Optimizing daylight with motorized window treatments

May 24, 2019

by Scott Blue

Images courtesy Nice S.p.A.[1]
Images courtesy Nice S.p.A.

Since the beginning of this millennium, architects and owners have increasingly adopted a daylighting design approach when constructing or redesigning buildings. This design concept promotes natural light through the use of windows and other openings, the strategic placement of walls, and with other tactics such as motorized window treatments (MWTs).

Daylighting has been shown to benefit both building occupants and businesses. For workplaces, the addition of sunlight to interior rooms sparks a satisfied, productive workforce while leading to a greener workplace. Developments in MWTs are increasing yields from sunlight.

For architects and building owners, many of their decisions on daylighting can be based on the desire to save money on lighting and heating costs. However, there is another factor.

Since most people spend 85 to 95 percent of the workday inside buildings, daylighting[2] is a step in the right direction for increasing one’s connection to the outdoors and creating a more stimulating work environment. The Construction Specifier author Michael J. Holz points out[3], it is important to consider the non-energy as well as the energy benefits of daylighting. Though return on investment (ROI) analysis may not give the nod to non-energy impacts, it is the occupants who count. Comfort, health, and workplace productivity are essential to design strategy.

Let the sunshine in

As an example of how approaches to room illumination have changed throughout the years, one must consider the history of the manufacturing plant. In the early days of the industrial revolution, factories had an abundance of windows. Eventually two factors led to the replacement of glass by solid walls—management’s desire to keep what was going on inside their plant undercover and improvement in artificial lighting technologies, a boon for 24-hour factories.

Tubular motors operate window treatments and can be controlled remotely by sensors.[4]
Tubular motors operate window treatments and can be controlled remotely by sensors.

Then came the oil crises of the 1970s and ’80s, forcing building designers and managers to find new ways to produce illumination using less energy. One significant change was the introduction of compact fluorescent lamps (CFLs). Light-emitting diode (LED) lighting started to find its way into general use in the early 2000s.

The search for natural replacements for carbon-based energy sources led to a fresh look at daylighting in the ’90s. Sunlight was re-introduced, bringing natural illumination back into buildings through the strategic placement of the structure and an increase in the number of apertures such as windows, glass doors, and skylights.

The savings make sense

The electricity[5] to power interior lights can eat up a considerable amount of energy—as much as 17 percent of a total energy budget. Effective daylighting design can significantly knock back the energy used for lighting by up to 75 percent.

Most people, other than night-shift workers, are up and busy during the day. This increases demand on electrical power utilities, particularly in the late morning and early afternoon hours, thereby raising the cost of providing power. Daylighting enables building managers to peak-shave their power usage for substantial savings on the power bill.

The sunny side of daylighting

Figure 1: Normal circadian rhythms based on the natural pattern of day and night.[6]
Figure 1: Normal circadian rhythms based on the natural pattern of day and night.

It is a simple formula—healthy employees are happy, and happy workers are productive.

Many employees feel more productive when they have adequate exposure to sunlight. This assertion is backed up by a number of studies that have analyzed the relationship between exposure to sunlight and a productive work environment for employees.

Researchers at the interdepartmental neuroscience program at Northwestern University, Illinois, reported[7] that the detrimental impact of working in a windowless environment is a universal phenomenon. The study[8] concluded there is a strong relationship between workplace daylight exposure and office workers’ sleep quality, activity levels, and overall quality of life.

Sunlight, or the lack of it, can have a profound effect on circadian rhythms, which are biological, mental, and behavioral changes following a 24-hour cycle and responding to light and darkness within an organism’s environment. Circadian rhythms are produced by natural factors within the body, but are mostly affected by signals from the environment. Light is the main cue influencing circadian rhythms. Figure 1 shows normal circadian rhythms based on the natural pattern of day and night.

A study[9] conducted by the German researcher Mirjam Muench compared two groups of people—one exposed to daylight and the other to artificial light—over the course of a couple of workdays. Muench found cortisol levels drop significantly under artificial lighting conditions. This means artificial or poor lighting can actually make workers more stressed.

A study[10] done at a warehouse for a cereal maker in Salt Lake City, Utah, found windows and skylights noticeably improved worker performance. The increase in natural lighting led to lower absenteeism and fewer product defects.

Figure 2: According to a study conducted by the University of Oregon, Portland, a combination of outdoor view and sunlight improves attendance. Image courtesy University of Oregon[11]
Figure 2: According to a study conducted by the University of Oregon, Portland, a combination of outdoor view and sunlight improves attendance. Image courtesy University of Oregon

In addition to the benefits of natural light, just having a view of the outdoors improves worker performance. Two different studies conducted in the Sacramento (California), municipal utility district offices found a clear link between employees having a view to outside from their workstations and their performance.

Another study conducted by the University of Oregon, Portland, analyzed the impact an outdoor view had on the percentage of days of work missed due to reported sickness (Figure 2). Group 5 had no view, while Groups 1 and 2 had the best views of the outdoors. As Figure 2 demonstrates, the combination of the outdoor view and the effects of sunlight made workers feel good to the point of improved attendance.

Designing for daylighting

According to a white paper from ETC, an architectural lighting controls firm, as daylighting for energy savings and conservation becomes a common design practice, daylight harvesting, will be required by some energy codes. Daylight harvesting is an advanced lighting approach that uses sensors and controls to adjust the interior lights to maintain a desired light level. ETC notes daylight harvesting will soon be adopted by other energy codes—over time, it will be required for new construction and, where possible, added to existing buildings.

California’s Title 24, the International Energy Conservation Code (IECC) 2012, and The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90.1, Energy Standard For Buildings Except Low-Rise Residential Buildings, already have daylighting guidelines[12]; these are likely to become mandatory nationally. Most commercial buildings with windows and skylights are required to have some type of daylight harvesting control in the adjacent area.

There are three main approaches for optimizing the effects of daylighting. One is building design, and other through interior features and systems.

Building design

This involves positioning windows for best exposure to sunlight. Building design can include skylights and clerestory windows. Optimizing the building orientation and footprint is also a tactic.

Interior features and systems

Figure 3: The relationship between times of day for sunlight, light-emitting diode (LED) light levels, and energy savings. Image courtesy Lighting Design Lab[13]
Figure 3: The relationship between times of day for sunlight, light-emitting diode (LED) light levels, and energy savings.
Image courtesy Lighting Design Lab

Design professionals can include daylight redirecting devices, daylighting-responsive lighting controls, and interior design focusing on placement of furniture and room surface finishes.

Systems adjusting to the available lighting from the sun

Static building positions and interior features can optimize the effects of sunlight. Given the sun’s position, time of year, and the presence of clouds—sunlight will change during the day. Ambient light sensors combining photopic, human-like sensitivity with wide dynamic range are enabling a new generation of lighting controls that may be built directly into replacement lamps and luminaires to take advantage of available daylight and shift more of the interior lighting burden away from artificial sources.

Consequently, controls[14] throughout the day can adjust LED light levels to compensate for changes in the position and intensity of the sun. Figure 3 depicts the relationship between time of day for sunlight, LED light levels, and energy savings.

Limitations on the daylighting benefits

Remote control of the motorized window treatment (MWT) system means adjustments can be made in shade position from the desk or work cell. Images courtesy Nice S.p.A.[15]
Remote control of the motorized window treatment (MWT) system means adjustments can be made in shade position from the desk or work cell.
Images courtesy Nice S.p.A.

To properly implement daylighting, best practices such as window position and building orientation can only be accomplished via new construction.

Sunlight can heat up a room, thereby making it uncomfortably hot. Many times, this causes the air- conditioning system to turn on to relieve the heat. The rise in temperature can negate the financial gains from daylighting. Too much heat and glare from sunlight can also impact occupant comfort.

“The biggest problem[16] with daylighting design is we still take a traditional building approach to a daylighting project,” says Eric Truelove, director
of sustainable design and HVAC engineer for the contracting firm Renschler.

In a typical case, the architect’s design offers plenty of glass for light, but the design inherently comes with too much heat. In turn, this requires the engineer to increase the cooling tonnage when the building is complete. Additional costs are incurred when occupants demand blinds to reduce glare. The blinds are drawn much of the day, prompting the use of electric lights. An owner who thought that daylighting was going to save money finds out the hard way the design not only costs more upfront, but also more to operate.

The sun changes position throughout the day and as the year moves along, whereas the windows and other apertures do not. As the direction of light beams changes, light is cast in a moving pattern.

Manual shades and blinds can control the sunlight pouring into the room. However, for a building with thousands of square feet of window area and dozens of apertures, managing window treatments in order to compensate for changing sunlight levels is an enormous challenge and impossible to do manually. In a workplace, constant adjustment of shade/blind position can be a major distraction. The occupants may, therefore, close their shades or blinds and leave them in that position for days.

Windows going from the floor to very high ceilings or skylights make manual blinds and shades unviable for controlling the amount of sunlight coming into a room. For example, one hospital with 13-m (40-ft) high windows in an atrium facing south experienced an enormous greenhouse effect. The sunlight caused intense glare on computer screens and made it difficult to check in patients. It also generated an uncomfortable level of heat for both workers and patients. As a result, the facility had to install tall moveable panels to block the sunlight.

Automated window treatments

Technicians can easily program the speed, sensitivity, and other variables for the MWT system.[17]
Technicians can easily program the speed, sensitivity, and other variables for the MWT system.

A growing number of functions are being managed by smart building technology, including MTW systems that can have awnings on the outside of the building and blinds and shades on the inside.

For commercial and industrial buildings with windows spanning hundreds of square feet, MWTs are critical for improved working conditions. Unlike most daylighting strategies, MWTs can be used in existing buildings.

First, some MWT basics. A motor, typically within the treatment’s roll-up tube, propels the shades, blinds, and awnings. Motors can be battery powered or, for larger-scale applications, wired into the building’s electrical system. They can even be solar powered if a building’s electrical system uses solar energy, thus adding to the facility’s sustainability mission.

Here is how MWTs allow commercial buildings to maximize and automate sunlight and help promote increased productivity in the workplace, while also helping a building attain its green mission.

The right amount of light

To maintain consistent and optimal lighting as the sun’s position in the sky changes, manual window treatments must be frequently adjusted. As explained earlier this constant alteration can disrupt a company’s workflow.

MWTs can be configured to regulate the amount of sunlight or artificial light that is coming into a workspace. The system can connect to sensors to detect when sunlight intensifies or diminishes. When low sunlight levels cause window treatments to be fully open, interior lights can adjust to the proper level of illumination. They can be programmed to intensify lighting in the deeper parts of a room away from sunlight.

Total interior comfort control while saving energy

As with artificial lighting, the MWT system controls the amount of sunlight entering a room—permitting extra sunlight to warm the room or restricting it to minimize solar heat gain. The smart blinds system can work with the building automation system (BAS) to maintain the room’s set point.

When the sun becomes too hot, the MWT system automatically closes, allowing a workspace to remain cooler for longer periods before the air conditioning system kicks in.

In addition to reducing the need for both generated lighting and room heating/cooling, some systems run on DC motors and save up to two-thirds of the operating energy versus standard AC motor alternatives. For facilities with hundreds of automated shade units, the savings can be significant.

Personal preference

There are a number of remote control and wall switch designs, including touchless, to manage the system. Workers can adjust window treatment position to ensure adequate sunlight for illumination while minimizing glare without leaving their desk.

Precision operation

Manually controlled window treatments can be subject to misalignment, permitting cracks between the window frame and covering. Depending on the time of day, this can produce an almost laser-like beam of light. The shade hems on MWT systems can be more precisely aligned to the windows to provide aesthetically pleasing alignment for adjacent shades.

These systems also can detect objects in their path and can reverse operation upon contact. Further, their smooth DC motor operation prolongs the component’s life.

An extra measure of fire protection

When a fire breaks out, the detection system will command the MWT to roll up, enabling firefighters to look into the building, assess the situation, and determine who is inside.

Building security

To discourage break-ins during periods of low building occupancy—such as evenings, weekends, or holidays—MWTs for one-story buildings or the first few levels of multistory buildings can be timed to cover the window. Once these are closed, it is possible to program sectors to turn lighting on and off to give the impression the building is occupied. Alternatively, the MWTs can close exterior rolling shutters to prevent entrance through a window or door.

Conclusion

Capturing sunlight through daylighting design creates more comfortable interior spaces, while lowering energy costs. Daylighting design promotes a more productive and engaged workforce by allowing for the illumination of sunlight, which has been proven to have positive effects on the human body and mind.

For deploying MWT systems for a daylighting project, it is advisable to seek expert advice from a window treatments contractor with commercial construction experience. It is important to engage with the MWT systems expert as early in the project as possible, evaluate all options, and consider all benefits.

Scott Blue is COO at the Nice Group USA, the North American branch for Nice S.p.A., an innovator in the home and building automation and home security sector. Blue has managed and owned companies offering access products and led product development. He can be reached at s.blue@niceforyou.com[18].

Endnotes:
  1. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/1-daylight.jpg
  2. daylighting: http://www.disd.edu/blog/daylighting-interior-design
  3. points out: http://www.constructionspecifier.com/are-we-thinking-about-daylighting-all-wrong
  4. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/Nice.jpg
  5. electricity: http://www.greeneducationfoundation.org/green-building-program-sub/learn-about-green-building/1224-daylight-harvesting.html
  6. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/Cortisol.jpg
  7. reported: http://blog.bufferapp.com/the-science-of-how-room-temperature-and-lighting-affects-our-productivity
  8. study: http://www.psychologytoday.com/us/blog/the-athletes-way/201306/exposure-natural-light-improves-workplace-performance
  9. study: http://eneref.org/reports/eneref_daylight_warehouse_post.pdf
  10. study: http://hammerandhand.com/field-notes/impact-of-office-daylighting-on-employee-productivity
  11. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/Chart.jpg
  12. guidelines: http://www.etcconnect.com/uploadedFiles/Main_Site/Documents/Public/White_Papers/WP010_Daylighting.pdf
  13. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/daylight.jpg
  14. controls: http://www.automatedbuildings.com/news/aug07/articles/zing/070723051101dilouie.htm
  15. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/2-daylight.jpg
  16. problem: http://www.automatedbuildings.com/news/aug07/articles/zing/070723051101dilouie.htm
  17. [Image]: https://www.constructionspecifier.com/wp-content/uploads/2019/05/window.jpg
  18. s.blue@niceforyou.com: mailto:s.blue@niceforyou.com

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