Health and Biohabitability
9 principles of bioclimatic architecture
Fundamentals and strategies for delivering net-zero energy buildings
We understand bioclimatic architecture as architectural design that takes advantage of favourable climatic conditions and the surrounding natural environment in which it is located, using locally sourced materials.
It involves integrating architectural solutions into the design process that optimise climatic resources and ensure home comfort.
Bioclimatic architecture represents a shift in approach compared to conventional architecture of recent decades. Buildings no longer turn their backs on nature; they interact with it. The configuration of spaces, orientation and openings, materials and colours, and the building’s own form are among the factors to consider in order to carry out a proper bioclimatic analysis.
Building according to bioclimatic design guidelines makes it possible to minimise the environmental impact of buildings. It is, therefore, an essential shift in mindset to help curb climate change.
OBJECTIVES OF BIOCLIMATIC ARCHITECTURE
Choosing a type of construction that incorporates the principles of bioclimatic architecture brings a range of benefits—not only for the environment, but also for the building’s occupants. A bioclimatic building creates healthy spaces, improving users’ quality of life.
Moreover, making the most of naturally available resources such as sun, vegetation, rain, or wind helps reduce environmental impact by limiting the building’s negative effects on its surroundings. In turn, this integration of the built space into the natural landscape results in buildings that are visually more harmonious.
Optimising site conditions, in addition to being a way of adapting to the environment, makes it possible to integrate passive energy-saving solutions. Therefore, bioclimatic architecture supports NZEB buildings—Nearly Zero Energy Buildings—i.e., energy efficiency, which is one of the key factors of sustainable architecture. [1]
BIOCLIMATIC ARCHITECTURE AND PASSIVE ARCHITECTURE
Bioclimatic architecture and passive architecture are two concepts that, although related, have different meanings that allow them to be distinguished. Both fall within the framework of sustainable architecture, focused on building with respect for the environment. Sustainability refers to architecture that endures over time without depleting non-renewable resources.
In this case, passive architecture focuses essentially on the idea of energy efficiency and the strategies implemented so that the building does not require an active energy input for its use and operation. This is possible, in part, thanks to bioclimatic design, which makes it possible to achieve comfort in the home throughout the year without the need to activate any additional mechanisms.
By contrast, bioclimatic architecture focuses more on the building design process itself, from the project’s conception phase through to construction. It seeks to make the most optimal use of environmental benefits by studying climatic conditions and local materials in depth and using all these factors to its advantage.
In other words, the concept of bioclimatism could be understood as going beyond the concept of passive architecture, in which only energy factors are considered, to go one step further in integration with the surroundings by making the most of available resources—whether climatic or material—in a given location. [2]
Thus, bioclimatic architecture is the design of living spaces that adapt to the climate and resources of the place where they are built—something that could be read as the most essential definition of what architecture should be.
THE 9 PRINCIPLES OF BIOCLIMATIC ARCHITECTURE
To design a building from a bioclimatic perspective, it is essential to adopt a holistic design approach, considering multiple factors that will be involved in the design, construction, and use phases of a building.
We have compiled the 9 principles of bioclimatic architecture, which make it possible to design built environments adapted to living beings, climatic conditions, and a place’s resources. [3]
MEDITERRANEAN CLIMATE
The concepts explained below are adapted to a Mediterranean climate. This type of climate is characterised by temperatures around 20°C throughout the year. Winters are mild and rainy—temperatures around 10°C—while summers are hot and dry—with an average temperature above 22°C. Peak rainfall usually occurs in autumn and spring.
In addition, it is important to consider the hemisphere in which the building is located, understanding that when we refer to south-facing solar gain, we are assuming a building located in the Northern Hemisphere. For buildings located in the Southern Hemisphere, solar gain is achieved with a north-facing orientation.
1. SOLAR GAIN and SOLAR PROTECTION
Solar gain
The star around which we revolve—the Sun—is the main source of life, light, and energy on our planet; it is an inexhaustible source available from any point on Earth.
Therefore, as it is an inexhaustible energy source, using solar radiation for energy-efficiency purposes is an obvious resource to draw on when designing a home.
To achieve significant levels of energy use, it is important to bear in mind that the main solar-gain surfaces are the building’s openings. In this way, the home’s orientation and the size of the openings become key factors to decide in an architectural project.
The building’s orientation is a strategic point for ensuring good bioclimatic design. Knowing the hemisphere in which we are located, it is advisable for the building’s openings to face, as far as possible, south, as this is the orientation that receives the most direct radiation throughout the year.
In winter, due to low temperatures, energy demand increases, which translates into a greater need to capture solar radiation than in summer, when, as temperatures rise, it is advisable to try to protect oneself from it. To this end, bioclimatic architecture proposes designing mechanisms that allow light and heat to enter on cold days and likewise prevent their effects in hot periods.
At the same time, the sun’s angle also plays a fundamental role in bioclimatic studies. In winter, the sun strikes at a lower angle than in summer, when it reaches its greatest height. The solution to summer overheating lies in providing an overhang element in front of the openings, such as a porch or an outdoor pergola, that blocks sunlight during the hottest months when the sun’s incidence is more vertical. In this way, greater thermal comfort is ensured in the home while also reducing the need for additional mechanical systems.
It is important to consider the characteristics of the glazing chosen for each home:
Double or triple glazing
Glass is a material that is sensitive to temperature changes; therefore, it is advisable to avoid single glazing and always seek to incorporate double or triple glazing systems in our buildings. This thermal insulation system is based on creating an air gap between the panes that make it up, preventing the interior temperature from equalising with the exterior.
Cavity between glass panes
Providing an air cavity between the two panes improves the window’s thermal performance. The air inside the classic sealed air-cavity system of double glazing can be replaced by gases with lower thermal conductivity than air. Filling the cavity with argon gas ensures higher thermal and acoustic performance.
Solar factor
The solar factor of the glass to be chosen depends on the amount of solar radiation that penetrates into the home and the corresponding reflection effect to the outside. To ensure comfort inside the home, there are laminated solar-control glazing options that filter the sun’s rays, allowing natural light through while preventing excessive heat radiation from the sun.
This is a characteristic that must be studied carefully based on the energy-demand assessment, since a high solar factor will reduce solar incidence and therefore decrease indoor temperature gains in winter. Conversely, a low solar factor will allow direct sunlight and will require additional solar protection. In general, it is usually advisable to use low solar factors that allow proper solar exposure and temperature gain, and to provide solar protections that allow us to decide and regulate the incidence of light and heat depending on the time of year and the indoor temperature.
SOLAR PROTECTION
Solar protections in bioclimatic homes aim to prevent the home from overheating during the hot months of the year.
Proper design of these protections avoids the installation of air-conditioning units, promoting energy savings and improving indoor environmental quality, since we must not forget that active cooling systems considerably reduce indoor relative humidity, drying out our mucous membranes and weakening our defences.
To ensure greater efficiency, it is important to place solar protection systems on the exterior of the building, preventing solar radiation from reaching the glass.
In addition, it is advisable to choose different solar protections that adapt to the circumstances of each façade. South-facing orientations are the most exposed to the sun, so they will require the best solar protection system.
The best solar protection systems are horizontal elements such as adjustable louvers, which protect from solar radiation while ensuring the passage of light and ventilation.
Porches or pergolas
Structures attached to the building, such as porches or pergolas, create shaded outdoor areas. In addition to reducing direct solar radiation on the building’s windows for indoor comfort, they create a high-quality outdoor space of generous dimensions.
They are designed with a geometry that allows solar incidence in winter while controlling summer radiation. As they are relatively permeable to light, it is advisable to combine them with deciduous vegetation that covers the entire pergola, improving the structure’s efficiency.
Deciduous plant species, in summer, create a vegetative cover that provides a feeling of coolness, while in winter, when they lose their leaves, the structure is left uncovered, allowing sunlight to enter and warm both the space sheltered by the pergola and the interior of the home.
EVAPOTRANSPIRATION
The feeling of coolness associated with vegetation layers is explained by the phenomenon of evapotranspiration. It is defined as the combination of two processes: the loss of moisture from a surface through evaporation together with the loss of water through the vegetation’s own transpiration. During the day, vegetation releases moisture into the air, which cools the air around the leaf.
Eaves
Horizontal elements are the most effective solution among the different solar protection systems. Eaves are a horizontal, fixed system option that provides shading for the home’s façades.
In summer, as the sun’s rays strike more vertically, the eave acts as a barrier, preventing the façade from overheating. However, in winter, due to the change in the angle of incidence, solar radiation reaches the façade and the corresponding openings.
Eaves are overhangs that project from the main façade plane far enough to provide protection from the sun in summer and, at the same time, enjoy its benefits in winter. It is advisable to calculate their size according to the building’s orientation—they generally reach 1 m.
Adjustable horizontal louvers
Mobile solar protection systems can be used and adjusted according to climatic conditions, controlled by the home’s user throughout the day. The best mobile solution is exterior adjustable horizontal louver systems.
Adjustable louvers prevent direct solar radiation from entering, but allow indirect light in. This promotes proper indoor lighting while mitigating the harmful effects of direct sun exposure. To enable control of heat and not only light, it is essential that the installation is external to the home.
This is a solution that offers numerous advantages over interior blinds. The latter do not allow ventilation, whereas horizontal louvers promote cross ventilation.
The Basic Document on Energy Saving of the Spanish Building Technical Code, section 1 of the DB HE of the CTE [4], sets conditions for controlling the building’s energy demand, establishing a series of requirements that consider controlling energy demand through movable shading devices on windows.
Façade colour
Façade colour affects solar radiation and the heating of the home. Light shades, such as white or beige, absorb less heat energy than dark colours. For example, white reflects heat and light, preventing the interior from warming up as easily.
2. CROSS VENTILATION
Wind is a natural, renewable, and inexhaustible resource, so understanding its properties in order to design in its favour becomes a fundamental strategy in any design process.
One of the most efficient systems in bioclimatic architecture is cross ventilation. It is an air-renewal system in which the building’s openings are arranged on opposite or adjacent façades, promoting the natural intake and exhaust of air. This systematic renewal of air naturally maintains healthy indoor environmental conditions without the need to install mechanical HVAC equipment—it is one of the most energy-efficient measures.