Dış Pencerelerde Performans Kriterlerine Bağlı Olarak Bileşen İlişkilerinin İncelenmesi

Abstract

Pencereler, bina cephelerini diğer cephe elemanlarıyla birlikte tamamlayan yapı elemanlarıdırlar. Estetik özelliklerinin yanında, pencerelerden beklenen bir takım performanslar vardır. Bunlar: Doğal aydınlatma, havalandırma, iç ve dış ortam arasında yeterli görsel bağlantı sağlamak, ısı yalıtımı, yağış suyu, hava sızdırmazlık, güneş ışınımı, yoğuşma ve gürültü kontrolüdür. Pencereler bütün bu özellikleri sağlayabilmek için uygun malzemeden yapılmalı ve doğru bir şekilde detaylandırılmalıdır. Ahşap doğramalar, doğal malzeme ve en küçük üretim birimlerinde (marangozhane, atölye) üretilebilmeleri sebebiyle yıllardır yaygın bir şekilde kullanılmaktadırlar. Günümüzde ilerleyen teknolojik gelişmeler sayesinde endüstrileşmiş ahşap doğramalar üretilmektedir. Bu doğramalar, normal ahşap doğramalara göre daha dayanıklı (atmosferik koşullara, böceklere,yangına ve çürümeye karşı) ve daha az bakım gerektirmektedirler. Böylece ahşabın bazı olumsuz özellikleri ortadan kaldırılmıştır. Fakat ahşap malzeme amacına uygun kullanılmadığı zaman (doğru yüzey koruyucular, malzemenin nemlilik durumu, uygun ağaç seçimi, budaklar) birtakım problemlerle karşılaşılmaktadır. PVC Doğramalar ilerleyen teknolojiyle birlikte özellikle son yıllarda önem kazanmış ve yoğun bir şekilde kullanılmaktadır. Dış hava koşullarına karşı (güneş ışını, bünyesine yağış suyu almama gibi) oldukça iyi performans göstermektedirler. PVC doğramalarda; üretim aşamasında doğru detaylandırmaya, profillerin birleştirilme tekniklerine, ısı köprüsü oluşturulmamasına, uygun menteşe ve kilitleme takımı kullanılmasına ve genleşme problemine karşı dikkat edilmelidir. Alüminyum doğramalar, doğal ve dayanıldı olmaları sebebiyle tercih edilmektedirler. Açıklık geçebilme özellikleri diğer doğramalara (ahşap, PVC) daha iyidir. Dış atmosferik koşullara karşı oldukça iyi performans göstermektedirler. Doğrama doğru detaylandırılmalı ve ısı köprüsü oluşturulmamasına dikkat edilmelidir. Doğramalar çevresindeki ve bünyesindeki bileşenlere karşı farklı davranışlar sergilemektedir. Doğrama-duvar ilişkilerinde, doğramanın duvara ankrajına, derz sisteminin seçimine, duvar boşluğu büyüklüğüne ve doğrama dış denizlik birleşimine dikkat edilmelidir. Kasa-kanat ilişkilerinde, uygun menteşe, kilitleme ve bini sisteminin seçilmesi gerekmektedir. Doğrama-cam ilişkilerinde; cam yuvasının genişliği ve yüksekliği, camın dayanma yüksekliği, oturtma, yerleştirme ve yan boşluk takozları önemli noktalardır.

Much more attentioh is being given nowadays to the performance of building components, so that they can be designed to do exactly what is required of them, and so that new systems and materials for which there no backround of traditional experience can be brought fiılly and quickly into use. Windows are important architectural features and must always be judged aesthetically, both as part of the exteraal building composition and as conspicious parts of the view for the occupants of building. 'Windows' are framed units which will usually be either built into a wall during construction ör fbced in a prepared opening after the wall has been built. The window will usually be an outside wall, where it will need to be made of maaterials resistant'to the weather. Less commonly, it may be in an interior wall, where weather resistance will be of the window will be filled by transparent ör transculent glass ör, perhaps, some alternative light-transmitting material. Windows are the building components which complete the building prowiding some functions- environmental view, ventilation, indoor climatic conditions, aesthetic appearence ete.- AH this main desires expected from windows should be prowided in a correct way. Because of this, at first, selecting correct type and matterial decided by architects, effect building occupents. Wood is a convetional window material and is using commonly in the buildings. But new technological devolopments offer us some new window materials (PVC, aluminum) which have better performances expected from windows. The technological devopments about the window type and material enter Turkey at the same time from the other countries. We have some big window productor companies which they product their windows in the world standards. We can resume the windows caracteristics like this order: 1. Geometrical Caracteristics Of Windows (Dimentions) Dimentions of windows are controlled by considerations such as length of reach for cleaning and the maximum area of glass given tickness to meet varying degrees of exposure to wind. Performance criteria such as daylight standards, view out and ventilation requirements are usually met by selecting suitable windows from a range and, so long as the number of sizes within a range permits a close approximation to the overall dimentions requierd by this criteria, the loss in performance is not likely be serious. in general way, considerations such as acceptable head and sili heights will also affect the required overall dimentions of windows, as will the location of transom members to avoid interfering with a clear view. xi 2. Environmental Control Conditions We can mention the environmental conditions like; daylight, Sound insulation, heat insulation, exclusion of the rain, airtightness, prevention of the spread, ventilations and draughts. 2.1 Daylight The planning of deep rooms and the incresing reliance on artificial lighting as a supplement to daylight are but two of the factors that are tending to change the emphasis on daylight and to foster a more critical attitude to the function of windows. None the less, the traditional assumption that the main purpose of windows is to admit daylight stili prevails and for many buildings the fenestration is designed on the assumption that daylight will be the working light for the greater part of the day. 2.2 Sound insulation in urban areas it is usually external noise from road traffîc that has to be considered but, equally, noise from rail traffic and from adjoining factories can be a problem where dwellings ör other buildings whose occupants require a quiet environment are sited too close to the sources of noise. it is also necessary to know the noise level that will be acceptable in the room ör building to be protected. This will depend on the function of the room and the general backround level of sound within the room. 2.3 Heat insulation The transfer of heat trough windows is a complex phenomenon which can involve ali the processes of conduction, convection and radiation. With double glazing, convection currents in the air within the cavity tend to complicate the pattern of heat transfer and, in metal framed windows, heat losses through the frame can add a further complication. The thermal transmittance of a window is usually stated in terms of the transfer through the glazing material alone, but in practice the design and material of the surrounding frame can modify the overall figüre and in certaın cases may need to be taken into account Gurtains and bhnds can reduce considerably the heat loss through a window, but their effect is usually ignored in heat-loss calculations because they are only used intermittently. 2.4. Exclusion of the rain There are various ways in which water can penetrate into and through windows, some resulting from defects in window manifacture, such as unsealed corner joints in frames and saches. There is leakage, too, round some windows at the window/wall joints. Penetration of water takes place most commonly, however, at the joints round xii opening lights, as a result of incorrect detailing or lack of care in manifacture or installation. 2.5. Airtightness The avoidance of excessive air leakage through windows is required partly to minimise cold draughts resulting from the leakage, and partly to avoid unnecessary wastage of heat. As with water penetration, the problem of air leakage through windows is associated mainly with the opening joints. Leakage occuring at the window / wall joints or round the edge panes, through the glazing joints, is usually the result of poor workmanship or inadequate maintenance and cannot properly be ascribed to defects in window design or manifacture, though imperfect design detailing may sometimes be a contributory factor. 2.6. Prevention of fire spread İn relation to the spread of fire, either from one room to another or from one building to another, windows must be regarded as areas of potential weakness. İn an average fire in a building the temperature is likely to rise to 800-900 degree Celcius within the first few minutes and ordinary annealed glass subjected to this kind of heating, usually from one side only, quickly cracks and is then liable to fall away from its frame. Wood frames will be attacked directly by flame on the side facing a fire, and by heating radiation through the glass and by reradiated heat on the side away from the fire. Because of this, the wood frames must be substential enough to allow for the charring that will inevitably occur in a fire. 3. Ventilation and Draughts The velocity of incoming air is of significance in relation to possible cold draughts and there are some points about the shapes of ventilating opening that have to be watched. Generally it is the current of air which penetrates deeply into a room without becaming mixed with the warmer room air which is troublesome. XX 11 4. Security We can group the "security" like; strength and stiffiiess and security against the human actions. human actions 4.1. Strength and Stiffness Generally, windows should be strong enough when closed to resist the maximum pressures or suctions that may be caused by wind loads, and when open the buffeting that projecting lights may receive from gale-force winds. They should also be capable of withstanding such accidental pressures and impacts as they might reasonably be expected to suffer during their normal use in buildings. To meet this requirements the windows need to have not only sufficient strength, but also a degree of stiffness that will prevent undue disortion by bending. This limitation of deflection under load is required partly as a safeguard to the glass in the windows, and partly to prevent damage to, and loss of weatherproofing in, the window / wall joints by excessive frame movements. It is also a psychological need, to prevent occupants of buildings being worried by large window movements. In this respect, windows must not only be safe, but must also look safe. 4.2 Security Against the Human Actions Windows are vulnerable to a variety of accidental pressures and impacts, and in general it would be uneconomic to design them so that they cannot be damaged in such ways. Certainly the ordinary window cannot be guarded against the thrown stone or the supping ladder of a window-cleaner except at considerable cost and with loss of appearance. The surprising thing is that there are not more cases of window damage caused by internal and external mishaps of various kinds. Some windows risks are of course lessened by the fitting of safety rails or other protective devices intended mainly as safeguards to people. 5. Decisions About the Window Material The choice of material for the window frames will be mainly on the basis of costs and appearance. On the latter, the choice may be influenced by the general style of the building and to some extend by what already exists in the neigbourghood. These are matters of architectural taste which must be left to the particular designer to settle. Where a strong feeling for any one of the materials exists, it may well override other considerations. On costs, it will often, regrettably, be necessary to minimise first costs, regardless of what maintenance costs may be incurred in later years. The selection will then he between the painted softwood window and the galvanized and painted standard steel XIV window, with the balance of costs probably fluctuating in accordance with the movements in costs of the raw materials involved. Where the need for initial economy is not so compelling and more attention can be paid to keeping down the maintenance costs, the situation is different, he main requirement will then be to avoid the need for regular painting. With wood windows, only a few timbers can safely be left unpainted, and these, in their unpainted state, may not satisfy the architect's requirements in relation to appearance. So the choice is then more likely to go to metals such as aluminum, bronze or stainless steel, or to plastics, for which the maintenance need to be no more than regular washing to keep the frames clean, here is an underlying assumption here, however, that the external parts of the frames will be accessible for washing, and it may be instructive to compare the "costs-in-use" of regular washing, including the costs of access, with those of repainting at much longer intervals. In doing sums of this kind, it has to be remembered that part of the costs of access, and perhaps a considerable part, will have to be incurred any way, for the cleaning of the glass. In relation to unpainted windows, aluminum, even with regular washing, may suffer corrosion in certain city atmosphere and may ultimately have to be painted. In such circumstances it may be better to go stainless steel, the use of which for windows is now steadily expanding. Plastic-faced windows may not need washing so frequantly as metals as an insurance against surfaces deterioration, but will still need washing at suitable intervals to remove dirth. If, despite regular washing, they suffer a deterioration of appearance, they may still be painted eventually. In exposed situation the all plastic window frame, unless made unacceptably large, may not be stiff enough for the job of resisting wind loading, and the other possibkities of obtaining maintenance adventage of the plastic surface, by moulding the plastics round a metal core or by using it is a long life finish on a wood or metal frame, may have to be explored. Decisions on the kinds of windows that are to be used in a building have to be made at an early stage in the design and it is often necessary to balance conflicting requirments against one another order ta arrive at the best overall solutions. The main decisions that have to be taken are what materials should be used for the windows; weather the windows should be fixed or openable, if openable, what forms of opening lights would be most generally satisfactory, and weather the opening lights should be weatherstripped; and weather the circumstances call for the use of double glazing, and what form the double glazing should take. The factors that have to be considered in various combinations in reaching these decisions are mainly: -Costs. -Appearance. -Exposure to wind and rain. -Provision to be made for external access. -External noise levels. -Heat conservation. -Ventilation. -Exposure to shine. -Daylighting. -Possible needs for fire-fighting and escape.