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Sunscreens for Passive Cooling

Sunscreens are designed to block sunlight and prevent the resulting radiant heat from bleeding into your interior spaces. Learn more about these useful louvers on the Newsstand. 

Cooling a building can be a challenging task in the summer. HVAC systems must work hard to cool air as temperatures rise outside. The system must be working at peak efficiency to meet these demands. Summers are tough for HVAC, but there are ways to alleviate system stress. Passive cooling from sunscreens can help ease the burden.

Sunscreens are louvered screen assemblies that are mounted over windows to provide shade. They have a similar build to louvers – angled blades contained within four frame members – but they have certain features that set them apart. The sunscreen’s frame will be flat and featureless by default since it won't be mounted in an opening. Designers can choose jambs with channels or other features for style.

Sunscreens are typically cantilevered over the opening and suspended from a point above the screen by cables or rods. Manufacturers will offer different mounting options to work with your project. The screen will be mounted to hang horizontally, so that it will shade the window as the sun passes in the sky. The angle of the screen’s blades will be variable, so that designers can customize them for the application. The blades should be set to an angle that prevents the most sunlight from shining into the window below.

Sunscreens shading windows during a cloudy day

Effective sunscreens are placed above windows that receive direct sunlight and are situated so that they provide the most shade throughout the day. By blocking incoming sunlight, sunscreens can help reduce the buildup of heat. To achieve this, designers need to understand how the sun will shine on their project.

Sunscreens should be placed on the eastern and western facades of the building. Windows on these sides will see the most sunlight during the morning for the eastern sides and the afternoon to evening for the western sides. In the Northern Hemisphere of the world, sunscreens should also go along windows facing southward. These windows will typically receive sunlight throughout the day. Although the directions of sunrise and sunset are constant, the solar angles of sunlight will change from season to season. You will need to consider these angles when designing your sunscreens.

For the best coverage, designers should determine the angles of sunlight at key points in the year and at key times of day. Designers will need to collect data when the sun is at its highest point in the summer, when it reaches its midpoint angle for the year, and when the angle will be at its lowest. These data points will help designers determine the size and location of the sunscreen.

Sunscreens shading a window in the afternoon

The specific dates of when these solar angles occur will differ depending on where the project is located. Projects in the US will have similar dates, but they won’t be the same. There are tools online that can help calculate solar angles across the world, like these tools provided by the National Oceanic and Atmospheric Administration. Their solar angle calculator can determine the solar angles for several US cities at various times of the year. Select a city from the list, or input the longitude and latitude of your project, then set the necessary date and time. The calculator will provide the angle as the solar azimuth.

Once they've collected the solar angle data, designers and engineers can determine where sunscreens should be placed, how big they should be, and the required angle of their blades. This data will ensure that each finished sunscreen blocks the most sunlight during the heat of the year. The same sunscreens may not block sunlight during the winter, but this can work to your advantage. As temperatures drop, the objective of your HVAC system will change from cooling rooms to heating them. Radiant heat from the sun can warm these spaces and ease the burden on the heating system. The most efficient sunscreen design allows for passive cooling in the summer and passive heating in the winter. Sunscreens conserve energy.

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With the specifics in place, designers can customize their sunscreens to fit their project’s style. Sunscreens can accept many of the same style options as louvers, including specialty powder paint finishes, color matching, and anodizing. Make them stand out from the building’s envelope, so that they draw attention to other surrounding features. Sunscreens can add a touch of style to your building.

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