Air quality damage cost contributions explained

An air quality damage cost contribution is a sum of money a council asks for because your development will emit nitrogen oxides and particulate matter, calculated by multiplying the predicted emissions by a published cost per tonne. It is not a fee and it appears on no fee schedule. It arrives through a section 106 obligation, usually after an air quality consultee has read your assessment, and the figure is open to argument in a way a planning fee never is.

Most developers meet it first as a number in a consultation response, with two lines of working and no explanation. Knowing how that number was built is what lets you reduce it.

Where the damage cost approach comes from

Defra publishes damage cost values that put a money figure on the health and environmental harm caused by a tonne of a given pollutant, for use in appraisal. The values differ by pollutant, by source type and by location, because a tonne of nitrogen oxides emitted at street level in a dense urban area does more harm than the same tonne from a rural stack.

Planning never had a national rule telling authorities to apply those values to applications. What happened instead is that the Institute of Air Quality Management's land-use planning guidance recommended an emissions mitigation assessment for schemes with air quality effects, and a number of authorities wrote that recommendation into supplementary planning documents with the damage cost values as the arithmetic. The result varies by council, which is why two similar schemes in neighbouring boroughs can be asked for very different sums.

So the starting question is never what the national rate is. It is which local document the officer is working from.

How a contribution figure is built up

The arithmetic has four inputs and they are all contestable.

1. Building emissions. The annual mass of nitrogen oxides from heating and hot water plant, derived from the proposed system, its capacity, its emission rate and its assumed hours of operation.
2. Transport emissions. The annual mass from predicted vehicle movements, usually from trip rates, assumed trip lengths and an emissions factor for the relevant fleet year.
3. The damage cost per tonne for each pollutant, taken from the current published values for the right location type.
4. A number of years over which the harm is counted. Five years is common in supplementary planning documents. It is a local policy choice, not a national one.

Multiply, sum, round. The illustrative shape is: tonnes of nitrogen oxides per year, multiplied by the published cost per tonne, multiplied by the number of years, plus the same calculation for particulate matter. Any worked figure you see in an officer report is only as good as the trip rates and plant assumptions behind it, and those are yours to correct.

The place that calculation belongs is the Air Quality Assessment. Councils expect a suitably qualified author for it, generally working to the Institute of Air Quality Management's methods, and professional review of any draft is strongly advised before submission.

Emissions mitigation assessment and what it replaces

The emissions mitigation assessment is the step that turns an impact finding into an obligation. Its logic is that a scheme which cannot avoid emitting should pay for offsetting measures elsewhere, in the same way a scheme which cannot avoid losing habitat pays for biodiversity units.

Two things follow from that logic, and both help the applicant.

First, the payment is a residual. It covers emissions left after on-site mitigation, so every tonne you design out reduces the sum. Second, the money is meant to fund measures that improve air quality in the affected area. An authority asking for a contribution with no identified use for it is on weak ground.

Measures that reduce or remove the payment

The smallest contribution is the one the design avoids. In rough order of effect on the arithmetic:

• Remove combustion from the heating strategy. An all-electric scheme with heat pumps has no plant nitrogen oxides at all, which deletes an entire input. This is also the direction Part L and the Energy Statement are pushing schemes anyway.
• Delete or downsize any gas boiler, combined heat and power unit or standby generator. Where a generator is required for life safety, state its tested hours, because annual run hours drive its contribution.
• Cut vehicle movements. Car club spaces, a reduced parking ratio and cycle provision all feed the trip rate side of the calculation through the Travel Plan.
• Specify electric vehicle charging beyond the Building Regulations minimum, and say what proportion of movements it is assumed to electrify.
• Where plant must burn something, specify low nitrogen oxide units with the emission rate in mg/kWh stated on the drawings, not in a covering letter.

A scheme that arrives with no combustion plant and a low parking ratio is often asked for nothing at all. That is the honest headline: this is a design negotiation dressed up as a payment.

Air quality management areas and local guidance

An Air Quality Management Area is declared where a local authority's review and assessment shows an objective is being exceeded, and it comes with an action plan. Being inside one does not automatically generate a contribution, but it raises the chance that the local supplementary planning document requires an emissions mitigation assessment and sets a formula.

Check three documents before you budget anything:

Where the authority has no published formula, a contribution demanded by a consultee is harder to justify, because the obligation must still satisfy the statutory tests.

Securing the money in a planning obligation

Contributions of this kind are secured by agreement or unilateral undertaking under section 106 of the Town and Country Planning Act 1990, and they must meet the tests in regulation 122 of the Community Infrastructure Levy Regulations 2010: necessary to make the development acceptable in planning terms, directly related to the development, and fairly and reasonably related in scale and kind to it.

Read the draft clause for the detail that costs money later. Is the sum index linked, and to what index? Is it payable on the start of works or on first occupation? Is there a clawback if the measures are not delivered within a stated period? Are monitoring fees added on top? Figures of this sort are commonly updated annually, in the same way that application fees are, as explained in our note on how planning fees are indexed each April.

Challenging a figure that looks wrong

Work through the inputs rather than arguing about the total. The questions that move numbers:

Which trip rate source and which filters were used, and does the site match the comparison sites at all? Has the assessment counted the trips the existing lawful use already generates, or treated a brownfield site as if it were empty? Which emissions factor year was applied, given that fleet emissions fall over time? Is the plant assumption still right after the energy strategy changed at reserved matters? And is the number of years in the formula the one the adopted guidance actually states?

Then test the policy basis. If the authority cannot point to adopted guidance, an identified use for the money, and a link to the development's own effect, the regulation 122 tests are the argument to make. Officers rarely defend a figure built on a superseded emissions factor once it is put to them in writing.

Budget for the assessment and the possible contribution separately, and get the heating strategy settled before either is priced. See PlanScope pricing for what a draft report costs, or check the full application fee basis in our note on application fees by floorspace and site area.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.