Outside design temperature

Also known as design outside temperature, design external temperature, DOT (design outside temperature)

Outside design temperature is the outdoor temperature used as the cold design point for heat loss calculations and heat pump sizing checks.

Outside design temperature is the outdoor air temperature chosen as the cold design point for a heating calculation. In heat pump work, it is used with an internal design temperature to calculate heat loss and to check whether the heat pump and emitters can meet the required load at the design condition. Some guidance shortens this to DOT (design outside temperature). MCS heat pump documents use outside design temperatures, design temperatures and postcode-based outdoor low temperature data in related design and pre-sale calculation contexts. The figure is not a weather forecast, the coldest temperature a property will ever see, a thermostat setting, a running-cost guarantee or proof that a heat pump has been sized correctly.