Approximate Heat Requirement Calculation
Multiply the room length in metres by the room width in metres by the room height in metres (LxWxH) to calculate the
total cubic volume of the room.
Multiply the room cubic volume by 45 to give you the Watt requirement.
Combine all of the applicable correction factors from the list below and then apply the total percentage to the
Watt requirement calculated in Step 2.
-25% Upstairs bedrooms
-20% Cavity filled walls
-10% Solid floor
-05% Double glazing
+10% Un-insulated cavity walls
+10% North facing wall
+15% Patio doors or French doors
+15% Two outside walls
+15% No loft insulation
+20% Ceiling height above 3 metres
+40% Three outside walls
PLEASE NOTE THAT THESE ARE APPROXIMATE CALCULATIONS FOR GUIDANCE ONLY