How do you fix brise soleil to a curtain wall?

We’re all familiar with curtain walls – non-structural cladding systems for the exterior of modern buildings.

They’re generally found on multi-storey buildings, and are usually made up of large glass panels... which brings us to two important questions. First, how to protect a glazed building from damaging sunlight? Second, how to fix shading to a non-structural wall.

Solar gain and the greenhouse effect

Sometimes sunlight is a good thing, cutting energy costs for light and heat. But too much can cause glare and over-heating (the greenhouse effect) and requires shading and expensive cooling systems.

Brise soleil systems help solve this problem by using horizontal blades that allow sunlight to enter a building in the mornings, evenings and during winter, but cut out direct sunlight when it’s at its highest, brightest and hottest.

Having recognised that brise soleil is required (the name comes from the French word for ‘sun blocker’), the second question is even more important. How do you fix the system to a curtain wall that is typically designed only to support its own weight?

Brackets

Specialist curtain wall brackets are required to fix the brise soleil system to the underlying sub-structure. But it’s usually too late when the glass or solid panels are installed. That’s why specialist façade companies 'free issue' the bracket to curtain wall contractors at an early stage.

There’s a lot more to think about than that. Fortunately, brise soleil specialists, curtain wall contractors and structural engineers will work together.

• The brackets will be tested using desktop simulation and advanced structural engineering to ensure they’re strong enough to carry the weight of the brise soleil system – plus additional loads.
• You should expect a façade company to review the curtain wall design at an early stage to ensure the brackets are compatible.
• Curtain wall contractors and engineers will ensure the structural integrity of the overall system (and factor in the weight of the brise soleil components).

Is the location of the building important?

Snow and ice is probably the last thing you’d think about when it comes to brise soleil. But the brackets need to be strong enough to cope with any extra loads. Wind load also needs to be taken into account, especially in exposed locations.

Are all brise soleil calculations the same?

No. Most brise soleil systems are bespoke. So, the design, material and size of the brise soleil, and the distance it projects from the building will all determine the type and number of fixings required.

What building regulations are particularly relevant?

In addition to the detailed guidance manuals relating to the safety and sustainability of buildings, BS EN 1991-1-1-4 2005 covers the effect of wind on the structure or component. It states that the fixings of external architecture should be inspected to identify wear and tear, check for vibration, divergence, and fluctuations that could cause fatigue and cracking.

What do facade specialists mean when they talk about ‘thermal breaks’?

In the drive to create energy-efficient buildings, cladding can insulate interiors from the elements, while solar shading systems are a proven method of regulating solar gain. However, fixings that connect exterior components directly to the building structure can create a ‘thermal bridge’ and conduct heat straight out of the building.

To address this problem (building regulations say that anything that penetrates the façade envelope must have a thermally efficient interface), facade specialists use thermal-break brackets and adaptors to reduce thermal transfer. They’re typically made from carbon fibre, but can be expensive, so this should be taken into account at the planning stage.

And finally, don’t spoil the view

You don’t need us to tell you that one of the benefits of having glazed curtain walls is the great view for occupants. So, while designing a brise soleil system to block the sun, you don’t also want to block the view. Ultimately it’s a balancing act – one that close collaboration between architect, client and brise soleil specialist can help resolve.

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