Since my letter was published in your April issue, I have been doing more research on the SBEM software - only to find that the results from SBEM are at least questionable, and most likely wrong.

SBEM says that the auxilliary energy used by a building with a standard radiator central heating system is twice that of the notional building. There seems to be no way of getting the energy below that of the notional building.

It also says that a fan coil system will use roughly twice the auxilliary energy as a VRF or multi split system (what do fan coil unit manufacturers think about this?).

With SBEM, it is easy to get a result where the heating kWh/m2, cooling kWh/m2 and lighting kWh/m2 is roughly 50% higher than the worst case in ECON 19 (this is both the actual and the notional building).

It does not appear that there is any approvals process in place as yet for other software to become licenced for use with Part L (presumably TM33 will become this). I have requested details from ODPM and have received nothing.

It is a totally unacceptable situation that the only approved way of complying with Part L is to use software that produces incorrect results.

Bart Stevens, partner Max Fordham LLP

Source

Building Sustainable Design