Copyright Goodheart-Willcox Co., Inc. Chapter 12 Radiant Heating Systems 267 Chapter Review Summary■ ■ In radiant heating systems, heat is conveyed in a direct physical path and heats the objects in the conditioned space, not the air. ■ ■ The human body responds more favorably to radiant heating sources than to forced-air heating sources. ■ ■ The difference between low-mass and high-mass radiant heating systems is the capacity and the ability to store heat energy. Low-mass radiant heating systems have a limited capacity to store heat as compared to high-mass heating systems. ■ ■ There are many different types of systems available for generating hot water for radiant heating, including conventional boilers, condensing boilers, geothermal heat pumps, and solar thermal storage systems. ■ ■ Radiant heating systems primarily use PEX and PE-RT tubing as a means of heat transfer. PEX tubing is classified as type A, B, or C. When used with ferrous types of devices and fittings, PEX tubing must include an oxygen barrier. PE-RT tubing is designed to operate at raised temperatures and is constructed with five layers of materials that give it significant strength and chemical resistance. ■ ■ There are two classifications for radiant floor heating systems: they can be wet radiant hydronic systems or dry radiant hydronic systems. ■ ■ A slab-on-grade radiant floor system is a layer of concrete poured over an existing grade with the radiant tubing embedded into the concrete. ■ ■ Steps for installing a slab-on-grade flooring system include laying down a vapor barrier over the existing grade, followed by a layer of insulation board. ■ ■ Radiant heating systems should be pressure tested for tubing leaks before the tubing is covered over. ■ ■ Another method of installing radiant flooring is the use of thin-slab concrete or gypsum over an existing floor. ■ ■ Radiant flooring can also be installed by means of prefabricated above-floor panels or underfloor suspended radiant tubing. ■ ■ When radiant flooring is not an option, radiant panels are also available for installation in walls and ceilings. ■ ■ The steps that go into designing a radiant heating system include performing an accurate load calculation, properly sizing and spacing the tubing, and properly sizing the circulation pump based on system flow and feet of head loss. ■ ■ Controls for radiant heating systems can be simple or complex depending on the desires of the designer and the needs of the customer. ■ ■ Modern digital controls for radiant heating systems offer advanced efficiency and user- friendly interfaces compared to conventional controls. ■ ■ A very practical application for radiant heating is snow and ice melting. Snow and ice melt systems can be used for residential and commercial applications. Applications for snow and ice melt systems include driveways, sidewalks, and parking garages. ■ ■ The design process for snow and ice melt systems compared to conventional systems is quite similar except for some key differences for snow and ice melt systems, which include determining the proper design outdoor air temperature and proper placement of the in-ground slab sensors. Slab or in-ground sensors can detect when a snow and ice melt system shall be energized and de-energized. ■ ■ Because snow and ice melt systems are located outdoors, their installation criteria differ from that of conventional systems.