Hockley Mills is a prestigious mixed-used development comprising 395 apartments and 28,000 sq ft of commercial space with a new entrance to Birmingham’s Jewellery Quarter train station – and undercroft parking for 116 cars.

Car parks present a unique set of challenges when it comes to the specification of soffit insulation and Hockley Mills was no exception. There were several factors to consider. As well as thermal performance, fire safety was essential – so the insulation had to be non-combustible. It also needed to reduce sound transfer to ensure that residents and workers in the building would not be disturbed by vehicle noise from the car park below.

As well as meeting the specification factors, the insulation needed to be delivered to site in line with a tight schedule of works; an issue that was more complex than usual because it was set against a backdrop of heightened demand for construction products such as insulation.

Meeting the brief

With this in mind, Sir Robert McAlpine Ltd approached its Strategic Supply Chain Partner, Knauf Insulation, to discuss the best available solutions for the Hockley Mills car park. Knauf Insulation’s Project Specification Team conducted U-value calculations and recommended that 130mm Rocksilk^® Soffit Linerboard would meet the three critical performance requirements of the brief.

Manufactured from rock mineral wool, Rocksilk^® Soffit Linerboard is designed to insulate structural soffits in applications such as open-sided car parks. It has a thermal conductivity of just 0.034 W/mK, so will deliver the stipulated 0.16 W/m²K U-value required for the separating floor.

It is non-combustible with the best possible Euroclass A1 reaction to fire classification, so will not add to the development or spread of fire should it occur. This means it is ideal for enhancing the fire safety of buildings of any height.

Rocksilk^® Soffit Linerboard also has excellent sound absorption characteristics, so will help to reduce the transfer of noise from the car park to the properties above.

Additional advice and support

Once the product had been determined, the Knauf Insulation Project Specification Team provided details about the choice of finish available. Sir Robert McAlpine Ltd opted for Rocksilk® Soffit Linerboard Standard, which has a black tissue face finish. The Project Specification Team also advised on the required fixing pattern and set up meetings with their fixing partner who provided technical support such as pull-out value calculations.

When it was time for Sir Robert McAlpine Ltd to order the insulation for Hockley Mills, there were high levels of demand across the whole construction sector causing significant challenges in obtaining materials. Knauf Insulation worked closely with distributor CCF to ensure the insulation was delivered to site in full within the required time frame.

Wider benefits of Rocksilk^® Soffit Linerboard Standard

Rocksilk^® Soffit Linerboard Standard has been designed for ease of correct installation. Its enhanced rigidity means it can be quickly manoeuvred into place. Once in position, the mineral wool adapts to the substrate preventing gaps that can reduce thermal, fire and acoustic performance.

Rocksilk^® Soffit Linerboard Standard also contributes to the building’s sustainability credentials. It is manufactured with ECOSE^® Technology, Knauf Insulation’s unique bio-based binder that contains no added formaldehyde or phenol. It is made from natural raw materials that are rapidly renewable, and is less energy-intensive to manufacture than traditional binders.

Products made with ECOSE^® Technology are soft to touch and easy to handle. They generate low levels of dust and VOCs, and have been awarded the Eurofins Gold Certificate for Indoor Air Comfort. This means they are kinder to the installers who use them too.

By working with their Strategic Supply Chain Partner, Knauf Insulation, Sir Robert McAlpine Ltd received the technical and product advice they needed to choose the right soffit solution for Hockley Mills. A solution that will ensure residents are warm and comfortable, as well as helping to keep them and their homes and businesses fire safe.