Your article, Government’s carbon compliance tool ’inadequate’ (2 July, raises an important question: why is the government continuing to spend money expanding the capabilities of SAP, when other alternative tools are already available in the form of SBEM and DSM?

These existing non-domestic compliance methods can equally apply to domestic properties and offer tools which are flexible enough to accommodate different levels of building complexity - the kind of complexity required in new housing to achieve zero carbon, with all the associated passive design strategies, clean technology and renewable energy sources.

The Part L 2010 version of SAP has already moved to a monthly calculation method, the same as SBEM. Surely opening up the choice of tools available for domestic dwelling compliance allows more flexibility - enabling designers to pick a tool sufficiently complex for the building in question.

At this time, when the government is asking for ideas on how to save money, surely making use of existing tools that energy assessors are already familiar with is the most cost-effective way forward without the need for more government investment?

D McLean