Jonathan Lewis and Andrew Mellor of PRP Architects explain how to comply with all necessary regulations when regenerating a big estate – now and in 15 years’ time

ith the inexorable expansion in energy and carbon-related rules, regeneration projects are becoming ever more complex, and require an ever more structured approach to energy provision. And as project can last up to 15 years, the current trend of revising planning and building control requirements on a three-to-five year cycle means that a long-term energy view is required from the inception. We present a five-step approach to today’s legislation that should help to control costs and manage risks throughout the design development process.

Stage 1: Options appraisal

Large-scale estate regeneration projects demand a considered approach to sustainability from the outset, irrespective of whether renewable energy is required. At the feasibility and options appraisal stage, redevelopment scenarios should be drawn up by the architect and costed by the QS, with the preferred option being presented to residents for consultation. The energy considerations at this stage include evaluating whether on-site renewable energy is required as a planning condition, or whether it is likely to come in as a requirement later.

If this is the case, a preliminary space planning and budgeting exercise is required to inform the options appraisal process. This study should consider issues that affect the options appraisal process, principally budget and space-planning, for example, whether a district heating network is likely to be required and what the budget costs for renewables are.


  • Undertake preliminary space-planning and budgeting for renewable energy provision

Stage 2: Outline planning

Once a preferred outline has been selected and approved by residents, an estate-wide masterplan can be produced for outline planning application. This will detail massing, heights, form, uses and overall quantity of units and the Greater London Authority would require an energy assessment as well as an energy strategy.

At this stage, benchmark figures for CO2 emissions and energy use are sufficient – more detailed, site-specific studies can be undertaken at the next stage, when more precision is required. Energy efficiency measures should be appraised as well as non-renewable low carbon technologies such as gas-fired CHP and heat recovery.


  • Ascertain CO2 emissions
  • Undertake energy efficiency and low carbon technology appraisal
  • Undertake full renewables options appraisal
  • Submit energy strategy with planning application

Stage 3: Detailed planning of phases

Once the masterplan has outline planning permission, detailed planning consent can be sought on a phase-by-phase basis. At this stage, it is worthwhile to undertake a Part L 2006 risk analysis as it can affect the aesthetics and the budget of a project. A dwelling will fail if it emits too much CO2 but also if it is will overheat – a pertinent issue considering the temperatures experienced this summer. The risk analysis comprises a few SAP calculations of dwelling types and SBEM for the non-residential elements. Interestingly, if communal spaces in residential buildings are heated, Part L2a will apply.

This exercise also provides a more precise calculation of the phase’s CO2 emissions, informing the detailed energy strategy for the phase. This is essentially a refinement of the energy study at outline planning stage, setting detailed layouts, servicing arrangements and budgets. Should a particular EcoHomes rating be a requirement for planning or funding, the uplift in energy and carbon efficiency from Part L should be quantified and budgeted for – up to two credits are awarded for improvements in insulation over Part L and up to 15 for the overall CO2 emissions performance. Refurbishments are assessed using the same EcoHomes methodology, although slightly different criteria apply to some credits.

Soon, the Code for Sustainable Homes is set to replace EcoHomes and will set minimum energy performance criteria above Part L.


  • Part L risk assessment
  • Refining renewables quantity, budget and integration into design
  • Preliminary EcoHomes assessment

Stage 4: Building control submission

Attaining detailed planning consent moves the project swiftly on to dealing with the legislative aspect to building, more formalised and defined perhaps than the policy side of things. Full design-compliance with Part L must be demonstrated through submission of SAP and SBEM calculations. Note that blocks of flats may be assessed on an individual basis or a whole-building method.

It is at this stage that the full EcoHomes assessment should be completed and the detailed design of the renewables system takes place. One of the issues with the provision of renewable energy is that from the end of the planning stage, there is no further policing of the implementation – this means that in theory, biomass boilers may be installed yet left idle.

Generally, the 10% renewables provision is not counted towards the Part L CO2 calculation – that is, the CO2 savings achieved by renewable energy should be separate from those achieved by Part L, although again, this can be a grey area if poorly understood by the local authority.


  • Undertake full SAP calculations
  • Submit design SAP calculations to building control
  • Undertake full EcoHomes assessment

Stage 5: Construction phase

Lastly, there are several measures that must be undertaken at the construction phase to ensure that the Part L design performance is met in practice. The most tricky is perhaps the pressure test – for this reason, it is worth undertaking some tests on the first completed units prior to the testing for Part L to shed light on potential construction errors. These can then be monitored during the construction of later units.


  • Confirm that building is built to standards set out in design
  • Fill in “key features” checklist
  • Confirm use of accredited details
  • Undertake site inspection
  • Undertake pressure test

The many ways of assessing ecological performance...

Renewable energy as a planning condition
About 90 councils now have policies requiring developments to offset 10% of their predicted CO2 emissions through on-site renewable energy technology. The Greater London Authority recently indicated that its policy requirement set out in the London Plan and the mayor’s energy strategy proposal 13, will increase to 20% for all referable projects by 2008. Other councils are likely to follow suit.

This planning policy document provides the legal framework under which local authorities can adopt such policies; indeed they are exhorted to “encourage such schemes through positively expressed policies”. There is also a companion guide to PPS22 that provides guidance, case studies and some technical information on renewable technologies. Both documents are available online through the Planning Portal.

This is a methodology rates the environmental ustainability of a development on a scale of “pass”, “good”, “very good” and “excellent”. All Housing Corporation funding requires a “very good” rating, as do schemes developed on English Partnerships land.

Code for Sustainable Homes
This is the outcome of the work of the Sustainable Buildings Task Group. This draft assessment methodology is suspiciously similar to EcoHomes in many ways. It differs in that some aspects, such as land use, will be dealt with by local authority sustainability appraisals
whereas more building-specific issues such as energy will be covered as in EcoHomes. Ecology was a glaring omission in the consultation document for the code and after widespread criticism, DCLG is revising the draft. Details are therefore unknown.

Part L 2006
Part L of the Building Regulations was recently revised from the 2002 version to the 2006 version. In short, L1a (new-build residential) now requires CO2 emissions targets to be met, rather than U-values. L1b (residential refurbishment/ extension) requires minimum U-values and minimum services performance to be obtained. L2a concerns itself with non-residential new build and L2b concerns itself with non-residential extension and refurbishment. L1a (most relevant to large regeneration projects) has five compliance criteria that must be met:

1 A dwelling CO2 emissions should be restricted by design to less than those of a similar, notional building with standard services – how this is achieved is up to the designer.
2 Services have minimum performance values that must
be met
3 Overheating must be avoided by design.
4 As-built building must reflect the design aspirations – and prove it with, for example, air-pressure tests.
5 Home information packs must be provided explaining heating and hot water systems.

SAP 2005
SAP 2005 is the calculation used for assessing whether a dwelling complies with Part L1a 2006 or not. Most firms will have a software solution to calculate this. It can be done manually, although we would advise against this as it can be complicated and time consuming.

This is the equivalent of SAP for L2a (new-build
non-residential) – a piece of software freely available
from DCLG that calculates whether a building complies or not. It also applies to heated communal spaces in residential buildings.