Being eco-friendly brought constraints of its own and of prime importance was orientation. The aim is to make the best possible use of passive solar gain and natural light. Passive solar gain is used to warm the house, so intrinsic to the design is minimising heating. Windows and their position also contribute to natural light penetration of the building, thereby minimising the use of electricity for artificial lighting. The principle of orientation influences the layout and use of the house, which does reflect on the manner in which the house is lived in and also its appearance and design.
Bedrooms are located to the east of the house, thereby benefiting from the morning sun. The south side contains the large main windows which allow natural light into the main living spaces while allowing the sun to penetrate and warm the floor during the cooler months of the year. To the west is an open living, dining and kitchen space, again with a larger window providing light to the area of the house devoted to cooking, living and relaxing as the evening sun descends.
The biggest eco decision was the form of construction and materials. It was decided to use straw bale external walls integrated within a large timber load-bearing frame under which the straw bale envelope would sit. Straw is considered to be a waste material after the seed crop is extracted, it is a natural product which locks in carbon during the growing process. The straw bales were eventually obtained from a field approximately three miles distance which minimised transportation to site. The timber for the frame was obtained from a timber yard approximately two miles from site, the trees having grown locally also locking in carbon.
The subsoil of the site was studied and identified to be sufficiently clay in its content to be used both externally and internally as a render finish to the straw bales. So, the eco decision was made to use earth render to protect and provide a finish to the straw bale walls. Extraction of the clay from the subsoil was hard manual labour, with stones to be removed and the clay graded and sieved to no larger than 10mm in order to be used, with sand, as a render coating.
An important principle of design was a large roof with generous overhanging eaves to protect the external earth rendered straw walls. Large overhangs also provide shading for windows during the summer months when the sun is high and passive solar gain is not required.