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Analyzing Climatic Conditions

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Lecture - 19Fundamentals of Climate Responsive Buildings-IIGood morning. Welcome to this lecture which is a continuation of the previous lectureon Fundamentals of Climate Responsive Buildings as part of the online course onSustainable Architecture. In the previous lecture, we looked at how the climate ofdifferent place can be classified, what are the different climatic zones which areclassified for our country India. The different five climatic zones, how do we define eachof these zones and then we also looked at the passive design strategies.The broad categories of the passive design strategies, then we moved on to see how canwe identify based upon the climate of a given place, that what is the right strategy andwe looked at two tools for that. One we looked at psychometric chart, where we couldidentify that depending upon the climate, the weather of a place what kind of strategywould be suited. For example, dehumidification or humidification or sensible coolinglike that or.So, this was a broad type of parameter, broad type of strategy that we could have usedand then we went in more detail about looking at the building specific strategies with thehelp of Mahoney’s table. So, after these two tools, today we will be looking at a littlemore advanced tool which is available in the form of free software which is calledClimate Consultant.So, today we will talk about the software Climate Consultant and how it helps us toidentify the correct strategies. I hope you have already downloaded the software ClimateConsultant and are ready with it. (Refer Slide Time: 02:25)So, let us go ahead with understanding how the software works. Climate Consultant therecent version, most recent version which is available for you to download and use isClimate Consultant 6. Once you download the software, install it on your computers youwill see a start up screen like this.(Refer Slide Time: 02:47)So, we start a new project, suppose this is a residential project and we are choosing themetric units. (Refer Slide Time: 02:57)And we can open an existing weather data file.(Refer Slide Time: 03:07)So, for example, suppose we are looking at New Delhi and we very clearly know thatNew Delhi is actually a composite climate, where it experiences the extremes ofsummers as well as the extremes of cold and it also has a monsoon season. So, there arethree seasons that this climate experiences. So, once we open this weather data file, wewould see that there is this entire data spread. So, we have global horizontal radiation, we have direct normal radiation for each of the months. We have diffuse radiation andglobal horizontal radiation which is maximum.So, maximum, average and average monthly, average daily, average monthly, averagehourly; so, this is what we have for the radiation besides that we also have illuminationhere. We have the normal illumination; we have dry bulb temperature which is averagemonthly, the dew point temperature. We also have relative humidity; wind direction andwind speeds and we have ground temperature which is the average monthly which is for3 depths underground. So, this is the weather data which we have and this is thesummary table which we see as the first screen after we have loaded the weather datafile.(Refer Slide Time: 04:25)Now, once we have selected the weather data file, then we come to selection of comfortmodel. So, when we were talking about the thermal comfort, we have looked at thedifferent comfort models which are there. If we look at this ASHRAE Standard 55 andthe Current Handbook of Fundamentals Model, we are looking at PMV, we are lookingat thermal comfort based upon PMV minus 0.5 to plus 0.5 is how we are defining it.If we are looking at the adaptive thermal comfort model as per ASHRAE Standard 55,the 2010 version; here we will be looking at the adaptive comfort. And, then it is not thePMV based model, it is adaptive comfort model. We can choose either one of this; youcan also try by varying these comfort models and then see what happens. (Refer Slide Time: 05:27)So, let us go ahead with say ASHRAE 55 for now, when we select ASHRAE 55 it givesus how the comfort is being defined, how the sun shading zone is being defined, thermalmassing zone and the clo values. So, all of that is already defined based upon the comfortmodel as per ASHRAE 55. So, you can very clearly see that what is the model which isbeing applicable here which is being used here to define comfort. This is inbuilt; there isnothing that we can change about it. So, this is just for information a kind of annexurethat we are using here.(Refer Slide Time: 06:07) Now, we start looking at the climate of Delhi, here we are looking at the temperaturerange. So, this is dry bulb temperature and it shows the monthly range for New Delhi.So, for each month it very clearly shows what is the average highest temperature in agiven month. This also shows the comfort zone which is for summer as well as winter.So, it shows the comfort zone which is shown in gray here and this is taking a relativehumidity at 50 percent. So, the comfort zone which is defined is at 50 percent relativehumidity. Now, this shows how the temperature is varying it, this one shows the averageannual spread of temperatures. Now, here we are looking at the design high and designlow. So, we are looking at 1 percent of hours above the design high temperature which ishere; suppose I change it to 0.5.So, we see that only 0.5 percent of the hours will be above the design high which impliesthat we are designing for a temperature, where only 0.5 percent of the hours will lieabove the design high temperature that we have taken. If we take it 0 percent; so, thedesign high temperature will be the maximum temperature that has been recorded ever ina given month; however, it is not a very good idea.So, this percentage actually defines how much of the loading is going to be there in abuilding, the peak loading, but we should always understand that the peak loading isgoing to be there only for limited, few hours. So, the maximum temperature which hasbeen recorded is going to be there for maximum 1 hour or 2 hour in an year. So, if wetake it to be 1 percent of the hours above, we are taking only 1 percent of the hourswhich will not be brought to the comfort range with the design strategies which we aregoing to adopt.The same is for design low. So, the lowest temperatures here have been taken as 0percent of hours below. (Refer Slide Time: 08:33)We can take it to 1 percent and we can see that we will not be designing for theremaining 1 percent which are below the design low temperatures, the set points.(Refer Slide Time: 08:43)Similarly, we go on to see the diurnal averages, how the wet bulb and dry bulbtemperatures are varying monthly. So, this is dry bulb mean, this is wet bulb mean, thisis dry bulb variation for all the hours. So, this is the hourly data and this is actually themean data. Along with this we also look at the radiation, the global horizontal radiations, the direct normal radiations and the diffused radiation. And, we see as the radiation goeson increasing the temperatures also increase, the ambient air temperatures also increase.So, this kind of gives the summary of the dry bulb temperature, wet bulb temperature,the comfort zone of summer and winter both here and the how the radiations are varying.(Refer Slide Time: 09:35)Then we are looking at the hourly average daylit hours. So, we are looking at the daylithours which are direct which are receiving the direct normal, global horizontal and thetotal surface which is being lit. This is giving the variation for the high, mean and low,how it is varying for a month. And, this is the theoretical availability of the daylightthroughout each month, throughout the year. (Refer Slide Time: 10:07)So, illumination data for New Delhi is not available in the weather data file.(Refer Slide Time: 10:12)If we had we would have that as well, then this is the sky covering; the total cloud coveris assumed to be 100 percent. So, out of that how much of the cloud cover is there so, wecan see that in July the cloud cover is quite high during the months of July and Augustwhich are the monsoon months. So, which implies that it is an overcast sky and in themonths of winters: October, November, December even January the cloud cover is quite low. In the month of April and March also it is reasonably low. So, that is what we cansee that what kind of cloud cover is available.(Refer Slide Time: 10:54)We can also look at the wind velocity range. So, what is the average velocity of the windwhich is present. So, we can see again the average wind velocities increased during therains, the monsoon period and slightly during the March and December. So, if you lookat this we would also simultaneously while we are looking at this climate data, we arealso going to make a mental note of what kind of strategies would be fitting; though thesoftware itself suggests.But, if you are looking at December and the wind speeds are increasing, we know thatwe have to block the wind during winter season say December and November. And,similarly when we are looking at June and July, that is the humid month in that periodwhich is the warm humid climate kind of climate; we would require more of wind to bebrought in. (Refer Slide Time: 11:49)So, once we have looked at that we would look at the direction of the wind which will beavailable subsequently in the form of wind rows, but here we are looking at the groundtemperatures at different depths. So, we are looking at the depth of 4 meters, 2 metersand 0.5 meters. And, we can see that the average temperature of the ground at a 4-meterdepth remains largely within the comfort range, comfort zone.So, in a climate like this earth air tunnel could be a great asset, it could be a very goodpassive design strategy. Because, if we overlap this graph with the dry bulb temperaturegraph, we would see that the dry bulb temperature actually varies quite large; if you arelooking at an annual variation. So, it would go from somewhere close to 10 degrees andgo up to 40 degrees during May, June and then come down to 10 degrees again byDecember. While, this earth temperature, the ground temperature will remain more orless constant at a 4-meter depth.So, what is the depth at which we can still, but if you look at this at 0.5-meter depth weare still not getting comfortable temperatures say during summers, in winters it is fine,but during summers it is still not comfortable. So, probably going at a 4-meter depth foran earth air tunnel is what would be desired in this climate. (Refer Slide Time: 13:17)We are looking at dry bulb and relative humidity simultaneously. So, this green dot is therelative humidity, how it is varying for each month of the year and we are looking at drybulb temperatures. So, we see that whenever the temperature is increasing in wintermonths the humidity is dropping, but overall if we look at the monsoon months, we seethat the humidity here.(Refer Slide Time: 13:51)This part of the analysis in Climate Consultant shows how the sun path is varying. So,we can see for different months from December to June, how this sun movement is varying along with the temperature, the ambient air temperature which is given which iscoded in three different colors. So, we know that when the sun is here in this zone in themonth of say December, it is actually quite cold outside. So, we would want more sunduring this period.While, if we are looking at these red ones and the movement of the sun along this; so, wewould want to block the sun, we would want to shade the sun. The ones which are in thecomfort zone which is approximately 25 degrees centigrade, that is where 24, 20 to 27degree centigrade that is where we would want to bring in. We may have sun penetratinginside the building and sometimes we may not require that depending upon the climate.(Refer Slide Time: 15:02)It is also showing the same sun path diagram here. (Refer Slide Time: 15:08)Here we are looking at how the temperature is varying at different time of the day; weare looking at different times of the day in each of the month and then we can see thatwhat is the time of the day which is hot in an entire year. So, we are looking at hourlytemperatures and we are also looking at the temperature profiles through color here.(Refer Slide Time: 15:35)This is the same 3D representation of the same data. (Refer Slide Time: 15:40)Once we have done this, once we have understood what the climate of the place is, wecome to a screen like this. Now, this is critical and we have to look at this screencarefully and this is what tells us what are the design strategies. Now, if we look at allthese strategies which can be employed to increase the hours of comfort. Here finally,with the employment of all these strategies which are given 100 percent of the time theindoors can be maintained comfortable. But, if we look at these strategies, we arelooking at sun shading of windows, we are looking at high thermal mass.High thermal mass which is also flushed during the night time. We are looking at directevaporative cooling. We are looking at two stage evaporative cooling, we are looking atnatural ventilation cooling, fan forced ventilation cooling. Now, all of these are notpassive design strategies, some of them are advanced passive strategies. For example, thefan forced ventilation cooling. So, which means the simple ceiling fan is installed that isan active strategy, but it may also be coming under the advanced passive strategies;because of the kind of availability of strategies that we have.We are also looking at say internal heat gain which is by heating up the interiors, this isagain an active strategy, passive solar direct gain low mass and high mass strategies. Weare looking at wind protection of outdoor spaces which is a passive design strategy.Humidification only, this is out and out an active strategy, dehumidification is also an active strategy. Cooling and dehumidification is air conditioning largely, HVAC andheating and humidification is again HVAC which we are adding.(Refer Slide Time: 18:08)Now, if we are seeing that without doing anything, suppose I remove these strategies; Ican take off these strategies. If I do not employ any of these strategies, I see that this isthe period as per we have selected the PMV ASHRAE PMV model. So, this is the periodunder which the climate of New Delhi would experience comfort. So, only these manyhours will fall under comfort here for the given climate; if we do not do anything, if wedo not employ any strategy.Now, through our understanding of composite climate we already know that what kindof strategies may work. So, let us look at the passive strategies first. So, suppose I addsun shading of windows. So, another 24 percent of the hours will be brought undercomfort. So, we see that additional 24 percent of the hours will be brought in undercomfort which is shown here so, this is the strategy 2. So, some of the hours around 2099hours will be brought under comfort, if we provide for sun shading of windows.So, that is a very highly effective strategy. If we look at the high thermal mass, suppose Iadd a lot of thermal mass; it will be able to add only 6 percent, bring 6 percent of thesehours under comfort which is very less. If I night flush it, it will add around 7.4 percentof the hours and bring it to the comfort range. If I add natural ventilation, it will add toaround 2.8 percent of the hours to the comfort range, comfort zone. Suppose, I add the passive solar heat direct gain; so, it will bring in around 3.5 percent of the hours duringwinters to the comfort zone.If I add the high mass, it will add around 10.8 percent which is further during theextreme winters to the comfort hours. If I add wind protection of outdoor spaces, we arenot able to bring any hour under the comforts so, let us take away that. Now, rest of theseand also direct evaporative cooling; so, we are looking at evaporative cooling, now weare also looking at the humidity, low humidity levels. So, here we are looking at directevaporative cooling where further more hours will be added to the comfort zone, otherthan these the rest are active strategies.So, if we look at all these passive design strategies which are mentioned through thesoftware, we would be able to bring in about 37 percent of the hours as comfortablerange within the comfortable range. The 63 percent would still remain not comfortable,now the hours that we are looking at are the high humidity period. So, the hours whichhave high humidity lying between 25 to 35-degree centigrade temperature and highhumidity, humidity of higher than 60 percent that is the warm humid season in acomposite climate. So, we know that the extremely high temperatures and low humiditycan be brought under comfort employing evaporative cooling which is like desertcoolers.The extremely low ones can be brought under comfort by adding direct heat gain, solarheat gain. So, that can also be partially brought under the comfort range, but theproblematic period for a composite climate would be this warm humid period. And, thatis where we would probably need cooling and dehumidification and we can see that 40percent of these hours. So, suddenly the comfort hours go up to 78 percent and a largeportion of this comes into a comfortable zone, when cooling along with dehumidificationis done, added as a strategy; now that is an active strategy. So, we can look at thestrategies, the design guidelines besides these. (Refer Slide Time: 22:43)So, we can also see what kind of strategies are available for us, we can look at how thedesign of a building should be done to bring about to bring in thermal comfort. So, itsays that the window overhangs or operable sun shades should be provided. They canreduce the need for air conditioning, the active air conditioning. The buildingconstruction it should have small recessed shaded openings.So, smaller windows are preferred which are operable for night ventilation to cool themass; so, night flushed. Then the minimization or elimination of west facing glazing toreduce summer and fall afternoon heat gain. So, each of these strategies can further helpto increase the comfortable hours. (Refer Slide Time: 23:46)Let us quickly look at another climate, let us look at the climate of Bangalore which is amoderate climate.(Refer Slide Time: 23:55)And if we look at the data, look at the temperature range; so, while the temperature rangein Delhi was quite high. Here we see that the temperature range is closed to the comfortrange. (Refer Slide Time: 24:08)Similarly, here we can see this variation coming in which is very close. We can see thatthe radiation is quite high even in the winter months, while for the climate of New Delhibased upon its latitude, the solar radiation received during winter month was quite low.And, during the summer and monsoon months it was quite high, that is what is availablein the form of the radiation range as well.(Refer Slide Time: 24:33) (Refer Slide Time: 24:37)This is the sky cover range and we see that the sky cover is quite high in the monsoonmonths here as compared to the Delhi climate.(Refer Slide Time: 24:47)If you look at the wind velocity range more or less it remains the same. (Refer Slide Time: 24:52)And, if we look at the ground temperatures if you remember the Delhi groundtemperatures, we saw that it was going a little higher for 0.5 meter depth and it wascrossing the 30 degree centigrade limit, while here we see that it is almost limited withinthe comfort range. So, we do not need to take our earth air tunnel down below up to 4-meter depth, but even a 0.5-meter depth would serve the same purpose.(Refer Slide Time: 25:25)If you look at this sun shading chart, we would see that for large part of the year it isspread in the warm temperatures under the warm temperature. (Refer Slide Time: 25:39)So, shading might be a very good strategy.(Refer Slide Time: 25:40)And, the same thing we see that the extremely high temperatures above 38 are not thereat all and we have the hotter months are actually March to May, while in New Delhiclimate we saw that the hotter months were somewhere in June, July, August, the mostproblematic months. (Refer Slide Time: 26:01)Now, we come to this. So, if I take off all these strategies, we can see that without doinganything the climate of Bangalore has around 18.4 percent hours as comfort, but we canalso see the spread. We see that there is no extreme winter climate here, there is noextreme summer climate here where the temperature goes above 35. There is rangewhere the at higher temperatures there is no high humidity. So, we have high humidity ata temperature range which is within the comfortable range.So, if we do not do anything, we have around 18 percent of the hours falling undercomfort. And, if I add just sun shading so, around 27.9 percent of the hours are added tothe comfort hours. And, if I look at the natural ventilation around 3.9 percent of the hourshere are added to the comfort and if I add fan forced ventilation another 3.5 percent hereare added to the comfort. If I look at passive direct gain and passive gain high mass thenalmost all the hours which are towards the lower temperature ranges are added to thecomfort range.And, if I add the high thermal mass and high thermal mass which is night flushed almostthe entire of this high temperature ranges are also brought within the comfort zone. Now,the problem in this climate Bangalore climate is also the high humidity temperatures,where higher temperatures with high humidity. And, here if we add onlydehumidification because it is anyways within the comfort range of temperature, but thehumidity is high. So, if I just dehumidify the environment, I would be able to bring in about 46.3 percent and that makes 81 percent of the times of the year, hours of the yearas comfortable. And, here only if I add humidification there is no change; so, there is nohumidification needed, because it is anyways quite a humid climate. And, if I addcooling along with dehumidification, it may not really serve the purpose.So, I can see that for with these strategies I can bring in about 81 percent of the hours inan entire year as comfortable.(Refer Slide Time: 28:56)So, if we compare the two climates and look at the design guidelines, we can actually seewhat kind of strategies works. So, use of light-colored building materials and cool roofswhich was also a strategy for Delhi climate, then minimize or eliminate west facingglazing. So, all these design strategies will then become available to you.With the help of this kind of a tool we can do preliminary identification of strategies thatwhat kind of strategies would work, what kind of strategies should be taken ahead. And,along with that a knowledge of what kind of passive design strategies are available, wecan make a judicious choice of what kind of strategy we should be using. (Refer Slide Time: 29:42)Now, once we have done this, we also have to know a little bit about some of theadvanced passive design strategies besides the ones that we have already seen.(Refer Slide Time: 29:56)So, some of those I have listed here, there are many-many more. The new ones are beingdeveloped and researched, but these are some of the identified and established oneswhich are also commercialized and popular. So, here we will look at thermal insulation,thermal mass, cool roofs. Courtyard effect has already been taken as a passive designstrategy, but it is advanced passive design strategy if we club it with a little bit of mechanical ventilation, forced ventilation. Wind tower is an advanced passive designstrategy, evaporative cooling, passive downdraught cooling which is very similar to windtowers, roof sprays and earth air tunnels.(Refer Slide Time: 30:38)So, when we are talking about thermal insulation, we are talking about adding a materialwhich has extremely low u value or adds a lot of heat resistance to the transfer of heatand that is added to the regular building construction. So, it could be added to the walls,it could be added to the roof. Now, depending upon the direction of heat transfer theinsulation would be added. So, suppose we are talking about an air-conditioned buildingin a hot climate, there the heat is actually coming from the outdoors and there is airconditioning which is happening inside.The insulation that may be provided in such a case would be in between the in betweentwo brick walls, where the insulation would be slightly towards the indoors. While, in anextremely cold climate where the outdoor temperatures fall extremely below much belowthe sub-zero temperatures, the insulation may be towards slightly towards the outside,but both the sides being covered with building materials. (Refer Slide Time: 32:00)If we are looking at the thermal mass as a strategy, here the mass will absorb the heat andit will re radiate it during the night time or the time when the temperatures fall down, fallbelow the surface temperature of the material. So, this strategy is often utilized as a verypopular passive design strategy when we are designing for extremely high temperaturevariation, high on heat or high on cold.(Refer Slide Time: 32:31)Cool roof is a new kind of concept, a passive design strategy where the albedo of theroof is high which implies that the roof reflects a lot of heat which is incident on it. The remaining portion of the heat which is absorbed by the roof is also emitted, almost 100percent of it is emitted during the night time.So, there is very little amount of heat which is transferred to the indoors, largely reflectedrest of it re-emitted; the ones which is absorbed and very little portion of it is transmittedinside that is what the overall functioning of cool roof is. So, there are cool roof paintsavailable, there are cool roof materials which are available and it is becoming quitepopular across the world.(Refer Slide Time: 33:29)Then we have courtyard effect, we have talked about courtyard as a passive designstrategy earlier also. Now, what courtyard does is that it shades the indoors from gettingheated, the interiors from getting heated and this open to sky courtyard; this open to skycourtyard facilitates the night ventilation.So, the heated air from the indoors is ventilated through the courtyard during the nightand that that is the time when the temperatures outdoors fall below. So, it allows for thestructure to bring in air from the outdoors during night and release it through thecourtyard during the night, that is what the fundamental functioning of a courtyard is. (Refer Slide Time: 34:23)Then we have wind towers. Now what is the wind tower? It is a tower which is slightlyraised, it has openings on towards the above end. So, suppose this is the wind tower; so,it will have an opening here. Now, through this opening, the wind it works two ways. So,it acts as an exhaust. So, there is hot air which is rising up; so, this acts as an exhaust andthe hot air rises up and goes out. In other times of the year, it may also help to bring in;so, there are improvisations to the wind tower. So, there are wind towers which have ashape like this, where the this is the prevailing wind direction.So, if this is the prevailing wind direction and there is a sloping structure on the top ofwind tower, the wind is forced to come inside the wind tower. Now, this wind tower willhave a high thermal mass and while the air moves down the heat is absorbed by thestructure of the wind tower.