ASHRAE Journal- September 2008

Radiant Floor Cooling Systems By Bjarne Olesen, Ph.D., Member ASHRAE I n many countries, hydronic radiant ﬂoor systems are widely used for heating all types of buildings such as residential, churches, gymnasiums, hospitals, hangars, storage buildings, industrial buildings, and smaller ofﬁces. However, few systems are used for cooling. People choose ﬂoor heating because it uses space wisely, temperature distribution is uniform and it is a low-temperature heating system. One advantage compared with air systems is that ﬂoor heating is a more efﬁcient means of transporting energy. The demand for comfort, better building insulation, and greater internal loads from people and equipment have increased interest in installing a cooling system to keep indoor temperatures within the comfort range. This resulted 16 ASHRAE Journal in the introduction of ﬂoor systems for cooling.1 – 3 Because these systems operate at a water temperature close to room temperature, they increase the efﬁciency of heat pumps, ground heat exchangers and other systems using renewable energy sources. More than half the thermal energy emitted from a ﬂoor heating system is in the form of radiant heat. The radiant heat exchange directly inﬂuences the heat ashrae.org exchange with occupants and surrounding surfaces such as walls and ceilings. In this way, a uniform thermal environment is established. Because of the high radiant heat output and the fact that occupants are close to the ﬂoor surface, it’s an obvious choice to use the same ﬂoor system for cooling. However, the convective heat exchange coefﬁcient for ﬂoor cooling is much lower than it is for ﬂoor heating. Several comfort factors such as acceptable ﬂoor temperature, vertical air temperature difference, radiant asymmetry and dew-point temperature may reduce the cooling capacity of a ﬂoor system. The ﬂoor construction (slab thickness, About the Author Bjarne Olesen, Ph.D., is director of the International Centre for Indoor Environment and Energy, and a professor at the Technical University of Denmark. September 2008 http://ashrae.org

Table of Contents Feed for the Digital Edition of ASHRAE Journal- September 2008

ASHRAE Journal- September 2008 Section: Contents Contents Section: Commentary Options for Sustainability Section: Industry News The Silk Route for Energy Solar Thermal Is Unrealized Opportunity Industry Groups Sue City of Albuquerque Section: Letters Letters Section: Meetings and Shows Meetings and Shows Section: Feature Articles Article-Radiant Floor Cooling Systems Article-HVAC Design for Sustainable Lab Article-Mixed Mode Ventilation Article-Single- Design Considerations For Active Chilled Beams Article-Acoustic Design In Green Buildings Article-Teams, Contracts & BIM Section: Building Sciences Some Old Lessons Distilled Section: Washington Report Energy in Federal Buildings Section: Products HVAC&R Product Showplace Section: Emerging Technologies Toplighting & Lighting Controls For Commercial Buildings Section: Special Products Fans & Blowers Section: Classified Ads Classified Ads Section: Advertising Index Advertising Index

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