Roof domes are ideal for providing homes with flat roofs and with extra light. This extra light not only ensures a pleasant atmosphere in the house, but it also makes your home appear larger. 

Dormer windows: Materials and shapes

If you want to place a skylight, you can choose from different versions, depending on the material and the shape. In terms of shape, you can choose from flat light domes, round, square, rectangular or pyramid roof domes.

Regarding the materials for the dome of a flat roof, you can opt for acrylic, polycarbonate, glass or a combination of materials. Acrylate and polycarbonate are the most frequently chosen.

1.Acrylic dome light:

Acrylate, also known as plexiglass, is about 10 to 15 times stronger than glass. In contrast to a polycarbonate roof dome, it is less strong, but cheaper.

Roof domes in acrylic are available in both transparent and opal versions. A transparent variant is 100% transparent and translucent. Opal (milky white) skylights allow diffused light to pass through it and absorb heat. So you do not suffer from annoying sun rays because the light is refracted. Because it is opaque, opal glass is also interesting for privacy reasons. In principle, there is no price difference between a transparent and opal version.

Properties: Stronger than glass, less strong but cheaper than polycarbonate.

2.Polycarbonate dome light:

Polycarbonate is an extremely strong and virtually unbreakable material. It is even 200 to 250x stronger than glass. In terms of safety, a polycarbonate roof dome is the best option. But it is expensive.

Just like the acrylic roof domes, polycarbonate light domes are also available in both transparent and opal versions.

Properties: Stronger than glass and acrylic, more expensive, and highly safe.

3.Glass dome:

Glass is the least strong, but the most expensive compared to the other materials. With a glass dome, you opt for an elegant look. Most of the time these are flat or slightly curved domes with thermally insulating glass and an accompanying frame. The glass is then placed with a slope of 15% on the frame for optimal drainage of rainwater.

Properties: More expensive and less strong than acrylic and polycarbonate, elegant look.

The insulating value of a dome:

The degree of insulation of a roof dome depends on the presence of glass, the number of shells and the thickness of the walls. Well-insulated roof domes are soundproof which is especially pleasant in case of rainfall and hail.


With a glass dome in a flat roof, it is advisable to opt for insulating glass. Roof domes with insulating glass generally perform very well. Values of 1.1 W / m²K (or even better) are possible.


A skylight for a flat roof is made up of 2, 3 or more scales. The more scales, the better the insulation. Usually one chooses 2 scales, an inner and outer dish. A plastic roof dome with two shells usually has an insulation value of 2.8 W / m²K. A dome with three scales has a U-value of 1.9 W / m²K on average.

3.Wall thickness:

Roof domes are possible with different wall thicknesses, which also has an influence on the insulation of the roof dome.

Single-skinned roof dome:  Moderately insulating, especially suitable for rooms that do not need to be heated.

Double-walled roof dome: Well insulating, limited heat loss through the dome.

Three-walled roof dome: Excellent insulation, protects against cold and heat.