Brise Soleil
Bonjour. I'm not a big fan of French imports into the English language but sometimes (think croissant) there is no good proper Anglo-Saxon equivalent. Literally broken sun, the idea of the brise soleil is to act as a sunbreak, reducing the amount of sunlight entering a window (or glass door) to reduce glare and unwanted solar heating.
Our house has more glass than average and most of it faces south. This is quite deliberate, to maximise passive solar heating on the winter months. We do not, though, have air conditioning and so, like most homes this last summer, the house got a little warm at times. This was the first time I recall it being advisable to keep windows closed to keep the heat out. Most of the south-facing glazing is quite well shaded by a 60cm roof overhang and (deciduous) trees which give summer shade but lose their leaves to let the sun and light through in winter (while simultaneously capturing CO2). However, our kitchen has a 5.4m run of glazing without shade and the kitchen was the warmest part of the house this summer: bring on the brise soleil!
Brise soleil normally takes the form of louvres and these can be arranged vertically in front of glazing or horizontally, projecting out above windows. In both cases the louvres should stop direct sunlight reaching the glass when the sun is high in the sky, while trying not to block the view or cause excessive loss of daylight. After considering the options I decided on a horizontal arrangement which could (and this is the clever bit) be retracted when not needed. The idea being that the overheating is only a problem during the summer months - June, July and August while in autumn, winter and spring we want all the light and sun we can get. In summer the sun is high in the sky - 60 degrees at midday in midsummer - and a horizontal projection will throw shade well down the window. In winter the sun is low in the sky and the projection does not stop it reaching the window.
The geometry suggested 50cm projection in addition to 20cm already provided by the fascia would shade the full height of the windows and most of the glass door height at midday in midsummer. Our house has larch cladding and so I used larch for the louvres. I wanted them to retract against the fascia below the gutter. The louvre blade width of 130mm was chosen to suit. After several iterations I refined the design as a full-scale sketch.
Four larch louvre blades are each supported by sliders at the top and three aluminium links join them together in such a way that when retracted they are packed together below the gutter (on the right of the sketch) but when deployed the links align them at 60 degrees (on the left).
The sliders rest on aluminium rails at each end. The 6m width was too far for a single span so two sets of louvres are supported at centre span by rails fixed to an aluminium post aligned with the post between the window and sliding door. Two more rails are screwed through spacers into the roof eaves and gable.
Stainless steel wires (as used in balustrades) give lateral support to the post and support the outer louvre blade at 60 degrees. The rails have shallow notches along the upper edge to locate the sliders in the deployed configuration. When retracted the louvres sit neatly against the fascia below the gutter.
The larch was supplied by a local sawmill and the aluminium bar, black nylon washers and bobbins to use as sliders and spacers, and the stainless steel cable kits were all sourced online. I shaped, drilled and filed the aluminium components then took them to a local company to be powder coated black. Everything seems to work but it's now September and overheating is not a problem. I have probably messed up our chances of another hot, sunny summer next year though, so... apologies.
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