The roof plays a crucial role in the building envelope as it is responsible for managing a significant amount of solar radiation. This can account for as much as 60% of the cooling energy used in a given space. The importance of roof design cannot be emphasized enough when it comes to alleviating the discomfort of residents, especially during extreme weather conditions.
Dome roofs play an important role in reducing the total heat gain from the roof and providing a passive cooling effect for the building.
The thermal performance of a dome roof is better than flat roof as Dome roofs help reduce the air temperature inside buildings.
Lower indoor air temperature in domed roof buildings is due to the lower absorbed solar radiation in comparison with flat roofs.
List of contents
1. Guidelines for incorporating domes into buildings.
2. How do dome roofs reduce temperature?
3. Types of dome roofs and alternatives.
Domes
Guidelines
Shape
Select a dome shape that complements the building's aesthetics while maximizing shade coverage. Click here to see different dome designs.
Material and Thermal Mass:
Choose materials with high solar reflectance and low thermal conductivity to minimize heat absorption.
Incorporate an air vent.
A curved roof is most effective when it incorporates an air vent. When air flows over a cylindrical or spherical object, the wind speed tends to increase as it approaches the top of the dome. This increase in wind speed is due to the phenomenon known as the "Bernoulli effect." As the wind flows over the curved surface of the dome, it experiences reduced pressure, which can cause the wind to speed up. If there is a hole at the apex of a domed or cylindrical roof, the difference in pressure allows the hot air under the roof to flow out through the vent creating a passive airflow that helps regulate the temperature inside the building.
Include clerestory windows in the design.
Dome-roofed buildings with ventilation openings near the top demonstrated lower energy consumption. This is because the clerestory windows create a stack effect, allowing rising hot air to escape through them and letting cool, fresh air to channel into the space through openings at a lower level. The geometry of the domed roof caused higher pressure difference between the windward and leeward sides of the house compared with the flat-roofed house resulting in better natural airflow.
Thermal Mass
Use materials with high thermal mass to absorb and store excess heat during the day, releasing it during cooler periods.
Dome-roofed structures are good at controlling indoor temperature due to a number of reasons.
1. Domes have a minimum surface area facing the sun. so, the interiors will be cooler.
It is considered to be a self-shading device, due to its configuration, half of the structure is exposed to direct sunlight while the other half remains in the shade.
2. The warm air, which rises, collects beneath the arched roof, ensuring that it remains well above the room's living space. In this way the room is kept more comfortable and heat transfer from the roof to the room is limited because a higher temperature is maintained next to the roof.
How do domes work?
3. In terms of the building geometry, the lower the building surface area to volume ratio, the lower the heat gain would be, so for a given volume, building with a spherical shape is more energy efficient than a typical cubic building in terms of heating and cooling requirements. a dome house has 30% less surface area than a similarly sized box house, which means one-third less heat transfer to and from its surroundings, resulting in an average of 30% savings on the cooling and heating bill.
4. A curved roof is most effective when it incorporates an air vent. When air flows over a cylindrical or spherical object, the wind speed tends to increase as it approaches the top of the dome. This increase in wind speed is due to the phenomenon known as "Bernoulli effect." As the wind flows over the curved surface of the dome, it experiences reduced pressure, which can cause the wind to speed up. If there is a hole at the apex of a domed or cylindrical roof, the difference in pressure allows the hot air under the roof to flow out through the vent creating a passive airflow that helps regulate the temperature inside the building.
5. The heat loss is proportional to the surface area of the roof. Dome roofs have a greater surface area than flat roofs, which increases the emission of radiant energy. Furthermore, due to its specific configuration, the wind speed increases over the domed roof which results in enhanced convective heat transfer and hence decreases the indoor temperature.
6. In dome roofs, the surface area exposed to the direct solar radiation is reduced by one-third compared to flat roofs resulting in a reduction in solar heat gain.
7. Dome-roofed buildings with ventilation openings near the top demonstrated lower energy consumption. This is because the roof vents create a stack effect. which lets the rising hot air escape through and allow the cool fresh air to channel into the space from openings at a lower level.
8. The geometry of the domed roof caused a higher-pressure difference between the windward and leeward sides of the house compared with the flat-roofed house resulting in better natural airflow.
Types of Domes in Bidar.
Alternative to Dome roofs.
Gable roofs can serve as an alternative to dome roofs, providing many similar benefits.
1. Both domes and gable roofs have a minimum surface area facing the sun, so the interiors will be cooler.
It is considered to be a self-shading device, due to its configuration, half of the structure is exposed to direct sunlight while the other half remains in the shade.
2. The warm air, which rises, collects beneath the arched roof, ensuring that it remains well above the living space of the room. This way, the room is kept more comfortable, and heat transfer from the roof to the room is limited because a higher temperature is maintained next to the roof.
3. In terms of the building geometry, the lower the building surface area to volume ratio, the lower the heat gain would be, so for a given volume, building with a dome or gable roof is more energy efficient than a typical cubic building in terms of heating and cooling requirements.
4. The heat loss is proportional to the surface area of the roof. Dome roofs and gable roofs have a greater surface area than flat roofs, which increases the emission of radiant energy.
5. Dome and gable roofed buildings with ventilation openings near the top demonstrated lower energy consumption. This is because the roof vents create a stack effect. which lets the rising hot air escape through and allow the cool fresh air to channel into the space from openings at a lower level.