A typical testing regime for a rooflight or flat roof window is similar to that for a vertical window or door and includes air permeability, water tightness and wind resistance.
Additional testing covers safety and impact resistance, which should be in accordance with the Centre for Window and Cladding Technology (CWCT) test protocols. This includes impact tests to assess the effect of both hard and soft bodies on the glazing. Further information can be found on our Specification and Non-fragility page.
Superb aesthetics and high performance – the basic checklist when selecting a rooflight product.
However, it’s important to look closely at the details and specification of a product. Testing for impact-resistance, durability, environmental and thermal performance, and security and safety performance are essential criteria.
Look for a glass unit that has specific design details that ensure the unit is fully watertight. Poorly designed frames can lead to water tracking back on the underside of the glass. Flat glass rooflights should also always be installed at a slight pitch to avoid ponding – typically a minimum 5 degree pitch.
The first, and safest, choice for the inner pane of a rooflight should be laminated glass.
A ‘true’ thermal break is achieved when a frame design incorporates specific features to achieve the thermal break. The use of foam strips cannot be considered as a true thermal break as these strips may deteriorate over time and therefore their efficacy will be affected.
The thermal performance of a rooflight must be considered for the whole assembly, because while glazing may be compliant, poor frame design can affect thermal performance.