// CODE SNIPPET
808.3 Daylit Area of Building Spaces
Go To Full Code Chapter
In buildings not greater than two stories above grade, not less than 50 percent of the net floor area shall be located within a daylit area. In buildings three or more stories above grade, not less than 25 percent of the net floor area shall be located within a daylit area. Buildings required to have more than 25,000 square feet (2323 m2) of daylit area shall comply with Section 808.3.2. All other buildings shall comply with either Section 808.3.1 or Section 808.3.2.
Exception: For buildings not less than three stories above grade with obstructed exterior walls or shaded roofs, the required daylit area shall be modified in accordance with Equation 8-1.
| Required daylit area ≥ 25% × TDP | (Equation 8-1) |
The total daylight potential (TDP) is a weighted average of the individual daylight potentials for each floor:
| TDP | = | Σ(DP1 ÷ FA1/TF) + (DP2 ÷ FA2/TF) + … |
For floors with roof area immediately above:
| DP1, 2 ... | = | 1 — [(OW1/TW1) × (OR1/TR1)] |
For floors without roof area immediately above:
| DP1, 2 ... | = | 1 — (OW1/TW1) |
| OW1, 2 ... | = | The length of obstructed exterior wall for each floor that does not face a public way or a yard or court complying with Section 1206 of the International Building Code or where the distance to any buildings, structures, or geological formations in front of the wall is less than two times the height of the buildings, structures, or geological formations. For the purposes of this determination, the maximum allowed heights of buildings or structures on adjacent property under existing zoning regulations is permitted to be considered. |
| TW1, 2 ... | = | The total length of exterior wall for each floor. |
| OR1, 2 ... | = | The roof area immediately above each floor that is shaded during the peak sun angle on the summer solstice by permanent features of the building, or by permanent features of adjacent buildings. |
| TR1, 2 ... | = | The total roof area immediately above each floor. |
| FA1, 2 ... | = | The total floor area of each floor. |
| TF | = | The total building floor area. |
808.3.1 Daylight Prescriptive Requirements
Daylit areas shall comply with Section 808.3.1.1 or 808.3.1.2. For determining the total daylit area, any overlapping daylit areas shall be counted only once.
The total daylight area shall be the sum of the area of all sidelighting daylight zones and the area of all toplighting zones, except that sidelighting daylight zones shall not be included in the calculation of the area of toplighting daylight areas.
808.3.1.1 Sidelighting
The daylit area shall be illuminated by fenestration that complies with Table 808.3.1.1 and Figure 808.3.1.1(4). Where fenestration is located in a wall, the daylit area shall extend laterally to the nearest 56-inch-high (1422 mm) partition, or up to 1.0 times the height from the floor to the top of fenestration facing within 45 degrees (0.785 rad) of east or west or up to 1.5 times the height from the floor to the top of all other fenestration, whichever is less, and longitudinally from the edge of the fenestration to the nearest 56-inch-high (1422 mm) partition, or up to 2 feet (610 mm), whichever is less, as indicated in Figure 808.3.1.1(1). Where fenestration is located in a rooftop monitor, the daylit area shall extend laterally to the nearest 56-inch-high (1422 mm) partition, or up to 1.0 times the height from the floor to the bottom of the fenestration, whichever is less, and longitudinally from the edge of the fenestration to the nearest 56-inch-high (1422 mm) partition, or up to 0.25 times the height from the floor to the bottom of the fenestration, whichever is less, as indicated in Figures 808.3.1.1(2) and 808.3.1.1(3).
| EA = (AF × VT)/DA | (Equation 8-2) |
where:
| EA | = | Effective aperture. |
| AF | = | Area of fenestration. |
| VT | = | Visible transmittance of the fenestration. |
| DA | = | Daylit area. |
TABLE 808.3.1.1
MINIMUM EFFECTIVE APERTURE
MINIMUM EFFECTIVE APERTURE
| SKY TYPE | MINIMUM EFFECTIVE APERTURE (percentage) | ||
| Sidelighting from fenestration in a wall [see Figure 808.3.1.1(1)] | Sidelighting from rooftop monitor [see Figures 808.3.1.1(2) and 808.3.1.1(3)] | Toplighting (see Figure 808.3.1.2) | |
| Aa | 10.0 | 5.0 | 1.0 |
| Bb | 12.0 | 6.0 | 1.2 |
| Cc | 16.0 | 8.0 | 2.2 |
- Sky Type A — more than 75 percent mean sunshine, in accordance with the NOAA Annual Mean Sunshine Percentage Table.
- Sky Type B — 45 percent to 75 percent mean sunshine, in accordance with the NOAA Annual Mean Sunshine Percentage Table.
- Sky Type C — less than 45 percent mean sunshine, in accordance with the NOAA Annual Mean Sunshine Percentage Table.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.017 rad.
For SI: 1 inch = 25.4 mm.
FIGURE 808.3.1.1(2)
DAYLIT AREA ADJACENT UNDER A ROOFTOP MONITOR
DAYLIT AREA ADJACENT UNDER A ROOFTOP MONITOR
For SI: 1 inch = 25.4 mm.
FIGURE 808.3.1.1(3)
DAYLIT AREA ADJACENT UNDER A ROOFTOP MONITOR
DAYLIT AREA ADJACENT UNDER A ROOFTOP MONITOR
FIGURE 808.3.1.1(4)
SKY TYPES
SKY TYPES
808.3.1.2 Toplighting
The daylit area shall be illuminated by a roof fenestration assembly such as a skylight, sloped glazing or tubular daylighting device that complies with Table 808.3.1.1 and Figure 808.3.1.2. The daylit area extends laterally and longitudinally beyond the glazed opening of the roof fenestration assembly to the nearest 56-inch-high (1422 mm) partition, or up to 0.7 times the height from the floor to the bottom of the rough opening of the daylighting well, whichever is less, as indicated in Figure 808.3.1.2. 
For SI: 1 inch = 25.4 mm.
FIGURE 808.3.1.2
DAYLIT AREA UNDER A SKYLIGHT
DAYLIT AREA UNDER A SKYLIGHT
808.3.2 Daylight Performance Requirements
Each daylit area shall comply with the requirements of either Section 808.3.2.1 or 808.3.2.2. Daylight analysis shall be conducted in accordance with Section 808.3.2.3.
808.3.2.1 Morning Illumination
Not less than 28 foot-candles (300 lux) and not more than 418 foot-candles (4500 lux) of natural light shall be available at a height of 30 inches (750 mm) above the floor 3 hours before the peak solar angle on the spring equinox.
808.3.2.2 Afternoon Illumination
Not less than 28 foot-candles (300 lux) and not more than 418 foot-candles (4500 lux) of natural light shall be available at a height of 30 inches (750 mm) above the floor 3 hours after the peak solar angle on the spring equinox.
808.3.2.3 Daylight Analysis
A daylight analysis shall be performed that complies with the following:
- Sky conditions shall be assumed to be clear.
- Address the effects of exterior shading devices, buildings, structures, and geological formations on the fenestration of the proposed building and on the ground and other light reflecting surfaces. Include the effects of movable exterior fenestration shading devices. The configuration of fenestration with automatically controlled variable transmittance shall be adjusted to accurately represent the control system operation.
- Exclude the effects of interior furniture systems, shelving, and stacks.
- Use the actual reflectance characteristics of all materials.
- Where blinds, shades and other movable interior fenestration shading devices are included in the analysis and the exact properties of such devices cannot be accurately modeled, such devices shall be assumed to be completely diffusing, with a visible transmittance of 5 percent for fabric shades, and 20 percent for horizontal or vertical blinds.
- Calculation points shall be spaced not more than 39.4 inches (1 m) by 39.4 inches (1 m). The calculation grid shall start within 20 inches (508 mm) of each wall or partition.
- Where details about the window framing, mullions, wall thickness and well depth cannot be included in the model, the visible transmittance of all fenestration shall be reduced by 20 percent.
Upcodes Diagrams
Related Code Sections
808.3 Indoor Environmental Quality and Comfort, Daylit Area of Building Spaces
In buildings not greater than two stories above grade, not less than 50 percent of the net floor area shall be located within a daylit area. In ...
808.3.2.1 Indoor Environmental Quality and Comfort, Morning Illumination
Not less than 28 foot-candles (300 lux) and not more than 418 foot-candles (4500 lux) of natural light shall be available at a height of 30 inches ...
808.3.2.2 Indoor Environmental Quality and Comfort, Afternoon Illumination
Not less than 28 foot-candles (300 lux) and not more than 418 foot-candles (4500 lux) of natural light shall be available at a height of 30 inches ...
608.5 ENERGY CONSERVATION, EFFICIENCY AND CO2e EMISSION REDUCTION, Automatic Daylight Controls
controls. Exception: Automatic daylight controls are not required for the following spaces and equipment: Toplighting daylit areas where the skylight ...
Section 808 Indoor Environmental Quality and Comfort, Daylighting
not greater than two stories above grade, not less than 50 percent of the net floor area shall be located within a daylit area. In buildings three or more ...