Orchard Fields is the latest development from the award-winning Stonewood Homes. The 88-house estate near Cirencester includes 26 affordable properties and has been constructed to meet the AECB Building Standard (now superseded by the AECB CarbonLite™ Standard) – requiring them to have very low energy demand and highly insulated building envelopes. To achieve the demanding U-values with a slim construction on the flat roofed areas of some properties, the Kingspan OPTIM-R Roofing System was installed with Kingspan Thermaroof TR27.

Location: Cirencester, England
Sector: Residential
Developer: Stonewood Homes
Architect: Stonewood Design
Products: OPTIM-R Roofing System, Thermaroof TR27
Application: Roof

The Project

Orchard Fields has been built with a sense of community at its heart. The “landscape led” layout incorporates four different courtyards planted with fruit trees. Stonewood Design developed a range of different property archetypes, ranging from 1 to 5 bedrooms, each taking their name from different varieties of the fruits in the orchards.

All homes have been built to the AECB Building Standard which requires that the properties have an energy and cooling demand of less than 40 kWh/(m2.a) – around a third of that of new homes built under the Building Regulations at the time of construction. To deliver this, the homes needed to be highly airtight, with mechanical ventilation heat recovery (MVHR) systems fitted to retain heat whilst providing a supply of fresh air. All elements also needed to be insulated to a high standard, with a typical average weighted U-value of just 0.10 W/m2K for each of the walls, floors and roofs. This demanding fabric target led to the specification of the Kingspan OPTIM-R Roofing System with Kingspan Thermaroof TR27.

Seamless Finish

The products were specified for flat roof sections above the kitchens in several of the properties. These areas sit below the master bedrooms which feature full height windows with Juliet balconies. To ensure a seamless finish, the parapet height of the flat roofs needed to sit level with the floor height within the room. This limited the depth available for insulation within the roof and would have made the target U-value for the flat roof sections challenging to achieve with commonly used insulation – potentially meaning the parapets needed to be raised or a section of the ceiling space in the kitchen lowered. This is where OPTIM-R could assist.

The System features OPTIM-R vacuum insulation panels (VIPs) with a microporous core which is evacuated, encased and sealed in a thin, gas-tight envelope, giving an outstanding declared thermal conductivity of 0.007 W/mK. As the VIPs cannot be cut or penetrated, they are offered in a range of dimensions, allowing them to be designed and laid out to cover the maximum possible area of roof. Rigid thermoset PIR insulation infill panels of the same thickness are then used to infill gaps or to be cut around features such as roof lights, ventilator kerbs or drainage gutters.

Kingspan Insulation provides a supporting design service for OPTIM-R Roofing Systems projects to develop the system layout. This ensures the best possible ratio of VIPs to infill panels – keeping the system depth to a minimum. The installation team is then provided with a clear layout to indicate where the panels should be fitted – allowing for a rapid installation.

Use of Kingspan OPTIM-R is also covered by BDA Agrément Certificate BAE 18-035-P-A-UK (in thicknesses of 20 - 50 mm) and ETA Certificate No. ETA-15/0090-v06.

On the properties at Orchard Field, the OPTIM-R System was installed in a 50 mm thickness and overlaid with a further 25 mm layer of Thermaroof TR27. This allowed the required U-value to be achieved with a total insulation depth of just 75 mm. Thermaroof TR27 achieves thermal conductivities as low as 0.24 W/mK and is fully compatible with a range of waterproofing systems, including fully adhered single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing. The current manufactured range (in thicknesses of 25 - 160 mm), produced at Kingspan Insulation’s Pembridge (Herefordshire) and Selby (North Yorkshire) manufacturing facilities, is covered by BBA Certificate 16/5332.