SAP Ratings explained
Building Regulations require that a SAP calculation and a Predicted EPC is submitted for new dwellings prior to the commencement of work.
A SAP calculation indicates a score from 1 to 100+ for the annual energy cost based on:
- The elements of structure
- The heating and hot water system
- The internal lighting
- The renewable technologies used in the home.
SAP calculations allow comparison to be made of the energy running costs of dwellings anywhere in the UK. This is achieved because the calculations are predominantly location independent and are based upon a notional standard occupancy that overcomes variations associated with physical location and the differing ways in which people utilise their homes.
A SAP calculation for a new dwellings is a desktop exercise, the client or their designer submits drawings, plans and specifications of the development to the assessor. It is recommended that the SAP calculation is undertaken early in the design process, this will help to prevent any costly redesign of the dwelling.
Design: Draft stage
From the specification provided the assessor calculates the performance of the thermal elements. These are expressed as ‘U’ values (the rate at which heat passes through the fabric of the building), the higher the ‘U’ value the greater the rate of heat loss. The assessor then inputs this data into the SAP calculation. Data is entered relating to:
- Type of dwelling
- Openings (windows, doors, roof lights)
- Main and secondary space heating
- Hot water generation
- Renewable technologies, including photovoltaic panels and solar water heating
- Energy efficient lighting
The software determines whether the proposed dwelling will comply with the requirements of the Building Regulations with regards to the conservation of fuel and power. The assessor is able to use the software to model different variations of the design if the initial specification doesn’t show compliance. The assessor should then advise the designer of the shortfalls and recommend solutions as required.
Built: Draft stage
The assessor will edit the SAP calculation to reflect the results of the air pressure test and any variations to the specification. The software is used to check that the completed dwelling still meets the requirements of the Building Regulations with regards to the conservation of fuel and power. If it does not the assessor recommends remedial action.
For new build dwellings the assessor checks to ensure that the dwelling is registered on the Government’s central database register of national property addresses. If it is not the assessor arranges for the address record to be created.
Built: Final stage
In addition there are other documents that are required by Building Control such as the SAP worksheet report and the SAP data input report.
The assessor provides the client with the reference of the EPC so that the client is able to obtain a copy from the Government’s central registry website at: www.epcregister.com/.
Building Regulations require that an Energy Performance Certificate is provided prior to a completion certificate being issued.
Since SAP calculations are based upon a desktop exercise, and not a site survey, it is critical, that the correct information is submitted, the following is a suggested list of the information sources and data items required.
- Site address and postcode.
- Site plan to include orientation of the dwelling(s).
- Plans of each storey, normally at 1:100 scale.
- Elevations drawings for each elevation.
- Sectional drawings of the dwelling.
- A written specification which must include:
- Details of the principal heating and hot water system to include make and model of boiler, details of heating emitters, hot water cylinder size (if applicable) and the system controls.
- Details of any secondary heating system present.
- Details of ventilation systems.
- Details of the internal and external lighting.
- Details of the construction of all different floors to the property to include type and thicknesses of insulation and any other building products used.
- Details of the construction of all different external walls to the property to include type and thicknesses of insulation and other building products used.
- Details of the construction of all different roofs to the property to include type and thicknesses of insulation and other building products used.
- Details of the doors and windows to include sizes, type of frame, type of glazing, thickness of glazing, any low emissivity applications.
- Details of any renewable technologies utilised such as ground source heat pumps, solar water heating or photovoltaics.