Kingspan OPTIM-R supports organic growth of Garden Museum

The Kingspan OPTIM-R Roofing System has provided a slim, lightweight and highly thermally efficient solution for the Phase II extension of the prestigious Garden Museum in London.

Situated within the deconsecrated St Mary’s-at-Lambeth, the Garden Museum is the only museum in the country dedicated to the design and history of gardens.

10 years ago, the previously ad hoc internal arrangement was transformed with a cross-laminted timber structure, creating exhibition spaces and galleries.

To complete its transformation, a second phase of works was designed by Dow Jones Architects, featuring a bronze-clad extension that provides two new learning spaces, together with a café and visitor facilities.

The extension is located above a significant architectural site – in order to protect this, and the surrounding tree roots, the building has been constructed on a reinforced concrete raft.

Consequently, considerable care was taken to minimise weight in all areas of the construction. The project team, which included main contractors Rooff, also adopted a passive-led energy strategy designed to fall within the Church of England’s 2050 sustainability plan and surpass the requirements of the London Plan.

Alun Jones, Partner at Dow Jones Architects, commented: “We had to achieve a 40% improvement on the standard carbon emission targets within Part L.

“That was a big ask for an extension on a listed building and we knew the insulation specification would play a key role in reaching this.

“We normally use Kingspan Insulation and we were particularly interested in the super thin OPTIM-R vacuum insulation panels (VIPs) as they would allow us to keep the overall thickness and weight of the roof as low as possible without having to reduce the thermal performance of the layer.”

With an aged thermal conductivity of 0.007 W/m·K, Kingspan OPTIM-R VIPs can deliver an insulating performance up to five times better than commonly available insulation materials.

The Kingspan OPTIM-R Roofing System combines OPTIM-R VIPs with infill panels of the same thickness which can be cut to fill awkward spaces and to allow penetrations through the layer including rooflights and ventilator kerbs.

All Kingspan OPTIM-R and OPTIM-R E applications come with a supporting design service, ensuring the best possible ratio of OPTIM-R VIPs to infill panels, allowing the desired thermal performance to be met with a minimal system thickness — just 50 mm for the Garden Museum.

The passive performance of the extension has been further enhanced through the buildings layout, which wraps around the old church, using the thermal mass from the stonework within the new structure.