The principle of bioclimatic architecture is very simple: it aligns construction practices with the surrounding climate, environment and ecosystem.In the past, architects considered natural elements such a climate, landscape, sun or wind orientation… to be important indicators in the building process.

These bioclimatic considerations were sometimes forgotten during the 1950’s and 60’s, when there was a great and urgent need for accommodation.Today, due to the high prices of electricity, oil and gas, the timeless principles of bioclimatic architecture are being reintroduced in order to reduce the energy needs of a structure, maintain comfortable temperatures, control humidity levels and maximize natural lighting.

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To achieve this aim, a bioclimatic approach mainly relies on the location, orientation and insulation of each room. It aims at protecting buildings from cold winds and heavy rain. It also mainly uses solar energy, in the form of light or heat, in order to consume the least amount of energy while providing the best level of comfort.

Bioclimatic architecture is therefore based on the following three pillars: capturing, distributing and storing solar heat.

Location and Orientation

A bioclimatic house faces south, with as much glass surface as possible exposed to sunlight. The ideal location is the sunny side of a hill or mountain, halfway between the valley floor, where thereis not be much sun, and the summit, where the building will be lashed by the wind.

The house is to be protected from cold climatic elements, such as the north rain and wind. It can be sheltered by an embankment, a tall hedge of evergreen trees or even “buried” under the ground. Obviously, windows, doors and main rooms should be limited on the northern side of the house. Less used rooms facing north can serve as a thermal buffer zone between the outside and the main living area.The most used rooms of the house should be located facing south, where it can take full advantage of the natural light and heat of the sun.

It is also advised to equip the main entrance to the house with an airlock entry which limits the output of warm air every time the front door is opened in winter. It is also very useful in summer as it then prevents hot air from entering the house.

Capturing the Heat

During the cool season, a bioclimatic house needs to capture solar heat. In winter, in the northern hemisphere, the sun rises in the East and sets in the southwest. It remains low in the horizon throughout the day. To pick up it radiations, windows must be oriented to the south.

Glass lets the sunlight in, absorbs solar heat and traps it inside the house, it is what is called the greenhouse effect. This concept is called passive solar energy: “solar” because the energy source is the sun, “passive” because the system works alone without mechanical assistance.

During the hot season, the bioclimatic house must be protected from overheating. In the northern hemisphere, the sun rises in the East and sets in the northwest. It is high in the sky at noon. To prevent sunlight from entering the house, windows need to be covered with shutters or sunshades. You can also plant deciduous trees that will offer shade on the southern facade of the house in summer and let the sun rays pass in winter.

Storing the Heat

Once the heat is collected, the goal is to store it and use it when needed. This is possible thanks to two complementary principles.

The first one being that bioclimatic houses are usually equipped with thick walls made of materials displaying high thermal inertia (concrete, stone, earth ...).They store a large amount of heat during the day and release it at night or during colder periods. They help smooth the inside temperature of the house throughout the year in order to avoid high temperatures during the day or summer and drops at night or during winter.

The material should rather be of a darkish shade in order to prevent it from simply reflecting the light without converting it into heat. It should not, however, be too dark, at the risk of heating up the house to unpleasant temperatures. A brown or terracotta color is a good compromise between thermal performance and aesthetic appearance.

The second principle to storing heat and preventing it from leaving a bioclimatic house is good thermal insulation. Insulating the roof is a priority, as it usually represents between 30 and 40% of a house’s heat loss, but the walls, windows and floors should not be neglected either.

Diffusing the Heat

For good thermal comfort, heat must be distributed throughout the house. Heat distribution is achieved by means of 'thermal masses', building components such as floor, wall, covering or partition, which can store daytime heat and release it at night.

To distribute the heat throughout the entire house, air circulation or ventilation is also essential, especially in a well-insulated house. Not only is it a performant heat transfer medium, but it is also a good means to ensure a high quality of indoor air.

Ventilation plays an important role in evacuating stale or humid air and replacing it with fresh air. Stale air requires to be extracted,for instance, from the kitchen, bathroom and toilet for instance, while fresh air needs to be injected into the living room and bedrooms.

The Life Cycle of Materials

In order to reduce the environmental impact of a construction, the life cycle of all the materials used in the building of a bioclimatic house need to be taken into consideration. This is called eco-construction: considering the thermal properties of the materials and their impact on the environment. What resources and components are used to manufacture the material?Is the material local? Can it be recycled?

Depending on the peculiarities of each habitat, personal requirements and priorities, multiple options are available. Each bioclimatic building should take into account the opportunities and constraints of the environment,along with the full life cycle of the materials and techniques used in the realization and destruction of the house.

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