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Field Test Best Practices: A Resource for Practical Residential Building Science

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Daylighting

Daylighting in a residential building has the potential to cut lighting energy during the day and bring natural light into the home. Daylighting can be as simple as drawing blinds or curtains to allow light to come into the house through the windows. The use of skylights allows natural light to illuminate interior spaces in the house in areas without windows or far from windows. One drawback of standard skylights is that they can be a large source of heat loss and do not distribute light evenly. .

A diagram of how light enters a house with a light tube skylight. The light enters the dome at the top of the light tube and is bounced down the tube until it reaches the room, after passing through a diffuser.

Diagram of how a tubular
skylight directs light into a house
Credit: www.lbl.gov

A more efficient alternative to the large rectangular standard skylight is a tubular skylight, shown in this figure. Tubular skylights have a domed collector on top, which can collect more light with a smaller cross-sectional area. The light goes through a diffuser before entering the house so the light is diffuse, which is better for reducing ultraviolet (UV) damage inside the house. The smaller penetration in the roof also reduces heat losses.

Other ways to introduce daylighting into a residential building include daylighting shelves and clerestory windows, both of which are more commonly found in commercial buildings. Daylighting shelves bring light into the building, while reducing the direct sunlight. This works well in office spaces and in multi-story buildings. Clerestory windows also bring light into the house near the ceiling, which helps to illuminate the space without the glare of direct sunlight. Clerestory windows are sometimes seen in residential buildings but are common in new, energy efficient commercial buildings.

A diagram showing how daylighting shelves bring sunlight into a room. The portion of the shelf on the outside of the building collect light and bounce it inside the room, towards the ceiling. An example of clearstory windows in a house. Clearstory windows usually are located at the top of a building and are used to bring indirect sunlight into a building.

Diagram of daylighting shelf bringing
light into a room through the top part
of the window
Credit: www.lbl.gov

 

A residential building with clerestory windows
Credit: www.solardecathlon.gov

Recommended measurements for a field test involving daylighting systems:

  • Light levels throughout house on a sunny day and a cloudy day.