Overview

 

Extracts from the following documents are reproduced with permission:

 

DTLR. The Building Regulations 2000. Conservation of fuel and power. Approved Document L2 – Conservation of fuel and power in buildings other than dwellings. 2002 Edition. The Stationery Office. Crown copyright 2001. Free download available at  http://www.safety.dtlr.gov.uk/bregs/brads.htm

BRE Digest 457. The Carbon Performance Rating for Offices. P F Grigg. Published by CRC Ltd, 151 Rosebery Avenue, London, EC1R 4GB. Tel: 020 7505 6622. Fax: 020 7505 6606. Email: enquiries@bre.co.uk

BRE, DEFRA, DTLR. The Government’s Standard Assessment Procedure for Energy Rating of Dwellings, 2001 Edition (SAP 2001).

 

Part L (2002) applies to buildings in England, Wales and Northern Ireland for which construction started before 6^th April 2006. If construction had not started before that date, the 2006 edition of Part L applies.

The Part L (2002) facility covers Part L1 (dwellings) and Part L2 (buildings other than dwellings).

Data for the Part L (2002) analysis is taken from the <Virtual Environment> model, supplemented where necessary by inputs specific to the requirements of Part L (2002).

Results of the Part L (2002) analysis are presented in three levels of detail:

Pass/fail verdicts for the methods tested.

A summary of the checks carried out within each method and their results (an HTML file).

A report setting out the analysis in detail (an HTML file).

Certain analysis results are processed and displayed immediately data is entered, providing instant feedback to the user.

The software covers both Part L (England & Wales) and Section 6 (Scotland). To switch between Part L and Section 6, click on ‘Regulatory framework’ on the <VE> Compliance toolbar.

There is considerable overlap between the Part L and Section 6 regulations, and data is shared between these software applications. Important differences are:

In Part L, the Elemental method may only be applied where the heating system is based on an efficient gas or oil boiler, on a heat pump, on community heating with CHP or on biogas or biomass fuel. In Section 6, the Elemental method may be applied regardless of the type of heating system, but with modified U-value requirements in some cases. Section 6 Elemental U-values tend to be more stringent than those in Part L.

Part L and Section 6 use different formulae for target U-value.

Unlike its Part L counterpart, the Section 6 Target U-value method does not allow the target U-value to be relaxed if the heating system efficiency exceeds the Mininum SEDBUK.

Section 6 Elemental and Target U-value methods allow some concessions for conservatories.

Section 6 elemental U-values are more stringent for external walls and display glazing.

For methods other than the elemental method, the poorest (maximum) U-value for roofs is less stringent in Section 6 than in Part L.

Section 6 has no requirement to avoid solar overheating.

Section 6 has different carbon intensity targets for heating systems and allows no trade-off between heating system carbon intensity and fabric losses.

Section 6 imposes a more stringent specific fan power requirement on non-office buildings.

Section 6 assesses office systems using a Carbon Performance Index. Part L uses the closely related Carbon Performance Rating. Process loads are excluded from the assessment in Part L but not in Section 6.

Section 6 has no counterpart of the L2 Whole-Building Method.

Guidance on using the Section 6 software is provided in the Section 6 (2004) User Guide.

 

The requirements of The Building Regulations, Part L (2002 edition) are set out in Approved Documents L1^[1]  and L2^[2]. These documents should be consulted in the course of any submission for Part L compliance.

The function and scope of the approved documents is set out in the ‘Use of guidance’ section:

“Approved Documents are intended to provide guidance for some of the more common building situations. However, there may well be alternative ways of achieving compliance with the requirements. Thus there is no obligation to adopt any particular solution contained in an Approved Document if you prefer to meet the relevant requirement in some other way.”

Guidance on the Part L regulations is provided on BRE and ODPM websites^[9,10,11,12]. Guidance on the Part L2 Carbon Emissions Calculation Method is provided in the CIBSE/ODPM publication TM32^[13].

Not all the requirements of Part L can be tested in software. However, IES aims to provide software covering all requirements that can be so tested.

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

Commissioning of heating and HWS systems

Operating and maintenance instructions for heating and hot water systems

The broad requirements of L2 are set out in Section 0: General guidance of Approved Document L2^[2] referred to in this document as ‘ADL2’. They cover:

L2 (a) Limiting fabric heat loss, summertime heat gains and heat losses by air infiltration

L2 (b) Limiting heat loss from pipes and ducts

L2 (c) Efficiency of heating systems

L2 (d) Limiting solar heat gains and their effects

L2 (e) Efficiency of mechanical ventilation and air-conditioning systems

L2 (f) Limiting heat gains to pipes and ducts used in air-conditioning.

L2 (g) Efficiency of lighting systems

L2 (h) 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 the conservation of fuel and power. These are:

“a) an Elemental Method (paragraphs 1.7 – 1.68). This method considers the performance of each aspect of the building individually. To comply with the provisions of Part L, a minimum level of performance should be achieved in each of the elements. Some flexibility is provided for trading off between different elements of the construction, and between insulation standards and heating system performance.”

“b) a Whole-Building method (paragraphs 1.69 – 1.73). This method considers the performance of the whole building. For office buildings, the heating, ventilation, air conditioning and lighting systems should be capable of being operated such that they will emit no more carbon per square metre per annum than a benchmark based on the ECON 19 data^[4]. Alternative methods are also provided for schools and hospitals.”

“c) a Carbon Emissions Calculation Method (paragraphs 1.4 – 1.76). This method also considers the performance of the whole building, but can be applied to any building type. To comply with the provisions of Part L, the annual carbon emissions from the building should be no greater than that from a notional building that meets the compliance criteria of the Elemental Method. The carbon emissions from the proposed building and the notional building need to be estimated using an appropriate calculation tool.”

 

The compliance routes available in Part L can conveniently be set out in terms of Methods and Requirements. For example, L2 offers three methods of compliance: the L2 Elemental Method, the L2 Whole-building Method and the L2 Carbon Emissions Calculation Method. 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.

L1 offers three methods for demonstrating compliance with the requirements on fabric and heating system performance: Elemental Method, Target U-value Method and Carbon Index Method. It also it sets out additional requirements under the heading of ‘additional checks by builders’ relating to issues such as air leakage, controls, hot water systems and the provision of information. The IES software places these additional requirements under the headings of the three main compliance routes.

The L1 compliance routes can be summarised as follows. The numbering system used here is that used in the IES <Virtual Environment> implementation. Paragraph numbers refer to Approved Document L1^[1].

L1 Elemental Method (L1E) (paragraphs 1.3–1.15)

L1E 1. Heating Efficiency Requirement (paragraph 1.7)

L1E 2. U-value (Table 1) Requirement (paragraphs 1.3-1.6)

L1E 3. Glazing & Door Area Requirement (paragraphs 1.8-1.10)

L1E 4. Additional Requirements (paragraphs 1.30-1.62)

L1 Target U-value Method (L1T) (paragraphs 1.16–1.26)

L1T 1. Mean U-value Requirement (paragraphs 1.16-1.26)

L1T 2. Maximum U-value (Table 3) Requirement (paragraph 1.29)

L1T 3. Additional Requirements (paragraphs 1.30-1.62)

L1 Carbon Index Method (L1C) (paragraph 1.27)

L1C 1. Carbon Index Requirement (paragraph 1.27)

L1C 2. Maximum U-value (Table 3) Requirement (paragraph 1.29)

L1C 3. Additional Requirements (paragraphs 1.30-1.62)

L2 offers three methods for demonstrating compliance with the requirements on fabric and heating system performance: Elemental Method, Whole-building Method and Carbon Emissions Calculation Method.