In Energy efficiency

A clearstory is an architectural term for high windows that allow light into a room. It can refer to windows on an outside wall that are placed too high for people to see out of, or to windows placed on a separate raised roof. The figure below shows a clearstory with windows located on a raised wall above the ceiling of the room that is receiving the daylighting.


The main purpose of a clearstory is to provide daylight to a building. If the windows are capable of opening, they also can be used for fresh air or as an outlet for rising hot air. As warm air is allowed to exit out the clearstory windows, cooler air will be drawn in from below.

In North America, clearstory windows typically face to the south to maximize the amount of daylight throughout the winter. This also maximizes passive heat gain, as they allow the square footage of the south-facing wall to grow proportionally larger than the north-facing wall. If the clearstory is designed to light an interior room, it also helps bring heat into the middle of the building instead of only the rooms on the south-facing wall.

Clearstories serve other purposes, too. In an office or factory, they provide light and air while still maintaining privacy and eliminating distractions for the building occupants. There is no glare, as with windows at eye level. They also can be used to light a ground floor that would be blocked by trees or other buildings, or to capture light for a room on the interior of a building, deeper in the building’s floor plan that an outside room. Plus, they add architectural flair.

On the other hand, clearstories add cost to a building and you have to consider the logistics of washing windows high up on a roof or wall. They also allow more heat escape in the winter — through stack effect — when the sun is not providing passive solar gain.

POSTED BY: / SOURCE: Cold Climate Housing Research Center (CCHRC)

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