Best Practice on Daylighting Extensions

There is a minimum

 

amount of glazing every new living space should feature in order to

 

achieve consistent natural daylight levels.

By Larry Bohan on 28 June 2019

It’s not just a lack of living space that is driving the renovation market. It’s a shortage of natural lighting too.

 

Daylight is becoming more and more of a focus when it comes to extension and loft conversion planning.

This has been partly fuelled by the increasing amount of time families are now spending indoors, along with a greater awareness of the health benefits of regular daylight exposure.

Aesthetically speaking, getting the level of daylight right right in a room

 

can enrich any room and transform it into a lighter and brighter space. And then there is the added bonus of potentially significant savings that comes with less reliance of artificial lighting.

But just how much natural light does a

 

converted loft bedroom, en-suite bathroom or open plan living-dining

 

area need?

The 15% Rule

We recommend

 

that a room’s overall glazing should cover a minimum of 15-20% of the overall floorspace. Any less than this leave projects susceptible to dark spots that could spoil the natural flow of daylight running through a room.

This 15% rule is also followed by the VELUX Group, market leader for roof windows. The

 

glazing area can be made up of pitched roof windows, flat glass rooflights, casement windows and exterior doors, in any combination.

When applying this rule, an 10m²

 

en-suite bathroom would require 1.5m² of glazed area. This it the equivalent of 2x VELUX PK08 (94x140cm) roof windows or 3x VELUX MK06 (78x118cm) windows.

Likewise, a larger loft space 25m² in size would need 3x UK08 (134x140cm) windows or 4 x PK10 (94x160cm) units.

If planning to daylight a project this way, remember it’s the visible glazing area spec that is the important spec to look at rather than the overall window size which, of course, also includes frame.