Understanding the Benefits of Interior and Exterior Shading Systems

Innovations and options in contemporary shading systems help create productive and healthy interior environments
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Sponsored by Draper, Inc. and Phifer Incorporated
By Jessica Jarrard
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Lighting Solutions and Shading Systems

Shading systems can effectively control daylighting in commercial buildings and also serve as integral design elements. They can be installed on the exterior or interior of buildings, and even between glazing units or within a double facade. There are many types and styles of modern shading systems used to control daylighting in modern commercial architecture.

Photos courtesy of Richard Wilson

Interior shading systems include shades that can be raised or lowered fully or left at intermediate positions depending on the time of day.

Exterior vs. Interior Shading Systems

Exterior shading systems have a big advantage over interior systems: they significantly reduce unwanted solar heat gain by eliminating one of the sources of that gain. Solar radiation is absorbed by shading material, whether installed inside or outside a building. The short-wave solar energy that is absorbed by the shading system is converted into long wave energy (i.e., heat). With an exterior system, this heat is radiated outside the building and never reaches the glazing. However, solar energy that is absorbed by an interior shading system and is then radiated as heat is trapped inside the building. An effective exterior shading system can block 90 percent or more of solar gain. This can contribute to lower HVAC demand, which in turn can contribute to a downsized HVAC system, lower capital costs, and lower operational costs over time.

Interior shading systems consist of shades or blinds that can be operated up or down. Interior blinds incorporate slats, the angle of which can be adjusted to control light, glare, and solar heat gain. Interior shades can be raised or lowered fully or to intermediate positions, depending on the time of day and amount of direct sunlight. Although they are not as effective as exterior systems at keeping solar heat gain out of the building, interior shading systems have other advantages. For instance, there are more material (fabric) options since the shades are not in direct contact with the elements (though they are still susceptible to UV damage). Because they are part of the indoor environment, however, it is important to consider how the material choice impacts indoor air quality. Interior shading systems can be motorized or operated manually.

Examples of exterior solutions include brise soleil systems (i.e., fixed louvers that are installed at the head of the glazing) as well as horizontal louvers and vertical louvers that are installed in front of the glazing. Roller shades and venetian blinds can be used in both interior and exterior applications and retracted into a pocket or a head box when not required. Retractable systems allow for responsive shading—shading that is deployed during certain times of day or under certain weather conditions. In addition, the slat angle of exterior venetian blinds can be adjusted according to the sun’s angle, allowing the maximum amount of ambient light into the building while preventing any direct sun penetration.

Images courtesy of Draper, Inc. and Richard Wilson

Exterior shading systems are more effective at keeping solar heat gain out of the building when compared to interior shading systems. Various types of external shade options are available.

Exterior shading systems are effective throughout the year, which means that they will prevent solar energy from entering the building in the winter as well as the summer months. An advantage of retractable systems is that they can be disabled and left in the retracted position during the winter months, when solar heat gain might be desirable. This is dependent on the building’s heating and cooling cycle. In more southern latitudes, a building might require cooling throughout the year. In more northerly climates, however, winter heat gain is beneficial, and retracting the shading systems to make maximum use of these gains therefore makes sense. If this is the case, however, an interior shading system will also be required to manage daylight and address glare.

Though designed for exterior conditions, these systems should be retracted fully during high-wind events; they also need to be protected from ice and snow. Exterior roller shades that incorporate zip technology are very wind resistant and are an ideal solution for exposed locations and taller buildings. Such systems include steel zippers welded onto the vertical edges of the shade that “lock” the shade into the channels and prevent them from being pulled out by the wind.

Shading systems also can be installed within a double facade. While this type of facade construction is not all that common in North America, it can be very effective in climates that are hot in the summer and cold in the winter. During summer months, warm air is ventilated from the plenum, generally to the exterior, to minimize solar heat gain. During winter months, warm air is trapped inside the facade, acting as a thermal buffer; alternatively, warm air may be brought into the building through interior vents to provide free heating. Venetian blinds work effectively in conjunction with this strategy. Solar energy absorbed by the aluminum slats helps increase the temperature in the plenum, assisting stack-effect ventilation during the summer months and the effectiveness of the thermal buffer during the winter months.

Photo courtesy of Richard Wilson

Double-facade shading systems can be effective in climates that are hot in the summer and cold in the winter.

The cost of this type of facade construction, however, means that it is normally only seen on institutional and owner-occupied buildings. Because the shading systems are installed within the facade, they are protected from the elements, allowing them to be used all year round. They can also be used on tall buildings where significant wind speeds preclude the use of exterior systems.

The construction of a double facade can vary significantly in terms of plenum size, ventilation strategy, and other factors. Normally, venetian blinds are installed within the plenum, although roller shades are sometimes used as an alternative. The shading systems are used throughout the year to provide control of light and glare and to manage solar heat gain. One of the challenges when selecting these systems is that every project is different with varying needs, so developing a shading solution that meets the specific project requirements is important.

Exterior shading systems and ones that are installed within a double facade are an integral part of the building’s environmental control. Because this is the case, they are almost always motorized and will normally be automatically controlled, enabling the systems to respond to sun conditions, being deployed and retracted as appropriate. In the case of venetian blinds, the slats are tilted between a number of preset angles to prevent direct sun penetration while allowing as much ambient daylight as possible into the building.

Modified Products Can Create Solutions

Off-the-shelf systems such as roller shades and venetian blinds may work well for many projects, but for larger projects, more modified and customized versions of off-the-shelf items can provide better solutions.

Interior roller shades are the most commonly used shading system on commercial projects. They can be manually operated or motorized and fully or partially deployed or retracted to address the sun conditions. However, there are challenges that can arise when installing roller shades. Many projects incorporate some irregular-shaped glazing where special shading systems are required. The move toward floor-to-ceiling glazing with narrow mullions can also mean that movements/flex of the glazing system under wind load can have implications on the way that roller shade systems are installed. The Marina Heights project in Tempe, Arizona, is an excellent example of how modified systems can be developed to address building-specific issues and to provide shading for occupants.

The Marina Heights project, which included buildings that are home to State Farm Insurance, needed shading systems to help with daylighting. The large project required more than 8,600 shades to be delivered and installed during the 19-month-long construction process.

Steve Hawes, principal at Progressive Commercial Interiors in Tempe, says the sheer number of 10-foot-high shades required scaffolds and ladders, making the project a major undertaking. “There were five buildings, 47 floors, and multiple floors often requiring simultaneous installation,” he explains.

After being awarded the first part of the project, Hawes got news at a preconstruction meeting with the general contractor that custom brackets were required for the storefront system that was designed to flex under wind load. “Attachments had to be made to horizontal mullions only, and they could not attach to vertical mullions as would normally be the case,” he explains.

Having identified the problem that needed to be addressed, the first step was to obtain a detail drawing of the mullion from the contractor.

Image courtesy of Draper, Inc.

Based on a detailed drawing of the horizontal mullion, engineers produced a 3-D drawing of a custom bracket. The design was slightly modified and approved.


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Originally published in Architectural Record
Originally published in October 2018