So, to start with the first terminology at a building level is energy performance index. Now,energy performance index is a metric to understand the annual energy consumption of abuilding per unit area. So, it is the energy consumed per unit area per annum in a building andit is an indicator of how much energy is being consumed by the building; lower the EPI of thebuilding more efficient is the building.(Refer Slide Time: 02:12)So, we have to try making a building which has a low EPI; if we look at the data current datafor energy consumption in buildings, which was published by LBNL in 2012. So, as per thisdata the standard annual energy use the EPI that is the conventional energy use for Indianbuildings is around 250 kilo Watt hour per meter square per annum and the best is around 60.Now, this we are talking about buildings which are using air conditioning. On an average alot of buildings in India do not use air conditioning and they have the energy consumptionannual energy consumption EPI of around 100; this is what the usual number is. And thereare buildings just by virtue of not using air conditioning and depending upon a naturalventilation and natural lighting day lighting.The energy use is reasonably low in our building. But, as we see that the commercialbuildings are growing in number and most of these commercial buildings are being centrallyair conditioned there are more and more of spaces are being air conditioned. The energyconsumption of our buildings in India not just commercial buildings, but also residences theenergy consumption is tremendously increasing.If we have to reduce the energy performance index, if we have to increase the energyperformance index which is reduce the number of the energy consumed. We have to changethe way in which the buildings are designed, the way equipment is selected and used and theway buildings are operated.(Refer Slide Time: 03:57)So, this is another report by energy technology perspective which was published in 2016 andthis is a global scenario this is not for India. So, currently this is in billion tons of giga tonequivalent of CO 2 released. And if we see the total is somewhere here which is related whichis the building related chg emissions. And if it continues to grow like this, it is going to reachsomewhere here by 2050 which will cause a global temperature rise of around 6 degreecentigrade.In order to reduce that and limit it at 4 degree centigrade of rise, we have to implement thecurrent global buildings priority for a 2 degree reduce which was still be 4 degree centigradehigher scenario. In order to further reduce it and bring it down to a level which is here, wehave to make all the new buildings as near or net zero energy buildingsSo, that the buildings produce all the energy that they will consume, in addition to that theexisting building will require deep renovations. So, the existing building stock will also haveto move closer to the net zero energy requirement. And the energy source on top of this willhave to be supplied through low GHG sources such as, photovoltaic or hydro or other low onGHG energy sources.In addition to that, the building materials will also have to be low GHG building materials.Once we do that we will be able to limit the 2050 scenario to a plus 2 degree rise which willstill be higher than the industrial level temperatures temperature limits.Now, this implies that a lot needs to be done in our buildings and buildings are going to bemore and more critical if we are talking about the global scenario the global temperature rise.So, what do we do? When we look at these buildings the building design what kind ofmaterials equipments, the first thing which is of utmost importance and concern to us isbuilding envelope.(Refer Slide Time: 06:38)And when we are talking about building envelope, we are referring to the external facade ofthe building which comprises of the opaque components and the fenestration systems. So,when I say exterior facade we are talking about the building envelope which is coming incontact with the outside environment so, these portions.Now, this can be opaque component like wall or it could also be the fenestration system. So,all of this together is the building envelope, the internal floors are not counted as part of thebuilding envelope. When we talk about the opaque components we are talking about thewalls, the roofs, the floors. When we talk about fenestration systems, we are talking about thewindows, we are also talking about the skylights and ventilators; we are talking about thedoors which are glazed and sometimes the doors which are also not glazed. So, this all of thistogether is building envelope.So, when we say that building envelope is the most important parameter for concern forconsideration within building envelope, there are several factors which need to be consideredwhich need to be taken care of when we are designing.(Refer Slide Time: 08:07)Part of it we have already seen when we started talking about sustainable buildings we sawthat the first thing that we need to do is climatic study. So, understanding the climate as towhat the climate brings with it, how can we deal with it through the buildings. So, we have toknow about the temperature ranges, humidity, solar radiation, wind speed and directionlandform, vegetation, water bodies, open spaces. And all these things as part of the climateand microclimate study. We have dealt with this in detail as part of our site analysis.Once we have this data with us the next is building orientation and form. Now, when we talkabout building orientation and form we are talking about two impacts of it or two properties;one is the surface to volume ratio and also the exposed surface area. Now, surface to volumeratio implies that there will be more surface of the building, which will be available for thisheat exchange. We have also seen the three different ways. So, we are looking at conduction,convection and radiation, but if the surface is higher it will be more prone to receive heatthrough either of the medium conduction, convection or radiation.Now, if we have we reduce the surface area to volume ratio, we are immediately reducing theamount of surface available for this heat transfer. Even after reducing that we have to designthe building because buildings on a site can mutually shade each other or a building itself canshade, through the grooves and niches that are created as part of the building design. So, wehave to see how much of the surface area is exposed and this is also dependent upon theorientation of the building.So, if we are in the northern hemisphere and we know very clearly that the north side of thebuilding will never receive the direct sun, because of us being in the northern hemisphere andthe sun path which is there. So, larger part of the building surface should ideally be exposedto the northern side in such a manner that the exposed surface area is reduced.(Refer Slide Time: 10:34)So, if we look at the heat gains in a building through the envelope indoors as well asoutdoors. So, indoors the load from indoors is either because of the equipment or because ofhuman beings. So, because of people because we also radiate heat. Now, this is a load whichcannot be altered which cannot be compromised, this is the metabolic heat this remains asconstant. The other load is through the equipment. So, miscellaneous equipment the lightingequipment there may also be the mechanical systems like fans which may be producing heatas they function.Now, here we can choose efficient equipment, which produce less amount of heat for thegiven task for the given output. In addition to this we have a lot of heat gain from theoutdoors, now this is through conduction, convection and radiation. So, there is direct solarradiation which is entering into the building and falling onto the surface. There is conductionheat gained through conduction and there is heat gained through convection because of theventilation and infiltration.So, all of this is contributing towards a lot of heat gain. And in addition to that if we look at alot of these factors which will be considered while designing. Here we are concerned mainlyabout energy, but we have whether to take into account largely we are talking about weatherhere. And in internal phenomena we have the occupancy and use HVAC system lighting,machinery, equipment, building materials, finishes and the agents which are both organic andinorganic.In addition to weather and climate which is a prime concern here we also have a lot of otherconcerns which will be present which cannot be ignored, but here when we are talking aboutenergy let us largely look at these. So, the building has a lot of these internal as well asexternal loads which need to be balanced to make it an energy efficient building.(Refer Slide Time: 12:48)So, we have insulation. Now, insulation is the amount of solar radiation which is received onthe building surface that is the insulation. So, when we are designing a buildings. So, firstthing which we have seen is orientation of the building to improve the surface to volume ratioand also the exposed surface area; now that is done because all these surfaces are exposed tothe solar radiation.So, we have to reduce the amount of insulation received during summer, but we also have tosee, what is the amount of solar radiation which is received during winters. Because thebuilding specially in composite climates the building may require heating in winters. And ifwe look at the total energy budget sometimes the cost of heating and the energy required forheating the building may surpass the amount of energy required for cooling the building, ifthe building is not properly designed. So, we have to see that how much is the amount of insulation which is received on eachfacade each surface during winters and during summers. An estimate of this will help us indesigning the building the geometry of the building.The next thing which we need to keep in mind is the possible orientation of the buildingplanform. So, different planforms will require or will have different optimized orientationsbased upon their climate.(Refer Slide Time: 14:28)So, suppose we are talking about warm climates, where reducing the amount of heat gainreceived by the building is a preferred criteria. And if we look at the simple rectangularbuilding the ideal orientation would be to orient your building such that the longer side of thebuilding faces north and south and the shorter side of the building faces east and west.Suppose we have an l shaped building, the ideal thing would be to expose the again the longerside but, with the projected end towards the north. If we are talking about the there are there ismultiple set of building in majority of these cases the longer axis should actually be facingnorth when we are talking about the hot warm climates, while it will change, when we aretalking about the extremely cold climates. In such climates we have to orient the buildingslightly tilted in order to receive maximum amount of insulation that too in winters. So, firstthing is building orientation.(Refer Slide Time: 15:53)(Refer Slide Time: 16:00)If we look at this particular simulation on the screen, we have to analyze through propersimulation tools what is the shadow pattern and at different times of the day and differenttimes of the year. So, we have to analyze the impact what a particular planning arrangementwould have, on the buildings on site the adjacent buildings and also on the buildings aroundthe site.So, alternatives of building design and placement have to be tried to improve upon theamount of insulation received optimize it. Now, I am not saying reducing it or increasing itthat depends upon the specific climate for which the building is being designed. So, here weare not even getting into the specifics of building design, but it is just orienting, it is justplacing it on the site together.(Refer Slide Time: 16:58)So, as we have already seen that the north south orientation for longer occupied spaces is abetter orientation. These are the simulation images and if we see that the same building whichis here has been oriented with its longer facade facing north. And we can see that the amountof radiation received on these surfaces is lower as compared to the same building if it isexposed to east and west. And there is a huge amount of sun to which this building isexposed, there is a larger amount of solar radiation which is received.So, before we actually design the building in detail the first thing that needs to be corrected isthe orientation of the building. And very good tools are available nowadays where we cancheck what is the amount of solar insulation, whether we want to increase it or reduce it weselect the optimum orientation.(Refer Slide Time: 18:05)The next is we have to plan, we have to design the elements which may provide shading treesare one such element. So, we have to optimize and we have to design accordingly theplacement of these trees. So, if we see what happens if we plant trees on the south? So, if weplant trees on the south, which are like evergreen trees we see that there is lesser amount ofshade which is received in summers.And there is more amount of shade which is received in winters which is something we donot want in a composite climate, which is what prevails during for the most geographical partof the country. However, if we see if there are trees which are planted on the west, in Julythere is a larger shadow which is cast on the building as compared to January when a smallershadow is being cast on the building. So, with such kind of exercises we can also see, whichis the optimum direction.Now, this one was for an evergreen tree where we have assumed that the foliage remains thesame. This could also be altered if we select less into as trees, which will shed their leavesduring winters. So, we may have plantation of trees in such a manner that they are able toshade the building in summers while when they shed their leaves in winters they allow for allthe solar insulation to receive the building.So, not just the planning of like the design of the landscape scheme, where the trees should beplanted but also a discussion on what kind of trees should be planted adjacent to thebuildings. So, that the desired impact on shading is achieved.(Refer Slide Time: 20:03)So, what we are essentially doing is, we are doing the insulation analysis through a lot ofsimulation tools this one is through ecotect where we load the weather data file. We knowalready how the sun is moving for a given place and then we calculate the amount of solarinsulation which is received indoors.So, you can see this grid here, we know the amount of solar insulation which is received by aparticular building for a given place. With the help of this right in the initial stages of designwe can orient it in a proper direction. So, that the daylight is maximized while the solarinsulation is optimized to. After the building has been properly oriented, we talk about thebuilding envelope composition, we talk about the materials. So, since more and morebuildings are becoming air conditioned and we are less dependent upon natural ventilation,we are talking about building insulation as an important part of the building envelope.(Refer Slide Time: 21:11)If it was a naturally ventilated building, there is not much difference between the indoor airtemperature and the outdoor air temperature. There is some difference because of theabsorption because of the heat retained absorbed by the building mass. But when it is an airconditioned building the indoor environment is absolutely different from the outdoorenvironment for most part of the earth. And there is a lot of difference between the indoor andthe outdoor.So, in extreme summers assume that there is around 23 degree centigrade which is to bemaintained inside or say 24 while outside it is like 45 or 46 degree centigrade. So, it is atemperature difference or delta of around 22 degree centigrade which is a huge temperaturedifference. And the same thing might happen in winters, when indoors we are againmaintaining an indoor temperature of around 20 degree centigrade while outside it is around 5degree centigrade.So, again a 15 degree delta is a huge temperature difference again. To reduce this, to reducethe amount of energy which is required to bridge this gap or to maintain the indoor conditionsas such, we need to insulate the building. So, that there is less amount of heat gained throughthe building envelope. So, we are talking about the walls, the floors, the roofs and thewindows all of them and also air leakage.So, what we have to do is, we have to insulate it we have to break the heat traveling, we haveto break the path which through which the heat travels from outdoor to indoor or indoor tooutdoor. We have already seen what our values are what are the properties for insulations, butthe aim for insulation is to have a high R value to select a material which has a high R valueand place it in such a manner that it breaks any thermal bridge.(Refer Slide Time: 23:35)So, there is no connection from outdoor to indoor because of this insulation which is patternbetween. If we do that in case of summers, the heat will be absorbed by the outer layer andthen it will be reradiated back when the outside temperature falls during night but, it will notbe transmitted inside. The same will be during the winters when the heat will be absorbed andthen reradiated back into the system and it will not be lost.(Refer Slide Time: 24:09)So, the insulation is increasingly become important not just involves. But in fact, moreimportant in roofs the inverted earthen pots has been a very common technique which wehave used in our buildings since old ages it is a traditional technique.So, what actually happens is that, these inverted pots they trap a lot of air inside them and thisair actually acts as an insulation material. So, just like what we just saw as a insulationmaterial in the wall which was installed, this air cavity acts air is the best insulator for thatmatter. So, this air cavity which has been created it acts as an insulation material.(Refer Slide Time: 24:55)So, if you look at the impact of insulation, without the insulation being installed used in abuilding, this is the amount of heat gain which was received through the roof and through thewall. And if an insulation was added so, we reduce the roof you value from 4.2 to 0.261 andthe wall new value from 2.1 to 0.44.The amount of heat received through the roof has substantially gone down, it is tremendouslylow from 24.6 kilo Watt hour per meter square it has been reduced to 2.1 kilo Watt hour permeter square. Now, this implies that this much less amount of cooling will be required forthis building.(Refer Slide Time: 25:51)The next important parameter or the component of the envelope is fenestration. Now, infenestration we are talking about two components; one is glazing and the other one is frame.Largely the fenestration is comprised of glazing as far as the area is concerned but frame, isalso important because sometimes even after using high efficiency glass; if the frame is leakyor if the frame is allowing for a lot of heat transfer then the performance of the high efficiencyglass will also be reduced.(Refer Slide Time: 26:42)So, when we are talking about fenestration, we are talking about two three things. One whichis the most important from a design point of view is window to wall ratio. Window to wallratio is the percentage of the wall area which is occupied by windows, higher is the windowto wall ratio higher is the amount of light which penetrates inside and also the amount of heatwhich comes in it is directly proportional in whichever climate it is.So, there is more heat transfer which takes place through the windows. Higher WWR impliesthere is an increased rate of heat transfer and also increased amount of daylight which isavailable as we go on reducing the WWR both of these reduce.(Refer Slide Time: 27:32)So, this is in one of the cases, where in the base case if a WWR of 60 percent was used versusif without doing anything just the WWR was reduced to 30 percent there was a direct savingof around 20 percent which was achieved. So, that high is the impact of window to wall ratiowithout doing anything without selecting the material. So, the first and foremost is designingit correct for designing it with optimum amount of windows. Once we have selected theoptimum amount of WWR, then we go on to select the right type of glazing.(Refer Slide Time: 28:20)Now, we are talking about selecting the glass as the first parameter. And we have alreadydiscussed how the glass transmits heat inside, it may be directly transmitted, it may beabsorbed and then reemitted heat. So, the total amount of heat which is transmitted to throughthe glass has to be seen. We have already reduced the WWR and then we select the right typeof glass which in warm climates or in cold climates who reduces this heat transfer through theglass.(Refer Slide Time: 28:59)Now, when we are talking about the glass selecting the high efficiency glass there are twovalues of utmost important when we are talking about the heat gain. We are talking aboutSHGC and we are talking about U value. Now, U value impacts the amount of heat which istransferred due to the temperature difference which is what we have also seen in the previouslecture.While SHGC is the property of glass, which impacts the heat gain due to direct solar radiationlesser is the SHGC, lesser is the heat gain due to direct solar radiation, lesser is the U value,lesser is the amount of heat transfer due to temperature difference.Now, often if you look at the specifications of the glass, reducing the U value automaticallyreduces the SHGC; this is often. If we have a doubly glazed unit for example a glass unitwhich has two layers of clear glass, with an air cavity in between in such a case the U value isreduced, but the SHGC is not reduced as much. Now out of these two, which one is moreimportant?(Refer Slide Time: 30:20)So, if we look at this particular example, if an if the SHGC of a glass is 0.3; which impliesthat 30 percent of the total direct solar heat which is incident on the glass is transmitted insidetransferred inside. While U value of the glasses 3.0 and if we have if we assume that this totalincident solar energy is 800 Watts and the temperature differential is 20 degree centigradewhich is in an extreme summer season.Because of SHGC out of 800, 240 Watts will be transmitted inside transferred inside out ofthe incident solar energy. While by virtue of the U value of this glass it will be transmittingaround 60 Watts of energy inside because of the temperature difference. So, the total isaround 300 Watts of which 80 percent is contributed because of SHGC.So, we know what is the importance of SHGC while selecting the glass, which is moreimportant. Now, the reduction in SHGC as the property of the glass happens because ofcertain coatings layers on the glass. They may be reflective coatings they are often, able toreflect the amount of heat which is incident and these coatings they come with specific typeof glasses which are also the high efficiency glasses, but the costly ones. The saving grace isthat if we reduce the amount of radiation falling onto the glass, there is direct reduction in theamount of heat which is transmitted.(Refer Slide Time: 32:07)So, earlier in the previous slide, if we saw that there was an 800 Watts of solar radiationwhich is incident of which 240 Watts is transmitted with an SHGC of 0.3. If I do not changethe glass property here, if I just introduce a shade almost 50 percent of this solar incidentradiation is cut off with the help of this shading. So, it is only 400 Watts of which around 120Watts will be transmitted inside, if we do not even change the property of the glass. So, herewe see that when we are talking about the window design the fenestration design, windowshading is an important parameter.(Refer Slide Time: 33:06)So, window shading should be provided, but it should be optimally designed.(Refer Slide Time: 33:13)Because the moment we provide for window shading, we are also cutting down on theamount of direct daylight which is penetrated inside. So, if you reduce the amount of daylight,we are increasing the amount of artificial light which is required in the building.So, we design the fenestration shading appropriately we orient the fenestration in such amanner that it allows for the winter sun to penetrate in while it blocks the summer sun. If weare planning for some skylights, we should plan them in the similar manner where the lowwinter sun is penetrated while the high summer sun is cut off. So, the fenestration shadingshould be optimally designed.(Refer Slide Time: 33:51)Next very important strategy is cool roof we have already discussed about cool roof. Now,cool roof is a roof which has a high SRI value which implies that its reflectance is also veryhigh and its emissivity is also very high. So, when it has a high reflectance it reflects almostall the heat that is incident on it, whatever little is absorbed it is all reradiated back because ithas a high emissivity.(Refer Slide Time: 34:27)So, cool roofs are also very impactful when it comes to reducing the heat gained through theroof and this was a study which was conducted by triple IT, Hyderabad in association withLawrence Berkeley national laboratory. And they found out that it is quite cost effective whenit when we look at the advantages.So, the overall estimated annual electricity savings by painting the roof with a cool roofmaterial was of this order. And the total savings over the expected life of the cool roof whichwas much higher than the investment which has gone in towards the installation of the coolroof.(Refer Slide Time: 35:18)The next is blinds. So, blinds cut off the amount of direct solar radiation which is penetratedwhich is passed from the fenestration to the indoors, but the location of the blind whereshould the blind be installed that plays a critical crucial role. If we install the blinds in sideswhich is what the common practice is. The heat has anyways penetrated inside and most ofthe heat which has penetrated inside will remain inside despite the blinds.So, we may have a feeling that there is less amount of heat which is coming in if blinds areinstalled inside. Actually most of the heat has anyways come in while if we install it outsidemost of the heat which is incident is blocked by the blinds and it is reflected back and verylittle amount of heat is transmitted inside.(Refer Slide Time: 36:18)So, this is a quick comparison for each of the facade side if the blinds are installed outside,when it there is a moveable shading which is externally installed. And in this case when it isnot installed there is a significant reduction in the amount of heat gained on all the sidesspecially the west. So, the blinds are very interesting and impactful components, which can beincorporated as part of the fenestration.(Refer Slide Time: 36:52)The next is skylights. The skylights they permit a lot of natural light the daylight, but at thesame time they also allow for a lot of heat to come inside the building. Again we have to lookat the U value and SHGC requirement for these skylights specially because they receive directsun and their part of the roof. So, a lot of sun is received and hence low U value and lowSHGC should be preferred for the skylights.(Refer Slide Time: 37:29)So, if we look at the overall ECBC envelope requirement we see there are two types ofrequirements for the building envelope.