Energy Performance Certificates (EPCs) and The Standard Assessment Procedure (SAPs)

The Standard Assessment Procedure (SAP) measures the energy rating of residential and commercial buildings, has been around since 1995, with updates every couple of years since then. It calculates the typical annual energy costs for rooms and space and water heating and, since 2005, lighting. CO2 emissions are also calculated. The SAP runs from 1 to 100, the higher the number meaning the lower the running costs.

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SAP has been used as the basis for checking new dwellings for compliance with building regulations in the United Kingdom requiring the conservation of fuel and power since 6 April 2014 in England or 31 July 2014 in Wales.

A number of comparisons have indicated that SAP does not provide an accurate model for low-energy buildings.

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The Standard Assessment Procedure evolved from the National Home Energy Rating scheme, which was based upon the Milton Keynes Energy Cost Index created for the Energy World demonstration buildings in the 1980s.

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The Standard Assessment Procedure (SAP) is a methodology introduced by the Government to assess and compare energy and environmental performance of buildings so they meet standards and environmentally important criteria.

The aim is to assess how much energy a new development will consume while delivering a level of comfort using standard behaviour and occupancy criteria.

The idea is that nationwide comparisons can then be made.

How are SAP calculations made?

All new dwellings have to achieve a dwelling CO2 emission rate (the Distributed Energy Resource rate) no greater than a target CO2 emission rate (Target Emission Rate).

SAP calculations:

1) Design-stage

2) As-built stage

SAP rates/figures are produced from the balance of energy on a new development, considering a range of factors that contribute to energy efficiency, such as:

-Construction Materials

-Thermal Insulation of the fabric of the building

-Ventilation performance and air leakage

-How efficient and controllable the heating is

-Solar gains (how the thermal energy increases as it absorbs incidental solar radiation)

-How much fuel is used to heat rooms and space, ventilation and lighting

-How much energy is required to cool the space

-Are renewable energy technologies used? How efficient are they?

The calculation doesn’t usually include individual characteristics of the household (such as household size and heating patterns and temperatures).

SAP calculations can determine fuel costs and the Environmental Impact Rating via the emissions of carbon dioxide (CO2).(How much does a property impact on the environment around it (from A to G).

L1B – SAP calculations for conversions

If you alter a building so that there is a material change of use, you need to provide SAP calculations to demonstrate compliance with Approved Document L1B.

They’re needed where there’s a material change of use where, after the change:

-the building is used as a dwelling, (where previously it wasn’t)

-the building contains a flat, (where previously it didn’t)

-the building, (which contains at least one dwelling), contains a greater or lesser number of dwellings than it did previously.

SAP assessments have been a legal requirement for all new-build, domestic properties in the UK under Part L of Building Regulations since 1995 and need the certification to be able to be cleared for sale or rent.

Many of the elements of the assessment are related to the construction of the development. Usually SAP scores are calculated and considered at the beginning of a building project and is part of good design communication with architects, builders, surveyors and suppliers.

As well as the regulatory aspect, factors such as energy consumption and carbon output can also be accurately predicted so the running costs of the home minimalised in an early-stage professional SAP assessment.

Is this just for new developments?

SAP Assessments are not confined to just new developments. New extensions or conversions may require a SAP Assessment under Part L1b of the Building Regulations, based on the following guidelines:

-Extensions with more than 25% glazing-to-floor area

-Barn conversions

-Commercial to domestic conversions

-Conversion of a single dwelling into flats or apartments

L1B – SAP calculations for heavily glazed extensions

If you build an extension where the glazing is greater than 25% of the floor area, you’ll need a SAP assessment to demonstrate compliance with Approved Document L1B.

SAP provides an economic and feasible solution to ensure your extension achieves compliance, no matter how much glazing you wish to include in the design.

Three steps to compliance:

-SAP is used to calculate CO2 emissions for the existing house along with the proposed extension.

-Used to calculate CO2 emissions for the existing house with a notional extension. A notional extension is an extension that meets the minimum standards of Approved Document L1B.

Compliance is achieved when “proposed” CO2 emissions are no greater than the “notional” CO2 emissions The four classes of the notional building are:

a) Side-lit, heated only

b) Side-lit, heated and cooled

c) Top-lit

d) Unlit