# Calculating heat loss and size a radiator

## Watch our heat loss calculation video

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## Calculation of resistances for an insulated wall

 Surface Area (m2) U Value (W/m2K) Thermal Loss (w/K) Floor 104 0.60 62.4 External Walls 102 0.40 40.8 Windows 16 2.00 32.0 Roof 146 0.35 51.0 Roof Windows 9.6 2.20 21.0 Internal Walls No Loss - - Total for building fabric 207.3

Assuming a Room Temperature is required at 20C and an outside temperature of 0C
The heat loss for the fabric = 207.3 X3=20 = 4146 W

Air Infiltration is assumed at one air change per hour.

Heat loss = Volume X specific heat X difference in Temperature
= 520m3 X 0.33 X 20 = 3432 W

Total Heat Loss = 4146 +3432 = 7578 W

Would suggest 6 radiators having at least 1263 W output.

From Manufacturers Catalogue 600mm high X 1000mm long double panel radiator gives 1336 W this would do the job

To test a U Value, watch our videos on calculating a U value and testing a U value