Introduction
Technological developments, maintenance problems of high-rise buildings, increasing thermal insulation requests, recent architectural approaches amended the design of building outer skins. Aluminium curtain wall systems entered our life as an alternative of window solutions. Basically, Aluminium curtain walls consist of thin extruded aluminium profiles which are bearded by building structure, glass fixed on profiles and subsidiary materials such as EPDM gaskets, membranes, brackets, silicone, mineral wool, cavity barriers etc. According to architectural design, metal panels, natural stone, composite materials may also be placed on curtain walls instead of glass.
Specifying the Features
The design process starts with determining design loads and performance criteria. It is important that this information indicates the profile sections, bracket design and insulation details. The information may be stated in Technical Specification document or submitted in tender period but also it needs to be crosschecked if there is any over-design or weakness.
All the features are related with each other and it will be better to consider every component and their specifications together. For example; thermal performance, acoustic performance indicates the glass combination which also related with structural calculation according to glass dimensions. Glass combinations and dimensions specifies aluminium profile sections and indirectly bracket dimensions.
Sometimes architectural design forces some features and this could force a choice between cost and design changes. For example; if the architect determines the profile sections, this may need using special solutions (inner reinforcement, cable solutions, embedded fixation etc.) to stay in current design.
Classification
Aluminium curtain walls are considered under 2 main type;
- Stick System Aluminium Curtain Walls: Aluminium profiles including EPDM gaskets are assembled on site then infill panes & panels are fixed on previously installed profile system.
- Unitized System Facades (Elementary Facades or Panelised Facades) : Aluminium profiles are assembled as a frame and glass (or other infill panels) installed in production plant. The glazed panels are transferred to site and hanged on previously installed brackets on site.
Comparison of Stick and Unitized System Curtain Walls
| Criteria | Stick System | Unitized System |
| Design | Easy | Difficult, requires experience |
| Purchasing | Fast, not requires new moulds in general | Longer, requires new moulds |
| Production | Easy and faster | Complex & Slower |
| Installation | Longer | Faster |
| Installation Team | Crowded | 7-9 skilled staff for each team |
| Installation Safety | Have higher installation risks (falling risks, crowded employees on site etc.) | Lower risks (panel falling etc.) |
| Site Management | Difficulties of people and material managing, | Difficulties of panel planning, access problems for crane & elevator locations |
| Earthquake | Limited safety | Safety according to design criteria |
| Cost | Cheaper | Expensive (between %10-%20) |
| Quality | Changes according to site conditions | Better; site processes are limited |
Stick facades are generally preferred for lower, small quantified, limited budget projects. Design and mould production costs and period effect small buildings to much (over %30). This system production period is so fast that in an average production plant it is easy to produce 1.000 m² facade profiles in a few days but in spite of fast manufacturing operation it takes approximately 1 month for installation. For small projects which don’t require complex design and calculations, it is possible to start installation with standard profiles in a month which is just a dream for unitized systems.
One of the difficulties of stick curtain walls is site management. It needs to work with a crowded team on site which have to use scaffolding or working platforms that occurs a risk for working safety. In addition, to perform the time schedule the operation must be executed all facades as possible and this results team and material management difficulties.
Unitized facades have some specific advantages against stick system alternative. If the project management works efficiently, it is possible to start the design and procurement period before main structure production. This means it is possible to win a period over 3 months which will be lost for procurement. Manufacturing period is more complex and 1.000 m² façade production in a singular line will take approximately 2 weeks which is also similar with installation period on site. But these 2 periods could be overlapped and total production and installation will take less than 3 weeks. This 2 weeks per 1.000 m² is a very important gain for big projects
Unitized facades not only have time precision advantages but also serve quality and performance gains. All critical manufacturing operations are executed in production plant and this helps to control much parameters correctly. For example; gasket directions, glass & frame conformity, sealants, fixation, consumable usage, material wastage etc.
Unitized facades are more adaptive to main building structure because the system is designed according to structural criteria. At the same time general design lets the system move in tolerances and provide the systems to compensate different deflections, loads and movements. This means, according to design parameters, the system may respond earthquake loads, lateral movements, long term creeps, column shortening and other design loads.
For more information about details please click;
- Stick System Aluminium Curtain Walls or
- Unitized Facades