Daylight, Sunlight and Amenity – Page 17
BRE 209 tests, the 45-degree rule, overshadowing, overlooking and neighbour amenity.
Daylight, Sunlight and Amenity articles – page 17
390 articlesTransient overshadowing: what a shadow study must show
Transient shadow plots show when a receptor loses sun, rather than only how many hours it keeps. Here is how to choose dates, model the baseline and present plots an officer can read.
Overshadowing gardens: the two-hour test on 21 March
Garden overshadowing is judged by whether half the amenity area still gets two hours of sunlight on 21 March. Here is what the test measures, which spaces it covers, how to build the shadow model and how to read a marginal result.
Daylight in new homes: BS EN 17037 illuminance targets
BS EN 17037 asks whether the homes you are building have enough daylight of their own, using climate-based modelling against lux targets. Here are the UK National Annex figures, the model inputs that matter and the geometries that cause failures.
No-sky line: assessing daylight distribution inside a room
The no-sky line divides the part of a room that can see sky from the part that cannot. Here is how the daylight distribution test is modelled, why the 0.8 ratio catches deep rear rooms, and what a defensible presentation looks like.
The 25-degree rule at the centre of a neighbouring window
The 25-degree obstruction angle in BRE 209 decides whether a detailed daylight assessment is needed at all. Here is how to measure it correctly, what to do when it fails, and how to record it for an application.
The 45-degree rule: how councils apply it in plan and section
The 45-degree rule is a council design-guide shortcut for judging whether a rear extension harms a neighbour's light. Here is how the line is drawn in plan and in section, and what to do if your scheme crosses it.
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