daylighting saves

While lighting designers have seen a recent trend towards daylighting over electric lighting spurred by the need for energy efficiency, there is still a lot of confusion on what a daylighting system entails. For most architects, daylighting simply means having large windows and letting a lot of sunlight in. But as lighting designers know, a successful daylighting system is more than just letting daylight in; it’s about letting just the right amount of daylight in and keeping lighting at its most useful and comfortable level. For many buildings, basic skylights make for a simple and cost-effective daylighting solution.

Skylights are also referred to as ‘roof windows’ and they are the most effective way for letting daylight penetrate into the interior of a building. Compared to windows or vertical fenestrations, skylights are three to five times more effective for allowing daylight entry, and it also produces the least amount of glare, hot spots or shadowing. Letting daylight in from the top of a building also allows for a more even distribution of light to all internal areas, delivering a high performance visual environment.

There are two kinds of skylights to choose from: active skylights and passive skylights, with the latter including prismatic skylights. Both have advantages and disadvantages which need to be considered when choosing the right daylighting solution for your building. Active skylights feature a mirror-tracking technology to ensure that it will capture as much direct sunlight as possible. This mirror-tracking technology is particularly useful during dawn or dusk. However, active skylights have been found to be more costly and less reliable than passive skylights for the simple reason that it is subject to more maintenance and repair.

With its simplicity and efficiency, passive skylights are the top solutions for maximizing the use of daylight, particularly prismatic skylights. While traditional skylights achieve diffusion through semi-opaque substrates that reduces the transmission of visible light, prismatic skylights feature a special glaze that effectively diffuses light without compromising the entry of visible light. The glaze in prismatic skylights is introduced during the prismatic extrusion process and is designed to maximize visible light transmission while also delivering 100 percent diffusion for soft and uniformly distributed lighting.

Beyond LEED qualification and cutting down on energy cost, the use of natural light has also been found to improve human performance dramatically in several studies. In retail, workplaces and educational facilities, the use of daylighting was found to have a correlation with improved employee morale, lower absenteeism, reduced errors, improved product quality and increased productivity. In a study conducted by the Pacific Gas & Electric as part of the California Energy Commission’s Public Interest Energy Research program, students that enjoyed more daylighting in their classrooms progressed 20 percent faster in math tests and 26 percent faster in reading tests in a year compared to those with less daylight.

To create a successful daylighting system, leading lighting designers also stress the importance of shade. For daylighting to be at its most energy efficient, daylighting has to reach a thermal balance of letting light in without creating glare, which well-designed exterior shades can achieve. Daylighting controls can also help in maintaining optimal daylighting levels by maximizing the natural light source while minimizing the use of electric lighting.

Daylighting, or daylight harvesting, is the method of utilizing natural light to boost both energy efficiency and visual comfort. To harness the full potential of daylighting in creating a high performance visual environment, daylighting solutions are used in conjunction with lighting control solutions to maintain the ideal level of lighting.

A full daylighting system makes use of an array of photosensors and dimmable electronic ballasts for electric lighting components. The photosensors and dimmable electronic ballasts work together to make the electric light fixtures respond to the natural light levels in a room or space. They allow the light fixtures to adjust their own light output, lowering it if there is an abundance of natural light and increasing the output when there is less daylight than needed.

Occupancy sensors are also often used to enhance a daylighting control system. Occupancy sensors ensure that the electric lighting components are used only when they are needed by switching them off when a room is unoccupied. They are also able to detect when people are present in a room or area and can automatically switch the electric lights back on when needed. With occupancy sensors, overlighting is effectively eliminated.

By allowing electric lighting and natural light to work together, lighting control solutions can help achieve an ideal level of visual comfort while also significantly reducing energy consumption. Maintaining ideal light levels for optimized visual comfort also results in an environment that is conducive for work, like in commercial and industrial applications, and for learning, like in educational facilities such as schools and libraries.

A daylight harvesting system, or daylighting system, is a lighting control solution that is designed to make use of natural light to lighten the demand on electric lighting and reduce energy consumption. Daylight harvesting is an appealing option for achieving energy efficient lighting because of its ability to deliver a high performance visual environment as well as energy savings. But with any daylighting system, letting light in and keeping heat out is always an issue.

With modern lighting solutions, there are a number of choices on how to block heat while still letting in a healthy amount of daylight for daylighting. Skylight venting is an option that uses natural ventilation during warm periods in spring or fall. A more advanced version of skylight venting is a barometric exhaust vent that provides building pressurization control and solar heat exhaust to reduce heat gain throughout a building.

Another option is glazed skylights. Prismatic skylights feature a triple-glaze that are spectrally selective and can keep out ultraviolet and long-wave radiation while allowing visible light to pass. The glaze in prismatic skylights also reduces thermal energy transfer to maintain comfortable visual and thermal environments.

A successful daylighting system is usually made up of a number of components that all work in optimizing visual comfort, energy efficiency and end user convenience. With a wide array of options for minimizing heat while allowing daylight into a building, daylighting is an ideal option for creating a sustainable, high performance and energy efficient lighting system.

As part of Pacific Gas & Electric (PG&E) initiative to raise awareness for good daylighting practices and improve daylighting design, the daylighting system in Dena Boer Elementary School in Salida, California is featured for its well daylit facilities. Working within a standard construction budget, daylighting was used throughout the entire school to minimize energy consumption and promote a conducive learning environment.

To achieve a successful and effective daylighting system, components that included skylight glazing, skylights, louvers, overhangs and skylight venting were used. These components were utilized with the understanding that daylighting is more than just letting a lot of natural light in; it’s about letting just the right amount of useful and comfortable daylight in and maintaining it at its optimal level.

1. Skylights

Skylights are often referred to as ‘roof windows’ or ‘ceiling windows’. They are a core component of any daylighting system because of their effectiveness in gathering daylight; studies show that skylights are three to five times more effective for daylighting than windows or vertical fenestrations.

The skylights and high ceilings at Dena Boer Elementary School provide pleasing classroom proportions that contribute to the school’s overall visual comfort. It also helps in providing plenty of full-spectrum light that is conducive for teaching and learning.

2. Skylight Glazing

Each of the skylights at Dena Boer Elementary School is triple-glazed with a prismatic and spectrally selective acrylic material.

The prisms were designed to refract the light, achieving an even distribution and diffusion while also eliminating directional sunlight and uncomfortable concentrations of light called ‘hot spots’.

Its spectral selectiveness is for allowing visible light entry into the interior of the school while blocking out ultraviolet and long-wave radiation that produces heat but no visible light.

3. Louvers

Louvers were installed at the top of skylight wells as a form of daylighting control. The louvers can be operated via an electronic wall switch, allowing occupants to modulate dalylight levels and to darken rooms as required.

For effective daylighting, shade and modulation is just as important as the entry of visible light. To maximize energy efficiency and visual comfort, optimal lumen levels must be achieved with the help of lighting controls and shading.

4. Overhangs

In addition to the daylight delivered by skylights, classrooms, offices and the library also receive daylight through side light via vertical windows. With the use of deep overhangs, direct sunlight associated with heat gain and unwanted glare is eliminated.

5. Skylight Venting

For a typical classroom in Dena Boer Elementary School, one of the four skylights can be vented. This offers an opportunity for naturally cooling the space using natural ventilation which contributes to cost effectiveness by reducing HVAC cost during warm periods like spring and fall.

The skylight venting is controlled by an electronic wall switch.

The daylighting system has significantly reduced the need for electric lighting during normal operating hours while also delivering a pleasing visual effect that contributes to the quality of the learning environment. It was also found that the school could rely solely on daylight for all its lighting needs during many months of the year, resulting in high energy savings.

Dena Boer Elementary School has documented its minimum annual energy savings from its daylighting initiative to be approximately $9 000. While the school does not currently utilize daylight controls like photocell-based controls and dimmable electronic ballasts for its electric lighting, the school is already looking to implement these new changes to further enhance energy efficiency.

Daylighting, or daylight harvesting, is a method of harvesting and utilizing natural light to reduce the energy consumption of artificial or electric lighting. A basic daylighting system is usually composed of skylights, electric lighting, a daylighting control system. These separate components work together not just to gather daylight but to maintain an optimal visual environment.

The key to a high performance visual environment is having a regulated level of lighting. In a daylighting system for commercial or educational spaces, electric daylighting control louvers are used to regulate the amount of natural light that enter a building through skylights. Louvers can be automatically controlled through photocontrols and set to modulate the right amount of properly diffused daylight to maintain a desired foot candle level. For manual control, daylighting controls systems can be utilized to allow occupants the ability to adjust daylight levels and darken rooms when desired.

With the use of electric daylighting control louvers, a daylighting system can not only reduce energy consumption and boost energy savings; it can also deliver a high performance visual environment that’s conducive for a wide range of building uses.

Conventional skylights have long been a feature of daylighting because of its ability to extract significantly more daylight than windows, resulting in less use of artificial lighting and energy savings. Compared to windows, skylights is three to five times more effective in delivering natural illumination. Skylights also evenly distribute the light to a wider range of internal areas while also reducing shadows. However, skylights also have a few drawbacks of their own.

Conventional skylights with clear glazing can deliver a lighting source to the building but they produce high levels of glare or high concentrations of light called ‘hot spots’. Skylights also traditionally utilize semi-opaque substrates through colorants to achieve diffusion of light, but this practice reduces the amount of useful visible light and the hours that daylight can be used as a main illumination source.

With the breakthrough prismatic skylights, a soft, yet bright natural light can be achieved using glazing designs that allow for the even diffusion of light while maximizing visible light transmission. Prisms in the prismatic skylights refract light throughout a room for a uniform distribution of light, eliminating the ‘hot spots’, glare and UV damage that conventional skylights can produce. Prismatic skylights have maximized visible light and diffusion more than any other daylighting solution. The light produced through high performance prismatic skylights have been documented to produce less than half the heat of the most efficient florescent lighting system (T5 HO) at the same foot candle level of light. This fact adds to increased energy savings in buildings with conditioned space.

Prismatic skylights can let you enjoy the energy savings of a daylighting system while also enjoying enhanced visual performance and operational efficiency. Designed properly, electric lighting use can be reduced for up to 80% of daylight hours annually making high performance prismatic daylighting the leading lighting solution for sustainability and visual comfort.

Story originally released under California’s ACT2 Energy Efficiency Initiatives in 1997 after a 7 year study commenced in 1990.

The Pacific Gas and Electric Company or PG&E is committed to raising awareness for daylighting as an effective means of saving energy as well as improving the practice of daylighting design, along with the Lawrence Berkeley National Laboratory. To create an operationally and energy efficient daylighting design for office applications, in 1990, PG&E renovated the California State Automobile Association’s (CSAA) district office in Antioch, California to feature the components of a successful daylighting system.

While most people think that daylighting is merely letting a lot of sunlight into the interior of a building, PG&E understands that it is about letting just the right amount of light in to achieve optimal visual comfort. Modulating light levels involves more than just large windows and open spaces. To achieve maximum energy efficiency, factors like heat and electric lighting also have to be taken into consideration.

To achieve a successful daylighting system in the CSAA Antioch office, the original two-story design of the building was changed to a single-story layout that fully utilized the daylight from skylights and perimeter windows as its primary light sources. The electric lighting system was also redesigned to use efficient T8 light sources and CFLs for task lighting and work tables. The goal was to create an environment that was conducive for a work-oriented and high performance visual environment in a cost effective manner.

The full daylighting system was created with components working in conjunction with each other, targeting energy efficient and high quality lighting:

1.  Skylights

The use of high ceilings and high performance prismatic skylights in the CSAA Antioch office allowed a uniform daylight distribution that effectively reduced uncomfortable high concentrations of light called ‘hot spots’ and shadowing. Because of the placement of the skylights on the ceiling (much like ‘roof windows’), the amount of daylight was abundant and provided high light levels.

2.  Louvers

The skylights came with installed louvers that were equipped with photocells. These louvers were daylight sensitive and could continuously regulate the entry of light by automatically opening or closing the aperture of the skylights. This ensures that the lighting was kept at optimal lumen levels.

3.  Barometric Exhaust Vents

Barometric exhaust vents were used in each skylight to provide building pressurization control and solar heat exhaust to reduce heat gain. One of the keys to an effective daylighting system is its ability to allow entry to visible light but not heat.

4.  Dimmable Electronic Ballasts

Dimmable electronic ballasts are used with the electric lighting to provide dimming capability that responds to daylight levels. They brighten and dim the lights in response to the amount of natural light available within an area. When the daylight level exceeds 60fc, the electric lighting shuts off.

5.  Workstation Lighting

Workstation lighting ensures that desks and workstations receive the task lighting that they require. They utilize energy efficient CFL sources that are also equipped with dimmable electronic ballasts.

6.  Glazing and Window Blinds

Special glazing in windows makes them spectrally selective, meaning that they allow visible light to enter the building while keeping heat out. The light transmittance and shading coefficients for each window was modified to match its location in the building and its exposure to direct sunlight.

Perforated window blinds were also use to eliminate glare without reducing visibility.

By using best daylighting practices and effective daylighting components, PG&E was able to reduce both the electrical and cooling requirements of the CSAA district office in Antioch. This allowed the building’s designers to downsize the heating-ventilation-air-conditioning system (HVAC). The full daylighting system also reduced the building’s annual energy consumption by 32%. With less cooling and electrical requirements, the daylighting system has enhanced the office’s cost effectiveness while also improving its visual comfort.

The employees of the building also responded favourably to the new daylighting system, stating that the atmosphere created by the daylight was calming and easier on the eyes.

Daylight harvesting, or daylighting, is fast becoming one of the leading methods of boosting energy efficiency for lighting systems. With its use of natural light, it can significantly cut down on electrical energy use while also enhancing visual comfort and lighting performance. But daylight harvesting is more than just having large windows that lets sunlight in; it’s all about having just the right amount of light in a room or space, which is where electric lighting comes in.

A successful daylighting system needs multiple components to regulate lumen levels, reduce solar heat gain and optimize energy efficiency. One of the key components of a daylighting system is its coordination with electric lighting solutions. With the help of photosensors and electronic dimmable ballasts, electric lighting solutions can be programmed to adjust their light output as needed in response to the available daylight. It also ensures that there will be sufficient lighting for areas that are used at night.

With a properly designed daylighting system, the use of electric lighting can be reduced up to 80% during daylight hours which contributes significantly to lowering energy consumption and cost. By using electric lighting in conjunction with daylighting, visual performance is optimized for a conducive work and learning environment.