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Regulating the amount of sunlight that is admitted into a building is an important aspect of passive solar design. It prevents excess heat gain in warm and sunny weather, which can otherwise lead to an increase in the consumption of energy required to cool the house.
Shading is an important technique used to regulate sunlight. It can be provided in several ways, for instance, exterior building elements like overhangs, interior glare control devices, low shading coefficient glass, and landscape.
The angle at which the sun’s rays fall on a house is mostly fixed and distinctly different during summer and winter. In this case, a fixed shading system can control heat gain. However, there is almost the same amount of sunshine in March and September, with the latter month being warmer in nearly all regions. In this situation, shading design requires more attention, and adjustable shading elements may satisfy passive solar design requirements.
Why is Proper Shading Design Important?
- Well-designed shading blocks sunshine during summer and subsequently reduces cooling requirements.
- It improves the quality of natural lighting inside the building.
- Shading enhances occupants' visual comfort by controlling glare and reducing the contrast ratio.
Shading or solar control uses building elements or other means like trees to regulate the amount of heat energy permitted into the living space during summers. The purpose of shading is to avoid overheating at times of maximum heat gain and reduce cooling loads.
The orientation of a building affects the design of effective shading. For instance, an overhang is effective to shade south-facing windows during summer. However, the same shading system is unsuitable for blocking low afternoon sunlight from entering the house through west-facing windows during summer. A wide spectrum of building components can be employed to provide shading:
- Exterior elements include awnings, overhangs, trellises, vertical fins, solar screens, roll-down blinds, eaves, pergolas, verandahs, shutters, and vertical louvers, see Figure-2 through Figure-4.
- Shading devices can also function as reflectors, called light shelves, which reflect natural light for daylighting into the building, see Figure-5.
- Low shading coefficient glass.
- Interior glare control tools such as adjustable louvers and Venetian blinds, see Figure-6.
- Natural landscaping like trees or hedgerows, see Figure-7.
How to Design Shading System?
- Employ fixed overhangs on south-facing windows to control direct solar radiation. For indirect radiation, use other solar controlling means like low-E glazing.
- If possible, limit the amount of east and west windows because they are harder to shade than south-facing windows. The best option to shade east and west glass is landscaping.
- Shading affects daylighting, so both of them need to be accounted for simultaneously. For instance, light shelves shade lower windows but bounce natural light into the room through high windows.
- In the tropics, shade north-facing windows and roofs because the former receives direct heat gain, and the latter is the main source of transmitted solar gain into the building. In other areas, shading of north-facing windows is not needed.
- Keep in mind that interior shading tools like vertical louvers or venetian blinds do not reduce cooling energy consumption because the sun's heat energy is already allowed into the living space. However, these tools control glare and improve visual comfort.
- Study and understand the sun’s angle. Different aspects of shading design, such as selection of shading devices and placement of building integrated photovoltaic panels, rely on the sun’s angle.
- Consider maintenance of shading devices at the design stage. Operable shading elements may require considerable cleaning, maintenance, and repair over time.
- If landscape elements are used for shading, the cost of maintenance and upkeep on the lifecycle should be considered.
- Shading design strategies that work well for a site at an altitude may be completely inappropriate for another place at a different altitude. Therefore, carefully study the design ideas of other buildings while considering adopting them for the site under consideration.
- Earthquakes and bird nesting may reduce the suitability of using exterior shading devices.
Applications of Shading Devices
Shading devices are particularly suitable for certain types of buildings which are:
- Barracks and other multistorey buildings in high temperature or warm climates.
- Offices, administration buildings, and other structures using daylighting.
- Almost all structures that are located in warm, sunny climates.
Shading or solar control is vital for the passive solar design of buildings because it prevents overheating during peak heat gain times and reduces cooling loads.
1. Well-designed shading blocks sunshine during summer and subsequently reduces cooling requirements.
2. It improves the natural lighting quality of the building's interior.
3. Shading enhances occupants' visual comfort by controlling glare and reducing the contrast ratio; as a result, satisfaction and production increase.
1. Exterior elements include awnings, overhangs, trellises, vertical fins, solar screens, roll-down blinds, eaves, pergolas, verandahs, shutters, and vertical louvers.
2. Shading devices can also function as reflectors, called light shelves, which bounce natural light for daylighting deep into building interiors.
3. Low shading coefficient glass.
4. Interior glare control tools such as adjustable louvers and venetian blinds.
5. Natural landscaping like trees or hedgerows.
1. Barracks and other multistorey housing projections in temperature or warm climates.
2. Offices, administration buildings, and other structures using daylighting.
3. Almost all structures that are in warm, sunny climates.