Parsons & Whittley
architects employed Passivhaus design principles for a 14 dwelling Hastoe
Housing Association rural affordable housing development in Wimbish, Essex, the first of its kind.
The houses, a mixture of homes for rent and shared ownership, are designed to be super
energy efficient, and not only comply with Passivhaus principles but meet Level 4 of the
Code for Sustainable Homes.
Passivhaus standard buildings retain heat created within the dwelling as well as from passive
solar gain, eliminating the need for central heating and reducing fuel costs. The standard
requires very high levels of insulation (in order to meet U-values of below 0.15 W/m2K for walls,
roof and floor), a design that makes the most of solar energy and superb sealing throughout.
Parsons & Whittley
’s design for the development is supported by 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.
Construction details have been kept simple and effective in order that they can easily
be replicated at future sites. Porches, meter boxes and Brise Soleil are independently supported
to avoid penetrating the insulation overcoat. East-West orientation of the blocks facilitates
passive solar gains, with careful attention to shading to avoid summer overheating.
The STYROFOAM Solution.
Key to effective insulation of the buildings was the specification of Dow Building Solutions
FLOORMATE 300-A STYROFOAM™-A insulation to run below the entire concrete floor slab
of the structures. 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 has a design load of 130 kN/m2 and is highly durable with excellent
moisture-resistance and compressive strength, enabling the insulation to perform outside
the waterproofing envelope. Installing insulation below the slab also helps to avoid thermal
bridges at floor and wall junctions and makes the most of precious internal space, meaning
it is fast becoming recognised as an effective way of insulating new buildings.
A U-value of 0.07 W/m2K was achieved for the floors of the Wimbish development.
FLOORMATE 300-A is available in a range of thicknesses: 50mm, 75mm, 100mm, 125mm
and 150mm.The material is manufactured using technology that takes CO2 from industry
and uses it as a blowing agent in order to create insulation foam with a Global Warming
Potential (GWP) of less than five.
For more details on FLOORMATE 300-A contact Dow Building Solutions
and one of the account managers will be in touch
or visit www.styrofoam.co.uk