How can energy savings be quantified in commercial buildings?
How much energy saving is possible in a commercial building and what key factors need to be considered while designing an energy efficient commercial building?
How should a commercial building be oriented and what form should it follow to be energy efficient?
A building should be designed such that it has a linear building form with shallow floor plates (<16–18 m) and with the longest façades facing north and south.
How should the opening of a commercial building be designed for optimum daylight and natural ventilation?
To achieve good daylight, the building shape should be linear (14–18 m width) in which the longer sides are oriented towards the north and south and the windows are provided only on the north and south façades.
For a typical office building, WWR of 20%–30% is sufficient to provide good daylight. The WWR should not exceed 40%. Other measures such as use of clear glass for best VLT in combination with adequate shading devices to cut off glare and heat and use of light-coloured finishes help in maintaining good daylight.
Cross-ventilation works well when the predominant wind direction is ±60 °C from the axis perpendicular to the building façade.If the predominant air direction is parallel to the building façade, the use of deflectors is helpful in increasing the flow.
In certain cases, stack effect can be used to enhance natural ventilation.
In places where the diurnal range is high, night ventilation is also a suitable option.
How can an energy efficient building envelope be created for a commercial building?
For an energy efficient envelope, the roof, walls and windows should be carefully designed. The roof needs to be insulated and treated to reflect the solar radiation. The U-value of the windows should be low and a trade-off is to be made between SHGC (heat gains) and the VLT (for daylight).
How should a commercial building be shaded?
The best solutions for solar shading are exterior dynamic shading solutions such as shutters or external movable blinds. The major advantage of such solutions are listed below:
- Flexibility of use according to weather conditions and seasons
- Provide good daylight, when opened
- Effectively cut 80% to 90% of the solar gains
- Can be applied on any façade, which gives more flexibility for the orientation of the building.
What type(s) of efficient cooling technologies can be used in an energy efficient commercial building and how should it be decided?
- The choice of the cooling system for a building depends on factors such as the local climate and the type of the building (its size, usage, area to be conditioned, etc.).
- Air movement helps in achieving thermal comfort; in warm climates, ceiling fans have an important role to play in all types of buildings. BEE 5-Star labelled ceiling fans or super-efficient ceiling fans should be used.
- Evaporative cooling can be an energy-efficient solution if the climate is suitable (e.g., semi-arid, and parts of tropical wet and dry region) and sufficient quantity and quality of water is available. Direct evaporative cooling systems with humidifying pad (desert cooler) or with high pressure pumps, which create a fine mist, can be used. Use of two-stage indirect evaporative cooling systems can result in achieving more than 100% cooling efficiency.
- For single zones, BEE star labeled unitary, split or inverter ACs can be used. All these are air-cooled systems. An alternative solution would be to have a centralised water loop, in which the water cooled in a cooling tower is supplied to the split units to cool the condensers, thus increasing the efficiency.
- In the case of centralised air-conditioning systems, the main strategies for improving energy efficiency on the chilled water side are listed below.
- Use of water-cooled chillers, instead of air-cooled chillers.
- Select efficient chillers as per the need.
- Select chillers with good part-load performance.
- Select efficient pumps and motors.
- Reduce pressure drop in the water circuit.
- Use of VFDs on pumps and cooling tower.
- Use controls to allow gliding of the temperature of the chilled water from 7 °C to 12 °C depending on the dehumification needs.
- In the case of centralised air-conditioning systems, the main strategies for improving energy efficiency on the cooling distribution sides are as listed below.
- Select efficient fans.
- Reduce pressure drops in the air circuit.
- Use VFDs on fan motors.
- Utilise free cooling potential.
- Size the cooling coils for removing sensible loads at 12 °C supply water temperature.
- Use treated fresh air with heat recovery.
- Use indirect evaporative cooling AHU
How can solar energy be utilized to make a commercial building energy efficient?
Solar energy can be harnessed through two main technologies: solar hot water panels, to produce hot water, and photovoltaic panels, which convert solar energy into electricity.