Information for SuperHeat users:

SAP Rating and Carbon Index Method Requirements - Domestic buildings

(not applicable to Northern Ireland)

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General

You can show compliance using the Elemental Method, Target U-Value Method or Carbon Index Method. You do not have to comply with all three, just one.

As early as Digest 94, issued in November 1956, the BRS (as it then was) had outlined a method for estimating the energy consumption of dwellings which took account of the orientation of windows and resulting solar gain, and internal gains from occupancy, cooking and water heating, and this work (refined over many years) has been published as BREDEM (BRE Domestic Energy Model). A simplified model, BREDEM 9.2 appeared in the 1990 Approved Document. To make calculations more simple this assumed a standard ventilation rate of one air change per hour regardless of the form of construction, draught stripping, and the number (if any) of flues. These factors were taken into account when the first edition of the SAP (Standard Assessment Procedure) worksheet appeared in the 1995 Approved Document, as were the type of heating system, degree of control, and the type and cost of the fuel used.. An updated version, SAP-1998, replaced in it in March 1999 and SAP 2001 (as used in SuperHeat 5) was published in December 2001

The SAP rating, a whole number between 1 and 120 (previously 1-100, the higher the better), reflects the notional energy cost per square metre of floor space. The SAP worksheet does not take account of regional variations or the occupants' lifestyle - the data used relates to average UK conditions. See also our web page Factors affecting SAP Ratings.

Using cost/m² as a measure of energy efficiency has not been without criticism: Peter Burberry argued (AJ 8.1.98) that one of the most effective ways of saving energy is to reduce building floor space to the minimum necessary: an under-occupied house, or one whose design incorporates a lot of wasted space, may have a high SAP rating but is not using energy efficiently. Note that changing the fuel from mains gas to LPG will reduce the SAP Rating significantly without much change to CO2 emissions whilst changing from mains gas to oil will increase the SAP Rating but also leads to a significant increase in CO2 emissions.

From cost to CO2

The importance of reducing CO2 emissions is addressed in the 2002 AD by using the Carbon Index as the third method of compliance, rather than the SAP-based Energy Rating method, as well as requiring higher efficiencies for oil burning appliances if you choose to show compliance using the Elemental or Target U-value methods.

As in earlier versions, the SAP 2001 worksheet is used to calculate the required energy inputs for heating and hot water and from these, their cost is used to calculate the SAP Rating. In addition these figures are used to calculate the CO2 emissions that result from producing and using the fuel(s) - this was an option in SAP-1998.

The Carbon Index, a number between 0 and 10.0, is a function of the total floor area and calculated CO2 total. If the dwelling has a Carbon Index of 8.0 or more it will comply with L1(a)i as long as the U-values of the various elements of the structure comply with §1.29 (see above).

Notification and display of SAP Ratings

Building Regulation 16 states that where a new dwelling is erected or created by a material change of use, the person carrying out the work shall calculate the energy rating and notify it to the local authority within five days of completion or at least five days before occupation. 16(4) and 16(6) state that the rating has to be displayed in a conspicuous position in the dwelling, or where this is not done, a notice stating the rating has to be sent to the occupier. These provisions do not apply where someone is constructing the dwelling for their own occupation.

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