L2 Elemental Method

 

The requirements laid down by the L2 Elemental Method, together with their constituent methods, are as follows. The numbering system used here is that used in the IES <Virtual Environment> implementation. Paragraph numbers refer to Approved Document L2^[2].

L2 Elemental Method (L2E) (paragraphs 1.7–1.68)

L2E 1. Fabric Requirement (paragraphs 1.8–1.16)

L2E 1.1 Pure Elemental Method (paragraph 1.8)

L2E 1.1.1 U-value (Table 1) Requirement (paragraphs 1.8,1.12)

L2E 1.1.2 Heating Systems Adjustment Factor Requirement (paragraphs 1.14,1.32)

L2E 1.1.3 Maximum Window/Door/Rooflight Area (Table 2) Requirement (paragraph 1.12)

L2E 1.2 Construction Trade-off Method (paragraphs 1.14-1.16 & 1.32)

L2E 1.2.1 Overall Building Heat Loss Requirement (paragraphs 1.15a & 1.32)

L2E 1.2.2 Maximum Traded-off U-value (Table 3) Requirement (paragraph 1.15b)

L2E 1.2.3 Average Traded-off U-value Requirement (paragraph 1.16b)

L2E 2. Thermal Bridging and Air Leakage Requirements (paragraphs 1.9-1.11 & 1.17-1.19)

L2E 3. Solar Overheating Avoidance Requirement (paragraphs 1.20-1.23)

L2E 3.1 Glazing Area Limitation (Table 4) Method (paragraph 1.22)

L2E 3.2 Solar Load Estimation (Appendix H) Method (paragraph 1.23a)

L2E 3.3 Detailed Overheating Calculation Method (paragraph 1.23b)

L2E 4. Heating Systems Requirements (paragraphs 1.24-1.40)

L2E 4.1 Heating Systems Carbon Intensity Requirement (paragraphs 1.25-1.32)

L2E 4.2 Heating Controls Requirements (paragraphs 1.33-1.37)

L2E 4.3 Insulation of Pipes, Ducts & Vessels Requirement (paragraphs 1.38-1.40)

L2E 5. Lighting Systems Requirements (paragraphs 1.41-1.59)

L2E 6. Air-conditioning and Mechanical Ventilation (ACMV) Requirement (paragraphs 1.60-1.68)

L2E 6.1 Office CPR Method (paragraphs 1.62-1.66 & Appendix G)

L2E 6.1(MV) Office CPR Mechanical Ventilation Requirement (paras 1.62-1.66 & App. G)

L2E 6.1(AC) Office CPR Air-Conditioning Requirement (paragraphs 1.62-1.66  & App. G)

The <Virtual Environment> implementation includes analysis of all these requirements and methods with the exception of:

Thermal Bridging and Air Leakage Requirements (cannot be analysed in software)

Detailed Overheating Calculation (CIBSE) Method (to be added)

Heating Controls Requirements (cannot be analysed in software)

Insulation of Pipes, Ducts & Vessels Requirements (cannot be analysed in software)

Lighting Systems Requirement (to be added)

The requirements laid down by the L2 Whole-building Method, together with their constituent methods, are set out below. Paragraph numbers refer to Approved Document L2. The application of the Whole-building Method to offices, schools and hospitals is based on procedures described in other documents, as indicated.

L2 Whole-building (Office) Method  (L2WO) (paragraphs 1.69-1.73)

L2WO 1. Whole-office CPR Requirement (paragraphs 1.69-1.73)

L2WO 1.1 Naturally Ventilated Areas CPR Requirement (BRE Digest 457^[3])

L2WO 1.2 Mechanically Ventilated Areas CPR Requirement (BRE Digest 457^[3])

L2WO 1.3 Air-conditioned Areas CPR Requirement (BRE Digest 457^[3])

L2WO 2. Maximum U-value (Table 3) Requirement (paragraph 1.71b)

L2WO 3. Thermal Bridging and Air Leakage Requirements (paragraphs 1.71b, 1.9-1.11 & 1.17-1.19)

L2 Whole-building (School) Method (paragraph 1.72)

L2WS 1. DfEE guidance note^[5] Requirement

L2 Whole-building (Hospital) Method (paragraph 1.73)

L2WH 1. NHS Estates guide^[6] Requirement

The <Virtual Environment> implementation does not currently cover:

The application of the Whole-building method to schools and hospitals

Thermal Bridging and Air Leakage Requirements (cannot be analysed in software)

The requirements laid down by the L2 Carbon Emissions Method are set out below. Paragraph numbers refer to Approved Document L2.

L2 Carbon Emissions Method  (L2C) (paragraphs 1.74-1.76)

L2C 1. Carbon Emissions Requirement (paragraphs 1.74-1.76)

L2C 2. Maximum U-value (Table 3) Requirement (paragraph 1.75b)

L2C 3. Thermal Bridging and Air Leakage Requirements (paragraphs 1.75b, 1.9-1.11 & 1.17-1.19)

The Carbon Emissions Requirement (paragraph 1.74) states

“To show compliance using the Carbon Emissions Calculation Method, the calculated annual carbon emissions of the proposed building should be no greater than those from a notional building of the same size and shape, designed to comply with the Elemental Method. This approach allows more flexible design of the building, taking advantage of any valid energy conservation measure and taking account of useful solar and internal heat gains.”

The <Virtual Environment> offers tools for calculating carbon emissions based on simulated performance of the actual and notional buildings over a typical year. Carbon emissions calculations are not performed automatically by the Part L facility.

Approved Document L2 lays down the following requirements in addition to those that can be tested by the three methods described above:

Construction – requirements on the methods used to construct the building

Providing information – requirements to provide the owner and/or occupier of the building with information about the building and its systems. The information should include, for systems serving an office area of more than 200 m², a design assessment of the building services systems’ carbon emissions and the comparable performance benchmark. In the case of the Whole-building (Office) Method, this information is provided in the <Virtual Environment> Part L results file. In the case of the Carbon Emissions Method, it would be provided by the results of the carbon emissions calculation.

The interface features in the Part L software are as follows.

This part of the interface deals with Part L data at the building or system level (for instance, whether the building is an office or a school, the characteristics of its heating system, etc). It can be accessed either via the Building Regulations option on the Apache view Settings menu or via the Part L analysis facility.

Part L building and system data may be stored in a database for future reuse.

Data specific to the building regulations relating to individual rooms (for instance, whether the room is heated) is entered via the Building Regulations tab of Space Data, or via the Apache view Settings menu.

Building regulations data relating to constructions (for instance, whether a window is classified as display glazing) is entered via fields labelled ‘Building Regulations’ within the construction data dialogues in APcdb.

For testing Part L2 compliance using the Elemental and Whole-building Methods it is not necessary to enter

Building location or weather data

Space Data other than that appearing on the Part L tab

Profile data

MacroFlo data

ApacheHVAC data

However, the Carbon Emissions Method does require data in some or all of these categories to be entered as input to simulations of the proposed and notional buildings.