While we worry about the almighty dollar and the reduction of our atmosphere into a smog of ozone-depleting global- warming gases, we are ignoring the lessons of the past. Radiant heating and cooling has been around for thousands of years. The Romans used hypocausts in heavy masonry buildings to keep them warm during the winters in northern Europe, and the Turks used stream water run through channels in walls and floors to cool their palaces during the warm summers. A common thread was the use of building mass to act as a thermal storage medium, while using radiant energy for thermal comfort.
Radiant cooling and the use of the building's thermal mass to provide off-peak cooling opportunities have been used with increasing regularity in Europe, mainly due to the much higher energy costs over there. Swiss "Batiso" buildings (Batiso = batiment isotherm, a French term for "constant temperature building") have become more common and the technology better understood over the last ten to fifteen years. Essentially, an exposed concrete slab is used as a radiant cooling device, and hydronic piping is cast into the slab to maintain its temperature. During the day, the slab absorbs the heat gains from the occupied space in the building, and then the slab is "recharged" at night using a fluid cooler (a type of cooling tower). Refrigerant-based water chillers are not usually required to maintain the building at a constant indoor climate during a peak summer design day. The building air system then only needs to supply 100% outdoor air at a rate to satisfy the occupant ventilation requirements. Essentially, the primary indoor temperature control is done with radiation, rather than with an air system.