6 Passive Design Strategies

Vaibhavi Dave Jun 28, 2022 0

With an alarming depletion of non-renewable resources such as fossil fuels and coal, it is crucial for us to shift towards renewable sources of energy. Adopting passive strategies helps to reduce the overall energy consumption of a place. Incorporating passive methods into a building’s design to interact with the site’s natural features (such as sun and wind patterns). It offers natural heating and cooling of areas throughout the year. Here are 6 Passive Design Strategies that effective incorporate their purposes:

Venturi Effect

The Venturi Effect is a fluid dynamics theory. It asserts that when a fluid flows through a confined channel, its velocity must rise. The velocity increases while the static pressure falls because of this. This applies to wind as well. Consequently, designers and architects have used this principle to enhance the wind flow and environment inside houses, palaces and other structures via the smart modification of lattice screens placed over fenestrations. A good example of this would be the Hawa Mahal in Jaipur, Rajasthan. The Rane Vidyalaya School by Shanmugam Associates is a modern structure that incorporates this effect.

Rane Vidyalaya School by Shanmugam Associates, Tamil Nadu, India, uses a series of intricate lattice work

Stack Effect

Stack Effect is the term used to describe passive air movement that occurs throughout a structure. This occurs because of changes in vertical pressure caused by thermal buoyancy. If the temperature of the air within a structure rises above that of the surrounding outdoor air, the warmer and lower-density air rises. Stack effect ventilation thus takes advantage of this activity by creating gaps in the structural envelope of a structure that are high enough to allow warm air to escape.

Schematic Diagram of Stack Effect

Negative pressure at the structure’s top pulls denser, colder external air in via low-level apertures. Although this process has a minor effect, while using a stack, it has the scope for amplification. Using longer stacks can therefore boost airflow. Controlled stack ventilation may provide passive cooling in hot summer weather, while also requiring little maintenance and being extremely cost-effective due to low running costs and very low energy costs (or none).

Environmental Building in Garston, England with Towers for Stack Ventilation

Trombe Wall (Insulation)

Trombe walls are a type of passive heating technology that is used in structures in regions that experience cold weather with low temperatures. Using Trombe walls decreases the demand for traditional heating techniques like furnaces or other space heaters. It also lowers the amount of energy consumed to heat the property.

A diagram depicting the workings of a Trombe Wall

Construction of these walls is of a dark-coloured material, such as concrete. Oriented toward the sun, the solar radiation impacts the wall. With a slight gap between the wall and the glazing, the glass thus acts as a tiny greenhouse, trapping sunlight. The walls therefore face south in the Northern Hemisphere.

Druk White Lotus School, Ladakh, India uses Trombe Walls to keep their classrooms toasty

Evaporative Cooling

Evaporative cooling works by cooling the air. This means pulling hot, dry outside air through the water body using evaporation principles. Lowering of air temperature occurs due to water evaporation. This is because of the absorption of heat when the air passes past these pads. The presence of a water body creates a cool microclimate around the structure. It is also helpful in the places where the climate is hot and dry and humidity is extremely low. 

Jixi Museum in China utilises the existing trees to create a water body around the structure

Sunlight Minimisation

Brise Soleil is a form of solar shading system that controls the amount of sunlight and solar heat that enters a structure. This is therefore done by using a series of horizontal or vertical blades.

The term “Brise Soleil” means “sun breaker” in French. To eliminate glare and reduce warming, Brise Soleil systems protrude over the windows. The blades or fins let low-level sunlight into a structure in the mornings, evenings, and throughout the winter. However they block direct summer sunlight, which in the UK reaches a maximum angle of 62 degrees.

Brise Soleil systems comprise a variety of materials. These include aluminium and sustainable wood, and can comprise blades or solid shelves (or even pathways).

Unité d’habitation, Berlin by Le Corbusier

Courtyard Effect

Courtyards are common in regions, where the primary goal is to decrease the thermal heat loads placed on the building’s internal areas. The microclimatic factors operating on a courtyard space, most notably those of radiation and wind, thus impact the amount of thermal comfort in that space.

Because of their exposure to the sky, the courtyard surfaces release long wave radiation, which dissipates the previously absorbed heat. The temperature of the neighbouring layer of air steadily lowers as the surfaces lose heat. A courtyard’s most essential feature is that it allows for “back-to-back packing,”. Thus the outside shell isn’t always necessary for light and ventilation. As the inner building envelope is being utilised for this, it is therefore possible to share the outer building envelope with neighbouring structures. This often results in a total shade of the outer envelope from any radiation and air movement.

Gandhi Ashram in Ahmedabad, designed by Charles Correa

Sources:

  1. What Is the Venturi Effect?
  2. BRE The Environmental Building 
  3. What is Stack Effect Ventilation in Architectural Design?
  4. Gandhi Memorial Museum (Sabarmati Ashram)
  5. Evaporative Cooling Technologies for Buildings
  6. Unite d’ Habitation / Le Corbusier
  7. Trombe Wall
  8. Druk White Lotus School – Green Building in Ladakh
  9. What is Brise Soleil?

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Disclaimer: The information contained herein have been compiled or arrived at, based upon information obtained in good faith from sources believed to be reliable. All such information and opinions can be subject to change. The image featured in this article is only for illustration purposes and does not in any way represent the project. If you wish the article to be removed or edited, please send an email to editor@biltrax.com

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