Roof light on 18 degree roof pitch

[Busholive]

Hi all I'm fitting three roof lights into a new pitched roof. Lots of connections to other walls so going with a GRP roof covering.

I aimed to put in a velux rooflight but the website doesn't show any installation details for a warm roof, and really I think all new roofs should be warm these days.

They do however offer a flat roof light that can be fitted up to 15 degrees with a warm roof installation.

Velux custom service is closed, do you guys think a flat roof light would do okay at 18 degrees?

 

[Busholive]

Roof pitch is 18 degrees to avoid windows on the second floor, it isn't 15 degrees as this looked a bit too flat!

 

[catlad]

I'm a bit confused, Why would you not put in normal roof windows if you have 18° pitch ?