Window Design IV

Architecture Design

Below we will develop a brief study on the position and spacing between windows. So far we have conducted three previous notes, as follows:

Window Design III

Window Design II

Window Design I

In previous posts we have studied how the area and position of the window affects the daylight in a room. As we know, the amount of light that comes into a room is directly proportional to the surface of the window. We also know that as higher the window lintel, the deeper the light.

A study to develop is the spacing between windows. We are going to observe the office model where different vertical windows are located. The window is resized, keeping the height of the lintel and varying the spacing between the jambs:

As we can see, the windows that are located far apart leave dark areas between them, causing uneven illumination. Moreover, the closer windows allow greater uniformity of light.

Accordingly, we conclude that the optimal spacing between windows is ½ the height of the lintel. If the windows are separated more than that distance, dark areas occur. If the windows spacing is less than that measure, the uniformity is preserved.

This work has been developed by the New Buildings Institute, which has done a great job in collaboration with the University of Idaho and Washington. My sincere congratulations for this study.

I hope that with this final note we will know more about the design of windows. Much remains to be discovered, such as how to quantify light produced by a window, but these issues will develop in future extensive notes.

Greetings:

Window Design III

Architecture Design

I propose to delve a bit more in, probably, the most important architectural element in daylighting: the window. So far we have made two previous notes, as follows:

Window Design II

Window Design I

We will develop the study of the height of the window and how it influences in daylight. Below we can see the model of an office where a longitudinal window is located. The window size is changing from 10% of the façade surface to 75%:

As can be seen, the windows that are between 10 and 20% of the façade surface (equivalent to 4 and 8% of the floor area) hardly provide enough natural lighting.

A window which occupies between 30% and 40% of the façade surface (equivalent to 12 and 16% of the floor surface) achieves an acceptable illuminance, since approximately half of the office is over 300 lux. Windows of larger sizes allows higher luminance. This is shown in false color map that measures the reflected luminance:

Note that the higher the window lintel, the deeper the light, as we deducted in Window Design I.

This work has been developed by the New Buildings Institute, which has done a great job in collaboration with the University of Idaho and Washington. My sincere congratulations for this study.

We will continue studying the windows in the next notes.

Window Design II

Architecture Design

Before looking at the role of other architectural elements, we will delve into the behavior of daylight through windows.

5. - The amount of light is proportional to the window surface: This is a logical argument, because when the window has more surface greater amount of light enters the room [1].  In fact, the window surface is directly proportional to the level of illumination.

6. - The depth of light depends on the position of the window: This statement was already observed in the previous text: an upper window allows a deeper illumination, while avoiding the glare of the occupants [2]. Consequently, if we want the daylight reaches the back of the room, we need upper windows with large surface.

7. - The horizontal windows are better than vertical: Le Corbusier put it well ... The long windows allow more uniform lighting in the room, while the vertical windows create shadowy areas and produce a high contrast.

All these statements can be seen in numerous studies on lighting. Currently, it should be noted the research of Diepens et al. [3], which analyzes the light distribution of different windows in a room.

Later we will talk about the appropriate spacing between windows, to produce uniform illumination.

Greetings and see you soon.

[1] Navarro, J.: Sobre Iluminación Natural en Arquitectura. Universidad de Sevilla, 1983.

[2] CIBSE: Daylighting and Window Design. London: Chartered Institution of Building Services Engineers, 1999. Cap. 2.2.3.

[3] Diepens, J., Bakker, F., Zonneveldt, L.: Daylight design variations book. TNO-TUE Centre for Building Research (en desarrollo, última actualización Octubre 2000).

Window Design I

Architecture Design

Windows are an essential element in the architecture, as they provide daylight in the inner spaces. However, little is known about the design and proportion of openings to maximize natural light.

In this first chapter on windows I will introduce the basic principles for design. I will set rules very simple and basic, that anyone can follow. In later chapters, we will study the quantification of light by a window.

1. - The daylight coming through a window is very unevenly distributed. The more illuminated surface is observed in the area close to the opening and it extends to a distance equivalent to the height of the lintel. Bellow, I show the lighting study (specifically the daylight factors, a concept to be discussed later) seen in a room with a window that represents 20% of the front surface [1]. As can be seen, the highest enlightenment is next to the window and decreases with increasing distance from it.

2. - Accordingly, it can be concluded that the optimum illumination which is provided by a window is equal to twice the height of the lintel. This is important to remember: the depth of light depends exclusively on the height of the window lintel [2].

3. - Other studies [3] conclude that the lighting in a room can be divided into five sections, depending on the height of the window, as shown in the following figure. Thus, for a centered window, the optimum illumination is observed at twice the height window or once the height of the lintel.

4. - Finally, it should be noted [4] that the bottom of a room may seem dark when the ratio of the illumination of the front half of the room between the illumination of the back half is greater than 3.

And that's all for now. We have much to talk about lighting through windows, I will gradually write more about them.

[1] Acosta, I., Campano, M., et ál.: Daylight in window design: optimization of proportion and position under overcast sky conditions. Portugal, Lisbon: 5th International Congress on Energy and Environment Engineering and Management, 2013.

[2] Baker, N., Steemers, K.: Daylight: Design of Buildings. James & James, 2002.

[3] Martín Monroy, M.: Manual de la Iluminación. Ay. Las Palmas de Gran Canaria, 2006. p. 42.

[4] Lynes J. A.: Principles of natural lighting. Elsevier, 1968.