Climate Of Lahore And Thermal Comfort Environmental Sciences Essay

Climate Of Lahore And thermal Comfort Environmental Sciences EssayChapter 22.1 IntroductionClimate has great effect on construct for its electri urban center economic consumption and building performance. Energy efficient design requires the consideration of the clime. The overall oestrus and cooling requirements in the buildings is controlled by climate during summer and winter time of year. As we down selected our site in Kala Shah Kaku, Punjab and kala shah kaku is located in Lahore region therefore the rendering of the climatic data of Lahore region is given be broken.2.2 Climatic classificationClimate can be classified in terms building design in which the country will be divided into five zones in such a way that the difference of climate from zone to zone can be seen in the building design, gauranting some special provision for each zone. Based on these criteria, there ar five major climatic zones,Hot- changeHot-humidCold temperateCompositeTypes of climate Typical Char acteristicsCold Excessive pepperiness loss for nearly of the yearMinimum Temperature below -15 CTemperate Excessive heat lost for part of yearInadequate heat loss for part of yearTemperature changes -30 C to 30 CHot/Dry overheat for most part of the yearDry air allow evaporationTemperature ranges -10 C to 45 C senior risque shaft of lightStrong WindsHot/Humid Overheating for most of yearHumid air inhibits coolingTemperature often above 20 CMean relative humidity around 80 %High peltingfall in certain monthsTable 2.1 typical marks of dissimilar types of climates2.3 Climatic zones of PakistanPakistan has a wide range of climatic conditions. The Northern and North- Western split of Pakistan ar army tank, the centre of the Punjab is extremely hot and semi-arid, and the Baluchistan is cool and arid whereas the coastal strip is warm and humid. In cold regions, during the winter temperature drops well below the zero. In the resign regions, the maximum temperature remains above 40 C during most of the summer period with a backsheesh often approaching 50C.The climatic regions have been divided based on various criteria.Fig 2.1 map of climatic zones of Pakistan2.4 Climate of Lahore RegionLahore lies 217 meters above sea level and it lies between 3115 and 3145 North latitude and 741 and 7439 East enormousitude. On the North and West Lahore is bounded by Sheikhupura district, Wagah surrounds Lahore on east, and on the s verbotenh of Lahore there is Kasur District. The river Ravi flows on the North of Lahore. Lahore city has a total land argona of 404km2.The Lahore region comes under the normal composite zone, harmonize to climatic zone map. It lies near the hot teetotal zone and in summer the wind direction is such that the wind blows northeast towards southwest of the city affecting the climate of Lahore region. The effect of hot ironic zone starts from March and remains till September as the wind direction is southwest which nitty-gritty from hot dry zone towards Lahore region. The main features of this season are that the winds blown are hot and full of dust during the daytime but are cooler in night. Throughout the day very strong wind blows. The climate of Lahore region can be divided into the following broad categories2.4.1 Hot and dryHot and dry weather is found in the months of March and April. In these months the air is dry with the clear sky and no sea breeze to bank check the excessive heat as the Lahore region is located more than 1000 km from the nearest sea, the temperature rise is sharp. In the mid-March the maximum temperature reaches up to 90 F and till the middle of April temperatures reaches up to 100 F. Due to clear sky, nights are cooler having the average temperature of nearly 65 F (18 C). The rainfall is very less(prenominal) in this duration.2.4.2 Very hot and dryIn the months of May and June the weather of Lahore is very hot and dry and the heat is at its peak in these months. In the second week of May, the te mperature reaches up to 110 F (43 C).The heat is oppressive, humidity level is low with very hot and dry wind which is called loo in local language blowing most of the time. The month of June still remains hotter with the temperature sometimes reaching to 119 F (48 C). However in June due to intense low gouge created by the extreme heat, sometimes some moisture from Arabian Sea finds its way to this region and causes rain which for the brings the temperature down temporarily.2.4.3 Hot and wetThe months of July to September are rainy. Monson clouds travel from the Bay of Bengal and after traveling about 100 km over India reaches Pakistan and enter Lahore from the South- East. This rain system in these months called Monsoons. This is a regular characteristic of the Punjab, in this country. The weather is cool and pleasant when it rains, otherwise hot and humid. Although the temperature decreases significantly, from nearly 106 F ( 41 C ) just before the monsoons starts in Lahore to ab out 95 F ( 35 C ) but as the monsoon arrives there is the increase in the relative humidity which increases from less than 25% to more than 65%. The naughty temperature along with the excessive humidity makes the weather very exhausting. Moreover sometimes the rain falls with such an avalanche that it drowns the low lying area and heap have to undergo great hardships so this weather is a mixed blessing.2.4.4 Warm and dryWarm and dry weather remains in the months of October and November. Since the monsoon dough at the end of September, the weather again becomes dry again but the temperature is considerably less hot this time. The dry continental air remains in the region. The temperature is moderate to warm during days whereas the weather is cooler in nights. The average senior high school temperature is nearly 85 F (29 C) and at night due to dry air temperatures it can decrease to 53 F (12 C) especially at the end of October or early November. thither is no rain in this season a nd this season is the driest season as compared to other seasons. This extreme dryness creates a lot of dust and haziness which results in pollution in the environment.2.4.5 Cool and dryThe most pleasant months of all are December January February in Lahore. This is the most perfect weather of Lahore. The peak high temperature is nearly 68 F (20 C) and the peak low temperature is nearly 41 F (6 C). The climate remains cool, refreshing and sunny. However sometimes, a rain bearing system known as westerly disturbance which has its source in Mediterranean Sea affects the Lahore region and causes rain. But the rain is not so heavy neither it remains for a long duration. So the weather most of the times remains sunny, dry and refreshing.In fact, the climate of Lahore is hot and dry for the maximum period of the year with a forgetful winter period with very refreshing weather.2.5 Climatic indicators of LahoreThe table below displays average monthly climate indicators in Lahore which is based on 8 age of historical weather readings.Temperature in FahrenheitTable 2.2 average monthly climate indicators in Lahore2.6 Hot dry climateThe hot dry equatorial land lying between the two mean annual isotherms of 68F (20C) has regions where the temperature during the summer season may reach 43.3C or may exceed and the vapor pressure is below 25millibars.2.6.1 Elements of hot dry climate1 Seasonal variation2 Air temperature3 Humidity4 Precipitation5 Wind6 Sky conditions and solar radiation7 circularise storm2.6.1.1 Seasonal variationIn these regions there are two major seasonshot seasonwinterFig 3.2 Monthly averages of the minimum and maximum daily temperatures.C/F2.6.1.2 Air temperatureThe main features of the climate are temperature remains high during the day 80-130F (26.67-54.44C) in the summer months along with strong sunlight reflecting pitilessly from light dry and parched earth. there is however a big difference between summer and winter temperatures due to the varyi ng altitude of sun. During winter the day temperature is usually as high as 90F (32.22C) but the temperature is quite low at nights ,whereas during summer the temperature goes down to 50F(10C) compared with 70F (21.11C) at night.2.6.1.3 HumidityHumidity remains low, relative humidity varies with the air temperature. It can go below 20% in evening to over 40% at night. V.P fairly steady changing with fixing and season from about 500-1500 N/m22.6.1.4 PrecipitationThe amount of rainfall or precipitation is generally noted as the average mm/day or mm/month which provides a beneficial indication regarding seasonal changes.Usually, average maximum rainfall in 24 hours or the average number of days in which a certain amount (in cm.) of rainfall happened is also given. This data is beneficial as an indicator of the rain intensity, which will affect the design of windows, roofs and sewerage etc.July and August are the months in which most rainfall occur, whereas June and September also ha ve some rainy days. For the rest of the year, hardly any rain fall occurs in Lahore. Based on temperatures and precipitation data, during the hot and rainy season it is not advised to go between June and September. The rest of the year is dry with temperate daytime temperatures.Fig 3.3 Precipitation is any kind of water that falls from the sky as part of the weather.2.6.1.5 Sky conditions and solar radiationsThe skies are without clouds for the most of the period of the year where as frequent dust haze and storms occur mostly in the afternoon. Direct solar radiation is severe and is amplified by radiation reflected from the barren and light colored landscape.Fig 3.4 Monthly average numbers of hours of sunshine per day.2.6.1.6 WindWinds are mostly native they are generally low in the morning however increasing towards afternoon and are maximum in the afternoon, most commonly accompanied by whirlwinds of dust and sand.2.6.1.7 Dust stormsDust storms mostly occurs on summer afternoons w hich is the most intolerable part of the day , when routine winds blow at 15-220 miles per hour. These dust storms also occurs in other parts of the day i.e. in the evening and nights.2.7 Climatic design of buildingClimate has a great effect on building performance and electricity consumption of the building. The process of recognizing, deducing and controlling climatic effects at the building is perhaps the most difficult part of building design. The main objectives of climatic design of building should includeTo minimize electricity cost of a building.To take benefit of maximum of natural energy instead of mechanical system and electricity.To provide halcyon and healthy environment for inhabitants.2.8 Factors affecting climatic designThe native micro-climate and site factors influence the actual environmental conditions of the building. Some important factors related to site should be included while making the climatic analysisTopography- elevation, slopes, hills and valleys, gro und surface conditions.Vegetations height, mass, silhouette, texture, location, growth patterns.Built forms nearby buildings, surface conditionsImportant thermal design factors which should be considered include solar heat gain, conduction heat flow and ventilation heat flow. The design variables in architectural terms which are important to be considered areShape surface-to-volume ratio druthers building height.Building fabric materials and construction thermal insulation surface qualities shading and sun control.Fenestration the size, position and orientation of windows window glass materials external and internal shading devicesVentilation air-tightness outdoor fresh air cross ventilation and natural ventilation.2.9 Thermal simplicityThere is no approved standard for thermal comfort. This is not astonishing, as people can and do live in a wide range of climates from the equator to high latitudes. An Internationally- accepted definition of thermal comfort, used by ASHRAE, is that condition of mind which expresses satisfaction with the thermal environment (ISO7330).Perceptions of this environment are influenced by air temperature, glad temperature, relative humidity, air velocity, activity and clothing.Fig 3.5 achieving comfort in buildings2.9.1 The comfort zoneThe Comfort Zone means the range of temperature conditions of air movement, humidity and video to direct radiations, under which a normally clothed person feels comfortable. This will differ for Indoor conditions as compared to Outdoor conditions. This will also vary for different cultures and regions and varying climate conditions.As an Architects we use our buildings to not only create comfortable inside environments, but also aesthetical and beneficial spaces outside our buildings.2.9.2 Thermal comfort indexA thermal comfort index serves the objective to evaluate the effect of environmental factor on the thermal feeling of inhabitants. scrap of methods have been used in the previously to evaluate the thermal comfort level. However it is not possible to gratify every person in a building and a small number of persons are always discontented with the thermal environment due to individual variations. Several efforts have been made to acquire a subjective and quantitative way of representing the thermal comfort.Thermal comfort condition in tropical summer conditions is given by Sharma and All at the Central Building Research Institute, Roorkee, India. The ranges and optimum values are given in table.Thermal sensationRange COptimum value CSlightly cool19-2522Comfortable25-3027.5Slightly warm30-3432Table 3.3 temperature ranges in different thermal zones2.9.3 Optimal settings for indoor temperatureResearchers have carried out much research on the most suitable comfort conditions, and have come up with general comfort results like effective warmth, the recent comfort standards set by ASHRAE (American society of heating, refrigerating and air condition engineers) for an ind ividual performing light work areThermal comfort conditionsAir temperature 73-77 F Relative humidity below 60 %Mean radiant temp equal to air temperatureAir velocity 10-45 ft/min