Since their earliest days, Structural Insulated Panels (SIPs) have been valued for their versatility.
During the Second World War, for example, De Havilland took advantage of the strength and lightweight construction of early sandwich panels to form the outer skin of its mosquito fighter-bomber nicknamed ‘The Wooden Wonder’. It’s small wonder, therefore, that specifiers have taken advantage of this adaptability when utilising SIPs in cladding applications, creating stunning and highly energy efficient façades.
One of the best examples of the creative freedom SIPs can provide is the Postgraduate and Continuing Professional Development (CPD) Centre at the University of Bedfordshire. When designing the multi-million-pound project, RMJM Architects sought a cladding material which would allow them to create a complex geometric façade which projects out on different floor levels, whilst also achieving an external wall U-value of just 0.15 W/m2.K. SIPs provided a clear solution.
The SIPs were lifted into place using a tower crane and bolted to the building’s concrete floor and ceiling slabs using an anchored angled bracket. Adhesive tape was applied to the joints to further reduce air leakage. Timber battens were screwed to the panels’ internal face and high performance rigid insulation boards were slotted between these. Plasterboard was then nailed to the battens.
A steel frame curtain-walling system was screwed between the SIPs to hold the full length windows and a breather membrane was stapled to the outer face of the panels. Steel carrier rails were screwed above the breather membrane for the champagne gold coloured ACM façade panels. Solar reflecting triple glazed windows were then fitted within the curtain walling.
To further reduce the installation timescale, the SIPs were installed in lengths of up to six metres, allowing them to span two storeys.
This same approach was used on the new learning block at Ravenor Primary School in Middlesex, designed to increase the school’s capacity from second to third tier entry.
Wooden packers were fixed to the steel structural beams of the centre at floor and ceiling height. 18 mm holes were drilled through the SIPs and headlock screws were fixed through the holes and into the packers. The holes allow for dimensional movement of the SIPs. The bottom plate of the ground floor SIPs was nailed to the soleplate and a breather membrane was stapled to the panels’ outer face.
An aluminium rail and bracket system was fixed to the outer face of the SIPs through the breather membrane. Fibre cement panels were then fixed to the railing system across the majority of the façade. Cedar battens were screwed into the fibre cement panels at equidistant intervals. Yellow, high gloss rainscreen façade panels were installed on the rail and bracket system on the back wall of the upper floor balconies along with the main entrance.
The two buildings were certified ‘Excellent’ and ‘Very Good’ under BREEAM and the fabric performance provided by the SIP constructions was a fundamental element in this. Such performance can allow SIPs to achieve the desired U-value with a much slimmer construction than traditional construction approaches, such as metal stud walls insulated with mineral fibre. For commercial buildings, this can help to create additional lettable space within the same building footprint, potentially increasing the value of properties, particularly in commercial applications.
Sweett Group has carried out a detailed study to investigate this issue. We will explore this research in detail in the next article.