A simple explanation of what SAP 10 is would start with the fact that it is the newest version of the SAP methodology.

The Standard Assessment Procedure (SAP) for new builds currently in use was introduced in 2012 and has had little in the way of changes made to it since. With the world, technology, and construction methods have changed since then, SAP2012 will be updated with more accurate methodology, to ensure that EPCs are reflective of dwellings built.

SAP 10 was announced by the government back in 2018, but no deadline has ever been confirmed. However, since then SAP 10.1 has been produced and a newer version 10.2 is currently being reviewed. It is anticipated that SAP 10.1/10.2 will finally arrive along with the updates to Part L of the building regulations.

 So what’s different about SAP10.1?

1.    Changes to fuel factors/prices and carbon dioxide factors

Different fuel types have had their fuel prices and carbon dioxide factors tweaked; this is especially true for electricity that has had its carbon factor tweaked to better represent the current mix of the electricity grid. That relies much more on renewable energy than it did in the past, therefore buildings that heavily rely on electricity will no longer be penalised in SAP due to the targets being based on mains gas. The table below shows the previous factors from SAP 2012 and the proposed factors in SAP10.1/10.2.

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2. Heating Patterns

Currently, heating patterns have been assumed to be different at weekends from weekdays, however, evidence suggests that the difference between them is less than assumed and not reflective of actual patterns. Therefore, as part of the updated heating patterns, it will move to be the same for all days from 07:00 – 09:00 and 16:00 – 23:00. This will result in reducing the default heating at weekends.

The default distribution loss factors have also been increased for heat networks as currently they are underestimated and therefore not accurate. This reduces the gains in SAP associated with heat networks.

3. The Calculation of Lighting Energy

Currently, the calculation of lighting energy is based on the percentage and number of low-energy lights. In SAP 10.1/10.2 the calculation will be more complex with the software creating a reference lighting capacity, that is based on the floor area of a dwelling and the potential solar gains. If the calculated capacity is not reached or exceeds the predicted lighting, energy will increase having a negative impact on the rating. This methodology will require additional data to what is required now and will be very similar to the non-domestic SBEM.  

4. Thermal bridging

A major update to SAP concerns thermal bridging details, with the default y-Value used in assessments being raised from 0.15 w/m2k to 0.2 w/m2k. This will penalise builders who do not consider heat losses from building junctions in their designs and construction methods.

As well as changes to the default values, accredited psi values from MHCLG have been removed. Therefore, assessors will now have to use other established construction details or model the junction details to produce accurate psi values. With the use of modelling being the preferred method.

Finally, the default psi values for junctions R1-R9 will increase, resulting in a negative impact for room in roof constructions. There will also be the addition of a new junction for roofs and room in roof constructions, that are currently not covered by junctions R1-R5.0 Thermal Mass Parameter (TMP).

The indicative TMP values of low, medium, and high, have all been removed from the future version of SAP. Therefore, all dwellings will now have to have the TMP calculated, based on the dwelling’s element areas and kappa values. The calculation that will have to be used for the TMP is based on the calculations from BS EN ISO 13786.

6. Overheating

The overheating in summer assessment will now change, with an assessment for the potential to leave windows open during day and night being required. To ensure that the overheating options detailed are suitable for the dwelling assessors will have to indicate in SAP 10 if the dwelling would have any issues relating to noise pollution or security that would prevent windows from being left open during the day or night. For example, if natural ventilation is selected and an issue is raised preventing the windows from being open at any point, then ‘trickle vents only’ would have to be selected instead.

7. Photovoltaic Panels

SAP 10 will introduce options for battery storage of electricity generated onsite into the calculation, as well as options to include a PV diverter, that uses PV to heat an immersion coil in a water cylinder.

SAP 10 will also allow for improved inputs of overshading data. With the option to enter MCS over shading data. This uses the MCS assessment procedure for assessing near and far field objects, which provides a more accurate assessment of overshading. Therefore this will be the preferred option when an MCS certificate is available.

Currently, SAP2012 will allow flats to claim the CO2 saving from electricity generated on-site, where the PV is supplying a landlord’s supply using a single inverter. From SAP 10 this will no longer be an option. The benefits of the cost and CO2 savings from PV will only be available to dwellings that have their own inverters. Therefore, landlords of blocks of flats will need to seek alternatives for cost and CO2 savings.

8. Hot water demand

Currently in SAP 2012 hot water demand does not consider the number of showers and baths present in a dwelling, as well as not considering the electricity used by instantaneous electric showers. SAP 10 will. This will therefore have a negative impact, in terms of energy use, in assessments of dwellings that have more showers/baths and that use instantaneous showers.

As Built Testing Ltd currently carry out SAP assents using SAP 2012. But with our assessors already training on SAP10, we are ready and waiting for its launch so we can ensure we provide accurate and efficient SAP calculations for your dwellings.

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