Solar Energy

Bioclimatic strategies in architecture

Bioclimatic strategies in architecture

Bioclimatic architecture strategies are based on three axes:

  • Capture solar radiation and use it for domestic activities.

  • Transmit solar energy and protect it.

  • Save energy or evacuate it according to needs.

Bioclimatic architecture aims to obtain the conditions of thermal comfort in a home by taking advantage of natural resources. In this way, it is possible to air-condition the house with a much higher energy efficiency.

These requirements are essential, especially in warmer regions (such as the Mediterranean). In these regions, the capture and conservation of energy in winter seems to contradict protection and evacuation in summer.

Bioclimatic strategies in architecture vary slightly when it comes to hot climates or cold climates.

A fundamental characteristic is the use of passive solar energy avoiding the presence of mechanical systems. The main source of energy for a passive home is the Sun. 

Strategies for capturing and protecting yourself from solar heat

Large areas of glass are often useful in temperate areas to capture direct radiation from the Sun.

The Earth is inclined on its axis with respect to the plane of the ecliptic at an angle of 23 ° 27 '. The height of the sun on the horizon and the path it travels in the sky vary during the seasons.

South facade in winter

In the northern hemisphere, at the latitude of Europe (around 45 ° on average), in winter, the sun rises in the southeast and is in the southwest, staying very low on the horizon (22). ° on the winter solstice). Only the southern façade of a building receives adequate sunlight.

To capture this solar energy, it is appropriate to place the main glazed openings to the south.

The glass lets in light, but absorbs the infrared re-emitted by the interior walls that receive this solar radiation, which is called the greenhouse effect. Solar radiation is converted into heat by the opaque surfaces of the building (walls, ceilings and floors).

Strategies for the summer

Even in the northern hemisphere, in summer, the sun rises in the northeast, is in the northwest, and is high on the horizon at noon. The facades of a building irradiated by the Sun are mainly the east and west walls, as well as the roof.

The angle of incidence of rays on south-facing glass surfaces is high. It is advisable to protect these glazed surfaces with solar protections to block direct solar radiation in summer and leave maximum sunlight available in winter.

In the openings of the east and west facades, the horizontal solar shading has a limited effectiveness, because the solar rays have a lower incidence. Opaque sunscreens (shutters), and even more deciduous vegetation, are effective on these facades.

Persistent vegetation is also effective in shielding cold winds, as long as it is not opposed to the winter sun.

In summer it is convenient to generate a night ventilation system to take advantage of the lower outside temperature. Through natural ventilation (using the cross ventilation technique) we will be able to renew the hot air from the inside with fresh air from the outside.

Bioclimatic construction in the northern hemisphere

In the northern hemisphere, at European latitude, a bioclimatic construction is characterized by:

  • Large openings in the south, perfectly protected from the summer sun.

  • Very few openings to the north

  • Few openings to the east, except for early-use rooms, like kitchens: morning sun.

  • Some openings to the west, especially for bedrooms, to protect from the setting sun in the summer.

In a bioclimatic approach, these generalities must be adapted naturally according to the environment (climate, environment, ...) and the rhythm of life of the users of the building.

How to transform and diffuse heat in a home?

Once sunlight is captured, a bioclimatic building must know how to convert it into thermal energy and distribute it where it is useful.

The transformation of solar radiation into heat is carried out through a certain number of principles, so as not to deteriorate interior comfort:

  • Maintain an adequate thermal balance.

  • Do not degrade the light quality.

  • Allow thermal diffusion through the ventilation system and the thermal conductivity of the walls.

In a construction, heat tends to accumulate upwards from the premises by convection and thermal stratification. Conversion to heat from light should be done primarily at ground level. 

Under a temperate climate, a bioclimatic building optimally designed from a thermal point of view requires little or no heating or air conditioning systems.

The absorption of light by a wall makes it dark and limits its ability to diffuse this light. This absorption should not prevent the scattering of light in less illuminated areas, and should not generate contrasts or reflections.

Good heat diffusion (or coolness) can also be achieved by proper ventilation methods.

To spread the color correctly it is important to:

  • favor very light ceilings to diffuse the light in the rooms without glare

  • darken the floors to promote energy capture at this level

  • use variable tones on the walls according to the priority given to the diffusion of light or the capture of solar energy, and according to the need for heat or freshness of the place in question.

What are the ideal colors to absorb heat?

The shades that are most likely to convert light into heat and absorption are dark (ideally black) and rather blue, those that are most capable of reflecting light and heat are light (ideally white) and quite red. Thus, one can, by means of a simple play of colors, direct the light and then the heat towards the areas that require it.

Matte materials with a granular surface (particularly natural materials) are also better at capturing light and converting it into heat than smooth, shiny surfaces (mirror effect, metallic or lacquered appearance, etc.).

How to keep warm and cool in a home?

In winter, once captured and transformed, solar energy must be conserved inside the building so that it can be used in a timely manner. In summer, it is the night-time coolness (easily detected with good ventilation) that needs to be stored durably to limit overheating during the day.

The simplest method is to use heavy building materials to store this energy as they have a higher thermal inertia. In this case, these materials should not be covered with thermal insulation, hence the importance of insulation. From the outside, or possibly the distributed insulation.

Valuing the environment

The environment (hills, forests, ...), as well as the vegetation planted around the construction also have a protective role: as windbreaks. A water point in front of the building, to the south, will also provide a one or two degree refresh in summer.

In architecture there are strategies to take advantage of natural resources to obtain thermal comfort in a home and reduce electricity consumption.

Data de publicació: March 29, 2021
Última revisió: March 29, 2021