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The logic of natural light

Excellent use of natural light
Excellent use of natural light
Andrew O'Dom

Everyday buildings account for 72% of the electricity consumption in the United States, much of which is used for lighting. Yet on average in Cincinnati there are hours of free lighting each day. This free light is light from the sun. Environmentalist and economist both can agree that the use of natural light is a must. Cincinnati’s main energy source is tapped from coal. While the use coal to meet the energy demand for the tri-state is unavoidable there are ways to easily reduce the amount used.

Natural light is one of the easiest ways to reduce energy use. Artificial lighting accounts for a large percentage of electrical use in buildings and can be minimized with the use of natural light. Opening the blinds and letting light in throughout the day will greatly reduce the cost of lighting in any building.

Natural light doesn’t just save energy; studies have shown that natural light is also more pleasing to humans. This can translate into healthier learning environments at schools, more productive employees, happier customers and a more comfortable home.

From a design stand point architects must deal with issues such as building orientation, percent of vision glazing per room, solar shading, and thermal properties of glazing. Orientation is very important as it dictates the effect of the solar path of sun on the building. Here in Cincinnati the sun maintains a southern path. This means the southern side of any building will be receiving greater amounts of direct light. The east and west sides are also a big issue due to the position of the sun in the morning and evening. The sun is at a lower solar angle at these times of the day. This intense direct light creates problems with glare. While getting light in the building is the main goal, glare must be controlled.

The most pleasing light is indirect light. The southern and northern faces will get the most indirect light. However, the northern face will receive the least amount due to the sun’s angle. The orientation controls the percent of glazing on each face. East and west sides should get the least amount of glazing without the use of solar shading.

Solar shading can be used to decrease glare and increase the amount of glazing used in a project. Solar shading can be done with the use of exterior or interior light shelves or plant foliage.

Thermal properties of glazing plays a big role in the amount of glazing that is acceptable. Natural light can reduce energy consumption. However, window glazing general has lower thermal insulating properties than exterior walls. This can increase the amount of heating and cooling load needed for the building.

The value of natural light is high yet the cost is low. Open the blinds and let in the only free source of light. It will be very rewarding.

For more information about natural light and other green building issues visit the USGBC Resource page.


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