Sizing & Measurements
Sizing & Measurements
Rooflights are available in various shapes and sizes, and different manufacturers may have different methods of defining these sizes. Some measure based on the external frame, while others measure the external upstand or the glazing size.

Vario by VELUX bespoke rooflight sizes are defined as the clear internal measurement after final installation, which means that the measurement of our rooflights is equal to the glazing area and daylight area obtained after final installation and plastering.
size vario by velux rooflight
Clear Internal Measurement

Specify More Daylight For Your Clients

All of our rooflights are based on the clear internal measurement, this is equal to the exact clear glass and natural light you will receive. If a rooflight is quoted using the external upstand measurement, the amount of clear glass and natural light is significantly less.

Why?

The image on the left shows how the external upstand measurement includes the width of the upstand, which reduces the amount of clear glazed area. Upstand widths can vary depending on the manufacturer and the type of rooflight, so you can’t be sure of the natural light you receive. For this reason, it’s important to us that we use the clear internal measurement – reflecting the actual size of clear glass and natural light you get.

Structural Opening

Structural Opening

When preparing the structural opening for a new bespoke rooflight, your starting point will be the rooflight measurements. You determine your structural opening by adding +30mm to the length and width of the clear internal rooflight measurements, this will leave sufficient space for the internal finishing: for example, installing 15mm plastering to create the lining, ensuring a proper fit and polished result. 

structural opening rooflight vario by velux
Opening Rooflights & Installation Pitch

Opening Rooflights & Installation Pitch

Vario by VELUX can be installed in roof pitches from 0° up to 15°. A minimum of 5° installation pitch is recommended to avoid ponding water on the glass surface. Our opening rooflights are top-hung meaning that the hinges should be placed at the highest point, whereas the actuator (motor), should be placed at the lowest point of the roof pitch.

In our illustration, you can observe how the length of the rooflight follows the slope of the roof, while the width incorporates the integration of the actuator.

It is crucial to ensure correct installation in order to maintain the 10-Year Rooflight Guarantee that we provide.

Rooflight Weight & Handling

Rooflight Weight & Handling

Compared to old plastic rooflights, more modern glass rooflights are significantly more durable. But with that enhanced durability comes additional weight, which is important to consider at the early design and specification phase.

The weight of a rooflight is very important. If you are specifying a rooflight for an existing building, structural considerations and calculations must be made to ensure that the roof structure can take the added weight of a new rooflight. When designing and specifying for new builds, weight and load must be defined for the entire roof structure and considered at the early stages of the build.

Modern rooflight weights depend on their glazing type (e.g., double layer glazing vs. triple layer glazing). You will always be able to obtain the exact weight of your rooflight order, but if an overall initial weight estimation is needed, the graph on the left is a very handy tool.

rooflight vario by velux weight
Contact us

Contact us

Our Daylight Experts are here to help you with information regarding positioning, dimensions, specification and more. 

by telephone 01592 778246

by e-mail: vario@velux.co.uk

or by using our contact form


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