Natural Ventilation In Buildings Engineering Essay

Natural Ventilation In Buildings Engineering Essay Proper design of energy conscious buildings requires a balance between two things: The thermal performance of the building envelope and the appropriate selection of techniques for heating, cooling and day lighting; An acceptable quality of the indoor climate in terms of thermal comfort, ventilation effectiveness or indoor air quality. Over the past years in all the western countries and more especially Europe, there has been a conscious limit of the availability of energy since the oil crisis of 1973. The main result of this crisis in term of the construction industry was therefore to reduce significantly global energy consumption, mainly used for heating and air-conditioning while neglecting its impact on the comfort and health of its occupants. During these periods, new regulations were made to regulate these, which also so the birth of real development of building research in western countries. However, these strict regulations on energy reduction in buildings was accompanied by an increasing number of disorders, mainly due to humidity condensation and the growth of mould, which affected the health of the occupants leading to SBS and building related sickness among the occupants, to overheating in the summer or in intermediate seasons, which affected the thermal comfort of the occupants and finally poor indoor air quality (IAQ) die to low air-change rates. The evolution began in the 1990s and it is now clear that energy conservation cannot be disassociated from the quality of the indoor and outdoor environment. These environmental criteria have even led to major modifications in manufacturing and technology, such as the abandonment of CFCs in HVAC. These criteria also highlight the necessity of full integration of the building site characteristics and potential in the design and this leads naturally to a focus on more integration of passive concepts on heating, cooling or more generally indoor climate conditions. (1) 1. Santamouris and Asimakopoulos, Passive Cooling of Buildings (1996) With these various aspects taken into account, natural ventilation appears to be a very attractive solution to ensure both good indoor quality and acceptable comfort conditions in many regions. Further more, natural ventilation seems to provide an answer to many complaints from users concerning mechanical ventilation, which appears to be noisy, to create health problems, to require routine maintenance and to consume energy. In contrast, natural ventilation is preferred by the occupants since it is energy efficient (no need of mechanical system), it can be easily integrated into buildings and it provides a healthier and more comfortable environment if integrated correctly. (2) Fundamentals of Natural Ventilation The magnitude and pattern of natural air movement through a building depends on the strength and direction of the natural driving forces and the resistance of the flow path. Good design involves the appropriate application of fundamental principles to the general strategies described in the following sub-sections. The driving forces for natural ventilation are wind and density difference. Wind Wind driven ventilation is caused by differences in pressures acting across the external surface of a building. The distribution of pressure depends on: the type of terrain surrounding the building (open country/city centre) and the presence of any obstructions (other buildings, tree belts etc) which provide opportunity for site layout and landscaping to enhance wind driven ventilation the wind speed and its direction relative to the building, and the shape of the building; this provides the opportunity for the architectural form and detailing to enhance the potential for wind driven ventilation. 2. Liddament, M. A Guide to Energy Efficient Ventilation. (1996) Air will flow through a building from areas of high surface pressure to areas of low pressure as shown in figure 2.5. In general terms, building surfaces facing into the wind will experience positive pressures; leeward surfaces and those parallel to the wind direction will experience negative pressures (suction) Source: Whole Building Design Guide Figure 2.1 Wind pressure field around a building Careful orientation of a building in relation to the topography of the site can maximise the potential for wind driven ventilation. This potential can be enhanced by landscaping, such as tree planting. Density differences Warm air is less dense than colder air. If two columns of air at different temperatures are separated by a boundary, there will be a difference in pressure across that boundary due to the different pressure gradients on either side. Normally, where it is warmer inside the building than outside, the pressure difference acts inwards at lower levels of the building and outwards at high level. When openings are placed in the boundary separating the two air columns, an upward air flow will be created through the building, exhausting warm air at high level and replacing it by cooler air at low level. This is known as the stack effect. These stack -driven flows rise vertically through a building, but will induce horizontal flows in spaces connected to the column of air rising. These horizontal flows replenish the warm air which is exhausted from the shaft. The shaft can take a variety of forms (see 2.3.3), but Figure 2.2 below illustrates the general principles associated with stack driven flows in an atrium. Source: Caroline Rock, Coventry University Fig. 2.2 Stack driven flows in an atrium Strategies for Natural Ventilation Wind and buoyancy, the driving forces for natural ventilation, may be used for different ventilation strategies: wind variation-induced single sided ventilation, wind pressure-driven cross ventilation and stack ventilation. Single-sided ventilation Single-sided ventilation relies on opening(s) being on only one side of the ventilated enclosure. A close approximation is a cellular building with opening windows on one side and closed internal doors on the other side. Single opening With a single ventilation opening in the room, the main driving force for natural ventilation in summer is wind turbulence. Compared with other strategies, lower ventilation rates are generated, and the ventilating air does not penetrate so far into the space Source: Dyer environmental controls Fig 2.3 Single-sided single opening ventilation Double opening Where ventilation openings are provided at different heights within the faà §ade, the ventilation rate can be enhanced by stack effect. The ventilation rate will be further enhanced by any wind pressures acting on the ventilation opening. As well as enhancing the ventilation rate, double opening increases the penetration of fresh air into the space. Effective to a depth of about 2.5 times the floor to ceiling height. Source: Dyer environmental controls Fig 2.4 Single-sided double opening ventilation Cross ventilation Cross ventilation occurs where there are ventilation openings on both sides of a space. Air flows from one side of the building to the other and leaves through for example another window or door. Cross ventilation is usually wind driven. As the air moves across an occupied space, it picks up heat and pollutants. Cross ventilation is effective up to 5 times the floor to ceiling height Source: Dyer environmental controls Fig 2.5 Cross ventilation Stack ventilation This term is used to describe those ventilation strategies where the driving forces promote an outflow from the building, thereby drawing in fresh cool air via ventilation openings at low level. The strategy makes use of the difference in density between a column of warm air and the surrounding cooler air. Because air flows into the building at low level, then up to a high level exhaust point, great care has to be taken into account when determining the different sizes of ventilation opening on each floor of the building. For equal ventilation rates, the ventilation openings at lower floors need to be smaller than those nearer to the top of the building. The effectiveness of natural ventilation can be enhanced by designing the stack outlet to be in a region of wind-induced negative pressure. The air may flow across the whole width of the building and be exhausted via a chimney, or it may flow from the edges to the middle to be exhausted via a central chimney and or atrium. e.g. Lanchester Library, Coventry University. Fig 2.6 Stack Ventilation strategy at Lanchester Library, Coventry Fig 2.7 Air exhaust via perimeter chimneys, light wells and the central atrium at Lanchester Library, Coventry Source: Pat Non, Coventry University Double Skin Faà §ade A double faà §ade construction consists of a normal concrete or glass wall combined with a glass structure outside the actual wall. Double skin facades offer several advantages. They can act as buffer zones between the internal and external environment, reducing heat loss in winter and heat gain in summer. In combination with ventilation of the space between the two facades, the passive thermal effects can be used to best advantage. Opening windows in the inner skin can draw air from the buffer zone into the building. The stack effect of thermal air currents in tall buildings offer advantages over lower buildings. Night Ventilation Night ventilation is not an additional mode of ventilation; it is simply a different operational strategy. It takes advantage of the natural diurnal variations in temperature to promote cooling. Night ventilation offers many advantages like cooling the fabric of the building at night and also ventilating during unoccupied periods

My Faith Essay -- Christianity Biblical Christian Religion Essays

My Faith During my life, I have had many experiences that have shaped my character. One of these moments happened when I was a junior in high school. This is when I decided to join my high school track team. I had always played many sports such as golf, basketball, wrestling, and football, but I hadn’t been involved in track. So I decided to give it a try. It may seem strange, but that track season, as well as certain circumstances that happened during the season, was very beneficial in learning some simple concepts of my Christian faith. When I first joined the track team, I was very excited. I was looking forward to the upcoming season and my chances to be a star sprinter. The first few weeks of the season were tough, but I was determined to reach my goals as a sprinter. I worked my hardest in all that the coach had us do, but I especially focused on the sprints because the next week was when the coach told us what our races were going to be according to how we did in the practices. I was almost sure of my spot as a sprinter because I was the second fastest kid on the team, but the next week was â€Å"the moment of truth.† Monday had come of the next week, and it was time for practice. I can still remember the anticipation as the coach read off the lists and positions of each person. I was shocked to discover that the coach had placed me in the middle distances rather than the sprints. I was a bit upset upon discovering this. After all, I was the second fastest kid on the team, and I didn’t run my hardest in the longer races on purpose just to ensure that I would get a spot as a sprinter. However, this did not happen. I told my parents about my position that night, and they gave the usual speech that probably many of y... ...ecause I thought I was about to be passed. The roar increased with every stride closer to the finish line. The next thing I remembered was crossing the finish line in first place and turning to glance back down the track. To my surprise, the second placeman was over 50 meters behind me. I had achieved first place, and fell only 1 second short of the 800 record. The rest of the day went the same way. Our four by 400 meter relay team took first place, and we ended up breaking the record in that race. After this I decided to stay in track, and I ended up being the second best in the state. I learned a few lessons from this. The first was that if we persevere and give everything our best, God will bless us. God also taught me a big lesson in humility. I have learned to rely on God and to listen to what my parents say. This was one of my most influential moments.

French Court System

The French court system is a double pyramid structure. There are two separate orders: administrative courts and judicial courts. Each order has a pyramid structure, with a single court at the top and various courts at the base. Litigants displeased with a court decision can seek a review before the next court up in the hierarchy. In each order, a single court of last instance ensures that the lower courts interpret the law in the same way. The administrative courts settle disputes between users and public authorities. The Conseil d'Etat hears cases in first and last instance. It is both adviser to the government and the supreme administrative court. †¢The courts with general competence are the administrative courts, administrative appeal courts and the Conseil d'Etat (as a jurisdiction). †¢Administrative courts with special competence are the financial courts (Court of Auditors, Regional Courts of Auditors, Court of Budget and Financial Discipline) and various other tribuna ls like the disciplinary bodies of professional orders.The judicial courts settle disputes between persons and sanction offences against persons, property and society. There are three categories of judicial court: †¢the courts of first instance: – the civil courts: district courts, regional courts, commercial courts, employment tribunals, agricultural land tribunals, social security tribunals; – the criminal courts: . ordinary courts: police courts, regional criminal courts, assize courts; . specialised courts: juvenile courts, military courts, political courts and the maritime criminal court; local courts, created by Act 2002-1138 of 9 September 2002 to meet the need to make justice more accessible, swifter and capable of dealing more appropriately with small claims and minor offences. Local courts have lay judges; †¢the courts of second instance: the appeal courts; †¢the supreme court: the Court of Cassation, responsible for ensuring compliance with th e rules of law applied by lower courts. It judges the form and not the merits, unlike the courts of first and second instance, which judge the facts.

Why The Cliffside Holding Company Of Massapequa ( Chcm )...

Introduction Critical thinking is a process that can help us make decisions in our life by thinking from different perspectives. It is a device that helps evaluate ideas through the testing of statements and the reasoning behind them. Just like any other skill, one must learn how to use critical thinking before utilizing it. In this paper I will use the 11-step method from the text â€Å"Asking the Right Questions: A Guide to Critical Thinking (11th Ed.), developed by M. Neil Browne and Stuart M. Keeley (2015). The book is an essential tool for developing critical thinking skills and will be used to conduct an evaluation on a memorandum identifying whether the Cliffside Holding Company of Massapequa (CHCM) would establish a†¦show more content†¦Finding an author’s main point is the first step in deciding whether you will accept or reject it (p.27). In order to search for the issue in this memorandum, Browne and Keeley (2015) suggests that we find what is causing ques tions and controversies in the discussion, and what the stimulus is for what is being said (p. 24). Throughout the memorandum, Mr. Anil Ravaswami (Vice President of Human Resources) is questioning whether a leadership development program is necessary for the junior financial executives and if it is even cost-effective for the company. Therefore, the issue in the memorandum is clearly stated as whether the Cliffside Holding Company of Massapequa should fund and establish a new leadership program for their junior insurance executives. Now this brings us to the question of what kind of issue this is: descriptive or prescriptive? Browne and Keeley (2015) describe descriptive issues as those that raise questions about the accuracy of descriptions of the past, present, or future, and prescriptive issues as those that raise questions about what we should do or what is right or wrong, good or bad (pp. 24-25). That said, this issue is prescriptive because they demand prescriptive answers bas ed on ethical or moral issues, and using the phrase â€Å"should† is a clear indicator of a prescriptive issue (pp. 24-25). Moreover, Browne and Keeley (2015) describe prescriptive issues as those that raise questions about whether something is good or bad, right or wrong (p.