The Best Way to Size Radiators for Rooms

Radiators are one way of heating a room that has heater, central heating or no fireplace. But they need to be sized correctly for the effective energy usage. When a radiator is little, it cannot keep a room’s occupants warm. When it is big, it can cycle on and off more often, using up energy.

Assess the length, height and width of the room in feet. Multiply all 3 values to determine the footage of the space. For instance, if you’ve got a room that measures 12 feet by 10 feet wide by 7 feet high, multiplying 12 by 10 by 7 generates 840 feet.

Multiply the result by 5 to get a radiator in dining and living rooms, 4 bedrooms for bedrooms, or 3 to kitchens and other regions of the home. For instance, multiplying the 840 feet from the bedroom by 3 produces 2,520.

If the room faces north, add 15 percent to the result. When it has doors, add 20 percent and if it has windows, then subtract 10 percent. For instance, since the bedroom to your radiator faces north, you add 15 percent to 2,520 to produce 2,898, that’s the number of BTUs or British Thermal Units your radiator must produce per hour to adequately heat the room.

Because most radiators’ specs list their heating capacity convert your BTU calculation to watts. Because BTUs are units of heat, the conversion is not exact and watts are units of electricity.

Divide the number of BTUs by 3.41. For instance, if you divide 2,898 BTUs by 3.41, the result is roughly 850 watts. You want an radiator to produce the 2,898 BTUs per hour desired by the foot room used in the instance.

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