L2 Carbon Emissions Calculation Method

The Carbon Emissions Calculation Method involves a deeper level of analysis than the two preceding methods. The comparison of carbon emissions for the actual and notional buildings must normally be performed using simulation, and tools for this are provided elsewhere in the <Virtual Environment>. However, certain requirements of the Carbon Emissions Method can be tested in a straightforward manner, and these requirements are included within the automated Part L analysis.

The requirements of the Carbon Emissions Method are set out in Approved Document L2, paragraphs 1.74 to 1.76. 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.”

Tools for calculating carbon emissions based on simulated performance of the actual and notional buildings over a typical year are provided elsewhere in the <Virtual Environment>. Guidance on setting up the simulations required and determining carbon emissions is provided in TM32^[14].

The notional building must be shown to comply with the Elemental Method in respect of insulation, air leakage, lighting and solar overheating avoidance requirements. The Part L software can be used for this task.

"...the proposed building fabric... performance should be no worse than [that] given in Table 3" (ADL2, paragraph 1.75b).

 

The Carbon Emissions Calculation Method imposes certain limits on the U-values of roofs, walls and floors . These checks are the same as those applied in the Elemental Construction Trade-off Method and the Whole-building Office Method. See, for example, section E 1.2.2 Maximum Traded-off U-value (Table 3) Requirement (above).

"... the proposed building fabric and air leakage performances should be no worse than those given in... paragraphs 1.9-1.11 and 1.17-1.19 respectively." (ADL2 paragraph 1.75b).

"The building fabric should be constructed so that there are no significant thermal bridges or gaps in the insulation layer(s) within the various elements of the fabric, at the joints between elements, and at the edges of elements such as those around window and door openings..."  (ADL2 paragraph.1.9).

"Buildings should be reasonably airtight to avoid unnecessary space heating and cooling demand and to enable the effective performance of ventilation systems..."  (ADL2 paragraph.1.17).

 

These requirements cannot be analysed in software but are included for completeness.