Architectural Theory, Building Design, Design Guide, Design Theory

7 Types Of Passive Building Cooling Systems Without AC

In a country with a hot, humid and dry climate such as India, some form of cooling system is required to be installed in any building design. These systems significantly increase the comfort levels by facilitating heat loss from the building.

Building Cooling Systems

Although there are plenty of cooling techniques and technology available in today’s world, they are mainly divided into two types:

Passive cooling

  • Evaporative Cooling
  • Stack Effect

Active cooling

  • Fans
  • Geothermal Cooling
  • Evaporative Cooling
  • Ground Coupling
  • Forced Ventilation

Passive cooling:

Passive cooling is a method of building design strategy which helps reduce heat gain with low or no energy consumption. It takes advantage of natural cooling to help maintain comfortable temperature over a long time. 

Evaporative Cooling

Evaporative cooling
Evaporative Cooling

Evaporative cooling uses the concept of evaporation for cooling interior spaces- as water evaporates, it cools the surrounding area by drawing in heat. Since air with lower humidity has a greater capacity to take up the evaporated water vapor, this method works best in climates with low humidity. 

  • Large bodies of water are placed close to windows and doors, so that they can cool the warm air entering the building. 
  • Careful location of large water features like fountains, artificial ponds and streams etc. should be done to create convective breezes. 
  • Small water features may not provide a noticeable effect as the surface area and depth of water exposed to moving air is important. 

Stack Effect

Stack effect helps hot air to escape the building and considerably cool the indoor environment
Stack Effect

Stack effect is caused by the passive air movement throughout the building due to variances in pressure caused by thermal buoyancy, in the vertical direction. If air within a building, which is of lower density, grows warmer than that of the surrounding outdoor air, it rises up. 

  • Stack ventilation uses openings made in the building’s structure, placed at a sufficient height to allow warm air to rise up and escape outside. 
  • Due to warm air being less dense, the negative pressure attracts denser and colder air from outside through low-level openings in the structure like doors and windows. 
  • Although the outcome of this process is not that significant, an effective result can be accomplished with the use of longer stacks. 
  • Controlled and carefully planned stack ventilation allows passive cooling throughout the hot summer weather while being low maintenance and cost-efficient. 

Active cooling: 

Active cooling systems consume energy in order to dissipate heat from the building. Although in terms of sustainability, passive cooling is a better choice, in some cases it doesn’t adequately cool the building. In those instances, installing active cooling systems might become essential. 

Fans

A fan is an equipment with blades rotated by a motor, which produces constant airflow. By inducing forced convection heat transfer, the air around is cooled. This method is a popular choice due to its low cost and maintenance.

Geothermal Cooling

Geothermal heating works by moving a temperature-conducting fluid like water through an underground system of pipes below the building.
Geothermal Cooling

Geothermal heating works by moving a temperature-conducting fluid like water through an underground system of pipes below the building. This allows the fluid to collect the heat and then evenly distribute cool air throughout the building. 

  • As air is circulated through the building, the pump removes heat from the air and transfers it to the fluid that circulates to the ground. 
  • Since the ground has a lower temperature, heat transfers from the fluid to the ground. 
  • Cold air blowing into the interior spaces is the result of the process of removing heat from the circulated air, transferring that heat to the ground and then returning the newly cooled air back into the building. 

Evaporative Cooling

Evaporative cooling can also be done as a form of active cooling methods. Although it uses the same method, rates of evaporation can be further increased by increasing air movement using breezes or fans. 

Ground Coupling

Ground Coupling uses a heat pump to capture and transfer heat to the ground.
Ground Coupling

A ground source heat pump or a geothermal pump is a cooling system for buildings that uses a heat pump to capture and transfer heat to the ground. This method takes advantage of the almost constant temperature of the earth throughout the year.

  • A ground source heat exchanger is an underground heat exchanger that can capture heat and then transfer it to the ground.
  • The pump uses the Earth’s near constant temperature to cool air in a building or other structures.
  • Ground temperature becomes more stable with depth.
  • Larger tubes are better since they use less energy, while also having more surface area for transfer of higher volumes in a shorter period of time. 

Forced ventilation

Forced ventilation used mechanical energy to tranfer indoor and outdoor air
Forced Ventilation

There are two main methods of forced or mechanical ventilation systems:

Pressure system:

In this system, air is blown through the building using a fan or other similar equipment placed at the openings. This arrangement is used when air pressure in the building is slightly greater than that of the outside environment.

Vacuum system:

This system allows an influx of fresh air by employing an exhaust fan placed at the outlet of the vent or any other opening. This is done when the air pressure inside the building is slightly lower than outside. 

Balanced system:

There is also a third method, which is a mix of the above two methods, called a balanced system. 

Although it is better to go for passive cooling methods wherever possible, more often than not, the use of active cooling methods can be unavoidable. The priority of every building design should be the comfort of its users and inhabitants. Hence, choosing the right and adequate cooling system for the building is highly important. 

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