The Standard Assessment Procedure (SAP) is the UK government’s recommended methodology for measuring the energy rating of residential dwellings. It calculates the typical annual energy costs for space, water heating and internal lighting. The CO2 emissions are also calculated for building regulations. The SAP rating is a scale from 1 to 100+, with dwellings that have a SAP over 100 being net exporters of regulated energy.
SAP 2012 has been used as the basis for checking new dwellings for compliance with building regulations (Part L1a and Part L1b) in the United Kingdom requiring the conservation of fuel and power since 6 April 2014 in England or 31 July 2014 in Wales. SAP calculations are used to produce an EPC once a dwelling is complete.
Here are some tips to improving the SAP rating (and the DER/DFEE):
SAP Calculation – Get a calculation done early in the design process. The earlier a SAP calculation is undertaken in the design process the more options will be available to demonstrate compliance with building regulations. It is often far more costly to retrospectively improve a specification once work on site has begun.
Low Energy Lighting – The minimum requirement for a new build is 75% of fixed internal lights are low energy. Fitting all low energy internal lights is a cost effective improvement. Low energy bulbs in standard ceiling pendent count as low energy light fittings.
Improve The Fabric – Heat loss through the fabric accounts for the largest amount of heat loss for most dwellings. Lowering u-values by increasing the amount insulation will enhance the thermal performance. Building in a sheltered location, look into using full fill PIR insulation board for some of the best u-values.
High Thermal Performance Windows – Many manufacturers offer windows with u-values as low as 1.0. In addition, using windows with a BFRC certificated U-value/g-value can offer considerable improvements.
Air Pressure Test – Most builders can achieve a rate of 5 m3/hm2. The more air tight a dwelling is the better it performs thermally. RJ Acoustics can carry out pressure testing and can offer advice on how to build an air tight dwelling (more information).
Thermal Bridging – As a minimum developers should follow the generic ACD guidance, this allows for an improved psi value to be used in the SAP calculation. There are hundreds of bespoke psi values, calculated by manufacturers of building products, retailers, trade bodies etc, that offer even better thermal performance. Using bespoke psi values for all or some junctions can be a very cost effective way of improving thermal performance and will help achieve a low air pressure test.
Boiler Efficiency – The headline efficiency is not always the most important when it comes to SAP calculations. As the heating demand for houses has decreased due to better thermal performance, the summer efficiency (water heating efficiency) has become just as important.
Heating Controls – Most properties will require a minimum of a programmer, thermostat and thermostatic radiator valves (TRVs) to meet building regulations. Larger properties (floor area greater than 150m2) will require time and temperature zone control. Including advanced controls such as a delayed start thermostat or a weather/load compensator offers a significant benefit.
WWHRS/FGHRS – Waste water heat recovery systems (WWHRS) extracts heat from shower/bath water after it goes down the plug hole. The heat can then be transferred to fresh water helping to raise the temperature of the water prior to heating. Similarly flue gas heat recovery systems (FGHRS) extract heat from flue gases to pre heat the water entering the boiler.
Renewables – Energy created from solar panels (photovoltaic), solar thermal (solar water heating), wind turbines or even hydro power can be incorporated into the SAP assessment. A form of renewable technology is likely to be required where there are special planning condition that require an additional reduction over the TER or a percentage of energy to be generated from renewable sources.