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[2] (‘ADL2’) and page numbers to BRE Digest No 457[3] (‘D457’).The application of the Whole-building Method to offices, schools and hospitals is based on procedures described in other documents, as indicated.
"To show compliance following the Whole-building method, the carbon emissions or primary energy consumption at the level of the complete building have to be reasonable for the purpose of the conservation of fuel and power." (ADL2, paragraph 1.69).
L2 Whole-building (Office) Method (paragraphs 1.69-1.73)
"The Whole-Office Carbon Performance Rating method is a development of the CPR described in paragraphs 1.62 and 1.63. In this compliance route, the rating is expanded to cover lighting and space heating as explained in detail in BRE Digest No 457[3])." (ADL2, paragraph 1.70).
WO 1. Whole-office CPR Requirement (paragraphs 1.69-1.73)
"The requirement would be met if... the whole-office CPR is no greater than the values shown in Table 12." (ADL2, paragraph 1.71a).
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Table 12 Maximum whole-office CPR (kgC/m2/y) (ADL2)
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Building Type
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New office
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Refurbished office
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Naturally ventilated
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7.1
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7.8
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Mechanically ventilated
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10.0
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11.0
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Air-conditioned
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18.5
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20.4
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The data required by the CPR Requirement of the Office CPR Method is entered via the tabs ‘Office CPR Nat Vent’, ‘Office CPR Mech Vent’ and ‘Office CPR Air Cond’ in the Part L Building & System Data dialogue. Compliance must be demonstrated separately for natural ventilated, mechanically ventilated and air conditioned areas of the building. Results from the analysis are displayed in boxes at the bottom of the data input tabs (together with results from the Elemental Office CPR Method) and are updated as the input data is edited.
As in the Elemental Office CPR Method, 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. D457 provides detailed procedures for setting parameters H, C and F.
WO 1.1 Naturally Ventilated Areas CPR Requirement (BRE Digest 457[3])
"The rated level of carbon emission is:
CPR(HL) = PB x HB x CB x FB + PH x HH x CH x FH + PL x HL x CL x FL."
(D457, page 5).
The suffixes B, H and L refer to plant for heating, heat distribution and lighting, respectively.
WO 1.2 Mechanically Ventilated Areas CPR Requirement (BRE Digest 457[3])
"The rated level of carbon emission is:
CPR(HLMV) = PB x HB x CB x FB + PH x HH x CH x FH + PL x HL x CL x FL
+ PD x HD x CD x FD." (D457, page 7).
The suffixes B, H, L and D refer to plant for heating, heat distribution, lighting and air distribution, respectively.
WO 1.3 Air-conditioned Areas CPR Requirement (BRE Digest 457[3])
"The rated level of carbon emission is:
CPR(HLAC) = PB x HB x CB x FB + PH x HH x CH x FH + PL x HL x CL x FL
+ PD x HD x CD x FD + PR x HR x CR x FR." (D457, page 7).
The suffixes B, H, L, D and R refer to plant for heating, heat distribution, lighting, air/cooling distribution and refrigeration, respectively.
WO 2. Maximum U-value (Table 3) Requirement (paragraph 1.71b)
"The requirement would be met if... b) the envelope meets the requirements of ... Table 3" (ADL2, paragraph 1.71).
The Whole-building Office 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. See section E 1.2.2 Maximum Traded-off U-value (Table 3) Requirement (above).
WO 3. Thermal Bridging and Air Leakage Requirements (paragraphs 1.71b, 1.9-1.11 & 1.17-1.19)
"The requirement would be met if... b) the envelope meets the requirements of paragraphs 1.9-1.11, 1.17-1.19..." (ADL2 paragraph 1.71).
"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.
L2 Whole-building (School) Method (paragraph 1.72)
WS 1. DfEE guidance note [5] Requirement
"For schools, a way of complying with the requirements would be to show that the proposed building conforms with the DfEE guidance note [DfEE, Guidelines for environmental design in schools, Building Bulletin 87, TSO, 1997]." (ADL2, paragraph 1.72).
The Whole-building (School) Method is not currently implemented.
L2 Whole-building (Hospital) Method (paragraph 1.73)
WH 1. NHS Estates guide [6] Requirement
"For hospitals, a way of complying with the requirements would be to show that the proposed building conforms with the NHS Estates guides [NHS Estates: Achieving energy efficiency in new hospitals, TSO, 1994]." (ADL2, paragraph 1.73).
The Whole-building (Hospital) Method is not currently implemented.
