In the years since studies pointed to a correlation between well-designed daylighting in classrooms and improved student performance, many schools and universities have been persuaded to incorporate daylighting into the designs of their learning environments.
To effectively carry out daylighting strategies, planners need to determine what types of windows should be installed, where windows should be placed, how much light they will admit into a learning space. And, in a lesson reinforced by the Covid-19 pandemic, windows that can be opened provide the ventilation that help improve indoor air quality and deter the spread of viruses.
“There is growing recognition that views, natural light and ventilation contribute to the satisfaction, health and productivity of students and teachers,” says the Efficient Windows Collaborative Tools for Schools guide.Multiple benefits
Daylighting can benefit learning environments in a variety of ways. U.S. Department of Energy’s Best Practices Manual for Building High Performance Schools lists several:
- Academic performance. Studies indicate that well-designed daylighting is associated with enhanced student performance, and poor daylighting design has been shown to correlate with reduced student performance.
- Energy savings. Daylighting can save energy and reduce peak electricity demand if electric lights are turned off or dimmed when daylight is abundant.
- Better light. Daylight provides the highest quality light for visual tasks. It enhances the color and visual appearance of objects and helps to see small details better.
- Connection to nature. Daylight provides a connection to the natural world by supplying information on time of day, season and weather conditions. Improved health. Views provided by windows contribute to eye health by providing frequent changes in focal distance, which helps relax eye muscles.
- Environmental education. Windows and solar gain through windows can provide opportunities to teach how the sun moves through the sky and how daylight can be controlled by overhangs and other shading devices.
View vs. daylighting
Daylighting strategies make a distinction between windows designed to admit and enhance daylighting and windows that provide occupants with a view outside the space.
“To balance daylight admission with glare and solar heat gain control and provide uniform light distribution, modern daylight design suggests that glazing is separated into glazing for daylighting and glazing for views,” the Efficient Windows Collaborative says.
Daylight glazing is typically placed high in the wall, or in the ceiling in the case of toplighting. Daylight glazing can be designed to keep light from entering a room directly and creating glare. Excessive glare may lead to eye strain that may negatively affect the learning environment. Incorporating light shelves, reflective blinds, or other reflective surfaces helps to reflect the light deep into the room.
View glazing is situated lower in the wall, offering a view to the outdoors for students seated in a classroom. If sufficient daylight is provided through separate daylight glazing, shading can be increased for view glazing to control glare and solar heat gain without detracting from the benefits of daylighting.
For daylighting to be most effective, a school needs control systems to adjust the amount of light as conditions change. Having occupants switch lights off can be effective, but it will require active participation and usually will not be done optimally to reduce energy use. Systems with photo sensors can switch off or dim portions of the electric lighting when sufficient daylight is present. This type of system is designed to operate optimally without depending on occupant participation.
In spaces where vertical windows do not provide sufficient daylight, toplighting techniques can bring daylight into areas not reached by vertical windows. “Since many schools buildings are low-rise with the classrooms directly under the roof, toplighting is a very feasible as a supplement to sidelighting,” the Collaborative says.
Toplighting includes skylights, tubular daylighting devices and clerestory monitors. Horizontal skylights admit light into a space from above; tubular devices capture daylight through a glazed dome protruding from the roof and reflect it down to the interior space through highly reflective shafts; clerestory monitors, with vertical glazing, capture low sun angles more easily than skylights. Baffles beneath clerestories can provide diffuse glare-free daylight to the back of a room.
Light shelves are another technique to capture daylight. They are flat or curved elements in a window façade that reflect incoming light to the ceiling— bouncing light deep into a room. Light shelves typically divide a window into a view window below the shelf and daylight glazing above.
An open mind
Not all windows in education facilities can be opened, but spaces having that option have benefited schools trying to use fresh air to combat the spread of Covid-19.
“Where opening doors and windows can be done safely and without introducing outdoor air pollution, this action can significantly improve ventilation rates,” says the Collaborative for High Performance Schools.
Before opening windows for ventilation, schools should take into account factors affecting the area around the campus, such as security, air pollution, pollen and other allergen counts, outdoor temperature, and outdoor humidity.
By the numbers
The National Fenestration Rating Council has a labeling system that calculates energy performance ratings so those acquiring and installing windows can compare the energy efficiency of different products.
U-factor: Measures how well a window keeps heat from escaping from the inside of a room. It is expressed as a number between 0.20 and 1.20; the lower the number, the better a product is at keeping heat in.
Solar heat gain coefficient: Measures how well a window can resist unwanted heat gain, an important consideration in the summer cooling season. It is expressed as a number between zero and 1; the lower the number, the less will be spent on cooling.
Visible transmittance: Measures how well a window is designed to effectively illuminate a space with daylight. It’s expressed as a number between zero and 1; the higher the number, the more daylight is let in.
Air leakage: Measures how much air will enter a room through a window. Typically, it’s expressed as a number between 0.1 and 0.3; the lower the number, the fewer drafts an occupant will experience.