Although this is an air-conditioned building, it attempts an interactive interface with the external environment to achieve greater energy efficiency.
The basic design strategy is inspired by the traditional inward-looking haveli plan. The central fountain courtyard acts as an environment generator for the office spaces opening toward it. The external skin is treated as a solid insulated wall with peep windows for possible cross-ventilation and higher windows for daylight. Selection of materials and system of environmental control is prioritised in favour of sustainability and efficiency in energy consumption so that a significant feature of energy saving is actually the economy of the building envelope.
ASSUMPTIONS, path toward energy conservation :
1. air conditioning is still an expensive technology to install and to run.
2. this cost is largely a resultant of heat transfer through the building fabric.
3. to make air conditioning more affordable, the most effective strategy is :
To design the building fabric itself to minimize air conditioning load.
This is effected at marginal extra cost of insulation and shading.
This is an office building designed to meet the demands of a modern office, with high level of environmental comfort, integration of systems to support information technology, with flexibility and adaptability for growth and change.
The building sits on a rectangular plot in an “institutional” area, which will have other office buildings surrounding it. Three stories of offices and a basement surround the central court. The basement houses building services and some work spaces too.
The entire building plan is based on a planning grid of 1.4 m x 1.4 m which coordinates the ceilings with air-conditioning and light fittings, locations for partitions as well as external windows - to permit a high degree of flexibility in layouts for offices.
The building opens towards its entrance through a planted and shaded forecourt with a water pool. The orientation of all the interior spaces is towards the central court, with the exception of the managing director’s suite which enjoys its own garden terrace on the top floor.
Interactive strategy for an air-conditioned building
Absorption technology for Air-Conditioning
Control on air-conditioning loads
Structural system and floor-to-floor height
Monitoring and Automation
The Building adopts a compact rectangular form and minimum height above ground to limit exposure to the external conditions. Openings on the external walls are designed for two separate functions : small peep windows at seating height provide for possible cross ventilation and views out ; larger windows at ceiling level are designed to distribute glare-free daylight across the office floor. Taking the daylighting function into account the window area is minimised to 18% of the external wall area.
Both the entrance forecourt and central fountain court, towards which the building envelope opens out with greater transparency, have a structural framework which would provide support for shading screens to be stretched according to seasonal demands.
The planting scheme along the edges of the site with tall evergreen (Silver Oak) trees, provides another protective layer for the building.
The orientation of the building is determined by the site. The small peep-windows, due to the deep reveal in which they are set allow insulation in favour of winter, cutting out the mid-summer sun by the shade of the reveal on to the glass. The large daylight windows house adjustable venetian blinds in a double-window sandwich. The blinds are to be adjusted seasonally (three times a year) by the building maintenance staff to control direct insulation and to reflect light towards the ceiling for distribution into the office spaces. The large glazed areas towards the central court and the entrance court rely on screens that will be stretched and gathered seasonally. The structural frameworks enclosing the courts provide the necessary support systems for the screens.
Heat Transfer :
In Principle, the building is a heavy mass construction insulated from the outside. Wall insulation is 25 mm thick polyurethane foam protected by a dry red-stone slab cladding system. The roof insulation is 35 mm thick and has a reflective glazed tile paving cover to minimise sol-air temperature on the roof surface. The daylight windows provide insulation by way of tight-sealed two layers of glass with a venetian blind installed between the two layers.
The glazing panels around the inner courtyard however are single glazed - it is anticipated that with the tall water fountain working, the courtyard temperatures would shift substantially toward wet bulb temperature. This would considerably reduce heat load from the courtyard side during summers, and during spring and autumn would act as a heat sink. While the choice of single glazing here evidently means savings in capital expenditure, considering the year-round operation of the fountain court.
Fountain Court :
The fountain is a re-circulating system in which a large body of water flows over extensive surfaces to maximise evaporation. The tall solid concrete columns of broad diameters over which the water trickles down the height of the courtyard, and the thin sheet that overflows the sides of the pool at ground level create a large heat sink and a body of air close to wet-bulb temperature.
The white marble sides of the tank reflect the courtyard light into the basement work areas.
Interactive strategy for an air-conditioned building :
Recognising that climatic conditions range on both the cold and the hot sides of the comfort zone, building systems are designed to draw upon the external environment to supplement the air-conditioning system.
The air-handling system has provision for 100% filtered fresh-air-intake. Coolth can be stored in the building mass by night flushing during spring and autumn. Similarly, during early and late winter, when internal heat is to be rejected, fresh air would be drawn in, replacing the function of the chilling plant.
Absorption technology for Air-Conditioning :
After a careful cost-benefit study, an absorption system chilling plant has been installed. Apart from not contributing to ozone depletion the plant results in reduction of the capital expense of the electrical system, particularly its electricity generation back-up. This is of critical value in a state like Haryana, where due to acute electricity shortage the electricity generation back-up must cater to 100% of peak load. The absorption chillers run on a diesel fired furnace. Electricity generation provides for illumination, office machines and mechanical equipment.
Air Distribution :
Each of the office floors is served with two air handling units. The allocation of areas handled by each unit is designed to balance out peak demands on each unit. This is done by responding to the orientation exposure of the building sides to the sun so that peak morning and afternoon loads are shared by the air handling units even as the loads shift from the easterly faces of the building in the morning toward the westerly faces in the afternoon.
Control on air-conditioning loads :
The primary level control on external gains has been described under “exposure” and “heat transfer”. And internal gain is controlled by minimising internal lighting loads.
The more significant saving, however, is affected by the clients agreeing to air-conditioning standards set according to acceptance level of their office staff, rather than by any international norms. The system is designed to following parameters :
Outdoor Summer 43.50C db 240C wb (ignoring peak temperatures)
Indoor Summer 240C db (± 10C)
Also, circulation passages and ancilliary function rooms have no air-conditioning. Toilets and pantries expel air to the outside at a minimal rate drawing relief air from neighbouring conditioned spaces.
Daylight is the primary source of illumination. All work spaces receive adequate daylight the maximum distance of a workstation from the daylight source being 5 M. The high windows on the external walls are designed to throw daylight deep into the office space. This is varied seasonally by adjusting venetian blinds installed in the window sandwich to control glare and to modulate distribution.
On the courtyard side fabric screens would be stretched over the structural frame to respond to each season.
Artificial illumination is on the ceiling grid with compact fluorescent luminaries at 19 watts per square metre of floor area. Most of the office work is done on computers and working hours are generally limited to daylight hours. The illumination level offered by this system supplements daylight when necessary, and is comfortable for short working hours. It has been agreed that task light desk lamps will be provided on desks for elderly people and those who have late working hours.
To provide visual interest and a feeling of brightness occasional spot lights are provided to light up wall surfaces with paintings and other artwork.
Control of ceiling lights is in the hands of the building management staff. The control circuits for ceiling lights are arranged in zones running parallel to the daylight source so that they can be switched on progressively to compensate for variation in and/or falling daylight levels. It is proposed that these will be controlled by automatic timer switches with timing set for each season. (with manual override for unusually cloudy weather)
Structural system and floor-to-floor height :
A flat-slab system is adopted for floors and roofs. This minimises the height required for accommodating air-conditioning and other services. With a clear ceiling height for office spaces at 2.65 M the floor-to-floor height of the building is 3.5 metres. This compactness of height means minimising heat transfer through vertical surfaces of the external skin.
Restricting the building height to three stories was a deliberate choice. With maximum ground coverage, this pattern of planning consumes the total permissible FAR with the least possible building height. The advantages are manifold : The energy consumed in transport of materials to heights during construction is minimised. Similarly the energy consumed in conveying water and diesel for the A/C plant on the roof is minimised. A major gain is being able to eliminate the necessity of lifts. Only one 6 passenger elevator is provided for disabled or ill persons and for special guests.
External envelope :
It is in the deployment of finishing materials of the building that some gains are affected by conscious choice. The criteria for choice of materials was that within the constraints of performance specifications demanded of the surface the material should be chosen from the nearest possible source and should call for minimum processing toward converting or installing it. The external cladding is undressed split red Agra sandstone with pre-cast concrete and terrazzo sills and jambs. For office areas floors are pre-polished granite from Jhansi (the nearest source to Delhi). For service areas it is Kota stone.
Glass and aluminium are the worst culprits whose areas, sizes and weights are kept to the minimum possible.
Monitoring and Automation :
For the present, automation in the air-conditioning system is limited the solenoid control valves and thermostats to regulate the flow of chilled water to the air handing units and the switching on and off of the absorption chiller units ; and for artificial illumination the use of switches on timers. More sophisticated computerised automation systems were found to be beyond budgetary provisions and of doubtful cost-benefit. However, it is proposed to install a simple monitoring system for illumination and air-conditioning to help in rationalising the systems management routines for the daily as well as the annual cycles of building use.
Architect : A B Lall Architects
Client : Transport Corporation of India Ltd.
Year of completion : 1999
Total Built-up area : 2750 m2
Cost : Rs 55 million
Infrastructure (electrical, HVAC, plumbing, lift, fuel oil tank, pumps and tubewells) : Rs 24 million
Civil, false ceilling, strong rooms, steel pergola : Rs 30,7 million
Landscaping : Rs 0,35 million
(Credits to Ashok b Lall Architect)