The main challenge of this design was security of the north and west elevations. It is normal practice to construct a high secure perimeter fence around medium secure units, but in this case it was not possible. The location of nearby hospital building meant that the north and west elevations were adjacent to a car park and other spaces which were publicly accessible, so a secure fence was not practicable. To create a secure perimeter for the new development, the security needed to be built within the building envelope, and specifically the curtain walling system itself.
Initial draft specifications called for the curtain wall to be made from steel and the glazing supplied to a ballistic level. Working closely with our experienced customer, Britplas, we already had experience of such requirements on previous projects in Europe and so specified the additional use of stainless steel plates within the construction, complete with a revised layout of fixing arrangements for the pressure plates of the curtain wall. The resulting enhanced construction was completed with powder coated aluminium cappings thereby offering a neat external curtain wall appearance.
The installation called for glazing to P4 and P5 levels as described in BS EN 356:2000, ‘Glass in building. Security glazing. Testing and classification of resistance against manual attack’. As the MB-SR50N curtain wall system offered a variable glazing depth within its design, these thicker more secure DGU’s was easily accommodated.
The resulting design was tested prior to installation to ensure that the designed levels of security were achievable and met the clients expectations. The final design offered both a saving in costs over steel whilst still meeting the clients specification required for a medium secure unit using an aluminium system.
So why specify aluminium? Some of the reasons that immediately come to mind are ‘strength’, ‘durability’ and ‘recyclability’, it is the latter that makes the specification of aluminium a green choice for architects as aluminium is virtually 100% recyclable many times over. Today over 50% of all aluminium extruded comes from recycled content which uses just 5% of the original energy used to create the aluminium in the first place. So why don’t we just use more recycled aluminium, well, we just can’t get enough to meet demand! Since 1880, when aluminium first became a commercial reality, 75% of all the aluminium ever produced is still in active service, I don’t think many other building materials can boast such credentials.
Compared to other materials used in fenestration, aluminium profiles are cheaper and quicker to produce, they are also capable of providing intricate shapes for various requirements and, as realised in this project, can be used with other materials to offer cost effective solutions. These composite designs can help the profiles not only achieve incredible strengths, they can also offer high levels of security performance.
When half-scales (the inside and outside aluminium profiles) are coupled with modern multi chamber polyamides and strategically located aerogel insulation profiles, as used in window designs, insulation levels of the frame can easily meet the Passivhaus standard. Thermal insulation performance for openable windows can achieve a UW from 0.53 W/m²K and for a door, a UD from 0,62 W/m²K. So aluminium systems are definitely not behind other materials when it comes to high insulation.
Recent studies in the industry suggest that coated or anodised aluminium systems can last the lifetime of a building. There are examples, such as the Bodleian Library, which has now been refurbished and renamed as the Weston Library. Here the original anodised aluminium windows on this building were installed in the 1930’s and when the facade was refurbished, were simply professionally cleaned in-situ within the original facade. These windows have already provided an eighty-year productive life and it is expected that the windows will perform for at least a further eighty years These attributes have helped aluminium become the specified material of choice for architects when it comes to fenestration systems but, it is the ‘bespoke’ nature of today’s facades that really inspires the use of aluminium in architecture.
Concept drawings for new extrusions can be completed between systems company and architect, or specialist fabricator, and once agreed, die drawings can be produced. From this approval stage which can take a matter of six to eight weeks for the extrusion die to be made and extrusion to be readily available. These lead times are well within a new-build or refurbishment programme and open up possibilities for bespoke shapes of profiles of mullions, transoms and curtain wall cappings for example. The other areas of bespoke design, could be edge detailing to an existing or a new facade material, detailing to accommodate a special glazing detail, or special profiles which will allow CNC work to provide a unique visual appearance.
The only limit to bespoke design is the specifiers imagination. Here at Aluprof we are pleased to look at any specific profile design requirement. With our very wide range of systems and profile portfolio we can quickly develop a specifiers requirement into a credible design. Please feel free to challenge us!
Aluprof systems are increasingly being specified on a wide range of residential and commercial projects across the UK. Systems are designed, fabricated and installed by selected, specially trained companies to ensure each fabricated product meets the Aluprof exacting standards. Further information is available on the company website.
