A shift away from gas to electricity
A large proportion of UK homes are currently served by gas-fired central heating systems. One key change in the new SAP methodology is an update to the carbon emission factor for electricity – it is envisaged that this will drastically reduce from 0.519kgCO2/kWh to 0.136kgCO2/kWh to reflect the decarbonisation of the national grid. We expect to see a significantly increased uptake of electricity derived from forms of space heating, primarily in the form of electrically driven air source heat pumps.
A better envelope
The new version of SAP will push developers to allow for a better insulated thermal envelope for new homes. The target thermal performance (U values) for roof constructions, windows and rooflights are being improved.
More waste water heat recovery systems
Waste water heat recovery systems (WWHRS) can be integrated into bathrooms to recover heat from shower and bath waste pipes. These systems are going to form part of the ‘notional’ building specification in the SAP methodology. This does not mean it will be compulsory for them to be installed but, if they are not installed, compensating measures (i.e. a further enhanced building fabric specification, a more efficient air source heat pump or further renewable technology provision) must be incorporated into the design. We expect these to be standard in most new homes.
More solar photovoltaics
Historically, we have predominantly seen the driver for PV panel installation on new homes as being the below:
In the revised SAP methodology, however, a PV array will now form part of the ‘notional’ building. We expect PV arrays to be standard in most new homes.
Bespoke Thermal Bridging Design
Thermal bridging can occur at the junctions between thermal elements in buildings (where there is a break in the otherwise continuous insulation layer, leading to a detrimental heat loss path). Typical locations for thermal bridges are around windows, at balconies, at junctions between walls and the roof, etc. Two key changes are being implemented in the revised SAP methodology:
The impact will be that developers must produce or commission bespoke PSI calculations for thermal bridges to prevent SAP penalisation for heat losses occurring at these junctions.
An air pressure test for every dwelling
It will no longer be permitted to test only a sample of dwellings on multi-dwelling development sites.
A separate Approved Document – Approved Document O – has been published by the government, covering the performance requirements for overheating mitigation in new residential schemes. This will require a more thorough formal assessment of overheating for sign off by the Building Control Officer / Approved Inspector. It is likely that, in some cases, this will require a dynamic thermal modelling overheating risk assessment to be completed.
Some schemes may still qualify for ‘transitional arrangements’ after the new Part L regulations come into force, meaning they can still be assessed against Part L 2013. Meeting the qualifying threshold requires that:
Ridge sees this revision of Part L as a positive change for the future of new homes in England and a step in the right direction towards a zero-carbon built environment.
For more information on the revised regulations, and on how to ensure compliance with them, please contact:
Associate, Building Services Engineering
Partner, Building Services Engineering