Avoiding Trapped Heat

Posted on 10/30/2013

Many people ask us why we recommend keeping items off a floor where radiant heat is present. Here’s why: items placed on top of the floor can trap radiant floor heat. This trapped heat can make the area much warmer than the surrounding areas. If you are not careful, in some cases, trapped heat can cause problems with the floor coverings and radiant heat system itself.

What is trapped heat?

Thermal image depicting trapped heat under mat placed on the floor for 30 minutes.
Image 1. A mat was placed on top of the heated floor for approximately 30 minutes. This image, taken immediately after the mat was removed from the floor, shows an increase in surface temperature.

To demonstrate this phenomenon, we took a heated mat and placed it over a laminate floor for 30 minutes.

Image 1 shows the thermal image of the floor immediately after we lifted the mat. You can see the surface temperature displayed near the illustrated boxes. The box on the top is 114 degrees, and the box on the unheated portion of the floor is 85 degrees. The deeper the red hue, the hotter the area is. Cooler areas are shown as shades of blue.

Surface temperature drops after mat is removed. Heat is still trapped beneath flowerpot.
Image 2. The surface temperature has started to decrease after the mat was removed. The dark red indicates that heat is still trapped under the flowerpot.

In Image 2, we can see the surface temperature is dropping, but there is still some dark red present near the base of the flowerpot where heat is trapped.

In Image 3, the flowerpot has been removed from the area. The area under the pot is still about 16 degrees warmer than the other areas that were under the heated mat.

Why is trapped heat a problem?

Trapped heat should be avoided because it can have some unwanted consequences. If 
the floor temperature sensor is located under the insulating item, false readings can occur. As a result, the system responds to the warmer temperatures at the sensor (under the object), and the rest of the floor will be colder than desired.

Leaving objects, like a beanbag chair, futon mattresses, boxed-bottom furniture or fixtures, in the same place on the floor for extended periods of time may result in localized areas of discolored carpet or laminate. The Environ™ radiant heating products are powered at 12 watts per square foot, which will not cause discoloration when installed and used under the conditions provided in the installation manual. However, problems can arise if excessive insulation (an object) is placed over a 
heated carpet area for long periods of time. Carpets that are lighter in color or lower in quality are the most vulnerable to discoloration.

Higher surface temperature is evident where the flowerpot was sitting.
Image 3. After the flowerpot was removed, the exposed surface where it was sitting is still much warmer than the rest of the floor.

Laminate,
engineered wood and carpet are more forgiving than hardwood, but they all
 can be affected by trapped heat. Gapping, cupping, and discoloration can 
occur in any of these floor coverings when the heat is trapped for long periods of time. For the best results, always follow the humidity recommendations of the flooring manufacturers.

In extreme cases, trapping heat for an extended period of time can be a safety issue resulting in a system failure if the floor covering fails.

What can be done about it?

Prevention is the best strategy to avoid trapped heat. Following the recommendations in the Environ™ installation manual will ensure safe, trouble-free operation of your radiant heat system for many years.

Those recommendations for avoiding trapped heat include the following:

    • • Never install radiant heat
 under permanent fixtures or items with flat or boxed bottoms.
    • • Ensure that there is a minimum clearance of 2-3 inches between the floor covering surface and the underside of the furniture to allow free movement of air through
that space for any large furniture on short legs (e.g. sofa or bed). Do not allow bedclothes or drapes to restrict the airflow under furniture.
    • • The following types of furniture should never be allowed onto the 
surface of the carpet or other floor covering where radiant heat is installed: pianos
, bookcases, closed-bottom furniture, and any stands that have sharp points as feet.

The system will work great if you let it. By following a few simple guidelines, you can enjoy the maintenance-free comfort, convenience, and other benefits of radiant heat for many years.

After all, if you just spent money on a heated floor, why cover it up and keep the
heat from getting into the room? Why place a barrier between you and the 
heat when instead you can enjoy the open space, additional warmth, and your investment?

Posted by:
Scott Rosenbaum
10/30/2013

Tags: warmlyyours blog, tech tips, home remodeling, radiant heating

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