Draft further alterations to the London Plan include a proposal to double the target for on-site renewable energy from 10% to 20%.
But the overall strategy and approach of the plan is called into question by a recent report for the British Council for Offices. Its author, Glen Irwin, sets out 10 key reasons why the London Plan isn’t working.
The current methodology for demonstrating carbon savings is too inflexible to consider any technology other than renewables. Instead, the BCO suggests base carbon emissions first be established for the building design this would be stripped down to the minimum energy saving features needed to achieve a pass, ie just meet the target emissions rate, the legal requirement under Part L2A.
After considering the energy demands that would need adding to the carbon emissions base point assessed by national calculation methodology (NCM), the design team would agree which energy saving features to apply to the basic design to make the 20% saving. This would allow technologies such as passive solar heating, facade optimisation, high efficiency central plant, low energy lighting and adiabatic cooling to be taken into account.
Usually when the design team has calculated the base annual carbon emissions and assessed the renewables most likely to deliver the required carbon savings, an energy statement is presented to the GLA. If 10% is being achieved, approval is usually given. However, particularly on office projects, the best savings are about 7%, which carries the risk of refusal.
There does not seem to be much recognition within the GLA that many projects are struggling to meet the full 10% renewables target, two years after its introduction. The BCO would like to see more detailed reporting of progress towards carbon targets using renewables, including data on percentage carbon savings actually being achieved on individual projects – perhaps listed anonymously. Unless the facts of current difficulties are openly reported and debated, solutions will not be found and the GLA will be seen as burying its head in the sand and carrying on regardless.
Acceptance under the London Plan relies on demonstrating how base carbon emissions can be reduced by 10% by use of renewables. Unfortunately carbon emissions calculated under Part L using the National Calculation Methodology omit assessment of things such as small power loads, lifts and escalators, external lighting and computer suites.
At the preplanning stage many of these are not finalised because there is no tenant. The only way to estimate loads is to use benchmark figures; for offices these are based on Energy Consumption Guide 19. Many data sets in the Renewables Toolkit - the supporting guidance to the Plan are out of date, based on buildings from the 1990s.
The BCO is calling for sources of energy data referenced in the Renewables Toolkit to be updated by a nationally recognised body such as BSRIA or BRE.
The energy policies produced for the London Plan essentially come from the steering group of the London Energy Partnership, which was established by the mayor in 2004. This steering group establishes the strategy and direction of its activities and then instructs the task groups to carry out work.
The London Energy Partnership is receiving feedback via the London Energy Forum, which functions as “a networking and discussion forum”, although the membership of this forum also appears to form the basis of the task groups.
There appears to be little or no feedback of the difficulties being faced in meeting current targets, and this is evident from the desire to forge ahead with the inflexible system of assessing carbon savings.
Take the example of an 11-storey office block in central London, with 22,750 m2 of treated floor area (TFA) and predicted annual emissions of 106.6 kgCO2/m2 TFA.
The London Plan’s Renewables Toolkit suggested ground source heating and cooling or a PV installation would meet the 10% target for just over 3% of the total project cost for the first option and 1.5% for latter.
In fact, the building could only meet 6.2% of its renewables target even with the addition of wind turbines and a biomass boiler. The cost came to £593,000 – 0.9% of total build. Assuming it is possible to use more PV to meet the 10% target, the total cost would be over £1.6 million 2.5% of total build.
Increasing renewables to 20% would not simply double the cost. Some BCO members fear new offices in London will be unviable.
The essence of the problem is that to achieve the total carbon savings from all buildings, the bulk of the improvement has to come from existing stock. The London Plan appears to pay very little attention to the potential carbon savings from more conventional energy saving systems, preferring to put most faith in CHP or renewables.
User control or the power the occupants have to reduce energy consumption themselves is likely to be
far more cost-effective than spending money and energy on massive amounts of additional plant.
Offices represent about 13.8% of London’s carbon emissions, but with only 1% of them replaced a year, a saving of 20% of carbon emissions per property is not a big contribution.
A BCO analysis suggests a very small improvement in the short term but a longer term shortfall of 7% against the GLA’s 2025 target of 30%. Renewables for new build, coupled with improvements due to building stock renewal, are not enough to meet overall long-term targets.
To achieve them, the GLA needs to find new ways of encouraging all building users to improve their operation of buildings.
Recently, for developments struggling to meet the 10% renewables target, the GLA has suggested the use of gas-fired CHP instead. Although not strictly in accordance with the rules, this seems to be an attempt to encourage wider use of CHP and a way of softening the overall target for difficult projects.
Unfortunately, as stand-alone office buildings do not have significant hot water demands, CHP can seldom be proved effective. While this flexibility is helpful on some projects, the current drive to use CHP has become so strong that it has been difficult to convince the GLA that it is not applicable to some projects.
The revised London Plan introduces a new policy that CHP must be considered for all projects, but it fails to provide proper guidance on which projects it should be considered for and those for which it should not.
Trigeneration has been suggested by the GLA energy team on a number of submissions which are failing to reach the 10% renewables target, and, like conventional CHP, it is often suggested as an alternative to renewables.
The idea is that if CHP cannot be justified because there isn't a significant hot water demand outside of the heating season, why not use the hot water to generate cooling.
However, investigations into the use of this technology on large office buildings have revealed a relatively poor overall carbon performance because the efficiency of the absorption chiller unit is relatively low compared to electrically powered chillers, and due to two sets of losses from the CHP unit in producing heat, and from the absorption chiller in converting it to chilled water.
Fuel cells are suggested in the London Plan as a way of saving carbon when coupled with renewables to generate hydrogen. Generation of hydrogen from renewables will only ever be practical on the scale of power stations, when the upstream supply of hydrogen is beyond the control of property owners. The most optimistic reports suggest the hydrogen economy will not begin to be commercially possible until 2020, and will not mature until 2050.
Glen Irwin is a divisional director with Foreman Roberts
Building Sustainable Design