FAQ | Ask & Answer Q: How Warm is a Radiant Infloor Heat? A: A heated floor normally "feels" neutral. Its surface temperature is usually less than our body temperature, although the overall sensation is one of comfort. Only on very cold days when the floor is called on for maximum output will it actually feel warm. Radiant floor temperatures are far more pleasant than being buffeted by hot-then-cool breezes, which are often associated with forced air furnaces. Q: Cooling a Home that has a Radiant Infloor Heat? A: A home that has a radiant floor heating system will typically have a separate system installed to provide the cooling. The reason is straightforward: heating is ideally delivered from the ground up. Radiant floor heating produces room temperatures very close to ideal: 75° at floor level, declining to 68° at eye level, then to 61° at the ceiling. Cooling, contrastingly, is best delivered through ductwork located near the ceiling of a room. Trying to do both functions with one system will render one or the other less effective. A separate system to deliver just cooling will not be as expensive as a combination heating/cooling system. Q: What Type of Floor can I Use? A: All types of flooring can be used with a radiant floor heating system. However, it is important for the designer of the system to know these flooring choices up front: the surface temperature of wood floors, for instance, should not exceed 80°. So a separate zone would be designated for wood floor areas. Surface temperatures over 80° may cause the wood to become excessively dry and then swell when it absorbs moisture. Carpet pads are rated for R-values by the Carpet Cushion Council. When added to the R-value of the carpet, it produces a total R-value of the carpeted section of the floor plan. The radiant floor heated system designer must be provided this information to make an accurate design. Know your flooring selections so the system designer can calculate the proper radiant floor heating system. Q: What is Thermal Mass? A: "Thermal Mass" refers to the ability of a material to retain heat. For instance, a heated stone will remain warm much longer than a block of wood. This is because the stone is denser, thereby containing more mass. The mass of the earth can be used as a flywheel when it is heated under a radiant concrete slab. This storage of heat can carry a building through a time when energy is not available. Where "off peak" electrical rates are offered, using a radiant floor in conjunction with the thermal storage of the earth beneath the slab can produce some very low electric bills. Thermal mass in a heated shop or hangar floor responds rapidly to the change or air temperature when a big overhead door is opened. All the heat that has been "trickled" into the slab over time is released quickly to combat the cold air rolling over the floor. This happens because of the sudden, dramatic increase in temperature difference between the slab and the air. Once the door is closed the building returns to its normal comfort setting almost immediately. The key to any radiant panel system is to provide an even surface temperature so some mass is required to spread the heat across the panel. This mass may be in the form of gypsum or other cementitious material or metal plates in the panel construction. Some under floor systems simply rely on air currents within the joist space and the mass of the wood sub floor to spread the heat. When properly designed, these systems are a good alternative for retrofitting an existing building.