Daylight and sunlight results tables an officer can check

A daylight assessment results table has one job: to let a case officer check your conclusions without opening the model. Most fail at it. They present room-by-room numbers with no plan reference, mix metrics between tables, round ratios to one decimal place in one appendix and two in another, and bury the windows that fall short in the middle of a forty page schedule.

Get the presentation right and the assessment becomes reviewable. Get it wrong and the officer either asks for the whole thing again or gives the objector's version more weight than yours.

Identifying rooms and windows consistently

Every value you report has to be traceable to a specific window in a specific room in a specific property. Build the referencing system before you run a single calculation.

Use a reference that carries its own meaning: property address or plot number, floor level, room number and window number, in that order and separated consistently. Room 2 on the first floor of 14 Mill Lane becomes something a reader can find on a plan. A bare W17 does not.

Then produce the plan appendix that the references point to. One annotated floor plan per property per floor, with room numbers and window numbers marked, the assumed room use labelled, and north shown. Where the internal layout was not surveyed and has been assumed from the elevation, say so on the plan itself rather than in a footnote. Assumed layouts are accepted routinely, but only when the assumption is visible.

Three columns belong in the header of every table: reference, assumed room use, and the source of the layout information. That last column is the one objectors attack and the one that protects you.

How to present existing and proposed values

Report the before value, the after value and the ratio, in that order, in adjacent columns. Never report the ratio alone, and never report only the proposed figure.

Two conventions save argument. Give vertical sky component as a percentage to one decimal place and keep that precision everywhere. Give ratios to two decimal places, because the difference between 0.795 and 0.804 decides whether a window passes and rounding to one place hides it.

Keep the no sky line results in a separate table with the same reference column, reporting the area of the working plane receiving direct skylight before and after and the ratio. Do not merge the two metrics into one table with a shared pass column, because a window can meet one and fail the other and a merged table forces you to pick.

Reporting shortfalls, including marginal ones

The instinct to soften a shortfall is what damages assessments. Report every window that falls below the guidance, list it in a dedicated table near the front of the document, and give the reason.

That table should contain the reference, the metric that falls short, the existing and proposed values, the ratio, the assumed room use and a short reason. Reasons that carry weight are specific: the window serves a room with another window that retains good daylight, the existing value is already low because of an existing outbuilding, the room is a bathroom or a circulation space, the window is a secondary one in a dual aspect room, or the existing property has an unusually deep balcony that suppresses the baseline.

Reasons that do not carry weight include an urban context assertion with no numbers attached, and a general statement that the scheme accords with policy.

Marginal cases deserve their own line. A ratio of 0.78 is not the same as 0.55, and a table that lumps both under fails invites the officer to treat them alike. Say how many windows fall between 0.8 and 0.7, how many between 0.7 and 0.5, and how many below 0.5. That distribution is the single most useful thing in the report.

Sunlight results and the relevant dates

Sunlight is assessed separately and only for windows within 90 degrees of due south. Say which windows those are and which were therefore excluded, because a reader who cannot see the exclusion assumes an omission.

Report annual probable sunlight hours as two figures, the annual total and the winter component, with the winter period defined in the table header as 21 September to 21 March. Then give existing, proposed and ratio for each, as with daylight. A single combined sunlight column is not enough, because a window can retain its annual total while losing its winter sunlight, and winter loss is what occupants notice.

Where a window falls short, state the absolute reduction as well as the ratio. The guidance treats a small absolute reduction differently from a large one, and giving only the ratio loses that.

Amenity space results

Assess sun on the ground for gardens and amenity areas on 21 March, and report the proportion of each area receiving at least two hours of sunlight before and after, with the ratio.

Identify each amenity area on a plan with an area reference and its measured area in square metres. Distinguish private gardens, communal amenity space, children's play space and roof terraces, because policy treats them differently and a single aggregated figure for the whole site hides a poorly performing courtyard.

On dense urban schemes the overshadowing result is often the most sensitive number in the whole package, and it belongs in the Overshadowing Study with its own plan set rather than as an afterthought in the daylight appendix.

Sensitivity and alternative massing runs

Where the scheme has been modified during design, show the runs. A table comparing the consented or original massing, an intermediate option and the submitted scheme, using the same window set and the same metric, demonstrates that the design responded to the results.

Keep the comparison honest. Use the same baseline for every run, state which parts of the massing changed between them, and do not quietly drop windows that performed badly in an earlier run.

Sensitivity testing is worth a short section of its own. Test the assumptions that matter most: assumed room use where the layout was not surveyed, glazing transmittance, the treatment of balconies and overhangs, and the baseline condition where an existing building is to be demolished. Report the range each assumption produces. An assessment that shows its own sensitivity is far harder to attack than one that presents a single set of numbers as fact.

A summary table an officer can quote

Finish with a one page summary, placed at the front of the document, that a committee report can lift directly. It should state the number of properties assessed, the number of windows and rooms assessed, how many meet the daylight guidance and how many do not, the distribution of shortfalls by band, the equivalent figures for sunlight, and the amenity space results.

Add one line stating which edition of the guidance was used, and one stating the software and version. Both will be asked for.

A Daylight and Sunlight Assessment presented this way is quicker to review, quicker to defend at appeal and easier to reconcile with the design narrative in the Design and Access Statement. Councils usually expect a suitably qualified author for this work and professional review is strongly advised, because the numbers are checkable and errors surface late.

For the underlying test itself, the note on the vertical sky component sets out how it is calculated and what the 27 per cent figure means. For the same discipline applied to financial evidence, see the note on a viability appraisal inputs schedule.

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.