One of the key objectives of the Greater London Authority’s (GLA’s) London Plan was to deliver carbon reductions – so how has it fared in the 15 years since it was introduced?
To measure success, you need a target, and the GLA chose to use the Building Regulations’ National Calculation Methodology (NCM). This is the same approach as used for Breeam, and the choice is unfortunate because the NCM is designed for compliance, not energy consumption.
By using this methodology, the GLA underestimated energy use significantly, sometimes by a factor of three.
The recent introduction of the Building Better Partnerships’ Design for Performance (DfP) standard gives an accurate methodology for predicting operational energy consumption and a realistic alternative to the NCM.
Initially, the key requirement of the London Plan was for renewable energy generation on site. The easiest and cheapest way to satisfy this requirement was to include biomass boilers, but because these resulted in significant increases in air pollution, most were never switched on and were quickly discouraged by the London boroughs.
Wind turbines were a popular alternative – some even featuring prominently within the architecture of buildings. However, they failed to deliver the estimated electricity outputs because of turbulent airflows around buildings, with some units failing to generate any power.
The focus then shifted to decentralised heat networks fed by low carbon technologies. For practical and financial reasons, natural-gas fired combined heat and power (CHP) units were the prevailing solution. These are classed as low carbon technologies, though still burn fossil fuels.
As a result, electricity generation through combustion was reintroduced into London after being phased out in the 1980s because of concerns about local air quality. This led to a contradiction within the planning process – the energy officer might be requesting CHP, while the environmental officer was asking for its removal.
This has been the status quo for the past five years or so, apart from a brief attempt to maximise low carbon heat generation through introducing ‘trigeneration’.
The case for carbon reduction from CHP was based on the large difference between the emission factors of natural gas versus grid electricity. However, since 2010 – when Building Regulations emission factors were last updated – the grid average emission factor has halved with the introduction of renewable energy sources.
By using the NCM, the GLA underestimated energy use significantly, sometimes by a factor of three
The next version of the Building Regulations is expected to update the electrical emission factor to reflect this, making CHP more carbon intensive than gas boilers or direct electric heating.
The new London Plan will discourage combustion on site – largely because of air-quality concerns – and, since January, has required the use of the new emission factors. The upshot is that carbon-emissions savings of up to 40% from CHP have disappeared, and their contribution to air pollution means they will be discouraged for new development (see air quality article on page 26. The only apparent solution now for achieving the CO2 and air-quality requirements are electric heat pumps.
So will the 2019 version of the GLA’s London Plan be more successful than previous attempts at achieving its objectives?
Unfortunately, it retains the NCM methodology for quantifying carbon emissions and applying carbon-offset payments; this bears little relationship to actual performance in use. Adopting the DfP standard, would have been a far better methodology to deliver in operation, with the performance predicted at design stage.
On paper, heat pumps offer significant CO2 savings. However, quoted seasonal efficiencies are rarely achieved, because when the heat demand is greatest, the outside temperatures are lowest, so reducing efficiencies.
In terms of CO2 savings, even at lower efficiencies, heat pumps are better and – with the decarbonisation of the grid – offer future-proofing. However, electricity is three to five-times more expensive than natural gas, which could result in higher bills and put more people at risk of fuel poverty.
For the past 15 years, the London Plan has promoted low carbon design with mixed results, and has failed to achieve significant reductions – while, at the same time, promoting policies that have been detrimental to our air quality. The GLA has a real opportunity to transition to a low carbon, fossil fuel-free future – but must ensure the methodology is robust and does not have unintended consequences.
- Simon Wyatt is sustainability partner at Cundall