North or south-facing roof lantern: what is the difference?

What is the difference between a north and a south-facing roof lantern?

From the north, mainly diffuse light comes in: light from the sky, not from the sun itself. That light is even, casts few hard shadows and brings hardly any heat. Artists like to work under north light for that reason. The downside: little solar heat comes in during winter.

Facing south, the sun is on the glass for most of the day. In summer it stands high and falls almost vertically on a flat roof. That gives a lot of light and free heat in winter, but in summer it can get too warm. Read more about overheating under a roof lantern.

Which glass do you choose for which orientation?

For a south-facing position we recommend solar control glass or shading. Read what a solar control coating does, or choose a screen for the roof lantern. For most living rooms and open kitchens facing south, HR++ double glazing is more than sufficient.

Facing north or west, and certainly above a bedroom, triple glazing can be worthwhile. It insulates better, with a U-value of about 0.5 W/m²K against about 1.1 for HR++.

• South: solar control glass or shading
• North: triple glazing often worthwhile
• West: watch for heat in the late afternoon
• East: soft morning sun, little heat

Does the direction of the pitch matter?

With a mono-pitch roof lantern, yes. A glass surface sloping towards the south catches more sun than one sloping towards the north. A gable and a hipped roof lantern have surfaces facing several ways and spread the light better.

This matters most with a roof lantern on a veranda facing south, because you often sit under the glass for long periods.

If you can choose where the roof lantern goes, also consider how the room is used. A workspace or studio benefits from even north light. A kitchen-diner or garden room used mainly in the morning and afternoon enjoys the sun. And above a TV or screen, direct sunlight is usually unwelcome because of glare.

Frequently asked questions