The first K-12 school on Earth to achieve a LEED-EB Platinum Rating
The United States Green Building Council (USGBC) has recognised Pathways School Gurgaon for its Leadership in Energy and Environmental Design (LEED), thus conferring it with the honour of being the first school serving all grades K-12 in the world to achieve LEED-EB Platinum certification from USGBC. Among all educational facilities worldwide who have achieved this top distinction, which includes only one high school and a small number of university projects, Pathways School Gurgaon is the highest rated.
At Pathways School Gurgaon we believe that in addition to imparting holistic education, it is our duty to sensitise our students about sustainability – and what better way than to make them experience and immerse themselves in a sustainable lifestyle through their everyday activities at school.
Hence, when designing the school, we particularly emphasised on creating a green campus with zero discharge and a low carbon footprint. We took on the challenge of finding simple and unconventional approaches that take full benefit of natural energies and minimal use of complex technologies. This made the project more cost-effective as well, thus disproving the general industry notion that green buildings are inherently more expensive to construct. The design takes cues from traditional Indian architecture where old forts and palaces remained cool in the summers and warm in the winters even in the absence of modern technologies.
The results have been rather overwhelming:
- Our total energy requirements are 40% lesser than those of conventional buildings.
- Our total HVAC (Air Conditioning) requirements are 60% lesser than those of conventional buildings.
- We saved about 8-10% in construction costs too.
Given below are some of the salient features of our sustainable architectural design:
Conditioning of Circulation Spaces without providing equipments
Central Atriums with Natural Ventilation on the top
- Because of the air cavity total thickness of the outside walls are about 18” to 20”. Windows are then placed on the inner edge of the wall. This automatically gives a shade of 18” to 20” and thus the sun does not strike directly on the windows;
- The Window profile used is UPVC which has a U Value of 1.7;
- The glass is used in a Double Glazed Unit having 6 mm Reflective Glass on outside, 12 mm Gap filled with Argon Gas and 6 mm Clear Low ‘E’ Glass inside. Glass specification include U value of around 1.6, Solar Factor of around .35 and light transmission about 25%. The Low ‘E’, U Value and Solar Factor ensure that the outside heat does not travel inside the room. The 35% Window to Wall Ratio and 25% light transmission on one hand takes care of the glare thus no blinds/curtains are required and at the same time it ensures maintaining of sufficient Lux Levels inside the room and there is very less dependence on the artificial light.
- Central Air Conditioning Plant consists of Chillers (Compressors) as the main Machinery. We use “Screw” chillers which give efficient power consumption even on part loads. The IKW is 0.62 per Tonne. The Refrigerant used is R134A which again is green compliant;
- While designing the Air Conditioning (HVAC) of a project, a careful working is performed determining the amount of Fresh Atmospheric Air to be pumped into the conditioned spaces. And since the temperature being maintained indoors is 24 degrees, it is the job of the Central Air Conditioning Plant to pick up the atmospheric air of 44 degrees, cool it down to about 23-24 degrees and them pump into the indoors. This consumes a lot of Air Conditioning Load and energy. Geothermally, 4 meters below the ground the temperature remains constant round the year. And this temperature is the average annual temperature of the place, which for the Delhi NCR is about 25-26 degrees. Therefore, we are routing the Atmospheric Air through Earth Air Tunnels 75 Metres Long buried 4 Meters below the ground. After travelling this 75 meters, this air picked up at 44-45 degrees cools down to about 28-30 degrees. Now we will cool this 28-30 degrees air to 24 degrees and pump inside. There are in all 6 Earth Air Tunnels of 1200 MM dia provided and each tunnel is reducing the HVAC load by 30 TR each meaning a total reduction of 180 TR. This results in less power consumption thus reducing the carbon footprint considerably;
- In a school environment there are various timings at which various facilities operate. And at the same time it is very difficult to ensure that the air conditioning and lights of the respective areas are properly switched off during these off hours. Here we regulate the electricity through a PLC (programmable Logic Computer) which shuts off the supply at the non usage hours thus ensuring no wastage at all;
- While we have saved the electrical energy by the above measure, there is still a lot of energy losses that happen with the chilled water flowing through the multi kilometer of chilled water lines irrespective of wherether the equipments of particular areas are being used or not. This is a passive loss which no one takes into consideration but has a huge impact on the Main AC Plant load. To arrest this, according to the usage time and pattern, we have devided all our buildings into various zones and intelligentally designed the chilled water piping providing motorised butterfly valved at the chilled water return of each zone. The PLC at the time of shutting the electricity of the non operational zone also shuts off this motorised valve thus cutting off the chilled water to unnecessarily run in the pipe lines of this zone. Thus on one hand reducing the pumping load and on the other arresting the unnecessary energy losses that otherwise are incurred with the excess flow of water in the non operative areas;
- All the Fan Coil Units and Air Handling Units are fitted with Pressure Independent Balancing Cum Control Valves that regulate the flow of water required thus optimising the flow which results in reduced Water Flow and hence saving in Pumping energy;
- All the Floor Mounted AHUs are fitted with Variable Frequency Drives which regulates the Air Flow according to the requirement. This optimisation reduces the total tonnage required for the AHU and hence reduces the load on the Chillers;
- All the pumps are fitted with Efficiency Class 1 Motors which give a better energy efficiency which further increases on part loads:
- Cooling Towers are selected with Lower Approach. This reduces the Condenser Water Temperature which in turn reduces the power consumption of chillers. Further the Towers are so designed where the highly efficient fans are selected which consume less power. For a 275 TR Cooling Tower, the total Fan KW is just 7.5;
- Condensate Water Collection and Usage. Normally in any HVAC facility the condensate water is channelised to the drain and goes waste. And actually this is near Distilled quality water and that too at a very low temperature. We have chanellised and collested the condensate water of all the FCUs and AHUs into a single tanle which then pumps this cold water to the cooling tower as the make up water. This on one hand utilises the water which otherwise goes waste. And on the other hand, providing chilled water to the Coolong Tower increases the effivciency of Chillers Condensate water by abut 6% resulting in huge power savings.
Indoor Sports Arena
- Pool Heating: Then for the winter heating, instead of going in for boilers we have gone for energy efficient Heat Pumps. The winter heating requirement of ours is about 300 KW. In case we had gone in for boilers, they would have incurred a power consumption of about 350 KW as boilers run on about 85% efficiency (which further keeps on reducing with times) and COP is almost 1. By switching to the Heat Pumps, this power requirement has come down to just 60 KW as the Heat Pumps work on a COP of 5 and in this case the efficiency increaes by the times. Further during non-operational hours the pool is covered with the Isothermic Pool Cover thus conserving the hest within the pool and just a fraction of heat pump is operated to maintain the heat level;
- Pool Ventilation: Out of the air with which the Indoor Sports Arena is cooled, about 8000 cfm is directed to the swimming pool for ventilation and maintaining the humidty levels. Using this technique has saved us from putting De-Humidifyers and a separate Ventillation System which otherwise would have consumed about 25 KW of power.
Plant Room placement and cooling
- Out of the 50000 cfm air that cools the Sports Arena above, 42000 cfm is routed and left over the DG Sets thus taking care of the DG Sets cooling;
- Rest 8000 which is used for Swimming Pool Ventilation becomes much more cooles with the fumes and is channelised to cool the complete plant room;
- The cooling tower at the terrace though cool the condensor water but also in the process throw a huge amount of cool air in the atmosphere. We have trapped this cool air going out of the cooling tower and brought it to the DG Sets installation thus adding onto the DG Ventillation.
By doing these measures we have done the Plant Room Cooling and DG Sets Ventillation without installing any equipment but using the cool air which otherwise would have thrown away. This has resulted in saving to the tune of about 85 KW of equipments which otherwise would have to be installed.