Writing daylight evidence a committee report can use

A daylight and sunlight report is read properly by one person: the case officer who has to compress it into four paragraphs of a committee report. Everything after that, including the decision, rests on what that officer wrote. So the practical test of a good report is not whether the modelling is correct. It is whether an officer under time pressure can extract an accurate conclusion from it without a specialist sitting next to them.

Most reports fail that test by being organised for the analyst rather than the reader. Two hundred pages of window by window tables, a methodology section quoting guidance at length, and a conclusion that says the scheme performs well in the context of its urban location. The officer then writes something approximate, an objector's consultant writes something sharper, and the committee hears two versions of the same data.

Give the officer the sentence they need to write

Start the report with a summary that could be pasted into a committee report and remain accurate. For each affected property: how many habitable rooms were assessed, how many meet the relevant targets, how many fall below, the range of the shortfall, and a one line characterisation of the effect.

Then the judgement. Not a restatement of the numbers, a view: whether the residual effect is within what is reasonable for this location and this type of development, and why. Officers are entitled to disagree with that view. They cannot summarise it if it is not there.

Avoid the construction where the conclusion sits in the final appendix. If the only place the report says what it thinks is on page 187, the committee report will say something else.

Separate the room types, and say why

The BRE tests apply to windows. The planning judgement applies to rooms people live in. A summary table that mixes a bathroom window with a living room window treats them as equivalent, and they are not.

Report habitable rooms in the headline: living rooms, dining rooms, kitchens where the authority treats them as habitable, and bedrooms, which most guidance treats as less sensitive because their main use is at night. Put bathrooms, halls, landings, stores and circulation in the appendix schedule where they belong.

Say which convention you have used, because authorities differ on kitchens and on whether a combined kitchen and living space is assessed as one room. Stating the convention in a single sentence prevents an argument later about whether the numbers were selected.

Show the existing condition as well as the change

A room that already sits well below the daylight target, because it is at the base of a light well or behind a deep balcony, is in a different planning position from one that is currently well lit. The proportional test can produce an alarming percentage from a tiny absolute change.

Report the existing value, the proposed value, the absolute change and the ratio. Four columns. It takes no more space than two and it removes the most common misreading in the whole field, which is a reported loss of a third in a room where the starting point was already marginal.

Balconies are the recurring case. Where the existing building has projecting or inset balconies, the rooms beneath them start low, and a report that does not say so invites the objection that the proposal caused the problem. The interaction between balconies and the flats beneath them is worth a short paragraph of its own when it applies.

Departures from the numerical targets

BRE guidance states that its numerical targets are advisory and should be applied flexibly according to context. That sentence is the foundation of most urban schemes, and it is routinely used badly, as a general assertion that dense areas are different.

Used well, it is specific. Name the context: the site is in a town centre allocated for taller development, the surrounding buildings already achieve values below the target, the local plan seeks higher densities at this location. Then show it, with measured or modelled values for the existing context rather than an assertion. Some authorities publish their own expectations for dense areas, and where they do, using them is stronger than arguing from first principles. The reasoning behind alternative targets in dense urban areas is worth setting out in a short section rather than a footnote.

Then say what the design did about it. Set-backs, chamfered corners, light wells widened, a storey removed from one block. A report that shows the scheme was tested and amended reads very differently from one that reports a result.

The parts officers need in an appendix

• The full window and room schedule, referenced to drawings, so every figure is traceable.
• The modelling assumptions: reflectance values, surrounding building heights and their source, window dimensions and their source.
• Where internal layouts were assumed rather than surveyed, a statement of the assumption and its basis. Where access was refused, the approach taken to modelling neighbouring rooms without access should be set out plainly, because objectors test it first.
• The existing baseline model and its date.
• Sunlight results for amenity areas with shadow plots at the standard dates.

Number the appendices so the officer can cite them. A committee report that says "see appendix C of the daylight and sunlight assessment" is doing its job.

Handling an objector's rebuttal report

On contested schemes a second consultant produces a report for objectors, and the officer then has two documents saying different things. The officer is not equipped to reconcile them, and the usual outcome is that the committee report records a disagreement rather than a conclusion.

You can prevent most of that by writing the first report in a way that makes disagreement specific. State every assumption that a second analyst would have to adopt to reproduce your figures: room depths, reflectances, the surrounding context model and its source, the treatment of existing balconies. Where a rebuttal then differs, it differs on a named input, and the officer can see which of you changed what.

Respond to a rebuttal in a short note rather than a second full report. Take each point of difference, state your input, state theirs, and say which is correct and why. Three pages beats thirty, and it is the only form the officer will read before the report deadline.

Writing for the legal reader as well

Officer reports are read by courts occasionally, and the approach there is well established: a report is read as a whole, for an informed audience, without excessive legalism. That works in favour of a clear, honest report and against a report that buries a material shortfall.

The practical consequence is simple. A report that discloses the harm, quantifies it and explains why the scheme remains acceptable gives the officer something defensible to summarise. A report that presents only favourable metrics gives the officer something that an objector can undermine at the meeting, and that is where schemes are deferred.

An illustrative structure

Illustrative example. Section 1, a one page summary by property with the judgement. Section 2, method and conventions, two pages. Section 3, results by property with four column tables, one page each. Section 4, context and departures from the numerical targets, with comparator values. Section 5, design measures taken to reduce effects. Appendices A to E with the full schedules and modelling assumptions. Total main report, fifteen pages. The structure is illustrative and the scheme governs.

If the report cannot be summarised in four accurate paragraphs by someone who did not write it, restructure it before submitting. A daylight and sunlight assessment only influences a decision through the officer who reads it.

Enter your site postcode on PlanScope to draft the supporting statement that sits alongside the technical evidence.

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. For specialist technical reports, qualified professional input may be required.