Why heat decides the skylight here
Summers that run hot for weeks
Adelaide usually has several days of 40 °C or more each summer, and in March 2008 it had 15 days in a row at 35 °C or higher. Glass in the roof lets in heat as well as light, so size and position matter more than style.
Hot northerly winds
Hot northerlies carry heat in from central Australia. A skylight on the north or west side of the roof catches the harshest sun, so ask about low-heat glazing, a blind, or a spot on a cooler slope.
Single-storey houses
Adelaide's suburbs have historically been single-storey detached houses, so most rooms sit directly under the roof. That makes a tubular skylight, which runs a reflective tube from the roof to the ceiling, practical in halls, bathrooms and laundries.
Cold, windy winters
Adelaide is a windy city with real wind chill in winter. A skylight is a weak spot for heat loss on cold nights, so the glazing and how well the ceiling diffuser seals matter in July as much as in January.
Hail on glass
The January 1991 hailstorm broke windows as well as roof tiles. Ask what the skylight's glazing is made of and how it handles hail, especially on a large roof window.
What the numbers say about roof glass
The federal Your Home guide says roof glazing takes in almost twice as much heat as an unprotected west-facing window of the same size, and that sloped glass loses heat about 40% faster than upright glass. It also says tubular skylights work best in sunny, clear climates, which suits a city with long, dry summers like Adelaide.
Size conservatively. Your Home suggests about 3 to 5% of the room's floor area for a conventional skylight or roof window, and 1 to 2% for a high-performing tubular skylight. Bigger isn't brighter in a useful way, just hotter.
Tubular skylight or roof window?
| Tubular skylight | Roof window | |
|---|---|---|
| Summer heat | Small opening, little heat gain | More heat, needs low-heat glass or a blind |
| Light | A bright patch in one room or hall | Wide light and a view of the sky |
| Fresh air | None | Some models open |
| Best for | Halls, bathrooms, laundries | Living areas with a raked ceiling |
Ask before anyone cuts a hole in your roof
- Which slope will it go on, and how much afternoon sun will it get?
- What glazing or diffuser does it have for heat, and how does it handle hail?
- How is it flashed into my tiles or corrugated sheets, and who warrants the flashing?
- Is my block in a bushfire-prone area, and does the skylight meet AS 3959 for my BAL?
- If the old skylight or manhole looks like cement sheet, will you test it for asbestos first?
- Who handles the ceiling, plaster and paint inside, and does your CBS licence cover all of it?
If it were our house
For a dark hall or bathroom, we'd go tubular: plenty of light, very little heat, and a good match for single-storey Adelaide homes. We'd save roof windows for rooms where you want the view and can shade the glass, and keep them off the west slope where possible. Whatever you choose, make sure someone warrants the flashing, because that's where skylights leak.
Want a roofer to take a look?
Tell us the job and your postcode. We match it with a Find My Roofer certified roofer who specialises in that kind of work, and they call you to quote. Your number goes to them alone.
Finding an installer
Tell us the room and your suburb. We'll pass the job to one licence-checked roofer or skylight installer in your area if we have one, and tell you straight away if not. Our national skylights page and the Adelaide hub have more.