Harnessing Solar Geometry and Natural Elements for Sustainable Design: A Bioclimatic Approach

Posted on Aug 21, 2024 in Geology

SOLAR COURSE: The Earth is the 3rd planet from the sun and is covered mostly by water. The atmosphere consists of nitrogen and oxygen. The temperature varies between -50 and 50 degrees Celsius, with an average of 22 degrees Celsius. Understanding solar geometry, ground motion, translation, Earth’s rotation around the sun, and the Earth’s rotation around its own axis is crucial for sustainable design. The Earth’s orbit is elliptical, and its axis of rotation has an angle of 23.45 degrees, which causes the seasons. December 21st corresponds to the summer solstice in the southern hemisphere, and June 21st is the winter solstice in the same hemisphere.

Sky:

Imagine a sphere located at the position of a building. As the sun moves, each point is marked on this imaginary vault. Tracing the path of all these points yields a day. The total displacement of the sun in its inclination goes from winter to summer with an angle of 49.6 degrees.

Solar Height Angle and Azimuth:

Solar height is measured in a vertical plane from a horizontal plane. Azimuth is measured in the horizontal plane. With both angles, the sun’s position can be defined at every instant.

Control of Direct Solar Radiation in Windows:

North-facing windows capture solar radiation, forcing us to look for ways to prevent heat gain. Eaves or projections are especially useful because they create shadows.

Natural Elements and Shadow:

The growth of plants in winter and spring can block the passage of direct radiation. Deciduous trees allow the entry of direct radiation in autumn and winter.

Dimensioning Eaves for North Orientation:

A horizontal element that prevents direct radiation can be mobile.

Sunscreens for East and West Orientations:

Horizontal elements do not work as effectively for east and west orientations. Lattice screens are a better option as they allow some light to enter the windows.

Heat Flow and Thermal Bioclimatic Design Aspects:

Thermal comfort is crucial for human well-being. The human body can maintain its temperature at 37 degrees Celsius. This heat has two sources: the air temperature and the temperature of surrounding objects and walls. The comfort temperature is around 20 degrees Celsius.

Several factors determine the thermal balance between the body and the environment:

• Physical: air temperature, temperature of nearby surfaces, relative humidity, air movement in contact with the body, and clothing thermal resistance.
• Physiological: body height and weight, and metabolism or production of body heat.

Several factors can contribute to achieving comfort in construction: the character of the place, local weather and seasonal design strategies, use, performance of materials, and strategies in their application.

Thermal Behavior of Materials:

Heat flow between objects or spaces occurs through:

• Conduction: heat transmission through the molecules of a solid.
• Radiation: heat transfer through electromagnetic waves.
• Convection: heat transfer through the movement of fluids (liquids or gases).

Thermal conductivity measures the amount of energy transferred through a material. Thermal transmittance measures all the heat transferred through a section of a material. Thermal resistance measures the opposition to the transfer of power put by the components of a building element. Thermal insulation offers several benefits:

• Saves energy and maintains interior comfort.
• Reduces the energy needs of a home at the country level, decreasing spending on oil and gas.
• Reduces public health expenditures.

The Alhambra Palace in Granada: A Case Study in Bioclimatic Design

Natural Ventilation and Cooling:

• Windows of the towers face each other and capture the wind from whichever direction it comes.
• Patio of the Lions: This courtyard features four filters: the patio itself, lush vegetation, fountains and canals, and a shaded porch that protects from the wind.

Light and Shadow:

• Uncontrolled climate: a window to the exterior landscape allows light to filter in and clearly marks its boundaries.
• Generalife: This courtyard recreates a paradise, engaging the senses with the smell of flowers, the sound of water and birds, the coolness of the shadows, the jets of the fountains, and the textures of plants, water, walls, and floors.
• Labyrinths, Andalusian patios, and narrow streets enhance the play of light and shadow.

Thermal Strategies:

In the palace and Arabic housing, rooms often overlook gardens, benefiting from the environmental conditions. The main room is typically located in a tower, and the courtyard creates a microclimate that is cooler than the outside environment. Evaporative cooling is achieved through water features and vegetation.

Three thermophysical elements are key to the Alhambra’s thermal comfort:

1. Circulation: Zenith windows heat the top of the space and initiate air movement. This creates natural ventilation.
2. Venturi Effect: The wind passes through the upper windows, creating air movement from the bottom to the top. Two levels of windows—at the top and at the bottom—and patios facilitate this effect.
3. Forced Wind Entry: Despite high exterior temperatures, the thermal behavior is much better in windy conditions. More ventilation leads to a more homogeneous air temperature. The shape of the tower promotes circulation, causing the air layer to be situated in the upper space, creating cross ventilation. The shape of the courtyard reduces air velocity. The portal allows both microclimates to remain strictly separated.

Natural Light in Architecture

Light behaves in three ways: reflection, transmission, and absorption. Light guides us and helps us understand the limits of space. Shadow allows us to perceive three-dimensional reality.

Light in the Natural Landscape:

We experience the beauty of light through phenomena like solar and lunar eclipses, the Aurora Borealis, the Aurora Australis, sunsets, rainbows, and the full moon.

Surfaces and the Action of Light:

• Reflection: the return of radiation incident on a surface.
• Specular reflection: occurs when the material has a very smooth surface; the angle of incidence is equal to the angle of reflection.
• Diffuse reflection: occurs when the surface material is rough.
• Mixed reflection: occurs in most materials, composed of both specular and diffuse reflection.
• Transmission: occurs when light passes through a material with a degree of transparency. Some materials transmit nearly all light (e.g., water, clear glass), while others transmit only a part (e.g., paper).
• Direct transmission: produced by transparent bodies, crystals, and glass.
• Diffuse transmission: produced by opalescent or frosted glass, resulting in less glare.

Sources of Natural Light:

• Daytime: direct sunlight, clear sky, clouds, reflections from buildings or floors.
• Nighttime: the moon and lightning.

Tips for Utilizing Natural Light in Design:

• Orientation of windows: depends on climate and location. North-facing windows generally gather better light, while south-facing windows also have good light but require careful consideration for managing direct radiation in the summer and maximizing it in the winter.