Part L1A of the English Building Regulations has required a SAP (Standard Assessment Procedure) calculation for every new dwelling since 1995. Because it forms part of the Building Regulations a SAP calculation must be provided to the Building Control department of the Local Authority with every Building Regulations application.
A SAP assessment calculates the estimated energy running costs, per square metre, of a domestic property. Including; it’s space and water heating systems, internal lighting and any renewable energy technologies. The SAP energy rating of a dwelling is presented in a scale from 1 to 100+, the higher the number the lower the running costs.
The SAP assessment also calculates the estimated amount of Carbon Dioxide emissions, per square metre, from the dwelling. Including; space heating, water heating, internal lighting and ventilation systems.
Energy Performance Certificates (EPC’s) were introduced in Scotland on 1st May 2007, in England and Wales on 6th April 2008 and in Northern Ireland on 30th September 2008 following the European ‘Energy Performance in Buildings Directive’ (EPBD).
All new build dwellings now require an EPC, which must be produced in a standard format. This will include:
• The energy performance of a dwelling with ‘benchmark’ standards;
• The overall energy costs per square metre;
• The carbon dioxide emissions per square metre;
• Recommendations for cost effective improvement of energy performance.
The figures contained within the EPC are taken directly from the SAP calculations mentioned above. The EPC presents the results of the SAP assessment in bands A to G, with A being the most energy efficient building and G the least.
Although the SAP calculations will usually be undertaken and submitted to the Building Control department at design stage, an EPC can only be issued once a dwelling has been constructed. It will consider the post-construction air pressure test and as-installed details of the building elements and systems. If a dwelling is to be sold off-plan or an energy rating is required before completion a Predicted Energy Assessment (PEA) can be issued at the design stage. However, this will be superseded by an EPC upon completion of the dwelling.
Limitations of the assessment
The SAP calculations have been developed to give a means of comparing the energy performance of dwellings, to provide benchmark performance figures and to aid the increase of energy efficiency and the reduction of carbon dioxide emissions. To achieve these aims the calculations must make certain assumptions about dwellings, the way they are constructed and the way they are used.
Location
The location of the dwelling will in reality have a large impact upon it’s heating requirements, due to the variance in climate across the UK. However, to provide a means of comparing the energy performance of all dwellings, a central location in the UK is used for all assessments.
Occupancy
By far the largest variance in energy used within dwellings comes from the way occupants use them. The amount of energy used can be affected by; the amount of time occupants spend in the dwelling, the temperature at which they feel comfortable or the appliances and equipment they use.
For this reason a ‘standard occupancy pattern’ has been adopted for all assessments. This assumes that, during the heating season, the heating is used for 9 hours per day during the week and 16 hours per day at the weekends. The main living area is heated to 21oC and the bedrooms to 18oC. Only the energy used for space heating, water heating, lighting and cooking is considered.
Fuel price
The fuel costs used in the SAP calculations are based upon an average price from the last three years deflated using the Retail Price Index (RPI) for fuels.
