When it comes to designing a sustainably oriented building, one of the most important aspects is using design to selectively minimize solar heat gain (i.e. heat from direct sunlight) in the summer, while maximizing sunlight and heat gain in the winter. The most effective way to balance these needs is through a careful site analysis to understand the direction of prevailing winds, the best orientation for the building (which we previously discussed), and the type and orientation of various shading devices.
These shading devices are critical to passive solar design, but they're not always the most aesthetically appealing. However, it's possible to create a design that's both beautiful and effective. Below, we highlight five of the sleekest ways to shield windows and openings.
1. Horizontal Louvers and Jalousies
Horizontal louvers and jalousies are some of the most common ways to shield a building and its openings from direct sunlight. Though they were originally developed hundreds of years ago in France, horizontal louvers are still used today across the globe in regions with mild winters. In terms of shading glass, they work best on south-facing facades (in the northern hemisphere) because of the high angle of the sun. They can also be used to direct sunlight into a building by putting a reflective material on the slats.
Haven’t heard of a jalousie before? You're not alone.
Most people refer to all horizontal slats as louvers, regardless of whether they're operable or not. In fact, a jalousie specifically is a group of horizontal slats that are always parallel to each other because they're set in a frame on a track together, which allows each slat to be tilted open and shut simultaneously with a crank or other device. Louvers, on the other hand, are fixed in their position, and can’t open or close.
2. Vertical Baffles
Vertical louvers, while not as common as horizontal louvers, are another effective way to mitigate and sometimes reflect sunlight in mild to hot climates. Like horizontal louvers and jalousies, vertically oriented louvers allow air to pass through while shading and diffusing direct sunlight. They can also maintain views to the exterior.
However, because of the trajectory and angle of the sun, vertical louvers work best on east and west facades of a building. In fact, some studies have shown that vertical louvers are better for reducing sun glare than horizontal louvers—but both are known to be extremely efficient.
3. Awnings and Brise-Soleils
Awnings are simple: usually cloth-based solutions for providing shade on a window or entire facade. Often constructed of thick canvas, vinyl, or other weather-resistant materials, awnings can vary in shape, size, and location and can also be retractable, depending on the time of day and season, to allow for sun penetration. In fact, awnings are so flexible that they can be large enough to cover entire stadiums and small enough to shield individual windows and doors.
One common type of awning is a brise soleil, which most typically takes form as a horizontal projection extending from the sunniest side of a building. Unlike many awnings, it’s usually fixed in place rather than being retractable, and often consists of louvered slats so that it can prevent the strong, high-angled summer sun from falling on a glass facade, but still let the low-angle winter sun through.
4. Fritted and Frosted Glass
Unlike louvers and awnings, frits, frosting, and other similar glazing treatments are applied directly to glass itself, rather than added to the exterior of a building. A frit—a ceramic dot or line adhered to glass usually through silk screening—is one of many ways of reducing the transparency of glass. After the frit paint is applied to the glass, it's then fired so that it's tempered (to improve the safety of the glass), and the frit is made permanent.
Like fritted patterns, frosted glass undergoes a process in which the glass itself is modified. In acid etching—the most common way of achieving solid frosted glass or patterned etching—a pitted surface is created on one side of the glass pane and thus makes the glass translucent. Although frosted glass does help diffuse light, it's generally not as effective at reducing heat gain as fritted glass, but does provide the added benefit of privacy.
5. Screens and Exterior Shutters
One final way of providing shade for window openings is through exterior screens and shutters. By placing these elements on the outside of a building, they prevent light from entering the interior, as opposed to interior screens and shutters that filter and deflect light after it's already filtered inside.
Screens can be made from a range of materials, from wood slats to perforated metal, but usually need to be lightweight enough to be supported by minimal framing. Because of their fixed nature, they also need to be translucent enough to allow for views and some light penetration. Shutters can also be made from wood and metal, among other materials, and operate through a swinging, sliding, or rolling mechanism. Although exterior shutters were traditionally operated manually, today, they're often mechanically controlled.
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