Calculating BTUH Output for Different Water Temperatures

The BTUH outputs are listed for 180° water. The following chart may be used to calculate the BTUH outputs for different water temperatures:

Water Temperature	Multiply the Listed BTUH output (180°) by:
120°	0.38
130°	0.48
140°	0.57
150°	0.67
160°	0.78
170°	0.89
180°	1
190°	1.13

To size the radiators it is necessary to calculate a house’s heating requirement. This calculation measured in BTU/Hour should be done on a room-by-room basis either by a heating contractor or qualified plumber. The following are some estimates of Heat Requirements for Sample Cities:

City:	BTUH per sq. foot:
Boston	40
Chicago	40
Denver	40
New York City	40
Philadelphia	35
Portland, OR	25
San Francisco	25
Seattle	25
Toronto	40
Washington, D.C.	35