What is the building base temperature?

The building base temperature is the outside temperature below which a building needs to be heated. The typical base temperature used for most buildings in the UK is 15.5°C - hence 15.5°C is the default value when you set up the building(s) you are energy monitoring in sMeasure.

Important: This is not the same as the temperature on your heating thermostat nor is it the room temperature inside the building.

In the case of heating of a building, the energy flow both through the building fabric and through normal air changes/ventilation is proportional to the difference between the internal and the external temperature. A building that wants to maintain an internal temperature of, say, 21C doesn’t need heating whenever the external temperature is below 21C because there are also heating gains provided by sunlight through windows, heat from devices, appliances and lights and even heat that comes from the people inside. The external temperature below which we need to heat a building is dependent on the building fabric, air-tightness and additional gains. It is generally several degrees below the internal set point temperature. It can be many degrees below for very well insulated buildings with lots of people and equipment.

You should not change the base temperature unless you know for certain that it is different from the default.

Use of the wrong base temperature ruins the linearity of a well run building and will make benchmarking erroneous.

Which buildings are likely to have a different base temperature?

An example of a building with a higher base temperature is a hospital. A hospital is likely to use a higher base temperature such as 18.5°C because there will still be a heating demand for maintaining the comfort of patients until the outside temperature is above 18.5°C.

Therefore, the base temperature depends on the temperature the building is heated to and the amount of heat supplied from people and equipment. The base temperature can and does vary greatly. It can be as low as 10°C for a thermally well insulated building with large internal gains.