Work continues on Crescent shaped eco house
The original Nudura quote for the pre-formed insulated formwork to be delivered with preformed curves would have been very expensive. Instead our contractor adapted standard blocks by cutting and infilling to achieve the wonderful curve that forms the building. Plywood gussets are used to strengthen joints prior to pumping the concrete in.
A GPS satellite system has been used for setting out and as the walls have gone up the essential need accuracy has become apparent. Because the shape is curved any discrepancies at one one end could have resulted in a 270mm difference in wall position the other end. When pre ordering high quality window this is extremely important. Windows have now been ordered, we eventually opted for Optiwin windows which are passivhaus certified with U values of 0.8 w/m2/k. The GPS was also used for position the steel posts which are situated at the point of the curved ends, and will be hidden within the window frame.
The Opdek system used for the floors has been installed. Progress on this was interesting as the men on site where notused to this kind of construction, and there was a learning curve with fitting and cutting it to the curve. The system is basically concertinaed steel with insulation sandwiched between and another thick layer on top. This building method, as it the Nudura, is standard practice in Northern America climates for construction, an industrial method also used in their car parks!
The point of this system is one of speed. Once the building is laid out the concrete can be poured all in one go.
It is also essential that all electric positions are known at the earliest stages as ductwork and appropriate sleeves were provided for wiring. A state of the art lighting design was undertaken by John Cullen from London during the planning process. This allows for lights to have various different ‘mood’ settings., up lighting to the entrance area and wall washing. John Cullen also supply all the fittings and specification for the design.
Post pour drilling for changes in the electric layout are not acceptable and endangers the air tightness as we are aiming for an air tightness of under 1 air change per m2/m3/hr at 50 pascals. A Mechanical Ventilation and Heat recovery system will be installed which has been designed by The Green Shop. This is to be a Paul thermos 300 with summertime bypass and frost stat. Plans are being discussed for a soil heat exchanger using the temperature of the ground to cool air on the intake in summer or preheat air in the winter.
The contractor had planned to pour the ground floor walls and upper slab in one go but was unable to as the underfloor heating on the upper floors hadn’t been installed as we lost the slot because of the snow! As a result the walls have had to be poured in two hits with extra reinforcement in the walls and concrete edges roughed up to ensure stability in the walls. Men working at height have also had to be extremely careful due to icy conditions.
Kithurst Builders www.kithurst.co.uk
The Green Shop www.greenshop.co.uk
Optiwin windows www.optiwin.ie
John Cullen lighting design www.johncullenlighting.co.uk