One of the most important aspects of the design and build of our new house was to minimise the environmental impact of both building it and then living there.

We still wanted a comfortable modern house but the aim was always there as a design starting point.

The initial basic design tried to make as much use of passive solar gain as the site allowed and we have tried to include draught lobbies on the external doors to reduce heat loss when open. These areas will either be unheated or at a reduced temperature from the rest of the house. The shape of the house has been kept fairly simple to reduce external walls.

The next step was to try to use reclaimed material where possible – slates and stone being obvious examples. Where reclaimed was not possible the next best thing was to use locally available materials – the examples being timber and stone flooring.

For the remaining items decisions have favoured less environmentally damaging options where possible. As with all aspects of life there have had to be come compromises.

We have an interest in the appropriate use of technology and this has resulted in a number of further decisions.

Heating will be provided using a ground couple heat pump. This works in exactly the same manner as a fridge in that warmth is taken from the food in the fridge and is expelled as hotter air from the radiator at the rear of the fridge. A ground coupled heat pump takes energy from the ground using buried liquid filled coils and moves this from a low temperature to a higher temperature using a compressor. These devices are very efficient, the normal comment being that for one unit of energy in you can gain about 4 units of energy in the form of heat. Heat pumps generally work best to deliver lower temperatures rather than the 70^oC used for radiators so this tends to make them best suited for use with underfloor heating.

Having made this decision we started thinking about the construction of the house. Deciding to use UFH meant that we needed to think about how to heat the first floor. UFH can work with wooden floors but is better suited to solid floors so we decided to use solid floors. This led us to a masonry house rather than timber framed. We then started thinking about how we will use the house. As we will tend to be around the house a great deal we decided to use the approach of having a thermally massive internal shell of the house with external insulation. This means a block built shell with solid floors acting as a heat store, smoothing out temperature fluctuations. It is true that the heating system will be slow to heat from cold but will also be slow to heat up in summer and slow to cool down in winter.

Looking at the external insulation we were limited to a degree by the need to match the wall thickness and insulation capabilities between the areas of wall with a stone external leaf and those with render. This was resolved by using a thick coating of cellulose under the render and phenolic insulation boards in the cavity sections.

In a previous house we have use evacuated solar tubes – we were so impressed by the performance of these that we will be including some in this build to provide domestic hot water during the summer and to preheat during winter.

We will also being using mechanical ventilation with heat recovery. However to match this we are also addressing a simple topic that should really boost the performance of the house – air infiltration. Basically most spec built house leak like sieves and with the air goes all of that expensive energy. To address this we have paid particular attention to detailing on joints in the building fabric to ensure that the only ventilation we have is designed rather than accidental. To this end we have also set a target of 1m³/m²/hr @ 50Pa. If this is achieved the house will be one of the best performing in the UK. Afgter the initial design work was well advanced we had a day's energy consultancy, the results of which can be seen in Energy Advice. It was this process that led to a large number of the fine details included in the design which will take the house from the ordinary to the extraordinary. For someone wanting to build a really high performance house I would recommend David Olivier's help. With hindsight I would have easily paid double for the help we received.

At the moment we do not have mains water to the site. It is available close by and finances may dictate that we go for mains rather than the abundant spring water available on site. To use the local water it would be sensible to use a borehole and this is about 4 or 5 times the cost the mains connection. However we will make use of the local water for non-drinking uses. This will be combined with ultra-low water usage toilets and appliances.

Foul water will pass to a septic tank (no mains sewerage either) and from there through a 3 stages reed bed before being discharged into the stream.  The design work on the reed bed has been done by Cresswater.

The remaining 'green' ideas relate to the land around the house and we would hope to be able to use micro-hydro power and possibly solar voltaic cells to generate electricity.