quickly and easily unrolled and installed in a fraction of the time it takes for traditional installation methods. These “rollout mats” greatly increase the efficiency and consistency of an installation and can also eliminate a lot of product costs as well. For example, one manufacturer’s mat claims to reduce install time by up to 60%, manifold ports by up to 80%, and wire ties or staples by up to 40%. Since these mats are custom-made, it is important to work closely with the manufacturer’s design department to ensure a proper design when ordering the product.

Conclusion

With radiant systems offering greater occupant comfort and contributing to improved IEQ, it makes sense to learn some installation basics to help guide customers who are interested in this application.

Again, be sure to have a radiant design professional help with the design or attend a training course from a reputable radiant manufacturer. Some manufacturers even offer on-demand online courses, so it’s easy to schedule the training to fit your needs.

For further information about radiant systems, visit radiantprofessionalsalliance.org, heatinghelp.com, healthyheating.com, or uponor.com.