GLA London Plan Air Quality Neutral Assessment
Specialist Air Quality Neutral (AQN) consultants for the London Plan 2021. Transport and building benchmarking, damage cost calculations and Air Quality Positive design advice for new developments across the 32 boroughs and the City of London.
Air Quality Neutral — The London Plan Benchmark Test
Air Quality Neutral (AQN) is one of the most distinctive features of the London planning system. Introduced in the London Plan 2016 and substantially updated in the London Plan 2021 (Policy SI 1 — Improving air quality), AQN requires that new developments do not exceed pollutant emission benchmarks set by the GLA. The intent is simple: London's air quality is improving, and the planning system should not allow new development to slow that trajectory. The mechanics, however, take care to get right.
Malcolm Pounder CEnv MIAQM has prepared AQN assessments under both the 2016 and 2021 London Plan and applies the GLA Air Quality Neutral Guidance 2023 — the document that defines the current benchmark rates, the calculation methods and the damage cost mechanism for offsetting any exceedance. Our assessments cover both the transport benchmark (emissions from trips associated with the development) and the building benchmark (emissions from on-site combustion plant), and where a scheme cannot meet either by design we calculate the damage cost contribution precisely using DEFRA's IGCB rates.
We also advise on the Mayor's proposed move from Air Quality Neutral to Air Quality Positive — an emerging requirement in several inner London boroughs — which goes beyond benchmarking and requires schemes to actively improve local air quality through design measures, green infrastructure and proactive mitigation. Whether your scheme is a borough major referable to the Mayor or a smaller scheme caught by a borough SPD, we deliver the assessment in the form the GLA and the borough expect.
Air Quality Neutral & Air Quality Positive
From transport and building benchmarking to damage cost calculations and Air Quality Positive design input, we deliver the full London Plan air quality policy response.
Transport Benchmark
Trip-rate-driven NOx and PM10 emissions calculation against the GLA AQN 2023 transport benchmark. We use TRICS trip rates, GLA-derived trip lengths and DEFRA EFT emissions factors to produce a fully traceable transport assessment that the GLA stage 1 referral team accepts.
Building Benchmark
NOx and PM10 emissions from gas boilers, CHP, biomass and standby generators against the GLA AQN 2023 building benchmark. We work with M&E engineers to optimise plant selection, stack height and Ultra-Low-NOx burner specifications so the scheme meets the benchmark by design.
Damage Cost Calculation
Where a scheme cannot meet a benchmark by design, we calculate the offset damage cost using DEFRA's current IGCB values for NOx and PM10. The figure is presented clearly with full workings for the s106 negotiation and is structured to be defensible if challenged.
Air Quality Positive Input
For inner London schemes where the borough or the GLA expects Air Quality Positive (the Mayor's emerging upgrade to AQN), we provide design input on green infrastructure, sustainable transport, electrification of heat, low-NOx plant and proactive mitigation that goes beyond simply meeting a benchmark.
Schemes That Trigger AQN
AQN applies to all major development referable to the Mayor under London Plan Policy SI 1, plus any smaller scheme caught by a borough SPD. Some inner London boroughs apply AQN to schemes of 10+ dwellings or 1,000 m² commercial; others apply it more selectively.
We routinely produce AQN assessments alongside the wider air quality chapter, transport assessment and energy strategy, working closely with the planning consultant and M&E team to make sure inputs are consistent across documents.
- Residential 10+ dwellings
- Commercial above 1,000 m² GIA
- Mixed-use major schemes
- Mayoral referable applications
- Schemes with CHP or gas boilers
- Hospitality with kitchen extract
- Student accommodation (PBSA)
- Build-to-rent (BTR)
Frequently Asked Questions
What is an Air Quality Neutral assessment?
An Air Quality Neutral (AQN) assessment is a London Plan policy requirement that demonstrates a new development's transport and building emissions do not exceed pollutant benchmarks set by the GLA. It compares the predicted NOx and PM10 emissions from the proposed scheme — from transport associated with the development and from on-site combustion plant — against benchmark rates per unit floor area (for buildings) and per unit dwelling (for transport). If a development cannot meet the benchmarks, it must offset the exceedance through a damage cost payment or design changes.
Which developments need an AQN assessment?
The GLA Air Quality Neutral Guidance 2023 applies AQN to all major development referable to the Mayor and to all developments subject to London Plan Policy SI 1. In practice this means residential schemes of 10+ dwellings, commercial schemes above 1,000 m² GIA, and any development with a combustion plant input above 50 kW. Individual London boroughs may set lower thresholds in their Local Plan or air quality SPD — for example, Westminster, Camden and Islington routinely apply AQN to smaller schemes.
What is the transport emissions benchmark?
The transport benchmark sets a maximum permitted level of NOx and PM10 emissions per dwelling (residential) or per unit floor area (commercial) generated by trips associated with the development. It is calculated using vehicle fleet emissions factors from DEFRA EFT, trip rates from TRICS, and trip lengths from the GLA's London-wide model. Schemes in central and inner London benefit from sustainable transport modes and tend to meet the benchmark more easily than schemes in outer London with higher car mode share.
What is the building emissions benchmark?
The building benchmark sets a maximum permitted level of NOx and PM10 emissions per unit floor area from on-site combustion plant — gas boilers, CHP, biomass and standby generators. The GLA AQN Guidance 2023 sets benchmark rates for residential and non-residential uses. Heat pump and all-electric schemes nearly always meet the building benchmark by design; schemes still relying on gas boilers or CHP often need careful plant selection and stack height optimisation to meet it.
What happens if my development exceeds the benchmark?
If a scheme cannot meet the transport or building benchmark by design, the GLA AQN Guidance allows offsetting through a damage cost payment calculated using DEFRA's IGCB damage cost values for NOx and PM10. The payment is typically secured by a s106 contribution and used by the borough for local air quality improvement measures. The preferred route, however, is always to meet the benchmark through good design — sustainable transport, electrification of heat, and low-NOx combustion where gas remains essential.