How to design an eaves before the sun. Sunning

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Introduction to sunlight and practical example of how to design an eaves before the sun.

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Introduction to sunlight and practical example of how to design an eaves before the sun.

In this article we delve into defining thesunning, its calculation and basic characteristics. Adopt measures of bioclimatic design in our projects it is an opportunity that we must not lose. Being able to take advantage of its benefits provides a multitude of advantages compared to constructions not designed in a coherent way.

To solve the case study of the calculation of an eaves first we will do a quick introduction and guide sunning in flat architecture for a better understanding of the exercise in a global way.

Sunning

Understanding and measuring the apparent path of the sun is a need that professionals must understand. We can define it as "Study that allows us to determine in what periods of the year and at what times an urban space or the different planes of a building receive direct solar radiation"

For a direct understanding of the sunning scheme and of the movement of the sun we present an interactive animation that will help us understand the inclination of the axis of rotation of our planet with respect to the plane of the earth's orbit around the sun: (By clicking on the image you access the application, we can see the four seasons and the path of our planet in front of the sun)

Now we must know the sun path placing ourselves in the center of the earth for which we have another interactive tool for sunning. (Both this tool and the previous one were created by The Nebraska Astronomy Applet Project and we can see the path of the sun in Buenos Aires, Spain or anywhere we want. We can access the interactive application to see the positions of the sun from HERE in the first image and the second from HERE. )

Solar diagram in perspective of the application where we see the path of the sun:

We should mention that the two intersecting curves in the animation are the Ecuador and theecliptic (curved line where the sun "passes"). To finish understanding all the aspects related to sunlight we can access this fantastic graphic manual HERE (Remember that it is explained from the positioning of Latin America, where the North is sunny and the South is shaded, the opposite of Spain)

How to design an eaves in front of the sun:

The simplest model is the design of a roof overhang. For this example we will be located in the city of Mar del Plata, Province of Buenos Aires, Argentina, with a south latitude of 38 ° and west longitude of 57.5 °. (We can consult the trajectory of the sun from anywhere in the world in a very useful portal that is sunearthtools.com where we will also find other useful applications)

If we see the image in which a sunshine diagramFor the city of Mar del Plata (Buenos Aires), we will observe that in the solar trajectory the sun rises around 30º towards the southeast in summer and another 30º towards the northeast in winter. Which presents us with a question…. How many times does the sun rise in the East?… Twice a year.

Another point to note is that the black line in summer runs for more than 14 h (Represented by the black dots) and in winter runs only a few hours, obtaining the variation of the length of the day.

The practical case lies in determining the height and length that our roof eaves will have to maximize the capture of direct solar energy in winter and protect us in the summer. For this you can use the graph of polar diagram or the next Cartesian diagram. (The Cartesian diagram of the solar path can be found for free at http://solardat.uoregon.edu/ as well as different tools that can help us to execute the sunshine diagram)

We can recognize in the previous image that:

Vertical axis = Marks the height in degrees from the horizon to the zenith.
Horizontal axis = At the center, locate the north.

The violet color of the image determines the angle that we want to prevent the sun from affecting us.Why do we adopt 53º to rule out sunlight and not other degrees?… The 53º are “arbitrary”, that is, it is to select the dates of the year that you need to protect yourself from the sun that will depend on each place where we carry out the project. With the dates and times you decide the angle to adopt.

Now, to be able to design the ceiling that covers the glazed surface (53º) we will have to work in plan and section like the following images.

To end, We will mark in plan where the ceiling ends (55º) and we will proceed to graph it in the cylindrical projection (Be careful with the orientation of the wall, the example is north). If we look at the graph we can see that some hours of intense sun - between 2:00 pm and 3:00 pm in summer - affect us. We could solve it by increasing the eaves to that side or with a vertical sunshade.

To understand more characteristics we can access the article on bioclimatic facades where we talk about the general aspects and orientation of the house.

Sunshine manuals

Basic notions about solar diagram… HERE.
A practical example in a building on the study of desolation and solar geometry… HERE.

We can learn more with the bioclimatic architecture articles and the urban bioclimatic design manual.

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Article prepared by Gabriel Salas (Architect - Teacher and / or researcher, lover of natural and sustainable life) Access to his website ggsalas.com. It should be noted that this article forms the union of two articles published on the portal Redminka. (Movement of the sun with interactive animations and How to design an eaves?)

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