Which of the following factors in daylighting design determines the depth of light penetration into the space?

The height of the window, specifically the height of the window head (the top of the window), is the primary geometric factor that determines the maximum depth to which daylight can penetrate a space. A well-established rule of thumb in daylighting design states that the effective daylight zone extends into a room approximately 1.5 to 2.5 times the height of the window head from the floor. A higher window allows light to enter at a steeper angle, reaching further into the interior before striking the floor.

B. shading device: Shading devices are used to control direct sunlight, reduce glare, and manage heat gain. They typically reduce or modify light penetration rather than determining its maximum potential depth.

C. glazing material: Glazing material affects the amount (transmittance) and quality (color, diffusion) of light entering a space, but it does not determine the geometric path or depth of penetration.

D. reflective surface: Reflective surfaces, such as light shelves or high-reflectance ceilings, are strategies used to enhance and redirect light deeper into a space, but the initial potential depth is set by the window's height.

1. Whole Building Design Guide (WBDG). (2016

October 18). Daylighting. National Institute of Building Sciences. Retrieved from https://www.wbdg.org/resources/daylighting.

Reference Point: In the "Design Objectives" section

under "Sidelighting

" the guide states

"The depth of the daylight zone is about 1.5 to 2.0 times the head height of the window." This directly links window height to penetration depth.

2. Lawrence Berkeley National Laboratory (LBNL). (2013). Tips for Daylighting with Windows. Windows and Daylighting Group. Publication LBNL-5345E.

Reference Point: Page 11

under the section "Window Height

" states

"The higher the window is on the wall

the deeper the daylight will penetrate into the room." This confirms that window height is the key determinant for depth.

3. Lechner

N. (2014). Heating

Cooling

Lighting: Sustainable Design Methods for Architects (4th ed.). Wiley.

Reference Point: Chapter 15

"Daylighting

" Section 15.5

"Sidelighting." The text and accompanying diagrams (e.g.

Fig. 15.13) illustrate that the daylight penetration depth is a direct function of the window head height

establishing this as a fundamental principle taught in architectural and design university programs.