 Good morning everybody. I am J.K. Naik, faculty in energy science and engineering IIT Bombay. Please bear with my throat. I will be giving a talk on thermal performance of building. You have had two nice lectures from two architects. I am going to organize the following manner. We want to do a little bit of quantification. We have understood the basic principle. Therefore, we want to see what is the objective of finding out the thermal performance of buildings. So that is what is its importance and usefulness. What are the various techniques? Jitgen just now introduced a number of techniques. I will add a few. What are the type of results one gets out of such simulation techniques? Then I will summarize my talk. I begin with some questions. You want to design a building. Where are you? Madam Monika had introduced you to the climate concept. This is just a pictorial view of climates. You can be anywhere. Would you copy the design meant for a particular climate? By now all of you are conversant. You will say no. These are the climate conditions in India. I think many of you might have seen it. There are five climates, hot and dry, warm humid, large junk is composite. There are some isolated packets where we have temperate climates. Then the north part is cold climates. All of us will understand that the requirements vary and therefore design features will change. So that is the first question. We cannot copy a design from one place to another. Then you would ask how good it will design? Would it meet the requirements? How does one identify that it is an energy efficient? One way is to build a house and then check oh it is not energy efficient. It is a very inefficient way of understanding one's fault. Therefore we do some calculations and that is what is called building simulation. Let me ask what does building simulation provide us? The quantification of temperature, quantification of load, how much energy can be saved and then we can compare the alternate designs which one would be the most suitable. So that is one advantage of building simulation. Let us ask a second question. Normally we choose materials, it should look nice, it should protect from weather and should provide structural strength. Is there anything else beyond this? Yes. We have to also worry about these properties of materials what we are choosing. Specific density, thermal conductivity, they will provide some other benefits which normally probably people do not look at it. That means what time difference I want to introduce as far as the heat flow is concerned into the building. If outside is hot enough do I want it to be hot enough inside immediately? What is the fluctuation happening outside? Do I want the same fluctuation inside? It is called decrement factor and the overall heat transfer coefficient would tell us what is the net heat that is coming into the building. There are other properties which we are touched upon by Jitain. How much it does emitting? How much it is reflecting? How much it is absorbing? So the building materials must be chosen not only because of the other consideration which I showed you a minute before. I am not discounting their usefulness or importance. These are also equally important. Let me introduce these two concepts time lag and decrement factor. Suppose this is the behavior of temperature outside the room and if this is the behavior of the temperature inside the room. So temperature versus time. Here I have not shown any axis. I can have anything I want. So I am just giving an example temperature versus time. Suppose I have this is outside and this is inside. This difference is called time lag. So the difference between the maximum of outside and the maximum of inside is the time lag. I want to be collapsed or I want to be increased. Typically a 30 centimeter brick wall gives about 10 hours of phase lag to give an idea. This is defined as decrement factor. What is the difference between maximum and minimum outside? What is the difference between maximum and minimum inside? That ratio is called decrement factor. I want it to be reduced or I want it to be large. So my materials decide and I just mentioned that how much it is lost, how much it is reflected and absorbed. So the material properties decide. So therefore, choosing materials also equally important from this point of view. So simulation helps us in establishing these facts. So to find out thermal performance of a building we do such simulation. What do we mean by thermal performance? I just told you earlier. I repeat it. How much heat load is coming inside the building? What is the temperature inside the building? What is the wind speed inside the building? What is the daylight inside the building? All those things that we find out, it is called the thermal performance of the building. So what are the input requests to do that? Then we have design the conceptual design, the implementation, what are the openings? What are the wall type? What are the roof type? What are the thicknesses? What are the type of charges? Where are these buildings going to be located? So weather data, radiation, wind, ambient temperature, humidity and what proposed material that you plan to use in the building? So material data and then who are the occupants? They decide what is the internal gain of the building. These are the input required and that is gives a flow path of simulation. You design what is the material and where is climate and where are we locate? I mean what are the occupants? All these things taken together and a balance is made and that is what is a simulation. One can do a steady state method, one can do a dynamic method, steady state method that means we assume your certain parameters remain steady, do not vary that frequently. It will give you average information as far as load is concerned or temperature is concerned either on a manual basis or on a monthly basis. They are much simpler to operate. There are many simulations that are available. I will list at least one and there are dynamic methods you want to know hourly information and therefore they are much more complex, require a very detailed input. So depending upon requirement one will choose appropriate simulation techniques. What is the basic requirement of simulation? You require external load, you need internal load, what is the ventilation and then finally you do the energy balance. It is just to give an example of tools which are available commercially which it and mentioned the code TECT and EQS. They are essentially using the DOE engine. The simulation engine is DOE 2.1E. Then there are transits energy plus E10 is steady state analysis. There are many front ends people have developed. Some of us may not be conversant with preparing input files for such huge computer programs. So lot of front ends have been prepared to create input files for such simulation tools. Just these are few citations. So there are more than 200 simulation tools available depending upon one's requirement. One will choose one. By the way there is no shortcut. One has to understand the physics of the simulation tool. Otherwise garbage in, garbage out. I will just give what type of results one gets out of such simulation tools. I will give some example. We have taken hot and dry climate. Many years back when Jitin was in IIT we have done these calculations. This is a building in IIT campus newly built. We did monitor this building and also we did simulation of this building. It is a low rise residential building, G plus 4 and these are all 4 flats in each floor used for campus staff. What are the features of the building? There are direct gain through windows. Fin's Chajas he just introduced these terms. We looked at external collar, glazing type, air exchanges, wall roof type and orientation. This is what he was referring to the parametric analysis. You can play with various parameters and understand which is the best combination for a particular requirement. So tool that we use was DOE 2.1E, energy plus, etc. we are not developed by that time. The type of results you will get on an annual basis which is the culprit to provide a certain heat gain into the building. Windows, walls, floor, infiltration. So all such things you will be able to understand and then take measure to reduce it or one can do a monthly of load calculation or one can define, suppose it is not air conditioned building, one can define a measure. What we defined is something like this. How many hours in a year? Temperature exceed 25 degree. If you consider 25 is your limit, after that you must air condition it or how many hours in a year? Temperature is more than 30. So it is up to you. You can play with all those things and then you find out what you are getting out of your simulation. Remember no simulation tool will tell you what calculation you can make out of it. It is your understanding that gives you what results you can extract from a simulation tool. Suppose you vary air change rate. You can calculate what the yearly minimum, yearly maximum, yearly average and the two parameters which we have introduced their values. You can introduce any other parameter you feel desirable for your building. Suppose you change the window size, what are the gain through window? You will be able to find out and then you can identify which is the hottest room, which is the coolest room in the building. You can do a lot of sensitivity studies, various parameters and understand which are the right set of combination for the requirement. For an example, we chose certain set of combination and you see the improvement is a non-condition building. The number of hours in a year exceeding 30 degree centigrade in a particular room was 4202 and the measures that we chose reduces by 50 percent. So this is just to indicate what is the power of a simulation tool. You want hourly variation, you can find out such hourly variation if that is the objective of your simulation. So there are plenty of simulation tools. The effective use is possible if one knows the theoretical background. So little bit of insight is necessary, otherwise people are all very much impressed by the show of a software. That does not mean anything and integration of building design with simulation is desirable. That is what Jithin emphasized and if some body is not very conversant with simulation tools, you can resort to the front ends available. Well, before I conclude, let me introduce the passive solar architecture, that phrase which has not been done in a formal way. I will give a textbook definition of passive solar architecture. Passive means of its own as opposite to active. So there is no energy being used in transferring heat from outside of the building to the inside of the building. So that is called passive. Solar is a really misnomer because we want to use everything available that is outside. It could be wind, it could be water, any other energy source available outside should be integrated into the building. So the energy flows from outside to inside by natural means of convection, radiation, conduction and mass transfer. That is the textbook definition of passive solar architecture. It does not mean that you will not use a small fan or a blower. So the objective is to design a building to minimize the auxiliary energy usage and that is what we call nowadays energy efficient building. I introduce simulation studies. What are the type of results one can get out of simulation studies and it is desirable to integrate building design and just to be more important because of the new challenges that architects are facing because of modern technology. Thank you.