【正文】 the system, there are various hardware ponents such as anchors, connectors, brackets, cramps, setting blocks, corner blocks, gaskets and sealants etc. This system has the following merits/demerits: Merits Low cost, ponents can be made in standard design and stocked as proprietary product for use in bulk quantity. Shorter time for design and fabrication. Fairly easy to fit the shape and form of a building. Require relatively simple sections to form the mullions and the backing frame. The design of the infilling panels can be very flexible and form various bination using different materials to provide the appearance or fulfill other functional requirements. With the provision of the spandrel panel (the opaque portion) in the design, more colour or design options can be achieved. Installation of the system only requires simple tool like a manually operated pulley setup. Easier to carry out replacement, alteration and maintenance. Demerits System is designed on a jobbyjob basis More labourintensive in the fixing and installation process Higher risk of leaking due to the existence of large amount of insitu joints between mullion and panels. Involvement of large number of framing members ing from the mullion, transom or other framing parts that make the fixing at spot quite troublesome and inconsistent. Less fashionable for the design limited basically to monotonous grid without the elegance that other systems may achieve. Unit System Unit systems are posed of modulated panels that are fabricated in factory and delivered to site in onepiece for installation. The panels are fully provided with all the glazing and/or the spandrel panels, incorporated with the required insulation and other architectural features, thus requiring very limited secondfixed installation works on site. The panels are usually spanned in a floortofloor arrangement and may be designed in a number of standard/optional panels such as fully glazed, glazed with opaque panels, fully opaque in metal or stone slab, louvered panels, or other special modules like the corner or bayed units. In order to get the best benefit of using this system, units are often produced to an optimistic large size so as to minimize the number of units used. This system has the following merits/demerits: Merits Easy to install merely by securing the modulated panels onto the building exterior using fixing/connection devices which are usually very dimensionally flexible. Saving up a lot of manpower due to ease of installation. Higher performance units can be produced to meet stringent requirements due to better control under factory environment. Preferably to be used in buildings with large walling area for the economy of scale in production as well as the elimination of countless assembly of minor ponents on site. Demerits It takes longer lead time to carry out the coordination, design and fabrication of the system/units. Require higher dimensional accuracy in the building structure for the fixing of the units. Lifting appliances may be required to assist the hoisting and installation of the largesized walling units Difficult to carry out replacement or maintenance due to the interlocking nature of the modulated units. Unit and mullion system This is a bination of the stick system and the unit system and may be regarded as a promise of the two. It is more suitable for use in mediumsized projects so as to balance the factors of lead time, ease of installation and economy of scale. Panel system A panel curtain wall system is similar to a unit system, the difference being that a panel system has homogeneous sheet or cast panel with few joints and may not have separate mullions. Unit systems are made up of smaller ponents fabricated together to form much plex panels that capable to perform heavier duties or other more specific requirements. However, due to the relative simplicity of the system, curtain wall of panel system design may not be able to fulfill the usual requirements most highrise buildings required under Hong Kong’s environment. Its use is therefore more limited to certain kinds of buildings like those of standardized design for lowine classes or for buildings of industrial purposes. In this case, the panels can be constructed of sheet materials and manufactured in large quantity in very low cost. Columncoverandspandrel system Columncoverandspandrel system consists of column covers, which are usually made of alloyed aluminum, metal sheet or other laminated/fibrereinforced sheet, and with glazing ponents and spandrel panels that fit between them. It resembles certain similarity to a unitandmullion system except that the structure of the building is exemplified by the column covers. With the exception of the stick system and the unit system, other curtain wall systems are seldom used in Hong Kong. Structural glazing system The merit of using structural glazing system as external wall is to minimize the unglazed elements as much as possible, leaving glass panel almost as the only glazed surface on the wall. This can be done by providing larger mullion supports which span out