Radiant Heated Floors
Radiant Heated floors are pipes, tubing, or mats which are installed under the top flooring which evenly distribute heat throughout a space. Unlike conventional baseboard heating or forced air heating, radiant heated floors can keep occupants comfortable in the space with lower ambient air temperatures. Energy savings can be achieved through the use of radiant heating in floors as opposed to conventional heating methods. There are three types of radiant heat: electrical, air, and hydronic.
The American Society of Heating, Refrigerating and Air-Conditioning Engineer (ASHRAE) 55 handbook; The Thermal Environment Conditions for Human Occupancy, is the referenced design guidebook for optimal human thermal comfort for the built indoor environment. This book outlines radiant heating installation guidelines.
The U.S. Department of Energy avidly promotes the installation and use of radiant heat flooring for energy efficiency through lowering the use of conventional heating methods that will consume more energy.
Radiant Heat is often installed either through a ‘wet’ or ‘dry’ method. ‘Wet’ installation methods refer to the radiant heat pipes or tubing installed into wet concrete. ‘Dry’ installation methods refer to the radiant heat pipes or tubing installed into the air cavities between the joist spaces. In the dry installation method thermal reflective plates should be used to increase the efficiency of the radiant heat pipes. Aluminum heat transfer plates can increase efficiency by 20% – 40%.
Using Radiant Heat Under Hardwood Floors
Radiant heat can be used under hardwood flooring, but with certain considerations. It is a misconception that radiant heating will cause issues for the wood flooring. Specific guidelines should be carefully followed, and only two types of subflooring material is allowed.
- Some engineered wood flooring can be installed over radiant heat flooring. Always consult manufacturers before installation.
- Solid wood floors should never be installed over radiant heat flooring.
- The narrower the boards, the better. Boards above 3″ are not recommended.
- Kiln-dried wood that is quarter-sawn will expand in thickness and not width.
- Radiant heat should be kept below 85° Fahrenheit.
- According to the ASHRAE 55 handbook, Thermal Environment Conditions for Human Occupancy, 74° F – 77° F is the flooring temperature at which the most amount of people will be comfortable.
- Pine floors should be kept in the range of 72.5° F – 82° F.
- Oak floors should be kept in the range of 76° F – 82° F.
- Tongue & Groove strips are recommended.
- Beveled-edge boards are recommended.
- Subfloor Recommendations: Plywood (⅝”) or Oriented Strandboard (¾”)
- Particleboard is not recommended as a subfloor material.
Types of Radiant Heating
Electric Radiant Heat
- Electric radiant heating can be a beneficial system to save on energy use if there are 2 considerations as part of this design system. 1) The electric company must allow a ‘time-of-use’ rate, which allows for the system to draw electrcity during off peak hours. However, this can only be done if, 2) The thermal mass of the flooring material is high enough to allow for the floor to store heat for 8-10 hours after the electrical heating system shuts off.
Hydronic Radiant Heat
- Water radiant heating is the most popular of all three systems. The water is heated up by a boiler and is then pumped up through the system and exits back out into the boiler. Heat transfer point controls should be installed in an efficient hydronic radiant heat system. These controls help occupants to monitor the wood floor temperatures and help to prevent overheating the flooring if the equipment fails. The set point control should would either reduce the system water temperature or temporarily cycle the system off.
Forced-Air Radiant Heat
- Air-heated radiant flooring systems are not efficient and not popular. There are two types: solar heated and furnace heated. The issue with the solar air-heated radiant system is that it works during the day. The issue with the furnace heated air radiant system is its inefficiency.