Controlling The Sun

Automated shading systems optimize building performance and prioritize occupant comfort.

Mermet’s Koolblack technology maintains the visibility and glare-control benefits of a dark fabric while enhancing energy reflection comparable with light fabric. Photo: Hotel Beaumont

Mermet’s Koolblack technology maintains the visibility and glare-control benefits of a dark fabric while enhancing energy reflection comparable with light fabric. Photo: Hotel Beaumont

By Colin Blackford, Mermet USA, and Brent Protzman, Ph.D., Lutron Electronics

With the power to provide light, heat, and energy, the sun plays an integral role in the design of interior spaces and impacts occupant comfort and productivity. However, specifying shading systems to align occupant comfort and energy efficiency is often a challenge. Is it possible to select a durable, functional shade fabric that meets aesthetic needs as well as building-performance conditions?

Advanced shading materials and automation that allows shading to respond to unique and ever-changing external conditions may hold answers to that question.

Often, standard dark shade fabrics enhance view preservation and glare control more than standard light shade fabrics. Light fabrics, on the other hand, reflect more solar heat and allow more daylight into a space, thus reducing energy costs for interior lighting. However, light or dark are no longer the only options.

Advanced technologies such as Koolblack from Mermet Corp., Cowpens, SC, 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. In addition, Mermet’s Chroma solar-shade fabric uses an aluminum backing to dramatically increase solar reflectance.

The measured fabric properties of solar reflectance (Rs), solar absorption (As) and solar transmission (Ts) allow the calculation of a shade’s performance as part of the overall glazing system, represented as the 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 now validate the performance of shading systems. The Attachments Energy Rating Council (AERC), New York, has been commissioned by the Department of Energy, Washington, to develop a methodology that will provide numerical evaluation on system performance with shading attachments. The Well Building Standard, solely based on occupant well-being rather than energy considerations, is gaining momentum among architects for similar reasons. Widely accepted standards, such as USGB’s LEED v4, recognize performance-based design is all about the occupant, providing credits for windows that enhance daylighting, view preservation, and glare control.

As the performance of shading systems moves to the forefront of daylighting design, installed systems must deliver on design intent, which has led to the development of specification-grade fabrics. Theia performance-compliant fabrics such as Mermet’s 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. (The Theia performance specification is a manufacturing specification for solar screen fabrics developed by Lutron Electronics, Coopersburg, PA, and Purdue Univ., West Lafayette, IN.)

The 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. Photo: © Doug Scott 2014

The 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. Photo: © Doug Scott 2014

Right position, Right time

No matter what fabric is selected, a shade is only effective in the right position at the right time. Automated controls ensure performance characteristics will consistently be enhanced according to the daylighting and energy needs of the space.

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% to help control heat and glare on a south-facing façade that receives intense sunlight in the afternoon. Conversely, an automated system may raise shades if a neighboring building casts a large shadow or when it’s overcast—particularly important considering the emerging trend in shading fabrics towards tighter openness in order to minimize glare.

Automated shading is especially valuable in building areas with no individual ownership, such as large atriums, open offices, and cafeterias. Intuitive software for shading and lighting systems allows facility managers to easily modify settings in these spaces, greatly reducing discomfort and disruption. Local keypads and similar controls allow occupants to adjust the conditions in spaces that require more flexibility, such as conference rooms. The results can be impactful and lasting.

Recent research conducted by Purdue Univ. showed that customizing automation in a series of private offices led 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 3% of the time.

The ability for occupants to respond to daylight variability with 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.

Automated shading can work in tandem with interior lighting systems, balancing daylight, glare, and view preservation throughout the course of each day based on sun position and other weather factors. Photo: Mermet USA

Automated shading can work in tandem with interior lighting systems, balancing daylight, glare, and view preservation throughout the course of each day based on sun position and other weather factors. Photo: Mermet USA

The value of automation

According to the Rocky Mountain Institute, Boulder, CO, companies spend, on average, as much as 100 times more on employee compensation than on their building’s energy consumption. For architects, the value of automated shading solutions is becoming evident through the lens of well-being and productivity. However, hard costs must also be considered. 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 ability to directly tie the benefits of high-performance shade fabrics and automation to occupant 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, Cowpens, SC. Brent Protzman, Ph.D., is the building-science manager for Lutron Electronics, Coopersburg, PA.


datacache

Learn about Koolblack technology

Watch a Kookblack video

Download product Information guide

Go to the Lutron Performance Shading Advisor

Attachments Energy Rating Council website

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