Daylight Factor calculation in courtyards

I recently published a very simple method to determine Daylight Factors within a courtyard. Daylight Factors determines the potential of natural light which reaches the center of the courtyard, to the corner or to the midpoint of the facade.

The development of this method is shown in the following article, published in Solar Energy. We are currently working in two papers more to determine the accuracy of this method, although the results are promising.

To calculate the Daylight Factors, you only need to introduce the dimensions of the courtyard (length, width and height) as well as the reflectance values of the inner surfaces.

The proper Daylight Factor depends on the location of the courtyard and the lighting requirements. Usually, the minimum Daylight Factor to reach a minimum illuminance of 250 lux is shown in the following table:

This method can be referenced as: I. Acosta, J. Navarro, J. Sendra, Predictive method of the sky component in a courtyard under overcast sky conditions, Solar Energy 89 (2013) 89-99.

See you soon.

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.

Luis Barragan: House-Studio

Great Masters

Luis Barragán (1902-1988) was the most important Mexican architect of his time and no doubt one of the most influential artists of the XX century.

After graduating as an architect, Barragán traveled to France and Spain, where he discovered traditional Mediterranean architecture, which influenced his architecture. Consequently, the work of Luis Barragán is infused with light, color, functionality and tradition, all essential qualities of architecture.

In 1947 he projected his residence, annex to a workshop, in Tacubaya, Mexico City, which was declared by UNESCO as World Heritage Site. Currently, the House-Studio is preserved as its author lived there until 1988.

But the key issue is: Why Barragan is considered a master of light? This question finds an answer in his most emblematic work: his house-studio.

Barragan distributed spaces of your home in an orderly manner, keeping coherence among all its parts, but each room is designed thinking in different lighting.

Thus, each room is defined by the light that is perceived: the library is bright, the dining room is intimate and the light is warm in the living room.

 

Great window in the library.

 Dinning room

Living room

Consequently, the light is an element that determines the function of space.

Furthermore, Barragan cares especially the relationship between light and color, creating different perceptions from the reflected light on color. Proof of this, is the hall where the author places a gilded mirror under a skylight that has two functions. On one side, the specular surface allows that light which is reflected in the mirror reaches the bottom of the hall. On the other hand the golden color of mirror transforms the reflected light with a warm color, even when the sky is cloudy.

The control of the hue of the light, from the reflection of light in the color, is a very common resource in the architecture of Barragan. Another example is observed in the skylight of the same project, where its inner walls are painted in yellow. Thus, the light that penetrates through the skylight is dyed as in the example of the mirror, with a warm color.

In conclusion, it is clear that Luis Barragán was a great master of the use of light in architecture.

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).