Control the Sun
Optimizingbuilding performance and prioritizing occupant comfortusing automated shading
Architect Louis Kahn once said, “The sun never knew how great it was until it hit the side of a building.” With the power to provide light, heat and energy, the sun plays an integral role in the design of interior spaces. Discussions surrounding interior architecture and design are shifting away from aesthetics and toward performance, and, more specifically, how performance can impact occupant comfort and productivity. In the shading industry, this dialogue is prevalent through a focus on daylighting, view preservation, glare control and solar heat gain.
Recent studies, including one conducted by the National Center for Energy Management and Building Technologies (NCEMBT)[1], explain how energy use can result in high occupant acceptability levels. Due to such studies, forward-thinking companies are quantifying the value of their staff and looking for products and systems that optimize comfort andproductivity, as well as the building’s energy efficiency. However, specifying shading systems to align both occupant comfort and energy efficiency is often achallenge for commercial architects. Is it possible to select a durable, functional shade fabric that meets aesthetic needs as well as building performance conditions? Would a passive shading system with overhangs to block direct sunlight be a better option?
Automation, however, allowsshading to respond to unique and ever-changing external conditions – optimization in its purest form.
Data as the Foundation
Daylightvaries basedon region, climate, building orientation, andother factors. It may range between approximately 100foot-candles on a dark, overcast day to more than 10,000 foot-candles on the brightest day of the year. To evaluate daylight availability using illuminance, a lighting consultant will measure the daylight and interior lighting– designed per the needs of the space – that falls on the working surfacein a 1 square-foot space, at desk height 30 inches above the floor.
Often, standard dark shade fabricsenhance view preservation andglare control more than standard light shade fabrics, which reflect more solar heat, and allow more daylight into a space; therefore, reducing energy costs for interior lighting. Advanced technologies such as KOOLBLACK® technology are adding more nuance to the conversation. KOOLBLACK®technology maintains the visibility and glare control benefits of a dark fabric while enhancing energy reflection comparable with light fabric. Chroma™ solar shade fabric utilizes an aluminum backing to dramatically increase solar reflectance.
The measured fabric properties ofsolar reflectance (Rs), solar absorption (As)and solar transmission (Ts) allow for the calculation of a shade’s performance as part of the overall glazing system, represented asthe solar heat gain coefficient (SHGC).Visible light transmission (Tv) and openness factor (OF) are used to calculate how much daylight will enter a space through shading and glazing. In addition to the variables listed above, the building type and use of the space helps determine the appropriate combination of high-performance shade fabrics and automation to optimize occupant comfort. Today, lighting and shading control systems that collect data on energy performance and occupant usage enable building owners to easily evaluate the benefits of good shading design.
Professional organizations are now involved to provide additional validity to the performance of shading systems. The Attachments Energy Rating Council (AERC) has been commissioned by the Department of Energy to develop a methodology that will provide numerical evaluation on system performance with shading attachments. Delos’s Well Building Standard®, solely based on occupant well-being rather than energy considerations, is gaining momentum among architects for similar reasons. And widely accepted standards, such as LEED v4,recognizeperformance-based design is all about the occupant, providing credits for windowsthat enhance daylighting, view preservation and glare control.
As the performance of automated shading systems moves to the forefront of daylighting design, installed systems mustdeliver on design intent, which had led to the development of specification grade fabrics. THEIA™ Compliant fabrics, such as ControlPlus™, are the first in the industry to have tight tolerance around performance properties. Without this control, architects cannot have confidence that the comfort and energy savings performance will meet the expectations of owners and occupants.
No matter what fabric is selected, a shade is only effective in the right position at the right time. Automated controls ensureperformance characteristics will consistently be enhanced according to the daylighting and energy needs of the space.
Integrating Automation with Shading and Interior Lighting
Sharing data from local wireless window light sensors, automated shading can also work in tandem with interior lighting systems. These systems balance daylight, glare, and view preservation throughout the course of each day based on sun position and other weather factors, such as daylight intensity.
Consider:deploying shades at 70 percent tohelp control heat and glare on a south-facing façade thatreceives intense sunlight in the afternoon. Conversely, an automated system may raiseshades ifa neighboring building casts a large shadow or when it’sovercast– particularly important considering the emerging trend in shading fabrics towards tighter openness in order to minimize glare.
Automated shading isespecially valuable in building areaswith no individual ownership, such as large atriums, open offices and cafeterias. Intuitive software for shading and lighting systemsallows facility managers to easily modify settings in these spaces, greatly reducing discomfort and disruption. Local keypads and similar controlsallow occupants to adjustthe conditions in spaces that require more flexibility, such as conference rooms.The results can be impactful and lasting.
For example, recent research conducted by Purdue University showed thatcustomizing automationin a series of private officesled to greater overall comfort with glare and view preservation as well as a reduction in manual overrides, with users choosing to adjust the automation less than three percent of the time.More data from this study should be available later in 2016.
The ability for occupants to respond to daylight variabilitywith manual overrides is critical to their comfort and productivity, as personal preferences change based on mood and task. At the same time, the undeniable trend in performance-based design is towards automation, which enables occupants to focus on their work with limited disruption from manual changes to shade position, while comfort and energy performance are maximized.
The Value Behind the Shift
According to the Rocky Mountain Institute, companies spend, on average, up to 100 times more on employee compensation than on their building’s energy consumption. For architects, the value of automated shading solutions is becoming most evident through the lens of well-being and productivity. However, hard costs must also beconsidered. While savings from automated shading systems are more noticeable in the long term, upfront spend can be reduced with simple techniques such as grouping or coupling multiple shades on one motor.
Like any investment, an automated shading system designed to enhance building performance comes with risk. Overlooking the quality and performance characteristics of the shading fabric selected for the system is a frequent mistake that can compromise the effectiveness of the automation. Fallout from this oversight typically includes high replacement costs and project delays. Fortunately, tools such as the Performance Shading Advisor have been developed to help architects avoid these situations.
Ultimately, the sun is powerful when it hits a building. The upside for controlling the sun –specifying these systems – far outweighs any additional risks. The ability to directly tiethe benefits of high-performance shade fabrics and automation tooccupant comfort and energy efficiency makes automated shading as important as any product or system in the building envelope.
Colin Blackford is the Innovation Manager for Mermet USA.
Brent Protzman, Ph.D., is theBuilding Science Manager for Lutron Electronics.
[1]Stetzenbach L.D., et al. 2008. Building Performance Characterization, Energy Usage, and Indoor Environmental Quality in High Performance Buildings, National Center for Energy Management and Building Technologies, Alexandria, VA, Final Report NCEMBT (Task 06-06)