Common daylighting techniques include solar tubes (or light tubes), light shelves, clerestory windows and skylights. See definitions in the Vocabulary section, as well as more information below.

Psychological Effects of Daylighting

Exposure to natural light is an important aspect of healthy living. In fact, daylight triggers the release of the chemical serotonin within the human eye; serotonin is essential for our emotional well-being. Also, healthy levels of serotonin often lead to higher levels of attention and alertness. Minimal exposure to daylight can often lead to mood disorders such as seasonal affective disorder (SAD). In addition to the benefits of visible natural light, ultraviolet radiation from the sun creates Vitamin D through our skin, providing myriad health benefits.

Solar Tubes

Installed between the roof and interior ceiling, solar tubes capture daylight, refract and reflect it through a tube, and disperse the light to an interior space using a diffuser. These "light tubes" are often preferred over skylights because they are easier to install, take up less space, and provide just as much lighting. The exposed portion on the roof consists of a dome that collects and refracts as much sunlight as possible from as many different directions as possible. The tube itself is lined with a highly reflective material to help light travel through with minimal loss. At the other end of the tube, the light passes through a diffuser that disperses it throughout the interior space. See an installation diagram at Quality Domains Limited website: http://www.solartubelight.co.uk/solar-tube-installation.html.

How light shelves work: (left) In a room with big windows and a light shelf, (1) the light shelf shades the space near the big window from glaring direct light, and reflects indirect (non-glare) daylight into the space to broadly illuminate the room. (2) A light-colored ceiling further improves the reflection of light into the room. (right) Exterior view of example light shelves. click for copyright

Light Shelves

Light shelves are (sometimes adjustable) reflectors installed on windows on the equator-facing side of a structure. They use a reflective metal or white surface to reflect daylight directly onto the ceiling of an interior space, resulting in a large amount of natural light supplied to the entire space by being dispersed onto the ceiling. A natural light shelf is created in the winter when sunlight is reflected off snow-covered ground and into the structure.

Daylighting examples: (left) Clerestory windows and ample side windows provide excellent lighting and views for a work space. (right) Windows, skylights and door windows help to illuminate a bathroom. click for copyright

Clerestory Windows

Clerestory windows are narrow windows located on the upper walls of an interior space. They provide a direct light path to the polar-side and allow for a significant amount of natural light when oriented correctly. On the inside, surrounding the windows with light-colored walls helps to diffuse the light more evenly.

Skylights

A skylight is simply a window cut into the roof of a structure, with a flat, dome- or pyramidal-shaped exterior casing. Skylights admit a great deal of natural light into an interior space, but have some drawbacks, such as heat loss /gain, condensation, and potential for water and ventilation leakage. Care must be taken to address these issues during installation, otherwise the skylight could cost more than it is worth, and thereby decrease overall energy efficiency.

Solar Geometry

Everywhere on the planet, the tilt of the Earth on its axis and your location relative to the equator result in sun paths that change throughout the year. To maximize daylighting, the orientation of the building and position of the sun must be considered when deciding exactly where to place windows. Then, to design any type of system that relies on solar radiation, it is important to take into consideration the seasonal and hourly changes in position of the sun, which directly influence the incident angle of sunlight, and if possible, incorporate a system that can adjust to the position of the sun.

Modeling daylighting: (left) A small model of an office space with a venetian blind (right) is rotated relative to a fixed sun source, enabling engineers to make measurements that can be used to predict interior illuminance levels for any sun and sky conditions. click for copyright

Modeling Daylighting

Engineers use physical models to analyze daylighting performance. Even simple models can provide information on how daylight will behave in a building. The best results come from models that are detailed and accurate in their daylight openings and material reflectance. They may be tested on the actual site or with artificial laboratory lighting that can simulate light angles during different times of the year. Engineers also create and use computer simulation models to test daylighting solutions by using 3-D digital models made with CAD (computer-aided design) software applications. Many of these programs produce realistic renderings of the proposed daylighting design.

• Gather materials.
• Make copies of the Daylighting Design & TechniqueWorksheet, Solar Azimuth vs. Elevation Plot Handout and Solar Geometry Handout, one each per group.

1. Discuss daylighting techniques used in various types of architecture, such as windows, solar tubes, light shelves, clerestory windows and skylights.
2. Explain the importance of solar geometry in designing the daylighting system for the house. Refer to the Solar Azimuth vs. Elevation Plot Handout, as appropriate. Refer to the Solar Geometry Handout for a more detailed explanation.
3. Divide the class into groups of two or three students each.
4. Give each group a worksheet and two handouts.
5. Have the groups follow along with Part 1 of their worksheets to design their model houses.
6. Have students incorporate one or many forms of daylighting into their design (Part 2 on the worksheet).
7. Have students gather all materials as specified in their model house designs.
8. Have students build their designed model house. Refer to the example model house procedure, below.
9. Once teams have finished their models, have each group test their house under the desk lamp, following along and completing Part 4 of the worksheets.
10. Have each group present their model to the class, explaining each type of daylighting used, as well as observations made during testing.
11. Have the groups complete their worksheets.
12. Conclude by leading a class discussion to review the worksheet answers. Incorporate the questions provided in the Assessment section. As time permits (or as a homework assignment), ask students to re-engineer their daylighting system, as described in the Assessment section.

1. Cut out a house base according to your scale and design. Scale the model house so that it is ~1,000 sq ft (~93 sq m). Recommended scale: 1 in = 3ft (or ~2 cm = 1m).
2. Measure and cut board pieces for all exterior and interior house walls.
3. Measure and mark windows and other daylighting holes to be cut out of walls, ceilings and roofs. Use the X-Acto knives to cut out all holes (see Figure 1). Be neat in making the window cuts, saving the pieces to make light shelves later.

Figure 1. Cut out daylighting openings for windows in walls (left) and solar tubes in ceilings (right). click for copyright

4. Cover window openings with packing tape, or other transparent film (see Figure 2).
5. Use hot glue to attach walls to the base of the house (see Figure 2).

Figure 2. (left) Use clear tape to represent glass for window openings. (right) Use hot glue to attach the walls to the model house base. click for copyright

6. To create a solar tube:: Determine the ceiling member that the tube will extend through. Create the bottom of the tube from a strip of thick paper wrapped in aluminum foil. Curl it and position it in the opening; secure it with hot glue (see Figure 3).

Figure 3. (left) Ceiling with cut-out hole for solar tube. (middle) Solar tube base sized to line the hole with reflective material. (right) Solar tube base installed. click for copyright

7. Extend the tube to the spot at which you want it to emerge on the exterior of the model (roof), curving as necessary along the way (see Figure 4).

Figure 4. (left) Curve the upper part of the solar tube above the ceiling, through the attic space. (middle) Further extend the solar tube through and above a hole in the roof board. (right) Interior view of the finished solar tube in the ceiling. click for copyright

8. After placing a roof on the model, cover the exposed top and bottom parts of the tube with packing tape to secure (see Figure 4).
9. To create light shelves: Gather the leftover pieces of foam core board from cutting out the window openings. For each light shelf, cut a piece of plastic drinking straw to the width of its window.
10. Use hot glue to adhere the straw pieces to the bottom edges of the foam core board pieces. Straighten out a paper clip and string it through the straws attached to the light shelves (see Figure 5), making a hinge.

Figure 5. (left) Light shelves ready to be attached to an exterior wall. (right) Adjustable light shelves attached to the model house. click for copyright

11. Use a glue gun to adhere the paperclip wire holding the light shelves to exterior walls of the desired windows, making sure to allow for rotation of the shelves (see Figure 5).
12. Glue paperclips to the roof, directly above each light shelf/window. Attach a piece of string to each shelf that is long enough to extend beyond the roof paperclips; this permits adjustment of the shelf angle by tightening or loosening the string (see Figure 5).

Figure 6. Seal up all the edges and corners to prevent light infiltration. Test for daylighting effect. click for copyright

13. To finish up the model house, close in all sides of the structure except for one, from which to make observations.
14. Use electrical tape to seal up all corners, edges and cracks so light does not leak into the structure (see Figure 6).

Sketch Discussion: Sketch the Figure 7 images on the board. For each design, have students explain the path that daylight will follow to get to the inside of the house. Use arrows to show the path of light entering the building. Extend the discussion to each of the designs as real-world daylighting technologies, exploring the amount of natural lighting each device provides within a structure. Ask the students.

• How do these daylighting techniques bring light into a structure? Where will the light go? (Answers: Solar tubes capture sunlight from all different angles throughout the day. They refract and reflect the light through the tubing, down to the ceiling opening where it is diffused throughout the room. Light shelves directly reflect sunlight through the windows onto the interior ceiling, which reflects the light into the rest of the interior space. Clerestory windows allow light to enter directly into the upper part of a room where it reflects off walls and becomes completely dispersed through the room. These windows bring in lots of natural light because they are so big.)

Figure 7. How do these daylighting techniques bring light into a structure? Left to right: solar tube, light shelf, clerestory windows. click for copyright

Worksheet: Have students complete the Daylighting Design & TechniqueWorksheet; review their answers to gauge their mastery of the subject.

Re-Engineering: Ask students how they could improve the daylighting system in their model houses and have them sketch or test their ideas.

Class Discussion: Ask students the following questions and discuss as a class.

• What are some examples of daylighting techniques used in buildings that you have observed? (Possible answers: Solar tubes, light shelves, clerestory windows, skylights, atrium windows, sliding glass doors, transparent portions of doors, Dutch doors, portholes, passive solar orientations, etc.)
• Why is it worth the trouble for engineers to design a system that lets natural light into a structure? (Answer: By bringing in natural light, we reduce the need for artificial lighting, which then reduces consumption of electricity and costs less for the inhabitants. It also helps to create a more pleasant and atmosphere with better overall illumination of inside objects and surfaces.)