What angle should horizontal blades be set at?

As you probably already know, brise soleil is a type of solar shading system that controls the amount of sunlight that enters a building.

In a nutshell

  • Brise soleil systems are designed to block the brightest and hottest sunlight
  • In the UK, the sun rises to a maximum 62 degrees above the horizon
  • Blades are usually set at a 45-degree pitch to allow some light to pass
  • East and west elevations may require different forms of solar protection – north elevations need none at all
  • Brise soleil systems are often used as a consistent aesthetic feature on all elevations

Sets of blades project from the building to block the sun when it’s at its highest, brightest and hottest.

Now, if shading was its only function, a brise soleil system could take the form of a solid shelf. But that would also block all ‘good’ heat and light from the sun at certain times of the day or year. Instead, the system is made up of a series of angled blades. The question is: what angle?

What’s the optimum angle for brise soleil in the UK?

In the UK, the sun never gets more than 62 degrees above the horizon (we’d need to be nearer the Equator for it to be directly overhead). However, that’s in the middle of the summer only, so brise soleil specialists typically go for blades that are pitched at 45 degrees.

Brise soleil systems like this are a good compromise. They take the ‘sting’ out the high summer sun, but allow softer light in.

However, they’re not designed to block glare from low-level morning or evening sun. For that, a vertical climate façade system is best, or interior blinds.

What about different building elevations?

This is an important point. When the sun’s at its highest, it shines on south-facing elevations. There are different shading requirements for north, east and west.

  • North – In the northern hemisphere, the sun never shines on north elevations, so solar shading isn’t required. So, why do you see brise soleil on north-facing façades? Purely as an architectural feature.
  • East and west – Here, we’re usually talking about low-level morning sun in the east, which gradually rises and then falls in the west in the afternoon. To protect against glare, vertical fins can be a good option.

Form vs function

Architects often specify different blade angles for aesthetic purposes. However, a shallower pitch may require the entire brise soleil structure to project further from the building to block the sun. This could be more expensive and require stronger fixings – and even compromise the design intent the architect was trying to achieve in the first place.

What else do you need to consider?

  • Although brise soleil systems are typically made from lightweight aluminium (heavier timber is also used), it’s still important to think about loadings on the sub-structure and curtain wall components - from the weight of the system itself, from wind loads, or from the weight of snow and ice.
  • Adjacent buildings in urban areas may provide shade (or reflection) at different times of the day than expected. It’s important to look at all the factors that could influence brise soleil design.

What next?

Although brise soleil has been around since the 1930s, modern building design, materials and even climate change are having an impact on shading design and installation. On any new project, it’s best to liaise with a brise soleil specialist as early in the design process as possible.

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