Sustainable ArchitectureProf. Avlokita AgrawalDepartment of Architecture and PlanningIndian Institute of Technology, RoorkeeLecture – 38Energy Efficiency – IIIGood morning. Welcome back to the third lecture on Energy Efficiency for this ongoingonline course on Sustainable Architecture. In the previous lectures on Energy Efficiency, wehave discussed about the various terminologies related to energy efficiency and we have seenwhat are the different components of a building envelope, which contribute towards heat gain.We have also seen the different factors of the indoor environment inside a building whichcontribute towards the heat gain.So, in the previous lecture, we talked about how the different building components should beoptimized through design, through material selection in order to optimize the heat gain fromoutdoor to indoor through the building envelope. In today’s lecture, we will be talking aboutthe equipments which are installed inside the building or are required to keep the buildingcool.Now, one of the most important systems in today’s building specially the commercialbuilding which a coming up is the HVAC system; Heating Ventilation and Air Conditioningsystem.(Refer Slide Time: 01:52)So, when we talk about the efficiency of these systems, we talk about the coefficient ofperformance and we also talk about the integrated part load values. Now, for different typesof these air conditioning systems, different coefficient of performances are specified. So,higher is the coefficient of performance, higher is the efficiency of the HVAC system.Depending upon the tonnage of the building, the highly efficient HVAC system is preferred tobe used.However, we have to look at the cost payback; what is the capital investment which is goinginto the particular HVAC system and then, we look at the corresponding efficiencies andcalculate the overall energy savings. (Refer Slide Time: 02:51)So, when we are talking about different types of efficient HVAC systems and controls, thereare different strategies. One very important type of equipment is a variable frequency drive. Itis called VFD commonly. What VFD does is it varies the frequency of the controller. So, thefirst and very important and also commonly used equipment part of the system is variablefrequency drive.Now, what variable frequency drive does is it varies the frequency at which these chillerpumps work. So, it varies the flow of the coolant into the U. So, by varying the amount of thiscoolant which is going into the U that is dependent upon the loading; if there is less load, thefrequency required is less. So, if we reduce this frequency of the chiller pumps, we are able tosave a lot on the energy.(Refer Slide Time: 04:06)So, besides the efficiency coefficient of performance of the HVAC system, there areadditional devices which we use for example, this VFD. Another one is VAV which isVariable Air Volume. So, in any building not just commercial building, but in any building,different amounts of cooling or heating is required at different times of the day. So, duringsay the office hours in an office building which is say 9 a.m. to 6 p.m. which is at 75 percentoccupancy, while from 6 p.m. to 10 p.m. it may be only at 25 percent occupancy.So, the same amount of cooling is not required; same amount of air flow is not requiredbecause the number of people have reduced. So, what is this VAV does is that it reduces theamount of air which is supplied through the ducts and sent into the space. The moment wereduce this amount of air which is supplied, we reduce all the back work and reduce theamount of air which is getting cooled or heated in the air chows; thereby, reducing the energyconsumption, the power consumption.(Refer Slide Time: 05:14)Another very important device is this heat recovery wheel. What heat recovery wheel does isthat when the air when the return air which is going back through the returned duct. So, this isinstalled in the ductwork. This return air is already reasonably cooled. So, instead ofexhausting it directly, this heat recovery wheel recovers the amount of coolth and it allows thecool to be taken from this return air to the supply air so that lesser amount of cooling isrequired for the supply air. This is what heat recovery wheel is.Now, this heat recovery wheel derives its name because in cold countries, in cold regions, thisreturn air is actually the heated air. It is the hot air and the supply air is also heated up to acertain degrees temperatures. So, while this return air is going out it is being exhausted. Theheat which is contained by this return air is taken up by supply air and it is supplied inside.The reverse phenomena is applicable where the buildings have been cooled. This is what theconcept of heat recovery wheel is.(Refer Slide Time: 06:42)Another important system component is piping and duct insulation. So, while all this air isbeing supplied, while all the coolants are being supplied to the air chows and then from airchows to the spaces, conditioned spaces. The ducts the pipes which carry these coolants andthese air, they themselves need to be insulated properly. There has to be proper insulation onthem which is usually done, but that has to be done properly in order to ensure that there is noheat loss, heat transfer while the coolant or air is being supplied.Now all these different components and systems which we have just seen. So, there arechillers, there are condensers, there are pumps, VAVs, VFTs and fans and all this thing,individually they may be working at very high efficiency; but all these components need to bebalanced as a system. So, if one component is working at a very high efficiency, but all othersare working at low efficiencies or they are not simultaneously working at high efficiency, thesystem efficiency will still remain low.(Refer Slide Time: 08:08)So, for that purpose proper system balancing has to be done in order to integrate all thedifferent components of this HVAC system to deliver the desired efficiency levels. (Refer Slide Time: 08:19)Another component within efficient HVAC system is the economizer; economizer could beair side economizer or water side economizer. So, what an air side economizer does is that ifthe outdoor air temperature is within the comfort limit, it will automatically shut off the airfrom being cooled and it will directly supply the outdoor air and allow it to be treated andsupplied indoors without getting cooled. So, no energy will be consumed in cooling orheating the air, if the outdoor air is within the comfortable range.(Refer Slide Time: 09:04)Through the waterside economizer, so if in the chilled water circuit, the water is at atemperature which is within the desired range, then it will automatically cut off from sendingthe chilled water to the cooling tower unit and thereby, saving on the energy for this throughthe circulation of this water through the pump. In addition to the back end of the HVACsystem, where all the chill one plant and air chows, piping and everything is there, there is afront end control, where the occupants are.(Refer Slide Time: 09:44)So, there we may have personalized thermal control. So, what personalized thermal controlmeans that not every occupant feels comfortable at the same temperature. They may increasethe temperature, thereby reducing the amount of cooling which is required and individually,the amount of air which is flowing into their space, the temperature will be varied.Collectively, this increases the occupancy comfort and the number of people, percentage ofpeople who feel comfortable who are satisfied with their environment; at the same time,reducing the amount of energy which is required.Besides HVAC which is the major component of energy consumption in a building. Thesecond most important system equipment system is lighting system and the control. Now,lighting is a major energy consumers specially in commercial buildings and it accounts forapproximately 15 percent of the total energy consumption in India.(Refer Slide Time: 10:54)In commercial buildings, it can go as high as up to 40 percent because a lot of artificiallighting is added into commercial buildings. Now, besides the energy which is required forlighting up these lamps, these lamps they generate a lot of heat when they are burning, whenthere on.So, the efficiency of the luminary depends upon how much of the power is supplied to theluminary and what percentage of this power is released converted in the form of light energyand what percentage of it gets converted in the form of heat energy.For any luminary, the maximum output of illumination as a percentage of the wattage ofenergy which is supplied higher is this number more efficient is this lighting system.(Refer Slide Time: 12:09)So, when we are talking about the lighting system, we are talking about the qualitative aspectsas well as the quantitative aspects. To quickly summarize, the qualitative aspects the first isreduction of glare and reflections from the luminaries; proper luminance ratios in the space; amix of direct and indirect sources; appropriate colour temperature and colour rendering. So, ithas to be a mix of all these qualities when we are selecting the luminary.Besides this, we are also talking about the quantitative aspects, where we are talking largelyabout the energy consumption of these luminary lighting systems. One very importantapproach when we are designing buildings for reduced energy consumption for lighting is byproviding the day lighting.(Refer Slide Time: 13:18)So, there are several day lighting approaches through the design of the building form, throughthe incorporation of skylights and atriums and through several different elements such as lightshelves, reflectors, louvers and blinds. All these together will help in reducing the dependenceon artificial lighting and thereby, reducing the amount of energy which is consumed.So, here we can see how different elements have been used. For example, light shelves whichreflects the daylight to the ceiling and helps it penetrate deeper into the building and that isalso the diffused lighting. The sky lighting with appropriate choice of the material such thatthe light is penetrated deeper and with the help of this atrium, the light is penetrated into thedeep areas of the building.Also, the shelves. So, light shelves. So, light shelves is at the top, but also the shelves whichreflect the building such that there is deeper penetration of direct light, daylight into thebuilding. So, with the help of such passive strategies, the building can be day lit and artificiallighting can be reduced.(Refer Slide Time: 14:38)Next, we look at the type of luminary which can be chosen, which has to be selected. So, nextwe talk about the type of glazing which has to be used on the windows which will allow formore day lighting, but less of the heat penetration. We were talking about it as part of thebuilding envelope, but with a greater emphasis on the heat transfers. So, we talked about theSHGC and u value for the glass. Here, we are also looking at the VLT, the visible lighttransmittance for glass.So, if we look at these different types of glass for clear glass, the visible light transmittance is0.82 which means it allows 82 percent of the natural light falling on to it to transfer inside and0.78 of SHGC which implies at 78 percent of the heat which is falling on the glass will betransmitted inside. If we look at all these glasses, probably a reflective dark reflected bronzetint glass which has a very low VLT 0.2, but also a low SHGC. So, it will reduce the amountof heat which is transferred inside; but at the same time, it will block almost all the lightwhich is penetrating in might not be a good idea.While if we to look at the spectrally selective low-e with the green tint, we see that 40 percentoff the light will be transferred inside, while 23 percent of the heat gain heat incident will betransferred inside. So, higher is this ratio of VLT to SHGC. So, if we look at this VLT toSHGC higher is this ratio, better is the glass. Because higher ratio implies more light ispenetrated while less of the heat is transmitted inside. If we place at here glass which is in thisrange is a good glass, when we are talking about a balance between daylight and heatpenetration.So, higher of VLT and low on SHGC is what is preferred. So, here a glass which issomewhere here and here both may perform equally good. So, spectrally selective low-e clearor spectrally selective low-e with green tint both could perform and result in almost the sameamount of energy consumption. Because if we will look at the spectrally selective low-e clear,it has a very high VLT 70 percent and SHGC is 0.43.So, slightly higher than this, but this increase in the heat gain may be compensated because ofpenetration of daylight and reduction in the energy required for artificial lighting. So, ajudicious choice has to be made and which can be helped through different tools which areavailable, which we will see subsequently.(Refer Slide Time: 17:56)Other systems include the redirecting systems, the light transport systems. For example, alight tunnel; this light tunnel, this light pipe actually has a cleared dome on the top whichallows penetration of light from all the sides because it is dome make a structure and then,inside it is a reflective surface. So, the light is reflected multiple times and from all thedirections and it allows for the penetration of light down into the habitable area. This is quiteuseful, where the light cannot be brought in from the fenestrations on the walls or the skylight cannot be provided because there are multiple stories here.In addition to that we also have prismatic glazing. Now, this prismatic glazing allowsselective cutoff based upon the angle of incidence. So, depending upon when is the lightcoming in. So, the light entering at a low angle may be cut off because that may be causingglare that may cause glare. So, there are different cutoff rangers which may be by virtue,which is by virtue of the design of the prismatic glazing, but the high angles of incidence areallowed to penetrate inside.So, these are some improvise and little high-tech systems, where the light can be broughtinside and it can be directed to certain areas and depend based upon certain conditions. Otherthan this we talking about the energy efficient lighting system.(Refer Slide Time: 19:45)So, when we are talking about the optimized lux levels. So, as per the codes, it is defined howmuch of the illuminance is required in a given space for a given function. So, based upon thatrequirement from NBC, we would know that how much of how much is the optimized luxlevel which has to be achieved in a given space and to achieve that proper lighting design hasto be done, uniformly distributed lighting in order to achieve this given illuminance level, thelux levels. (Refer Slide Time: 20:22)Besides the design which is the uniformly distributed illumination level, we are talking aboutthe efficacy of the lighting fixtures which implies the amount of light in measured in terms oflumens which are produced per watt of the energy supply to the luminary, the lighting fixture.So, if you are look at the different luminaries starting from candle to the incandescent bulb tothe tungsten filament incandescent bulb to the CFL which is the compact fluorescent andthen, we also have the LEDs.(Refer Slide Time: 20:58)we see for the same given luminance level in terms of lumens, the amount of light which isamount of energy which is consumed by these different types of luminaries lesser is thisenergy consumed for the given lumen output, better more efficient is the luminary which wesay it has higher efficacy.So, if we see here for 450 lumens, the standard incandescent bulb would require 40 Watts,while an LED would require only 8 Watts. A fluorescent,a CFL may also require very lessamount of energy. LED is have revolutionized the lighting industry, you know it has justleapfrog. So, we today consume very less amount of light for producing the same amount ofluminance in our buildings these days.(Refer Slide Time: 22:07)So, highly efficient luminary should be used, high efficacy luminaries should be used and thatis why you would see that almost the entire a market is now moving towards the productionand sale of LED lights and it comes us no brainer because they consume less amount ofenergy while giving the same amount of lumen output. In addition to the luminaries, thelighting fixtures, we also have to add the lighting controls. Now, these lighting controls couldbe of two types; they would be on and off type of controls and they would also be thedimming controls.So, we have manual switches, the elapsed time switches, clock switches, energy managementsystems, photocell controls and occupancy controls as part of the on off controls. We willquickly see each one of these what do they do and how do the function and in dimmingcontrols, we have the dimmers. So, where just like we reduce the speed of the fans, we canreduce the luminous the lumen output of the luminary by reducing the amount of energywhich is supplied to it.So thereby, reducing the energy demand less amount of light is required instead of turning offthe light and making certain portions of the building certain portions of the space dark, wejust dim; we just reduce the amount of luminous which is being produced.(Refer Slide Time: 23:41)So, what we have is we have three different types of controls, the dimmer controls, themotion or occupancy sensors of photo sensors and timer control. So, dimmers are the deviceswhich are used to lower the brightness of a light by changing the voltage which is supplied toit and thereby, reducing the amount of energy which is consumed.(Refer Slide Time: 24:02)The motion sensors or the occupancy sensor, they sense the motion, movement of people andit is through the infrared sensing. So, the moment there is movement, the lightest turned on inall other times the light would be just turn off.So, the moment somebody passes where the sensor is placed, the subsequent light whichfollows, it will be turned on. So, when there is no movement in the corridor or certain areas ofthe building which may remain empty most of the time, the lights could just be turned offtheir by saving the energy.(Refer Slide Time: 24:49)The next is a timer control. So, it is a kind of a clock for measuring time intervals and it isefficient for outdoor lighting. So, for example, in commercial buildings after 7 p.m. forexample, when it is getting dark, the building outdoors have to be maintained lit for up to say10 p.m. for certain types of lights; but beyond 10 p.m. only very few lights are required. So,for this series of light which needs to be turned on only from 7 to 10, a timer control isinstalled where the timer is set for a say 4 hour duration from 6 to 10. So, for after this 4 hour,automatically all the time all the lights will be turned off.The other types are photo sensors. So, in photo sensors which all of you might have seen, itmeasures the daylight levels and after the daylight levels have dropped to a certain level, thelights would automatically turn off. Besides HVAC and lighting systems, we also haveseveral other equipments which are required in the buildings and we need to install efficientequipment and appliances in our buildings. The bureau of energy efficiency has come up witha star rating scheme for different appliances, for different equipments.(Refer Slide Time: 26:18)Now, higher is this star rating, I am sure all of you would already know because this isavailable out in the market. Higher is this star rating implies higher is the energy efficiency ofthe equipment or appliance that you are buying and lesser is the amount of energy which isconsumed for the same amount of output.So, the different equipments which are required in the building include the transformers,pumps, motors and appliances which include refrigerators and air conditioners. So, all theseare available with very high efficiency in the market and we must choose the highly energyefficient equipments and appliances to be used in the buildings.(Refer Slide Time: 27:12)Now, that would collectively reduce the amount of energy which is consumed in the buildingboth for comfort creation and day lighting and also through the regular equipment usage. So,to summarize this generalized discussion about energy efficiency of buildings, let me quicklygo through the steps.(Refer Slide Time: 27:46)The first and foremost is to optimize the building design and improve the energy efficiencythat is through day lighting, the regularly occupied areas in order to harness more and more ofday light through windows and skylights and minimize the use of artificial light.(Refer Slide Time: 27:52)Second is through the use of low embodied energy materials in building construction.Preferring natural ventilation wherever possible. (Refer Slide Time: 28:00)So, the first is to address the thermal comfort and the visual comfort issues to passive design.So, designing the building and building envelop properly in order to reduce the energyconsumption of the building.(Refer Slide Time: 28:25)Next step would be through HVAC by avoiding the over sizing of equipments which is whatis a usual practice because we always take a very high safety factor. Linking the thermostatwith the occupancy sensors so that the thermostat and occupancy sensor are in sync and it isnot that even when the occupancy is less, the thermostat is still allowing for a lot of cooling.Use the air conditioner in energy saving mode which is setting it at 25 degree centigrade orhigher that is for specially for Indian subcontinent, the region in which we are in.Using the ceiling fans along with the higher set point of AC. Now, these are the operation,these are the operation mechanisms, these are the practices which we can use when we areoperating the buildings to achieve a higher energy efficiency. Seal the building envelop toreduce the loss. So, that the coolth, when the building has been cooled is retain inside or theheat is retain inside of the building is being heated.Maintaining the equipments at regular intervals of time and strategically positioning the airconditioners. This is for individual buildings, but when we are talking about large buildings,then also strategically positioning the ducts, the supply ducts and also the return ducts, returnair ducts in order to increase the area which is cooled by the same supply duct.(Refer Slide Time: 30:07)Next will be through lighting and electrical units so, the practices such as turning off thelights, using spotlight, maintaining the lights at regular intervals using sun to drawing insteadof dryers. So, using computers in power saving modes and not plugging in the electronicswhen they are not in use. So, some of these are the practices which will lead to saving ofenergy through lighting and electrical units.Besides this, selecting the luminaries properly, designing the illumination system such thatuniform lighting illuminance is provided and also using sensors and controls such that turningthem off automatically when the illumination is not required.(Refer Slide Time: 31:09)So, what do we do; how do we know that where is our building consumption? We can do thatby monitoring our energy consumption and regularly comparing our energy bills. So, if wesee that a energy consumption is going high, we can immediately adopt some practices whichwill help us reduce the energy conservation. Now, this was from a user perspective, from anoccupant perspective.But from a designer’s perspective our first aim should be to design the building passively inorder to bring in thermal comfort and ones that energy demand has been reduced by ensuringthermal comfort, we would then go on to add the HVAC systems and lighting systems.When we are talking about the new buildings, as I have been at different intervals I have beentalking about the different tools which are available. So, there are energy modeling toolswhich use simulation, computer based simulation to actually simulate how the design is goingto affect.(Refer Slide Time: 32:20)So, how the daylight is going to be when we are talking about a particular design of thefenestration or what will be the overall energy consumption for one alternative versus theother alternative in a proposed new building.(Refer Slide Time: 32:41)So, what we would do is when we stimulating this building, we would incorporate all thesedifferent components of lighting, HVAC, window shading which is the passive design andalso the plug load and calculate and also integrate it with the building integrated systems ofenergy generation and calculate the overall total energy consumption and how we canoptimize on each of these systems.So, I was stop here for this and in next lecture, we will look at the compliance criteria for thegreen building rating programs, rating systems and how to comply with them what are thecalculations we have to do and how can we goead with the compliance criteria.In addition, to that in subsequent lectures which will be towards the end of the course, we willbe looking at use of one of the simulation tools for this energy compliance how to simulatethe building for energy compliance. So, we will also look at that towards the end of thiscourse.So, thank you very much for being with us today. See you in the next lecture.