South Gloucestershire Housing Standards
Client: Local Authority
Delta Q were employed by a local authority to advise on potential new planning policy for housing. The concept was to consider a housing proposal submitted for planning by a local developer and model the building in PHPP and SAP, comparing the results. The model included the developer proposal, emerging policy and an interim specification, between the two.
The emerging and interim policies used heating energy demand, air tightness and energy use intensity (EUI) as their metrics.
Through our modelling we were able to advise the client about the internal consistency of their proposed standards and about the ability to model buildings using SAP. For example:
- an EUI of 35 kWh/m2a is not realistic in combination with an air permeability of 3m/hr @ 50 Pa
- SAP under-predicted the heating energy demand by 40-70% compared to PHPP
- Meeting an EUI of 35 kWh/m2a is not feasible using SAP because the regulated energy assumptions do not allow improvements associated with good design.
- Meeting these exacting standard requires well designed and installed heat recovery ventilation.
We highlighted short-comings in the SAP approach which meant that it was not an appropriate tool.