Radiant floors provide both energy efficiency and superior comfort particularly when powered by geothermal systems or state-of-the-art high efficiency condensing boilers and controlled by carefully designed control systems. They are somewhat more expensive than most forced air and hydronic baseboard systems but for some the extra expense is well worthwhile.

But...
A poorly designed, poorly controlled radiant system can be uncomfortable and expensive to run.

Advantages of Radiant Floors

•Radiant heat is transmitted directly to the room occupants rather than being transferred by warm air. This tends to overcome the radiant cooling effect of cold windows and creates a more balanced, comfortable temperature gradient from floor to ceiling. Hot air systems tend to result in cool air lying near the floor and hot air collecting near the ceiling. Comfortable room temperatures with radiant heat are usually lower than those needed with forced air resulting in energy savings.
•Forced air systems often result in uncomfortable drafts which radiant systems avoid.
•Noise is reduced to a minimum with a radiant floor. A quality boiler makes little noise and a well controlled radiant floor should be silent.
•Radiant floors do not fill the air with dust and pollution picked up in dirty ducts.
•Well controlled radiant floors can continuously deliver just the right amount of heat to rooms to provide optimum comfort.
•Forced air and baseboard systems take up valuable wall and/or floor space and often overheat valuable furniture which 'gets in the way'. Radiant floors take no space and provide gentle, constant warmth.

Disadvantages of Radiant Floors

•Radiant floors tend to cost more to install than forced air and baseboard systems.
•Floor coverings can create problems. A radiant floor designed to work under a wood finish may provide insufficient heat if a thick carpet is then added.
•'High thermal mass' radiant floors hold large amounts of heat which may result in significant overheating of a room if a secondary source of heat (such as the sun shining in) suddenly enters a room. Good controls can alleviate this problem.

Energy Efficient Homes and Radiant Floor Heating

This article discusses the pros and cons of radiant floor heating in an energy efficient home. It points out that radiant floor heating may not be the optimum selection in a new, well-insulated and 'tight' home.

Points and Options to consider when planning your radiant floors

High thermal mass or low thermal mass
High thermal mass radiant floors with pipes encased in concrete or a gypsum overpour are renowned for their comfort but they must be carefully controlled by a sophisticated system which monitors both the outside and the inside temperature. A poorly 'controlled' floor will result in significant overshoot or undershoot of the temperature in the room as the outside weather and temperature changes.
Low thermal mass radiant floors are now available which have heating pipes inlaid in the surface of the floor with a thin layer of aluminum to carry the heat from the pipes and distribute it evenly. The temperature of this type of floor can be changed much more quickly and therefore sophisticated control is unnecessary.
Pipes laid under an existing floor and backed with insulation, as in many retrofits, can be considered medium thermal mass floors and usually require careful control.

Zoning
Most radiant floor systems have several zones but are they optimally connected. You should ensure that rooms which will have similar heat demands are using the same thermostat.

Warm bathroom floors
Many people like to have warm bathroom floors in the morning when heating in other rooms is unnecessary. A separately zoned bathroom with a timer easily provides this little luxury.

Electric systems
If all you want is a little floor warming in a bathroom it may be more efficient to use electric heating under the tiles rather than go to the expense of a hot water system. Electric systems are cheap to lay and control. Electric heat usually costs more than gas heat but if you have a forced air system already this may be a good solution.

Pipe layout
Has the pipe layout for your radiant floor been well planned? Areas near windows or doors often need more heat so a closer pipe spacing may be called for.

High efficiency, condensing boilers
High efficiency condensing boilers work best when the water returning to them for reheating is relatively cool. Radiant floors provide just this condition so this type of boiler is an obvious choice. With the heating efficiency of a radiant floor and an efficient condensing boiler your heating costs can be significantly reduced compared to most other systems.

Control systems, overshoot
To ensure that your investment in a radiant floor system provides the comfort you expect you must ensure that the control system for the floors matches their quality. Without efficient, 'thinking' control, high thermal mass floors can provide heat when it's not required or be too cold when the rooms need heat. This can result in uncomfortable temperature 'overshoot' or 'undershoot' in the rooms.