Acknowledgments
Extracts from the following documents are reproduced with permission:
DTLR. The Building Regulations 2000. Conservation of fuel and power. Approved Document L1 – Conservation of fuel and power in dwellings. 2002 Edition. The Stationery Office. Crown copyright 2001. Free download available at
http://www.safety.dtlr.gov.uk/bregs/brads.htm BRE, DEFRA, DTLR. The Government’s Standard Assessment Procedure for Energy Rating of Dwellings, 2001 Edition (SAP 2001).
Introduction
Methods for demonstrating compliance with The Building Regulations Part L1 (2002 Edition) are set out in Approved Document L1[1] (‘ADL1’), The Government’s Standard Assessment Procedure for Energy Rating of Dwellings[8] (‘SAP 2001’) and related publications.
This manual describes how the methods described in Approved Document L1 are implemented within the <Virtual Environment>.
An outline of the Part L regulations is provided in the Part L User Guide. ADL1 and SAP 2001 should be consulted for a detailed account of the L1 provisions.
Guidance on the Part L regulations is provided on BRE and ODPM websites[12,13,14,15].
Not all the requirements of Part L can be tested in software. The scope of the <Virtual Environment> implementation is described in the Part L User Guide.
The broad requirements of L1 are set out in Section 0: General of Approved Document L1[1] referred to in this document as ‘ADL1’. They cover:
L1 (a) Limiting fabric heat loss, summertime heat gains and heat losses by air infiltration
L1 (b) Limiting heat loss from pipes and ducts
L1 (c) Efficiency of heating systems
L1 (d) Efficiency of lighting systems
L1 (e) Providing information on the operation and maintenance of building services systems.
Section 1 of the Approved Document sets out three methods that can be used for demonstrating that reasonable provision has been made for limiting heat loss through the fabric. These are:
a) an Elemental Method (paragraphs 1.3 – 1.15). The Elemental Method can be used only when the heating system will be based on an efficient gas or oil boiler, on a heat pump, on community heating with CHP or on biogas or biomass fuel, but not for direct electric heating or other systems. It is suitable for alterations and extension work, and for new-build work when it is desired to minimise calculations. The main requirements of the Elemental Method are i) limits on U-values, ii) stipulations on the type and efficiency of the heating system and iii) limits on the area of windows, doors and rooflights.
b) a Target U-value Method (paragraphs 1.16 – 1.26). Within certain limits, this method allows greater flexibility than the Elemental Method in selecting the areas of windows, doors and rooflights, and the insulation levels of individual elements in the building envelope, taking into account the efficiency of the heating system and enabling solar gain to be addressed. It can be used for any heating system. The Target U-value Method requires that the average U-value of the dwelling does not exceed a Target U-value, corrected for the proposed method of heating.
c) a Carbon Index Method (paragraphs 1.27 – 1.28). The aim of this method is to provide more flexibility in the design of new dwellings whilst achieving similar overall performance to that obtained by following the Elemental Method. The Carbon Index is defined in the Standard Assessment Procedure for Energy Rating of Dwellings[8] (SAP), and the requirement is met if the Carbon Index for the dwelling is not less than 8.0.
In addition, ADL1 lays down requirements covering:
Poorest acceptable U-values
Limiting thermal bridging at junctions and around openings
Limiting air leakage
Space heating system controls
Hot water systems
Operating and maintenance instructions for heating and hot water systems
The IES software places these additional requirements under the headings of the three main methods. Within each method a number of requirements are laid down. In some cases compliance with a requirement may be demonstrated by more than one method. Each method specifies certain requirements, which in turn may be complied with by various methods, and so on.
