E 6.1 Office CPR Method (ADL2 paragraphs 1.62-1.66 & Appendix G)
"In the case of an office development, one way of achieving compliance ... is to show that the Carbon Performance Rating (CPR) is satisfactory." (ADL2, paragraph 1.62).
“The CPR is a rating based on standardised occupancy patterns that relate the performance of the proposed building to a benchmark based on the measured consumption data contained in ECON19[9]. The rating of the proposed building is calculated from the rated input power of the installed equipment as this combines the effect of load reduction by good envelope design and energy efficient system design into a single parameter.” (ADL2, paragraph 1.63).
In the context of the Elemental Method, the CPR Method applies only to offices. For the method to be applied the building type must be set to ‘Office’ and the check-box ‘Include Office CPR Method’ must be ticked.
The data required by the Office CPR Method is entered via the tabs ‘Office CPR Mech Vent’ and ‘Office CPR Air Cond’ in the Part L Building & System Data dialogue. If both mechanical ventilation and air conditioning are used in the building, compliance must be demonstrated for both systems. Results from the analysis are displayed in boxes at the bottom of the data input tabs (together with results from the Whole-building Office CPR Method) and are updated as the input data is edited.
A CPR value is calculated as a sum of contributions of the form
CPR = P x H x C x F
where
P = Input power rating of the plant (kW/m2 for the calculation, but W/m2 for data entry)
H = Number of hours per year that the plant operates (standard values assumed)
C = Conversion factor for the fuel used (kgC/kWh)
F = Factor depending on provisions made to control and manage the installed plant
Parameter P forms part of the input data. ADL2 Appendix G provides detailed procedures for setting parameters H, C and F.
E 6.1(MV) Office CPR Mechanical Ventilation Requirement (ADL2 paragraphs 1.62-1.66 & App. G)
The method is set out in ADL2 paragraphs 1.62-1.66 and Appendix G, from which the following extracts are taken:
"The assessment is based on the calculation of a Carbon Performance Rating using the following relationship:
CPR(MV) = PD x HD x CD x FD" (ADL2, paragraph G10).
The suffix D refers to plant for air distribution.
"For new ACMV systems, compliance would be achieved if the CPR is no greater than the values shown in Table 11 [6.5 for a new building, 7.35 for an existing building]." (ADL2, paragraph 1.64).
"For a building that already contains an ACMV system and substantial alteration is being made to that existing ACMV system, compliance would be achieved if the CPR is improved (ie reduced) by 10% as a result of the work, or does not exceed the values in Table 11 column b [7.35 for mechanical ventilation]), whichever is the least demanding." (ADL2, paragraph 1.65).
E 6.1(AC) Office CPR Air-Conditioning Requirement (ADL2 paragraphs 1.62-1.66 & App. G)
The method is set out in ADL2 paragraphs 1.62-1.66 and Appendix G, from which the following extracts are taken:
"The assessment is based on the calculation of a Carbon Performance Rating using the following relationship:
CPR(ACMV) = PD x HD x CD x FD + PR x HR x CR x FR" (ADL2, paragraph G13).
The suffixes D and R refer to plant for air distribution and refrigeration, respectively.
"For new ACMV systems, compliance would be achieved if the CPR is no greater than the values shown in Table 11 [10.3 for a new building, 11.35 for an existing building]." (ADL2, paragraph 1.64).
"For a building that already contains an ACMV system and substantial alteration is being made to that existing ACMV system, compliance would be achieved if the CPR is improved (ie reduced) by 10% as a result of the work, or does not exceed the values in Table 11 column b [11.35 for air conditioning]), whichever is the least demanding." (ADL2, paragraph 1.65).
E 6.2 Methods for other buildings with ACMV (ADL2 paragraphs 1.67-1.68)
"For other buildings, it is only possible at present to define an overall performance requirement for the mechanical ventilation systems (whether or not the air being supplied and/or extracted is heated or cooled). In such cases, the requirement can be met if the specific fan power (SFP) is less than the values given in the following sub-paragraphs…” (ADL2, paragraph 1.67).
“Mechanical ventilation systems should be reasonably efficient at part load. One way to achieve this would be to provide efficient variable flow control systems incorporating for instance variable speed drives or variable pitch axial fans. More detailed guidance on these measures is given in GIR 41 [8] .” (ADL2, paragraph 1.63).
These requirements are not analysed by the software.
