RIBA‑approved CPD
Enhance your extension projects with deeper insights into daylight, ventilation, regulations and smart roof window design. We offer online and in-person RIBA‑approved CPD sessions tailored to architectural practices.
Tools, principles and guidance
Extensions often struggle with a dark core even when there’s lots of façade glazing. Adding roof windows changes how light reaches the room, improves uniformity and supports natural ventilation. Use the guidance below and apply EN17037 daylight analysis early to get better outcomes.
Why extensions develop dark cores
Deep plans, overshadowing and limited sky view mean light stays near the façade and drops sharply in the middle of the room. Stair cores and light shafts can move daylight into the centre, and roof windows can pull light deeper into the plan than vertical glazing.
Roof windows vs. façade glazing – performance and comfort
Sloped roof windows typically bring twice the daylight compared with vertical windows of the same size, and flat roof windows bring up to three times more daylight. They produce higher wall illuminance and a softer transition between window and wall, which reduces glare around the façade and brightens the room core.
Methodology: LCA (Life Cycle Assessment) - how you choose products matters
- A single sloped roof window delivers double the daylight compared to a facade window, making it equivalent to the light from two facade windows
- A single flat roof window delivers triple the daylight compared to a facade window, making it equivalent to the light from three facade windows
Roof windows make it possible to maintain a low LCA profile while boosting daylight levels, ensuring sustainability and daylight performance go hand in hand.
Case examples for extensions
Light, connection and heritage
Westwind: a sympathetic renovation in South-West London
Bigger, brighter kitchen and dining room extension
Meet Sarah and Andy, whose extension brought a stronger sense of family togetherness.
Designing an open-plan flat roof extension
Meet Tiffany and Cameron, who created an inviting family space filled with fresh air and daylight.
Extending their living space to the great outdoors
Meet Stacey, who extended the back of her house to create a multi-functional room – ideal for entertaining and unwinding.
Victorian cottage kitchen extension reimagined with flat roof windows
Find inspiration from Ian and Ross’ Victorian cottage renovation as they introduce flat roof windows to the heart of their home.
Technical tools
Start your extension daylight design
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