Clerestory windows: advantages and disadvantages; a critical view

Clerestory windows can be great for natural ventilation, natural lighting and passive solar heating strategies. But they can also be a cause of serious thermal problems (overheating, excess glare, heat loss during the heating season.

Be aware Of the Potential Disadvantages of Clerestories

Clerestory windows definition:
Clerestories are
vertical windows, located high in the walls, extending up from the roofline, designed to let sunlight and breezes inclestory window positioning...

Clerestories are located high in the walls, close to the roof, which leads some people to say that they are wonderful because they allow to see the sky and the top of the trees from within the house, and so on...

But that’s not the role of clerestories, or should not be.

Clerestories should be properly designed and positioned to avoid serious overheating and heat loss problems. Clerestories should not be seen as an aesthetic issue.

Even their role as a source of indirect lighting should be questioned; statements saying that they are a way of bringing natural light into the core of the house, should be regarded with care. Even if it is true, clerestories can also have a very negative impact on the thermal balance of the house, and you should take it into consideration.

Passive solar Techniques With clerestories

Clerestory windows can be used in conjunction with high mass walls and floors, properly designed and positioned to store solar heat during the sunny parts of the day (and to heat the house during the coolest parts of the day)

Clerestories are, in this case, located in the sunny side of the house, protected from the summer’s sun by the roofline or by overhangs or other projecting architectural features. That's very important: clerestory windows should be recessed into thick walls; or protected by other means.

See:
Thermal Mass Strategies
High and Low Thermal Mass Strategies
Thermal Mass Rules for Floors and Walls
Overhangs for shade and home moisture protection

Clerestories, blinds and coverings

It’s hard to find blinds, shades, coverings or other sunlight control devices for clerestory windows. But the devices used for skylights, roof windows, or for common windows can be used or adapted for clerestories. See: Window blinds and shades

Just remember the basics: blinds, curtains, and other coverings will not prevent overheating (or freezing), unless the clerestory windows are properly built and sized. The energy coefficients of the glazing and the type of framing are of the utmost importance. See: The best windows for cold, mixed and hot climates.

Clerestory size

Do not oversize. Clerestory windows – like roof windows or skylights – can cause serious overheating and heat loss problems - much more than common windows.

Clerestory windows can have a negative trade-off. They can be a source of energy loss (even with the best glazing) and can produce unexpected glare and overheating.

Use of Clerestories for Ventilation

Clerestories can be used for natural ventilation strategies, in hot climates.

They can be designed to open and to allow a rapid removal of the inside air, while breezes get in through lower openings on the leeward side of the house.

See: Natural Cooling Guide

Clerestories, design and Glazing

The glazing and the frame of clerestories should be properly chosen, according to the rules of common windows. See: Window glazing and Window frames

Clerestory window manufacturers

See:
Double and triple glazed window manufacturers.
Residential window prices and paybacks
The best windows for cold, mixed and hot climates

 

 

 

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