HEM, the replacement for SAP, is intended to have more functionality that enables its use in a greater number of applications. In contrast, SAP is primarily used for EPC production using a significant number of standardised inputs. It does this through a move to half-hourly calculations (from monthly) and allowing variation of more inputs values.
There are a number of potential implications of this:
- Need for upskilling of SAP assessors (especially for existing home assessments)
- Potential increased costs for delivering assessments
- Potential overlap with dynamic modelling for overheating purposes – will it be possible to avoid dynamic modelling in some circumstances?
- Supposed quicker inclusion of new technologies
Moving to half-hourly calculations also provides the potential for benefit to be obtained from smart appliances, batteries, thermal storage and other load shifting methods. However, there appears to be a missed opportunity here, as carbon factors seem to be fixed rather than varying on a daily and seasonal basis.