Heat loss calcs are used to work out the quantity of energy required to heat a building and the amount to invest in efficient heating technology (when the external conditions are colder). The size of the heating installation depends largely on the performance of the building fabric.
To calculate the size of the heater(s) required to heat a building, we need to know:
– The temperature to be maintained withing the structure.
– The lowest ambient (outside temperature) which can be expected for the area.
– The direct heat loss from the overall surface area of the structure.
– Heat loss through natural or mechanical ventilation.
The difference between the ambient and internal temperatures gives the temperature lift required.
Temperature lift = Internal temp. – Ambient temp.
The heat loss for a structure is calculated by taking each surface in turn, calculating its overall area and multiplying by its thermal transmittance co-efficient or U value.
Heat loss through surface = width (m) x length (m) x U value
The area of windows and doors should be calculated and deducted from the area of the surface they are in and their heat loss should be calculated separately. The total surface heat loss for the structure is the sum of all surface heat losses.
These types of calculations are useful at the design stage of a development to check if the envelope of the building is adapted to the local conditions. In effect, if the thermal behavior of the construction is insufficient, then a bigger, more expensive heating system with a greater energy consumption will be required, leading to higher bills and more CO2 emissions.
