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How does Passive Solar Cooling Work?

how does passive solar cooling work

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Passive solar cooling is one of the two design approaches of passive solar design. It means the utilization of design choices and materials to decrease heat gain and increase heat loss. 

The purpose of passive solar cooling is to dissipate heat inside a home if it becomes uncomfortably hot. So, it is specifically beneficial in hot and humid or hot and dry weather conditions.

A comfortable and cool temperature in a building can be maintained with less energy by using a combination of adequate insulation, daylighting, energy-efficient doors and windows, shading, and ventilation.

Why is Passive Cooling Important?

How does Passive Cooling Work?

Movement of air is the key to almost all techniques of passive cooling. It needs well-designed openings and unobstructed breeze paths. The air carries heat out of the building and replaces it with cooler external air, resulting in reduction in the inside temperature of the building. 

Some strategies of passive solar cooling include operable windows and doors, natural ventilation, wing walls, shades, insulations, thermal masses, and landscape and garden designs: 

1. Ventilation and Operable Windows

The design and placement of windows in a building play a significant role in passive cooling.

Casement windows provide good airflow, but hopper windows offer the best rain protection. The hopper windows need to be opened completely; otherwise, the air will be directed toward the ceiling. 

If a window needs to be placed at one side, provide two widely spaced windows rather than one.

Figure-1: Different Designs of Windows Openings

2. Wing Wall

Wing wall is vertical solid panels installed alongside windows transverse to the wall on the windward side, see Figure-2. It increases the speed of the natural wind and subsequently improves the cooling effect inside the house.

Figure-2: Top View of Wing Wall Airflow Pattern

3. Thermal Chimney

The provision of a thermal chimney is another way to improve the cooling effect in a building. It draws air out of the structure using convective currents. 

Air can be drawn inside the building by generating a hot or warm zone with an exterior exhaust, hence ventilating the structure. Adequate detail of the thermal chimney is shown in Figure-3.

Figure-3: Thermal Chimney
Figure-4: Thermal Chimney Effect Built into Home

4. Internal Layout of the Building

The arrangements of walls, doors, and rooms influence the heat distribution within the building.

5. Thermal Mass

The function of thermal mass is absorbing heat during days to moderate internal temperature. During nights, thermal mass is cooled through the use of ventilation. This makes the thermal mass ready for the next hot days to absorb heat and avoid the rise of temperature in the living space.

6. Earth Coupling

Earth coupling is a technique that aids in achieving passive cooling in a building, see Figure-5. The earth coupling helps draw up the stable, deeper ground temperature to the floor's surface, providing the building a headstart to regulate temperature.

Earth coupling is particularly effective in a well-insulated and properly shaded house. It is beneficial in areas where deep earth temperatures are low at a depth of 3 m or more. 

Figure-5: Earth Coupling Uses Cooler Ground Temperatures to Control the Temperature of The Slab 

7. Insulation

Selecting suitable insulation products and paying attention to their placement will improve thermal comfort and avoid condensation. 

Generally, applicable codes provide minimum insulation levels for floors, roofs, and walls based on the climate and other building features.

8. Shading Glazing

Shading windows is critical to prevent heat gain and improve the cooling effect. Based on the angle of the sunshine in winter or summer season, a designer can choose deep overhang shading or vertical shading to control heat gain.

If it is not possible to install proper shading, providing glass with a solar heat gain coefficient (SHGC) of not more than 0.20 is highly recommended. Double glazing is also helpful in achieving passive cooling as it has low conductivity, which reduces the effect of the hot air. 

Figure 6: Deep Overhang Shading Option
Figure 7: Vertical Shading Option

9. Landscape

Landscape helps cool homes and neighborhoods. For example, gardens and trees can reduce the heat of air flowing into the building.

Figure-8: Landscape Used to Improve Passive Cooling of a Building


What is a solar passive cooling design?

The passive solar cooling design is one of the two design approaches of passive solar design. It is the utilization design choices to decrease heat gain and increase heat loss.

What is the purpose of passive cooling design?

The purpose of the passive solar cooling design is to dissipate heat inside a home.

What are the passive cooling design strategies?

1. Ventilation and Operable Windows
2. Wing Walls
3. Thermal Chimney
4. Internal Layout of the Building
5. Thermal Mass
6. Earth Coupling
7. Insulation
8. Shading Glazing
9. Landscape

What is the effect of passive cooling on sustainable architecture?

1. Increases energy efficiency in a building,
2. Declines the environmental impacts of energy consumption,
3. Improves sound insulation,
4. Offers more appealing indoor spaces,
5. Enhances the quality of air inside the structure.

Is it possible to apply passive cooling strategies for existing buildings?

The passive cooling design strategies can be applied to both new and existing buildings. Nonetheless, it is much easier to use in new constructions.

Read More

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