This 14 dwelling development follows classic Passivhaus principles of design, specification and construction but adapted for the UK and to allow simultaneous compliance with Level 4 of the Code for Sustainable Homes.
The built form is simple without unnecessary steps and staggers which add to the heat loss area and complicate the design and construction process. A number of construction options were evaluated before finally adopting solid aircrete external walls wrapped externally in over 250mm of foam insulation. With insulation running under the ground floor slab and a conventional insulated ceiling the construction details have been kept simple and effective. Even so specialist thermal modelling was undertaken to calculate thermal bridges and advise on the impact of small changes in the design.
UK social housing has additional challenges in delivering the Passivhaus standards which have resulted in insulation levels below 0.1 W/m2K for walls roof and floor. Using the Passivhaus Planning Package – the software used for assessing Passivhaus dwellings - Inbuilt has monitored the impact of all design changes to ensure that Certification will be achieved. The crucial impact of small changes to window designs was modelled to help value engineer the project and feed into the specification of future sites. Regular contact with the Passivhaus Institut in Germany has also been maintained to minimise the risks to achieving Certification.
The choice of servicing strategy had to balance familiarity for residents, availability of components, client requirements and cost. Conventional gas boilers were eventually selected coupled to large thermal stores to prevent cycling and supplemented by solar thermal systems. The thermal stores will supply domestic hot water as well as feeding top-up heat into the air supplied by the heat recovery ventilation system.
