A insulation material manufactured by Dow Building Solutions – was used to insulate the UK’s first rural affordable housing scheme to gain Passivhaus certification: Ravenscroft in Wimbish, Essex.

Produced at Dow’s facility at King’s Lynn, FLOORMATE 300-A was installed below the concrete floor slabs of the ground-breaking 14 dwelling development which celebrates its first anniversary in summer 2012.

The Hastoe Housing Association development provides affordable homes for a rural community - whilst at the same time achieving high levels of sustainability. The houses, a mixture of homes for rent and for shared ownership, are designed to be super energy efficient, and not only comply with Passivhaus principles but also meet the demands of Level 4 of the Code for Sustainable Homes.

According to Hastoe, the buildings use around a 10th of the energy used by a typical UK house and average gas bills in the summer of 2011 were £12/quarter, inclusive of all heating and hot water.

Passivhaus standard buildings retain heat from passive solar gain, eliminating the need for central heating and reducing fuel costs. The standard requires very high levels of insulation, a design that makes the most of solar energy and superb sealing throughout.


“As well as air tightness we needed to achieve U-values below 0.1 W/m2K for the walls, roof and floor in order to meet Passivhaus standards - which meant specifying effective insulation throughout,” explained Chris Parsons of Parsons & Whittley architects, the Norfolk-based designers of the scheme.

“Installing insulation below the slab helps create an ‘envelope’ of continuous insulation which minimises heat loss, requiring a material which can maintain strength and good thermal performance, even when used externally.”

FLOORMATE 300-A is highly durable with excellent moisture-resistance and compressive strength, enabling the insulation to perform outside the waterproofing envelope.

“We’re continuing to see interest from architects and developers in building methods such as Passivhaus, but it requires a different way of thinking when it comes to maximizing the thermal performance of the building fabric,” said Matthew Dyke, Account Manager for Dow Building Solutions.

“Installing insulation below the slab helps to avoid thermal bridges at floor and wall junctions and makes the most of precious internal space, which is why it’s becoming recognised as a more effective way of insulating new buildings.”

Parsons & Whittley’s design for the development, which was built by Bramall Construction and assessed against Passivhaus standards by specialist consultancy Inbuilt, was based on FLOORMATE 300-A insulation running below the entire floor slab, solid aircrete external walls wrapped in over 250mm of foam insulation, and conventional insulated ceilings.

FLOORMATE 300-A is available in thicknesses ranging from 50mm to 200mm, and has a design load of 130 kN/m2. The material is manufactured using CO2 as a blowing agent in order to create insulation foam with a Global Warming Potential (GWP) of less than five.

To find out more about the Wimbish Passivhaus development visit the microsite at www.wimbishpassivhaus.com.

For more details on stockists of FLOORMATE 300-A and other insulation products, contact Dow Building Solutions by email on FKLMAIL@dow.com and one of the account managers will be in touch, or visit www.styrofoam.co.uk.