How can energy savings be quantified in residential buildings?
An EETC residential building does not heat up abnormally during long summer season and the requirement for use of coolers and ACs is also minimized. It is also affordable as there are no/low additional construction cost, low electricity bill for occupants and easy and low-cost maintenance.
How much energy saving is possible in a residential building?
What should the orientation a residential building be to minimize solar exposure on vertical surfaces?
The buildings should be oriented North-South i.e the longer facades should be facing North-South, to minimize solar exposure on vertical surfaces.
What should be the shape of a residential building be to minimize solar exposure on vertical surfaces?
The building shape for a particular orientation can reduce the solar exposure by 20-30%. For a north-south oriented building the preferred typologies are:
- Liner double-corridor
How can an energy efficient building envelope be created for residential buildings?
The 3 components that comprise the building envelope are walls, windows and roof. The key factors to be considered while designing these are:
- Limited Window to Wall Ratio (WWR): WWR between 10-30% for bedrooms and 20-30% in the living rooms allows a good balance between adequate daylight and minimising solar radiation.
- Windows should be shaded
- Use of double glazed windows
- The northern facade of the building needs better solar protectin as we go further south in India.
- Over-deck insulation and high reflective surfaces should be used on the roof to minimise heat gain through the roof.
What features should be considered to ensure adequate daylight enters into a residential building for energy efficiency?
Usually 10% WWR in bedrooms and 20% WWR in living rooms are needed to provide sufficient daylight. However, when building blocks in a residential complex are located near each other, daylighting in bedrooms and living rooms located on lower floors is reduced substantially. The daylight on the lower floors can be improved by: (a)
- increasing the window area (maximum WWR 30%),
- using light colours with smooth finishes on the wall opposite to the window, and
- using light colour interiors
How should the windows in an energy efficient residential building be designed to ensure proper natural ventilation?
Wherever possible, provision for cross-ventilation at the flat or room level is to be made. Cross-ventilation brings about higher air-change rates, i.e., better ventilation. In the case of cross-ventilation, openable window area should be at least 10%–15% of the floor area, for both inlet and outlet openings.
In the case of single-sided ventilation, i.e., having window(s) on one wall of the room, tall windows should be designed. These windows should have openings at the bottom (for entry of cold air into the room) and at the top (for the exit of warm air to the outside). The height/width ratio of 2 is practically feasible for such windows for regular bedroom sizes.
As far as possible, openings should be placed normal to the prevalent wind direction. If the wind direction is >60° from the normal direction of the opening, i.e. parallel to the wall, design features like wing walls or providing louvres on the outside surface of the wall can help in steering the wind inside.
Casement windows are recommended over sliding windows as they allow more openable window area.
What kind of cooling systems and other appliances should be used in an energy efficient residential building?
It is recommended that higher BEE star-labelled energy-efficient equipment and appliance should be used for:
- Common services
- Distribution transformers
- TFLs for the lighting of common areas
- Electronic ballasts for the lighting of common areas
- Diesel-generating sets Space cooling, water heating, and lighting inside flats
- Ceiling fan
- Electronic ballasts
- Storage-type electric water heaters/geyser
Although the star rating is presently not available for inverter ACs, super-efficient fans, and LEDs, they are recommended for cooling and lighting applications, as they are more energy efficient.
How should common services be designed in an energy efficient residential complex?
The three main electricity-consuming common services that are found in almost all multi-storey residential complexes and need energy efficiency features are:
- Common area lighting
- Design for daylighting of corridors, staircases, parking areas
- Minimise the use of basement that would require artificial lighting
- Choose energy-efficient artificial lighting
- Indoor spaces: Use light-emitting diodes (LEDs), compact fluorescent lamps (CFLs), and higher BEE star-rated tubular fluorescent lamps (TFLs)
- Outdoor spaces:
- Use LEDs and metal halide lamps
- Optimise for height and distance
- community water pumping
- Pumped gravity system
- Selecting a pump whose head and flow parameter for the ‘DutyPoint’ matches with that of the ‘Best Efficiency Point’ of the pump
- Design piping so as to reduce frictional losses
- Use variable frequency drives (VFDs) on pump motors
- Hydro-pneumatic system
- Install VFDs for all pumps
- Measures to reduce standby electricity consumption
- Use LED or CFL for the lighting of the lift car
- Avoid dark interiors in the lift car
- Use high-efficiency motors for the ventilation of the lift car
- Provide auto-switch off for lights and ventilation fan
- Measures to reduce running electricity consumption
- Use of VFDs in motors
- Opting for lifts with gearless systems as they usually consume less electricity
- Incorporation of regenerative braking
How can solar energy be utilized to make a residential building energy efficient?
For buildings and neighborhoods, which are 4-storey high and are designed with energy-efficiency principles, it is possible to meet the annual requirement for electricity and hot water using rooftop solar PV and SWH systems. Such a building can become a net zero-energy consumer.
However, in case of multi-storey residential buildings, the electricity generated from rooftop solar PV systems (assuming utilisation of 60% of the roof area) in a year is sufficient to meet either full or a substantial portion of the electricity consumption for common services during the year.