The Problem With Shading Glass Boxes

We are noticing an increase in enquiries to shade glass boxes (as pictured above), an all glass extension using structural glass to create a frame free conservatory that maintains a seamless connection to the outside. Whilst these structures certainly have a wow factor they often end up becoming unusable due to excessive solar heat and light that causes both thermal and visual discomfort.

There are specific external blinds designed to shade glass roofs often referred to as conservatory awnings or external roof blinds. They sit close to the glazing to ensure that the suns energy cannot creep underneath and use fixed runners (guides) to the left/right that mount down to the outer glazing bars, to ensure the leadrail that opens/closes with the blind cannot come into contact with the glass roof.

However, the frame free design of glass box extensions means it is not possible to install a conservatory awning as they don’t have any glazing bars to attach the guides to at the sides. The only type of non-fixed frame external shading system therefore that can be used is a projecting folding arm awning (patio awning), that use articulated folding arms to extend and project out and when retracted close back into a streamline cassette casing.

Whilst patio awnings are not designed for use above glass roofs, as the name suggests they are designed for providing shade and shelter to patios and terraces, they can in certain (limited) applications be safely installed.

Patio awnings are designed to move in the wind to prevent damage to the awning itself, therefore to safely install an awning above a glass roof, there needs to be a minimum of circa 50cm (half a metre) between the top of the glazing and underside of the awning to allow for this movement to ensure the awning does not come into contact with the glazing causing both damage to itself and the glass. The issue with this though, other than the fact there is often not enough space between the top of the glazing and underside of the first floor windows to allow for an awning to be installed in the required position, is that sitting so high above a glass roof, a patio awning is only effective when the sun is directly overhead, as when the sun moves around the glazed roof the sun will always be able to creep in the large gap underneath the awning, striking the glass and causing unwanted solar heat build up and glare.

We therefore would advise anyone considering or undertaking a glass extension, to carefully consider the design so that appropriate external shading designed specifically to be mounted safely above glass roofs (conservatory awnings) can be incorporated should it need to, either during or post build, that will provide effective shade so the new space can be enjoyed comfortably all year round.

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