33 Case study 5 Sampson Close, Coventry Contributed by Paul O’Driscoll Wates Living Space paul.odriscoll@wates.co.uk Name of project: Sampson Close Town or city: Coventry Brief description: Five two and three-bed terraced houses and 18 twobed apartments built using the Passivhaus approach Total cost: £3.5m Average cost per unit: £152,000 Principal partners: Orbit Homes (client), Wates Living Space (contractor), Baily Garner (architect), Stewart & Harris (consulting engineers) Length of time to build: 12 months Is the project complete? Yes When was it completed? Apr 11 Estimated length of time to build if using traditional methods: 14 months Were there any additional/ unusual approvals needed and what were they? Passivhaus certifi cation to ensure that all parameters set by Passivhaus were achieved, such as extremely low air leakage of 0.6 Briefl y describe the construction method Composite panel super structure (including windows and services) with 250mm of cellulose insulation, external brickwork, render and thermowood. Why was this method chosen? To ensure that the thermal qualities and low air leakage requirements were achieved. How did costs compare with traditional methods? High premium due to this scheme being an R&D type project. Not many manufacturers of specialist heat and ventilation product in the UK, if any, at the time and the frame and mechanical/ventilation equipment was sourced from Europe. Would you use this method again? Method of using Germanpanel system with pre-installed Passivhaus certifi ed windows is a tried and tested method on the continent. However, in the UK, this is expensive and still has risks attached. In Germany apartments are larger than apartments in the UK which helps with achieving the air leakage requirements, but it is more diffi cult in the UK. Preference to use traditional method of construction in the UK for cost reasons, although more diffi cult to achieve standards. What are your reasons? There are various methods which could be adopted, such as traditional build, the main factor being that building regulations in the UK requires air leakage at 7 (was 10 at the time), whereas a Passivhaus requires 0.6. Were there any diffi culties with the method chosen? Method chosen was the correct method, although there was not enough understanding of the design, which has a huge impact on the cost to build and the ability to achieve Passivhaus certifi cation. Properties need to be designed larger; products to cope with air movement need to be sourced from the UK; and robust methods for achieving air leakage need to be readily available in the UK. Any other comments on offsite manufacture for housing construction? Offsite manufacture allows the precision required, and the panel system used on this scheme was erected and water/weather tight within two weeks of being delivered to site. The frame and windows were nearly 50 percent of the scheme costs.
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