In line with Grade 2 listing requirements, the new building façade on each of the four, three storey blocks is required to be aesthetically very similar to the original, which was singularly glazed and included a distinctive lead feature. However, with the need to increase solar gain and reduce heat loss, a goal of decreasing the existing thermal transmittance or U-value of the glazing is also of paramount importance. Specialist curtain walling contractor Parry Bowen was tasked with replicating this façade with a system which meets the project specific criteria and includes increasing the thermal insulation – a considerable task given the prevailing space constraints.
The bespoke design features a curtain wall system which incorporates FW50 profiles manufactured by Schuco UK Limited.
Increased insulation is achieved in two ways. Firstly, the replacement of the single glazing with vision and spandrel dual sealed insulating glass units. The vision units were manufactured using 6mm thick vision Sunguard super neutral 51 toughened glass on the outer pane with a 20mm argon filled cavity with black spacer and a 6mm clear inner toughened glass pane. The spandrel glass unit components are similarly configured but consist of a 6mm toughened clear outer glass treated with a ceramic coating which was specially colour matched to RAL7016 anthracite grey. The vision glass has a U value of 1.1 and the spandrel glass, a U value of 0.239. DOWSIL™ 993 Sealant was selected as a secondary seal on all insulating glass units and for bonding the outer pane to the spacer bar thereby transferring the dynamic load back to the frame.
Secondly, insulating glass manufacturer Crystal Units Ltd proposed the installation of high efficiency Dow Vacuum Insulation Panels (VIP) in between the glass panes in the spandrel units. The spandrel panels are being installed in areas where total concealment of the internal structure is required to hide existing services and floor slabs. VIP is a recent innovation and provides an ideal solution given the severe space restrictions, as Dow were able to optimize the thickness of the panels to 18mm which is expected to achieve a 0.239 U value W/m²-K.
Vijay Halai, Managing Director of Crystal Units commented ‘As a Dow Quality Bond™ member, we are in the privileged position of being kept informed about innovation and developments in Dow’s range of products and services. Advance information on the development of VIP allowed us to quickly identify and solve the challenge of increasing the thermal resistance in the façade where space limitations were prevalent’.
Thermographic surveys are carried out using high resolution thermal imaging cameras which permit a non-invasive and non- destructive way to highlight a variety of potential issues in a building structure. They are typically conducted in cooler temperatures during hours of darkness to eliminate any possible effects of sunlight and ensure the minimum 10°C temperature differential required between the inside and outside of the structure.
A recent inspection of the University of Birmingham, commissioned by Dow, has helped to establish the thermal condition of each facade following the VIP installation. This survey has confirmed there are no apparent defective panels and that they are working well with significantly reduced heat loss recorded through the glass and seals.