Maximize your project’s energy efficiency by embracing the power of Natural Light
Natural light is a key feature in architecture and interior design that can transform spaces, make them healthier and lower electricity costs. Daylighting—the controlled admission of natural light into a building to reduce electric lighting and save energy—is an important resource for architects striving to make their affordable housing projects energy efficient.
Lighting can be one of the most expensive aspects of any building project, costly to those paying the bills and to the environment. Architects, therefore, have a responsibility to incorporate daylighting strategies into their designs.
Increased natural light can save energy, increase the quality of the visual environment, improve user satisfaction and reduce operating expenses—all crucial to a successful affordable housing project.
Daylighting goes beyond the strategic placement and size of windows. It is an integrated design concept that involves the whole building and that factors climate, orientation, floor plan and interior lighting design and controls.
ENERGY SAVING BENEFITS OF DAYLIGHTING
In addition to cutting electricity costs for building owners, daylighting lowers carbon emissions, which is why green-building rating systems such as LEED (Leadership in Energy and Environmental Design) from the USGBC (U.S. Green Building Council) encourage daylighting and daylight harvesting systems that adjust electric light levels based on daylight availability to maintain an overall target light level dependent on occupancy.
How much energy can be saved? Lighting usually accounts for 25% to 40% of energy consumption in a typical building. According to a number of studies, the average lighting energy savings from daylighting and daylight harvesting systems ranges from 24% to 80%.
The dynamic nature of daylight throughout the day and throughout the year poses numerous challenges when designing buildings to take advantage of natural light and save energy. Following are a few of the techniques available to architects:
- window size, shape, position, and orientation
- windows assemblies (frame and glass) with low u-values and low SHGC
- shading devices
- light shelves
- sloped ceilings
- skylights and roof lights
- atrium spaces
- light wells
- fiber optic cable networks connected to rooftop light traps
- tubular daylight devices (sun pipes)
- reflective or pale painted surfaces and interior decor
- daylight responsive electric lighting controls
12 WAYS TO INCORPORATE DAYLIGHTING IN YOUR PROJECT
Daylighting and solar control strategies are more effective when properly integrated into the overall design of a building during the planning stages, before construction, and not as an afterthought or something to be added later.
During the design process, the following strategies should be considered:
1. Increase daylight zones
Extend the perimeter footprint to maximize the usable daylighting area.
2. Control artificial lighting first
Occupancy and daylight sensors should be used to dim or extinguish indoor lights when these are not needed.
3. Use appropriate materials and colors to finish spaces
Daylighting benefits from lightly colored and smooth interior surfaces that reflect light.
4. Allow daylight penetration high in a space
Windows located high in a wall or in roof monitors and clerestories result in deeper light penetration and reduce the likelihood of excessive brightness.
5. Reflect daylight within a space to increase room brightness
A light shelf, if properly designed, has the potential to increase room brightness and decrease glare.
6. Slope ceilings to direct more light into a space
Sloping the ceiling away from the fenestration area helps increase the surface brightness of the ceiling further into a space.
7. Filter daylight
The harshness of direct light can be filtered with vegetation, curtains, and louvers, among other methods.
8. Consider building orientation
Remember that different orientations call for different daylighting strategies. Light shelves, which are effective on south facades, are often ineffective on east or west elevations of buildings.
9. Account for climate and geography
Interior light shelves are most effective for relatively clear climates at mid-latitudes and a southern orientation. To control low-angle sun, use darker glazing, interior shading other than shelves, or exterior shading devices. In higher latitudes, windows get larger and equator-facing, while in lower latitudes they become smaller, especially on the east and west sides, where the sun is lower in the morning and evening.
10. Position lighting for maximum effectiveness
Daylight-corrected fluorescent lamps integrate more seamlessly with natural daylighting strategies. Luminaires should be zoned and positioned parallel to windows.
11. Consider skylights
Though this natural lighting strategy is viewed as a potential source for excessive heat gain and heat loss in the winter, proper installation can reduce these discomforts and enhance its main benefits. Using translucent glazing can potentially reduce glare. A ceiling diffuser placed at the bottom of the skylight shaft can help improve even distribution of light. Solatubes—a dome-like skylight on the roof and a tube covered with a reflective material to bring light to the interior—can be beneficial, particularly in existing buildings to reduce the impact on the envelope.
12. Use daylight harvesting systems
Daylight harvesting systems will allow you to monitor and control electric lighting as well as maximize energy savings.
THE ENERGY SAVING POWER OF DAYLIGHT HARVESTING
To achieve energy efficiency in affordable housing, electric lighting must be controlled. The simplest way is to ensure there is adequate daylight saturation so that electric lighting is used mostly at night. The more complex approach involves daylight harvesting through the use of photo sensors, timers or other central electronic control strategies.
A daylight harvesting system uses technology that automatically and gradually dims or increases interior lighting as the level of natural daylight changes throughout the day. These controls can also adjust the color temperature of light to mimic natural outdoor lighting and add to the comfort of occupants while saving energy.
Unlike occupancy sensing, which turns the lights down or off when the space remains unoccupied, daylight harvesting adjusts electric lighting based on the amount of natural light entering the room or the total amount of light—natural and electric—in a given space. To track and interpret changes in daylight, the daylight harvesting systems needs data that is provided by sensors but instead of motion sensors it uses photo sensors.
Daylight harvesting is one of the most powerful techniques for reducing electric lighting usage and boost energy savings. Even the simplest daylight harvesting strategy is a big step towards energy efficiency and sustainability in affordable housing.
To implement efficient daylight harvesting systems, designers should follow these steps:
- Conduct a daylight simulation and use these plans when designing the lighting system and its controls.
- Prepare plans that document daylight zones and establish independent control zones that work optimally with these patterns.
- Locate the photo sensor on the reflected ceiling plans and interior elevations.
- Identify light fixtures that are controlled by individual sensors or controllers.
- Write a daylighting controls narrative.
- Require the contractor to submit shop drawings based on design documents and control narrative for your review.
- Include the requirement for calibration of controls in the specifications, and require calibration logs to be submitted by the contractor.
- Provision building operator training by the controls manufacturer.
Daylight harvesting done right proves that green design is good business.
ADDITIONAL BENEFITS OF NATURAL LIGHT
The benefits of natural light go beyond ambiance and energy savings. Light has a greater effect of a person’s experience within a space than any other architectural design element, according to industry experts.
Natural light contributes to health, productivity, and sustainability. Research shows employees are happier, more productive and more engaged in work spaces with ample daylight. Happy employees stay, and higher retention rates lower the costs associated with employee turnover. Comfortable, happy employees also are more productive, which translates into higher profits.
Daylighting not only enhances employee satisfaction, performance, and learning, it can even impact retail sales. A study conducted by Heschong Mahone Group found retail sales were up to 40% higher in stores with skylights compared to those without any daylighting.
WHEN HISTORY AND INNOVATION MEET
Daylighting is not a modern phenomenon. Natural light has been an essential element of building design and architecture for centuries. Gothic cathedrals are great examples of daylighting.
However, natural light is not without its issues, and they must be addressed for a truly successful design:
- Privacy issues
To reduce glare, sunlight must be kept out of the field of view of building occupants while protecting them from disturbing reflections. Overheating can be dealt with by adding adequate exterior shading and filtering incoming solar radiation. Solving privacy issues requires creative ways to block or alter light patterns and compensate with other light sources.
Advances have been made and more surely are underway. Innovative architects will find new ways to incorporate natural light in their designs, simulate its effects indoors, and control electric lighting in order to contribute to the comfort, well-being, and satisfaction of occupants and those paying the electric bills.
Effective daylighting and daylight harvesting practices in affordable housing development—along with good design, modest goals, consistent maintenance, and follow-up—should result in significant energy savings and satisfied clients.
See how we successfully integrated efficient Daylight practices in our own corporate office design: