Radiant Heating

We rented a cabin a few years ago the only source of heat was a fireplace in the main room. The bedrooms were freezing cold. My daughters thought that their father was a genius when I created some bed warmers by heating rocks in the fireplace, wrapping them in towels and placing them under the blankets at the foot of the beds. I had created a radiant heating system!

Alas, my daughters have since found out that their father was not a genius. I am a bit of a history buff and understand some basic radiant heating principles. The heated rocks absorbed the heat from the fire, held the heat and then slowly radiated the heat out in all directions. Materials with mass do this quite well, for example: stone, concrete, and water.

Materials with little mass don't store a lot of heat or radiate the heat. For example, air heats up quickly during the day and cools off quickly at night. Water has much higher mass than air. The water in lakes and oceans warms up slowly but retains the heat for a longer time. The water will absorb the sun's heat during the and thus the air around it will feel cool. At night, the water will radiate out some of that stored heat and the air around it will be warmed.

These basic principles of radiant heat can be used in home heating systems. With good design they can be a very efficient and extremely comfortable form of heat. - George


  • Radiant heating systems can have many advantages. For example:

    Comfortable and Even Heat

    A warm object heats nearby objects by heat radiation. For example, a person standing on a heated floor is warmed by the radiant heat in the floor. This makes for a very comfortable and even form of heat.

    We feel warmer in an evenly heated space then in a space with some very warm and some very cold surfaces. And this holds true even if the average temperature in the evenly heated space is lower than that in the unevenly heated space.

    Kitchen Floor

    Zone Heat

    Radiant heating systems lend themselves to zone heating. Heating levels that can be adjusted to the needs of different areas. For example, heating rooms to a higher level when they are in use and a lower level when they are not in use.

    The right amount of heat in each space equals wise energy use and savings.

    Wirsbo Thermostats

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    No ducts!

    Heating ducts are large and can use up a lot of space. Radiant heat uses wires or pipes to get the hot water or electricity to each area of a home and these wires and pipes take up very little space.

    Wirsbo Manifold

    Wirsbo Manifold Courtesy of our sponsor PexSupply.com

    For example Pex piping and pex manifolds can be used to bring the hot water to various parts of a house. Pex piping systems can be used in new construction and may simplify the heating system in a remodel or upgrade.


    Radiant heat can be delivered in all sorts of ways:

    This versatility allows for the customization of the heat delivery to various parts of the a house.

    For example, when used in an existing house, it might be possible to install heating panels under the floor on the main level of the house and baseboard and kick space heaters in other locations.

    Many Boiler and Water Heater Options

    Heating water for radiant systems can be accomplished in many ways. Boilers of various types and tank or tankless water heaters can be used. Sizes and configurations depend upon each application. The same boiler or water heater can also be used to provide domestic hot water.

    Natural gas, propane, oil, biodisel and electricity can be used as fuels and in today's de-regulated energy market the the choice of fuels often depend upon local availability more than price.

    "Mix and Match"

    My clients had a very nice 'craftsman' style home. The old furnace had been updated with a new forced air unit but the duct system was old and inefficient. Many parts of the home were cold. Installing a new duct system for the whole house would have destroyed many of the fine features of this home.

    I recommended removing the old ducts, and installing a partial duct system in half of the home. The other areas could now be heated with some floor and kick-space heaters and the old coal burning fireplace could also be converted to a thermostatically controlled gas unit. This combination of systems would provide for excellent heat control without damaging the home.

    And what about cost?

    The relative cost of radiant heat vs. other forms of heating will depend upon the design of the system. "The devil is in the details".

    In my work I see many town homes with radiant heating system that use a water heater for the heat and the domestic hot water. In some units like this a thermostatically controlled gas or propane fireplace is used for the living area and an electric wall mounted heater maybe used in a bathroom. Relative cost - low.

    Start adding spiffy details and make this a much larger home and the relative cost of a radiant heating system can be more expensive to install.

    And what about operating costs?

    Once again, operating costs will depend upon a host of details. Here are some suggestions:

    • Good insulation and well designed tight construction practices are essential in making any heating system efficient.
    • Homes and spaces must be designed for optimal use. If a home is too large, it will require too much energy.
    • A good heating system starts with a good system design.
    • Neat and careful installation layout and work reduces heat loss due to unnecessarily long pipe loops and uneven heat.
    • All heating systems need regular maintenance.