Watts Radiant | Floor Heating & Snow Melting

Fequently Asked Questions

What type of floor construction should I use?

Any type of floor construction can be used with a radiant heat system. The most common will be a slab on grade, or a frame floor. Some variations of these may include a thin slab over a frame floor or a Sandwich application. The important thing to remember is to inform the radiant designer of the exact construction of the floor. There will be design variations between a frame floor project and a slab on grade. Keep in mind, it is better to design the building for what is required structurally and let the radiant system be designed around the construction details.

What type of floor coverings can be used over a radiant heat system?

Most floor coverings can be used over a hydronic heating system, keeping in mind that the system is designed for that particular covering.

Tile is the most efficient, since it is the most conductive. Hardwoods come next, and then carpet and pad. Even vinyl or linoleum can be used. Typically the only design variance between these three common floor coverings, is supply temperature.

I've heard hardwood floors should not be used. Why is that?

Hardwood floors can be used over a hydronic heating system if extra time and care is used during the installation process. Wood floors are what we call hydroscopic. That means the wood reacts to water, in much the same way a sponge does. If the wood is dry and goes into a wet environment, then the wood floor will adsorb moister and expand. Likewise, if the wood is too "wet" and is installed into a dry environment, it will dry and shrink.

Wood floors continuously move, just like the door jams in your home. In the summer they expand due to the increased humidity in the air and become harder to shut. In the winter the humidity is typically lower, and the doors shrink, becoming easier to close.

Wood floors will also experience this seasonal change in dimensions. However, there are some "tricks to the trade" that will help minimize these swings.

  1. Use a wood that is kiln dried. This helps to ensure the wood's moisture content is the same on the inside as it is on the outside.
  2. Try to use a wood that is no wider than 3" to 3.5" in width. The narrower the strip, the less movement it can induce.
  3. A quarter-sawn wood is better than a plane-sawn wood. Plane sawn woods tend to "grow" or expand in width, while a quarter-sawn wood will tend to expand more in thickness. This helps reduce visual cracking and gapping.
  4. The wood should be around 7% - 10% in moisture content. This may require an acclimation period in order for the wood to reach this level. Sometimes, it is best to have the radiant system installed before the wood. This will help accelerate the acclimation process.
  5. The wood floor should not be higher than 4% in moisture content than the floor it is being installed onto. This will allow for the subfloor and hardwood floor to move and react as a single unit. Otherwise, moisture maybe able to travel from layer to layer.
What about the nails used with a hardwood floor?

Typically, hardwood installers use one nail that will allow for the most use in the most variety of applications. However, this single nail tends to penetrate the lower surface of the subfloor, placing the radiant heat tubing in jeopardy. To eliminate this threat, ask the hardwood installers to use a shorter nail, one that will not penetrate the subfloor. And, if possible, ask them to try to keep the nails around the joists below. This way if there is some penetration, it will more likely go into the joist and not the tubing. As with any radiant heat installation it is a good idea to visually inspect the tubing after the wood floor is down, along with the factory recommended pressure test.

Is there anything in my floor that can cause problems?

In new construction there really isn't much that can is used that can cause a problem with a radiant heat system. If a vinyl floor is used, make sure the adhesive used can withstand elevated temperatures.

However, in a remodel, one thing that can be problematic is the use of tarpaper. This was used as a slip-sheet for hardwood floors to reduce squeaks and to act as a vapor barrier. Tarpaper can "off-gas" when heated up, causing an unpleasant odor to filter into the home. With today's construction techniques, rosin paper is used instead of tarpaper, which removes the off-gassing problem.

How many zones can I have with my radiant heat system?

A hydronic heating system can be designed with as many or as few zones as desired. Some systems will have one zone per floor, while others will have each individual room a zone. Keep in mind the more zones there are, generally the higher the radiant heat system cost.

I'm remodeling my garage, do I have to install a boiler?

Heat sources are chosen based on the water temperatures required and the total heat load needed for the space. For most full home hydronic heating systems a boiler will be used, but in some cases, such as a single room addition, a dedicated water heater may be used. This will be based on local code allowances and other design considerations.

If a water heater is used, it is not recommended that his same unit be used to supply the domestic hot water needs. The radiant fluid needs to be isolated from the potable drinking water.

What is the best way to control my radiant heat system?

Controls are chosen mainly on how the homeowner/project owner wants their system to respond to changes in outside conditions and on operational ease. Most systems will use a type of relay control with standard thermostats. More advanced systems will use outdoor sensors to anticipate climate changes. These systems are called outdoor reset and they tend to operate more efficiently, but they do cost a bit more.

Who should I have install my radiant system?

There are professional installers in most areas of the United States and Canada that specialize in radiant systems. But, any professional building or plumbing person can install a radiant system.

Can I install part of the system myself?

It is really up to the local code to dictate whether an installer needs to be licensed. In some areas the general contractor will allow homeowners to install the tubing while they supervise the work. In most areas a licensed installer is required to install the heat source, especially if a boiler is being used. Watts Radiant recommends a professional installer be consulted or used to install the mechanical package used to control the radiant heat system.

Please note: This FAQ document is designed to answer common questions. Refer to the product's installation manual or appropriate instructions and warnings regarding installation, use and maintenance.

Please note: This FAQ document is designed to answer common questions. Refer to the product's installation manual or appropriate instructions and warnings regarding installation, use and maintenance.

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