Exterior sunshades are an important and increasingly popular part of an energy reduction strategy. Blinds help with glare and heat from direct light, but unlike blinds, exterior shading reduces the heat transfer from the exterior façade to the interior of a building. They also provide opportunities to exercise decorative flair and make buildings unique. Selecting or designing the right solution for the job and budget takes some upfront planning and coordination, but will ensure the best results.
University of Iowa Foundation Advancement Services Building
Design begins with the orientation. Sunshades can be oriented horizontally over the window, or vertically next to the window. Horizontal shades generally have outriggers, blades and fascia attached with brackets to a structural element. They are designed to block sun for the majority of the day. Vertical blades, often solid or perforated fins attached with brackets to a building’s structural element, are intended to reduce low angle sunlight. In either case, consider the orientation of the building and sun angles at the times the building is in use. Complex daylight models can provide an in-depth look at performance throughout the year. For a quick check for maximum effectiveness without a detailed study, reference the sun angle on June 20 at noon.
Budget and time constraints also play a role in selecting a system. Many curtainwall manufacturers offer simple sunshades made from a set of standard extrusions that are pre-engineered for most applications and generally shipped to the site knocked-down for field assembly. They have limited projections but do provide some benefits in terms of shading. For projects with a horizontal sunshade more than 36 inches deep, wide units, corner units and vertical options, a custom solution is the answer. This adds complexity to the project, but a few basic considerations will make design and installation go smoothly.
Key considerations include timing, engineering, attachment methods and surrounding conditions. Getting a custom sunshade manufacturer involved early in the design process will help with each one of these. Designing a shade with the available structure is critical. Manufacturers can ensure that design intent can be met with the structure available. Changing structure when a project is underway is often difficult or costly. Early coordination, especially when a custom shade is being installed on curtainwall, will also ensure all curtainwall warranties can be maintained.
Sunshades must attach to a structural element of a building and be engineered to handle ground snow loads and wind speeds appropriate to the project. IBC 2018 and ASCE 7-16 provide the guidelines for calculating design pressures for the area in which the building is located. Manufacturers use the building location and design pressure to provide engineering calculations and ensure the shade can meet the requirements. Use the project’s structural design criteria to determine the loads. If unavailable at the time of design, estimates can be found on the Applied Technology Council (ATC) website. Risk category of the building is also an important consideration.
ASCE 7 classifies buildings and other structures based on risk to human life, health and welfare in the event of flood, wind, snow, earthquake and ice loads. Buildings are classified on a scale of I to IV. Higher risk categories increase the design load. Substrate and anchorage type also help determine the required design loads. Substrates may include concrete, steel or wood. Anchorage options into these substrates vary. Thru bolts into steel provide the most substantial option and can be used with each of these substrates. Other substrates, listed from most to least substantial, are concrete columns or walls, concrete beams or slab edges, aluminum or curtainwall, wood and CMU. Stronger substrates allow for larger projections and wider tributary widths of the shade. Meeting design loads may include a variety of strategies. Increasing structure by adding steel reinforcements to curtainwall, reducing the shade’s projection or tributary width, increasing the size of the bracket attaching the shade to the structure, or changing the bolt pattern on the outrigger may all contribute to meeting the requirements. Custom sunshade manufacturers understand and can help determine the most effective options given the project constructions.
One of the final considerations is the finish of the shade. Components of most custom aluminum sunshades will be made from aluminum extrusions and several different aluminum alloys. They are generally also required to match surrounding curtainwall or window mullions. Both anodizing and painting are options, but anodized finish colors vary and show up differently on different alloys making them difficult to match. A painted finish is recommended for its consistency and warranty. Anodizing generally has a short one-year finish warranty, while paint carries a 20-year warranty.
There are many details to consider when selecting a sunshade, but a qualified manufacturer will help you navigate these to offer you the best solution.
Lisa Britton, CSI, CCPR, LEED AP BD+C, GGP, is the director of sales and marketing at Industrial Louvers Inc., Delano, Minn. For more information, visit www.industriallouvers.com.