The detailed drawings for the new house and the outbuildings have been mostly finished since Christmas, as have the detailed specification documents. There were just a couple of technical details needing attention before issuing the tender package – and then there was the question of who should be on the shortlist of contractors that get invited to tender for the build.
The outbuildings are throughly conventional in design and construction and in some ways the main house is too – the basic structure is a block-work cavity wall (albeit one with a very wide cavity) – and many of the less conventional features (like the curved roof) will be outsourced to specialist subcontractors. However, aspects such as the very high degree of air-tightness which is critical to the thermal performance of the main house are fundamental to the success of the building and not yet that common in East Midlands construction. (Passivhaus requires a level of air tightness more than 15 times better than current UK building regulations.)
In some ways it would be best to use a contractor who has previous experience of Passivhaus or near-Passivhaus standards of construction, and in other ways it would be ideal to use someone local who is used to working with local suppliers and sub-contractors. Hopefully there are some contractors who are both local and who have relevant experience, and are available in the right timescales, and offer good value for money…
Justin Smith and his team have worked up a shortlist of contractors who they think would be suitable and the requests for tender went out today. It will be interesting to see what responses come back.