Choosing a daylight consultant where no licence exists

There are no statutory daylight consultant qualifications. No licence, no register, no protected title, and no accreditation scheme that an authority will treat as decisive. A daylight and sunlight assessment is judged on whether the method follows recognised guidance and whether the assumptions behind it stand up, which means the choice of consultant is a procurement problem rather than a compliance one.

That matters more than it sounds. On a dense urban scheme, daylight is frequently the issue that decides the application, and a weak assessment loses units rather than losing an argument.

Why there is no statutory qualification

Daylight and sunlight in planning is assessed against guidance, not legislation. The reference document is the Building Research Establishment's guide to site layout planning for daylight and sunlight, now in its third edition, which sets out the vertical sky component test, the no-sky line, annual probable sunlight hours and the overshadowing test for amenity areas.

Guidance of that kind carries weight through the development plan and through decision-makers choosing to follow it. Nobody is licensed to apply it. The nearest things to a professional anchor are membership of the surveying institution for those working on rights of light, and membership of the building services engineering body for those coming from a lighting or environmental engineering background.

Those two routes produce different practitioners. A rights of light surveyor thinks about legal injury to an easement and about compensation. A building services engineer thinks about illuminance, daylight provision inside a room, and how daylight interacts with overheating and energy. Planning daylight sits between them, and the meaning of competent person in planning legislation offers no help here, because no statutory competence requirement attaches to this work at all.

Experience to test for instead

Ask for three things and read them yourself.

A list of schemes of comparable type, scale and context, from the last three years, naming the local planning authority. Urban infill next to Victorian terraces is a different problem from a tall building next to a 1960s slab block, and a practice strong on one may have never done the other.

Two assessments the named individual personally authored, not the practice's best work by someone who has since left. Look at whether the report explains its assumptions or buries them, whether it identifies the transgressions honestly, and whether it offers a considered judgement rather than a table.

And the names of the authorities whose officers have reviewed their work. A consultant whose reports are familiar to the borough you are applying in starts from a position of credibility, and you can ask the officer informally what they think of the practice.

One warning sign is worth stating plainly. If every scheme in the portfolio fully complies with every numerical target, either the schemes were undemanding or the assessments were written to reach that conclusion. Dense urban development rarely complies fully, and the guidance itself says the numerical targets should be applied flexibly in city centre contexts.

Software and modelling capability questions

Ask what the model is built from, and how.

A three dimensional model derived from a measured survey and verified against aerial imagery is different from one traced off a location plan and extruded to guessed storey heights. Ask how the surrounding buildings were modelled, how window positions on neighbouring properties were established, and what was done where a window could not be seen.

Then ask which tests the software performs natively and which are calculated by hand. Vertical sky component and annual probable sunlight hours are straightforward. Daylight distribution requires internal room layouts for neighbouring properties, which are usually not available, so the consultant has to make assumptions and say so. Climate-based modelling of the proposed interiors, using target illuminance and spatial daylight autonomy, is a different calculation again, and it interacts with the glazing specification, so it should be coordinated with whoever is doing the overheating work. The same coordination question arises with dynamic thermal modelling competence.

Finally, ask for the model file and the input assumptions as a deliverable. If the consultant will not release them, you cannot get a second opinion without paying for the model twice, and you cannot respond quickly when an objector's consultant produces different numbers.

Whether they have given evidence at appeal

This is the single most useful discriminator.

Someone who has given evidence at an inquiry on daylight has had their assumptions cross-examined by a barrister. They write differently afterwards: assumptions are stated, sensitivity is tested, and weak points are acknowledged rather than hidden. Ask which appeals, in what role, and what the inspector concluded on the daylight issue.

A consultant who has never been tested may still be excellent. But on a scheme where daylight is contested, the person writing your assessment may end up in the witness box, and finding out at that point that they are uncomfortable there is expensive.

Ask also whether they have acted for objectors or for authorities. A practice that has argued the other side knows where an assessment gets attacked.

How they handle room use assumptions

Most of the argument in an urban daylight case is about assumptions, not arithmetic.

Which neighbouring rooms are habitable, and on what basis. Whether a room served by two windows is assessed on both. How a room behind a conservatory or a balcony is treated. Whether a window belongs to a bedroom, which the guidance treats as less demanding of daylight than a living room. What happens where the neighbouring property is an office, a shop or a building with an extant permission for conversion to housing.

A good consultant sets these out in a table at the front of the report, with the source of each assumption and a note where it is uncertain. A poor one presents results with no assumptions stated, which means an objector can produce a different answer and the officer cannot tell which is right.

Push on the uncertain ones. Where a room use assumption is doing real work in the conclusion, ask for a sensitivity test showing the result under the alternative assumption. That costs a day and it removes the most common line of attack.

Presentation to committee

Daylight results are hard to explain to a committee in three minutes, and many applications are lost in that three minutes.

Ask to see how the consultant presents. Clear before and after images, a simple explanation of what the numbers mean in human terms, and an honest account of which windows are affected and by how much, will do more than a matrix of percentages. Members respond to "this window keeps most of its daylight, this one loses about a fifth, and here is why we think that is acceptable on this site".

Check they will attend. Some practices price committee attendance out of the fee, then charge a day rate at short notice. The professional review route is worth considering for a second pair of eyes before the report is finalised, particularly where the scheme is finely balanced.

Fee scopes that include a redesign iteration

The most common commercial mistake is buying a single assessment of a fixed design.

Daylight analysis is most valuable during massing, when a storey can come off a corner or a lightwell can be widened at no cost. A fee that covers one run of the completed scheme produces a report telling you what you already feared, with no budget left to fix it.

Scope it in three stages instead:

1. An early appraisal of the massing, with sketch-level results and advice on where the pressure points are.
2. Testing of two or three design options, priced per option.
3. The formal Daylight and Sunlight Assessment of the submission scheme, plus an allowance for responding to consultation comments.

Add a named allowance for committee attendance and, where the scheme is contentious, a provisional sum for appeal support. Where garden and amenity space is also in issue, an Overshadowing Study may be needed alongside, and pricing it at the same time avoids a second mobilisation.

Councils usually expect a suitably qualified author for this work, and professional review is strongly advised. For specialist technical reports, qualified professional input may be required.

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.