Where possible, space heating should always be considered as a major energy use for sub-metering purposes.
Where space heating cannot be separated from hot water, this must be fully justified by the design team at QA.
See KBCN0329: Combined system for space heating/cooling and domestic hot water.
Where electric space heating is used, this in itself cannot be used as justification for combining the space heating along with lighting and small power unless there is a clear justification for doing so.
See KBCN00068: Combined sub-metering of electric heating and small power equipment.