Every window shows the room a piece of sky. The question is how much sky it can see, and what is standing in front of it.
Sideways
What a side window sees
A window in a wall faces the horizon. Between it and the open sky stand the garden fence, the house next door, garages, hedges and trees. Each one takes a slice of sky out of the view, and each slice is daylight that never reaches the room. Ground floors lose the most, because everything around them is taller relative to the glass.
Milton Keynes was planned with trees and planted verges along its grid roads and through its estates. It is a green city to live in, and that greenery is also in front of a lot of windows.
Straight up
What a rooflight sees
A rooflight faces up. Nothing in the street stands between it and the sky overhead, so the view it has is open whatever happens next door. The light it brings in falls from above into the middle of the room and spreads outwards, instead of entering at one edge and fading across the floor.
That is not a promise of a number. How much light any rooflight gives depends on its size, its glass, the depth of the opening and the shape of the splay. Our guide to how much daylight a rooflight gives goes through each.
In practice
Why our surveys start by looking up
Before we talk about products, we look at what each room can see overhead: which part of the roof faces open sky, what sits in the loft or ceiling void, and which way the roof is built. Then we match the product to the roof: a roof lantern or flat rooflight on a flat roof, a roof window in a slope, a sun tunnel where the roof is out of reach.
