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This page provides an introduction to energy assessment. It introduces the currentrequirements for energy assessment, and outlines the three kinds of assessment used in England:

It then discusses the energy assessors who provide these assessments.

Some relevant references are given.

Introduction to Energy Assessment

The European Union's Energy Performance of Buildings Directive 2002/91/EC, inspired by the Kyoto Protocol, was published in January 2003 and aimed at cutting back on energy consumption and ecological deterioration due to CO2 emissions. Itshould have been transposed into law by each EU member state with effect from 4 January 2006. It can be summarised as seven different but interrelated requirements:

  1. a calculation methodology to determine the energy performance of the building, which must be adopted at national or regional level.
  2. minimum energy performance standards for all new buildings.
  3. minimum energy performance standards for buildings with a useable floor area of more the 1000 m2 undergoing major renovation - at the level of the whole building or applying only to the proposed works.
  4. an energy performance certificate when a building is being sold or leased.
  5. the public display of an energy performance certificate, not older that 10 years, in certain public buildings.
  6. regular inspection of boilers and air-conditioning systems.
  7. qualified and/or accredited experts to provide the certificates and carry out the inspections in an independent manner.

There is a European Union requirement that all buildings should have Energy Performance Certificates (EPCs) by January 2009 .

EPCs summarise energy performance in 7 grades - from A (best) to G.

In England and Wales the directive as it applies to domestic housing was implemented in Part 5 of the Housing Act 2004. supported by new requirements in the Building Regulations 2005 which came into force in April 2006, and assessment methods published by the Building Research Establishment (BRE).

Scotland and Northern Ireland have similar requirements.

An example of an energy performance certificate

     Energy Performance Certificate


August 2007Home information packs (HIPs) including energy performance certificates are required for all 4 bedroomed houses for sale or let.
September 2007HIPs now also required for 3 bedroomed houses for sale or let.
December 2007All houses for sale or let must have HIPs.
April 2008Commercial Energy Performance Certificates (CEPC) required for all buildings above 2,500 square metres that are being constructed, sold, having major renovations or being let.
October 2008All buildings homes, commercial and public must have an energy performance certificate whenever the building is sold, built or rented.
April 2010Requirement for HIPs is dropped by new government, however energy performance certificates are still required.

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Requirements for Energy Assessment

On sale or letting a property

The Housing Act 2004 introduced a new method of house sale in England and Wales. This requires the supply of a home information pack(HIP) by the seller. HIPs were initially intended to simplify the sale process by including a building survey, but the government backed down from this and much of the initial motivation was therefore lost.

However the home information pack must include a home condition report that contains an energy performance certificate.The intention is to make energy performance a factor in the valuation of housing. The introduction of HIPs was delayed because of a shortageof trained energy assessors. However it was then introduced in stages and now applies to all dwellings.

An energy performance certificate must also be supplied when a property is offered for let and when a lease is renewed.

On new buildings and alterations

Building regulations for new developments must now include a calculated energy assessment report for the development.

Building regulations are being used to increase the energy efficiency of new construction.The change in part L of the building regulations in 2002 required an increase in energy efficiency of 20%.The version of building regulations part L introduced in April 2006 required another 20% improvement in energy efficiency.This process is likely to continue as the government seeks to make all new housing from 2016 carbon neutral.

Assessment Procedures

The standard assessment procedure

The Standard Assessment Procedure(SAP) is the government's recommended system for energy rating of new self-contained dwellings. The main calculation uses details of the construction and the materials used. It generates two main estimates.

  • The SAP rating, on a scale from 0 to 100, estimates the annual energy costs per m2 for space and water heating assuming standard energy costs and notional occupiers with specified requirements for heating, lighting and hot water. At a rating of 100 the building requires no external energy. Numerical ratings are converted to seven grades A to G. The SAP report should also suggest changes to improve energy efficiency and should indicate the energy rating achievable if the suggested improvements were made.
  • The domestic CO2 emission rate (DER), based on the annual CO2 emissions associated with energy usage. This is also converted to one of seven grades A to G, based on comparison with a notional building of the same shape.

Changes introduced in 2005 to this measure included:

  • Energy for lighting is included.
  • Solar water heating is revised.
  • Hot water cylinder energy loss is revised, manufacturer's data for heat loss becomes the preferred source of cylinder loss.
  • The effect of thermal bridging is taken into the account.
  • It allows for additional renewable and energy saving technologies.
  • It provides a method for estimating the tendency to high internal temperatures in summer.
  • Data tables are updated (e.g. fuel costs, CO2 emissions, boiler efficiency, heating controls, etc).
  • The measure of energy is now kWh rather than GJ.

The reduced data standard assessment procedure (RDSAP)

RDSAP is defined in an appendix to the SAP 2005 document. It is a method of generating SAP ratings fairly rapidly for existing buildings where the assessor does not have access to the construction details.

The assessor collects readily observable data about the building, for example room height and floor area, and other factors which indicate the likely design, for example the building's age. This data is then expanded to produce an assumed building construction.

The SAP rating is calculated for this assumed building, using the same process as is used for new buildingswhere the actual construction is known.

The simplified building energy model (SBEM)

SBEM provides an analysis of the energy consumption of buildings other than dwellings. It is intended for the smaller public and commercial premises.

Dynamic simulation modelling

Dynamic simulation modelling is used to estimate the energy performance of larger buildings taking account of air conditioningdaily variations and heat flows within the building. It is typically used to improve the expected energy performance of the building before it is built.

Energy Assessors

The generation of energy performance certificates depends on energy assessors, supported by suitable software.The tendency is to include the software, or access to it, on a personal digital assistant, so the data can be collected and checked on site.

Energy assessors for existing or new domestic premises must be accredited by an approved accreditation body, of whom there are about ten at present. They must achieve a Level 3 Diploma in Domestic Energy Assessment (Dip DEA).For this they must pass a criminal records bureau check, have appropriate professional indemnity cover,undertake a day or two training on the software they will use, gain experience by shadowing of an experienced assessor, and then have five surveys of different kinds of houses checked.

In August 2008 about 8,000 domestic energy assessors had been accredited, though it is not known how many are actually practising.

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The housing act 2004

Standard assessment procedure (SAP) 2005

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