An ambitious project, and one of the first certified PassivHaus homes in the UK - the Denby Dale PassivHaus in West Yorkshire, had to to use 90% less energy for space heating than the average UK dwelling – with a space heating need of only 15 kWh/m2/ year. The three bedroom property is the first UK Passivhaus to be built in a traditional style using cavity wall construction and had to be built to a tight budget of £141,000.
“We decided to go down the cavity wall path and arrived at the design for several reasons including: planning restrictions, thermal store, cost, and maybe most important of all, buildability,” explains Bill Butcher, Project Leader.
Excellent performing insulation is obviously fundamental to Passivhaus construction and the Denby Dale house has 300mm DriTherm 32 Ultimate cavity slabs in the walls, 500mm CarbonZero Loft Roll 44 in the roof void (both of which incorporate ECOSE® Technology) along with 225mm of high-performing Polyfoam® Floorboard Standard insulation in the floor.
“We’re fully filling the cavity with glass mineral wool insulation for the walls above ground, because it helps minimise air movement in the cavity and offers greater flexibility, fitting snugly around the ties, openings and imperfections of the masonry surface.” comments Bill Butcher.
Economics, performance, availability, ease of fitting and reducing thermal bypass were all among the benefits of the Knauf Insulation products chosen.
Glass mineral wool was specified over rigid insulation to ensure a tight thermal fit. DriTherm Cavity Slabs are flexible enough to eliminate air gaps and prevent heat loss due to their inherent ability to knit together at joints between the slabs. If rigid insulation is used and fitted badly with too many gaps, air movement around and between the insulation boards is increased, which can drastically reduce its insulation value.
DriTherm Cavity Slabs are BBA Certified for all exposure zones and formally guaranteed for 50 years to prevent the transmission of liquid water from the outer masonry leaf to the inner masonry leaf.
In addition to its thermal performance glass mineral wool also has other sustainable features. In manufacture it uses a high content of recycled glass bottles and requires less overall energy consumption than some alternative products, resulting in less carbon emissions. In addition, it can be recycled at the end of a building’s life and has zero GWP and zero ODP. ECOSE® Technology further extends these established green credentials as it is manufactured with 70% less energy than traditional binders and the products contain no dyes or added formaldehyde – providing the ideal solution to the eco-friendly house.