In-floor hydronic radiant heat systems, due to their configuration, require relatively low water temperatures to provide comfort and meet setpoint temperatures. These systems heat surfaces rather than air. Depending on a variety of factors, water temperatures anywhere between 70°F and 170°F may be required. "High-temperature" hydronic designs (baseboards, etc.) generally call for water closer to 180°F.
The temperature needed in each room should be accounted for in the design of any radiant heating system. Keep these rules of thumb in mind: do not exceed 150°F water temperatures for any installation, except those in which the tubing hangs in a joist bay. Floor surface temperatures above 87.5°F can cause discomfort and burn bare feet. Wood floors can be damaged if surface temperatures get above 82°F, although this figure may vary by floor manufacturer.
