Daylighting Consideration in Buildings

Present day buildings are generally having facade which is made up of Glass. Daylighting consideration becomes important here. The orientation of tall multi-storied buildings become very important as the spatial orientation is responsible for energy performance of the building throughout its life. The wider vertical faces are generally oriented towards either facing North or South direction so as to have lesser incident solar radiation on the buildings. In case there is ample space and the buildings can be oriented in either way, it is always preferable to orient the building in the Composite and Warm/Humid climates in a way so that longer facades are facing north/south directions. In such a scenario the building places comparatively lighter loads on the air-conditioning systems for cooling requirements.

For a residential dwelling unit which is a 2/3 Bed Room apartment, the average energy consumption is of the order of 44-50 kWhr/sq m/year in warm and humid climate.

DaylightingLimiting Glaze area helps in reducing cooling loads. Window-to-wall ratio (WWR) of 10% in bedrooms and 20% in living rooms allow a good balance between adequate daylight and reduced heat gains. The lower floors in multi-storied buildings where the daylight gets limited are generally allowed a bit higher WWR i.e up to 30% to bring in more of the daylight.

Altering schedules and  resetting the thermostat temperatures goes a long way in reducing the cooling/heating loads and improving energy efficiency. Use of daylighting while modelling the buildings definitely reduces the cooling load burden on the air conditioning system and improves the Energy Performance Index of the building drastically.

Another very important factor in Building Design is availability of proper ventilation. The multi-storied apartments are generally constructed in very close proximity to each other. Wind direction becomes very important. In cases where the towers have not been designed well, there are chances that between the towers wind tunnel effect may take place.

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