Looking for the actual numbers behind a daylight and sunlight assessment? This page puts the headline BRE 2022 (BR 209) daylight targets and the BS EN 17037 recommendations for new homes into two plain reference tables — the figures consultants test against and planning officers expect to see, all in one place.
Bookmark it, cite it, and if you need the assessment itself, our daylight and sunlight report service covers the same metrics.
Table 1 — Protecting existing neighbours (BRE BR 209, 2022)
These tests apply when a proposed development might affect the daylight or sunlight of existing nearby homes:
| Test | Metric | Headline target | Also acceptable |
|---|---|---|---|
| Daylight to windows | Vertical Sky Component (VSC) | At least 27% | No less than 0.8 times the former value |
| Daylight distribution in rooms | No Sky Line (NSL) | Area seeing the sky should not fall below 0.8 times the former area | — |
| Sunlight to windows facing within 90° of due south | Annual Probable Sunlight Hours (APSH) | At least 25% annual, including 5% in winter | No less than 0.8 times the former values |
| Sunlight to gardens and amenity space | Two hours of sun on 21 March | At least 50% of the area should receive 2+ hours | No less than 0.8 times the former area |
What is the 0.8-times rule?
Running through every test above is a simple principle: a reduction is generally treated as noticeable when a value falls below 0.8 times its former level — a loss of more than one fifth. If a neighbour's window keeps at least 80% of its previous VSC, APSH or daylit area, BR 209 regards the effect as unlikely to be noticed in practice. That is why daylight reports talk about "0.8 times" so often, and why marginal schemes live or die on a few percentage points.
Table 2 — Daylight and sunlight inside new homes (BS EN 17037 via BR 209 2022)
The 2022 edition of BR 209 aligned the assessment of proposed dwellings with BS EN 17037, which sets room-by-room target illuminance levels to be achieved over at least half of the assessment plane for at least half of the daylight hours in a year:
| Room | Target illuminance | Over how much of the room | For how long |
|---|---|---|---|
| Bedroom | 100 lux | At least 50% of the assessment plane | At least half of annual daylight hours |
| Living room | 150 lux | At least 50% of the assessment plane | At least half of annual daylight hours |
| Kitchen | 200 lux | At least 50% of the assessment plane | At least half of annual daylight hours |
For sunlight, BR 209 (2022) recommends that at least one habitable room — preferably a main living room — should receive at least 1.5 hours of direct sunlight on 21 March.
Which metric applies to which situation?
- Neighbouring existing homes → VSC, NSL, APSH and the two-hour amenity test (Table 1).
- The new homes you are building → BS EN 17037 illuminance targets and the 1.5-hour sunlight recommendation (Table 2).
- Both at once — a typical urban infill scheme is assessed in both directions, which is why a full report covers the neighbours and the proposed units.
Are the BRE targets mandatory?
No — and this matters. BR 209 describes its numerical values as guidance to be applied flexibly, and the National Planning Policy Framework supports a flexible approach where justified, for example in dense city-centre and conservation contexts. In practice, though, most UK planning authorities use the BRE targets as their benchmark, and a scheme that fails them without good justification should expect objections. The realistic approach is to test early, understand which targets are at risk, and design or justify accordingly.
How Fortress Associates can help
Our daylight and sunlight reports assess VSC, NSL, APSH and BS EN 17037 compliance to BRE BR 209 (2022), with reports typically delivered in 4–5 days and no advance payment. If your scheme is borderline against any table above, we can tell you where it stands before your neighbours' objections do. Browse our other planning report services or contact us for a quote.
Sources & further reading
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