02 Jul Sustainable Homebuilding
Our clients Dennis and Emma Wiehahn embarked on a journey to build a sustainable home in Cornwall, here is their story:
We started the design process to build a house in the South East of Cornwall several years before buying the derelict cottage.
We went on courses, such as building with straw bales, using lime, natural materials, and alternative methods of both building and thinking about the house. We also attended many shows and seminars about the ecological impact of domestic architecture in England.
The more people we spoke to the more it became apparent that a lot of the expensive solutions offered were unnecessary and even wasteful. We decided to make a simple house that incorporated everything we had learnt from people who had built and lived in modern ecological houses.
This breaks down into four parts:
1. Whole house insulation is design to a very high specification, including triple glazing and significantly smaller windows on the north elevation.
2. Air-tightness with controlled ventilation and heat recovery (very efficient and not expensive to run or install).
3. Optimum orientation and design for solar gain including; large south-facing glazing with massive passive heat storage in the form of a visible concrete floor slab. In the main central large living room (living, dining, kitchen) a very heavy masonry stove sits directly onto the concrete floor slab and forms part of the heat sink either from firing or as part of solar gain. This, apart from two other very small wood burners (to use in the very depths of winter), is the only form of heating in the building. We have no underfloor heating, no ground or air source heat pumps, no central heating boiler, no radiators and with only the occasional need to wear an extra jumper in the winter. This orientation also used for solar water heating with a large storage tank.
4. Construction materials and methods used to promote sustainability. One example that is common practice is to burn off cuts and unused timber on site. Instead we have stockpiled this timber as a resource for the builders themselves during construction and for use as heating fuel for a local farmer. Instead of throwing everything in skips, we have sought out people who needed left-over insulation and building materials.
Although the house has a modernist feel with its large horizontal windows filling the house with light, it is balanced by the simplicity of the fewest possible number of elements on the elevations and roof. On the north elevation a painstakingly careful arrangement of windows (inspired by Mondrian) enables low windows over the two baths, windows on stair half-landings and high windows in the kitchen, downstairs WC and first floor bedroom to be placed above or below one of only two horizontal invisible lines, thus enhancing simplicity.
The whole design is based on the vernacular of modern agricultural buildings, where cost effectiveness results in the simplicity of vertical timber softwood cladding, a concrete block plinth, very simple detail on openings and industrial roof designed for lightness, low maintenance and in the case of our house complete and simple recyclability.
This design ethic has the effect of producing a building which is already familiar to anyone who loves our countryside and will, over time, blend further into the landscape with its range of silvery grey roofs, walls and dark simple openings. We were conscious that in our current need for housing a quiet solution might be more welcome.
The air is controlled and managed by a Mechanically Ventilated Heat Recovery System (MVHR). Ducting runs throughout the building allowing stale damp air to be extracted and replaced with fresh air. Up to 90% of the heat from the stale air is recycled and transferred to incoming fresh air. During hot days there is a summer bypass option which doesn’t recover the heat and allows cooler outside air in at night thus lowering the indoor temperature. Because fresh air is continually pumped in from outside the quality of the air in the house is always fresh not musty and yet feels warm and dry.
The floors, walls and roof are thickly insulated with a combination of materials including cellotex and rockwool. A final layer of Pavatherm has been wrapped around the whole building to ensure there are no thermal bridges which could leak energy. Pavatherm is a wood wool product with extraordinary high levels of insulation. The windows are insulated with double glazing on the south and west elevations and triple glazing on the north elevation.
This house nearly faltered half way through the construction process, due to unforeseen challenges with the timber frame contractor. At this point we appointed Ward Williams Associates to help us rectify the problems and continue the build. Despite this massive hurdle, we have persevered with the integrity of what we originally set out to do and are delighted with this thermally efficient, beautifully designed family home.
Ward Williams Associates provided cost management, building surveying and sustainability advice on this project, which was ‘Highly Commended at the Cornwall Sustainability Awards 2014, in the Built Environment Category.