You always order by daylight size: the clear opening visible from inside. Your new skylight fits straight away.
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Daylight size= your order size
The clear opening visible from inside. Measured along the inside of the curb, from edge to edge.
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Roof openingstraight curb = daylight size
The opening in your roof. With a straight curb (/00), it equals the daylight size. With a sloped curb (/20 or /30), it is 20 or 30 cm larger.
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External skylight size= daylight size + 160 mm
What you measure on the outside of an existing skylight. The flange extends 80 mm on each side. Subtract 160 mm to find your daylight size.
Sizing questions
What is the difference between daylight size and roof opening?
I am measuring my skylight from the outside. What do I order?
You already have a Skylux curb
You are creating a new roof opening
You have a curb from another brand
20/00 EP-S curbs
The best-insulating PVC curb in the Skylux range. The 20/00 EP-S achieves a Uup value of 0.64 W/m²K. The height of 20 cm is suitable for roofs with a thick insulation package. UV-stabilised for long-lasting quality under a skylight or flat roof window.