Ecohouse

Sue Roaf

• Publisher: Routledge
• Year: 2014
• ISBN:
  9781317535614
• Edition: 4
• Topic: Architecture
• Subtopic: Architecture General

Sue Roaf is famed for her approach to design and her awareness of energy efficiency. Here she reveals the concepts, structures and techniques that lie behind the realization of her ideals. By using her own house as a case study, Roaf guides the reader through the ideas for energy-efficient design or 'eco-design'.

Now in its fourth edition, the bestselling Ecohouse continues to be both a technical guide and an inspiration for thousands of architects, designers and eco-builders all over the world.

Ecohouse provides design information about the latest low-impact materials and technologies, showcasing the newest and best 'green' solutions. Revised and updated, this edition also includes new case studies inspiring readers with more real-life examples of how to make an ecohouse work.

1

STARTING YOUR DESIGN

Starting your ecohouse design with a blank piece of paper in front of you, is an exciting experience – all those endless possibilities! But coming up with the ‘right’ design for you, that is fit for your own purposes, that makes good use of all the opportunities that your site and budget have to offer, is what lies at the heart of what constitutes ‘good’ design. This chapter first outlines how you might approach the writing of a good brief and what is involved in developing your project programme. Then some of the issues that might influence the way the actual form of your house begins to take shape in your mind are raised as a precursor to the detailed chapters that follow it.

THE BRIEF

So how to begin? The quality of the final design will be vastly improved with a good design brief that helps you understand what your needs for the house are, and will be, and how the house might meet those needs. Your lifestyle will change over time and at each phase consists of a different range of activities that need to be appropriately housed. Priorities evolve, and early on they may include keeping an eye on the children at play in the heart of the house, or later on allowing them more freedom and privacy at its edges, which may be more expensive to heat. Your focus on working in the home office in middle age may be dovetailed into reducing your running costs when you retire by co-locating the warm office and its equipment with the winter snug to share that warmth. If home-working is important in a hot climate then the cool living areas and study could become an integral part of the whole ventilation system of the house design (Chapter 5).

In a brief you describe the range of those activities over time and the conditions you need to perform them properly at different times of day, year and over your whole planned life in the building. Mapping the relationship between these activities and the outdoor climate is also vital for building up the information you need to give shape to your design ideas. Three dimensional thinking helps when designing an ecohouse, because the section of the house can be as important as its plan.

A good brief can really add value to a home.¹ Value depends on how much can be achieved by the building for the price you pay for it. This in turn depends on the efficiency of the design. An elegant design solution will be very efficient – doing more for less – and costing you less as you live on in it in a future of rising grid energy and water prices, in a changing climate and as your less ablebodied future self (Chapter 4). To design such a multi-phase and multi-function house increases its market value when you eventually do want to sell it and also the range of people to whom it might appeal then.

Why not start on your blank sheet with the big picture, the main selling point or ‘vision’ for your home? What is the most important thing you want to achieve in your building – its USP, Unique Selling Proposition or marketing concept? In Oxford I wanted my ecohouse to (a) remain comfortable in the more extreme climates of the future (see Box 1.1.) and (b) reduce its carbon emissions to a minimum, so it was designed to need minimum grid energy to stay comfortable and to use as much free natural energy as possible with photovoltaic (PV) electricity, solar hot water and passive solar heating. Different people in different places will want different USPs for their own reasons – to be built, say, of natural local materials, to be healthy or water efficient. In Appledorn in Holland, where homes of various types were built in the early 1990s in blocks within one ecotown, the most popular house type was surprisingly the ‘quiet’ house, giving occupants peace of mind. Perhaps it also helped that these were relatively high-mass homes and very comfortable as well.

BOX 1.1 DESIGN FOR CLIMATE CHANGE IN THE OXFORD ECOHOUSE – TURNING AN ASPIRATION INTO AN ACTION PLAN

Designed for heatwaves

1. The building has a hot (south-facing) and a cold side (shaded all year).

2. The slope of the site is such that the cooler air from the north flows around the building into a sunken patio to the south of the sunspace.

3. During heatwaves the whole south of the building is closed down to ventilation air and the windows facing north opened and driven by a strong stack ventilation up the central stair and out through the Velux roof-light over the stairs, thus only cool air is drawn through the house.

4. Night cooling. The very high levels of well-insulated internal mass mean that on summer evenings and nights when all the windows are opened the heat can be flushed out of the structure in a very effective night-time cooling system.

5. The four sets of French doors on the ground floor facing south are shaded in midsummer from the direct sun by a balcony and its roof above so little direct sunlight enters the house in summer.

6. Windows are limited in size to the south, so avoiding excessive solar gain into the house in summer.

7. There are no west-facing windows in the whole house. The west is the most difficult to shade and low afternoon light coincides with the hottest time of day.

8. The roof insulation is 250 mm to prevent excessive heat gain through the roof.

9. There are large trees along the west fence of the garden shading much of the sunspace patio, there is a deep shade, vine-covered trellis by the patio, an umbrella-shaped shade tree to the east of the house and more garden trees – all reducing to a minimum the direct solar and the re-reflected heat gain from surfaces to the south of the house. Up to 60 per cent extra heat gain can come from a highly reflective pavement via a glass wall of a building, adding to overheating.

10. There is a vine-covered trellis over part of the south patio to lower ground temperatures around the south of the house.

11. There are wisteria vines growing up both sides of the south wall of the house to prevent radiation actually reaching the south wall to reduce indoor temperatures.

12. The sunspace has a wide range of low- and high-level openings to rapidly dump heat out of the sunspace so it can be used in mornings and evening in mid-summer but of course not during the afternoon. These windows are also left open for night-time cooling of sunspace surfaces.

13. Internally in the first-floor doors are chamfered and aligned with the bedroom windows to allow for very effective cross-ventilation of the rooms.

14. All thermal bridging of the structure removed to eliminate heat paths from the external to the internal leaves of the wall.

Designed for cold spells

1. Form is a cube to minimise volume-to-surface ratios, so conserving heat.

2. Super-insulation standards to keep heat in.

3. All cold bridging of the structure eliminated in construction.

4. Triple glazing.

5. Draughts have been largely eliminated through the structure.

6. In winter all air is taken in through the pre-warmed air lock spaces of the front porch and the south-facing sunspace.

7. Sunspace used for clothes drying and all paints are water-based on wet plaster on high-mass concrete blocks so absorbing excess humidity, meaning that relative humidity is stable at around 40 per cent all winter, so ventilation of rooms is not necessary for moisture purging with its low occupancy rates.

8. Solar geometry of the house is such that even in mid-winter with snow and full sun the house passively heats well.

9. Use of small and flexible windows into the porch and sunspace means that natural ventilation uses pre-heated air from the buffer zones.

10. 5m² solar hot water panels generate around 60 per cent of the domestic hot water, working well even in winter.

11. Kachelofen – high-mass wood-burning stove located in a central warm core of the house means that even if the grid fails the house is kept warm.

12. High mass of the internal walls provides a stable inter-seasonal heat store that can ride out several weeks of intense cold.

13. Thermal breaks between the concrete of the main house and the sunspace and porch stops cold creeping indoors through the floor.

14. Wide strong gutters for heavy snow and rain.

Your big vision is then translated into a series of design instructions – the brief itself – on how you want that vision to be translated into practice in the design. These may take the form of guidelines, that are more qualitative or benchmarks and targets that are quantitative with actual performance numbers attached. A guideline might be that the house is to be calm and reflective. This soft quality of how the house is to be felt or perceived may be achieved with the physical fabric of the building that is perhaps to be heavyweight, quiet, painted in matt pastel colours with natural views and so on. A house that is designed to be vibrant and exciting may be noisier, more open, with reflective and colourful surfaces, lightweight and interactive with busy views and so on. The soft guidelines (Chapters 1 and 4) will need hard performance benchmarks woven into the design brief on form (Chapters 1 and 3), materials (Chapters 2 and 6), ventilation (Chapter 5) and technologies (Chapters 7–15).

Stages of the brief²

The brief is all about defining the problem to which the building is the solution and a good brief might include:

• a design statement: of your big idea / vision / mission for the building;

• a scoping brief: with the hard and soft guidelines and performance criteria;

• activities list: for each phase of your life in the house / each season / each time of day;

• draft requirements: of the conditions you need to provide to enable those activities to happen to the standards specified by the owner / client in terms of guidelines and targets for the house (it does get more complex!);

• testing the requirements: against possible design solutions – with drawings, sketches, calculations, simulations or models to (a) see if it is feasible to meet the requirements and (b) evolve improved iterations of the design so they do it more and more efficiently. Always use drawn sketches first to avoid the pitfall of being locked into a design just because it is modelled on the computer and difficult to change – and insist your architect does the same;

• approval: the point at which you have a general solution you / the client are happy with and the requirements of the brief are elegantly met – then detailed design begins in earnest and the final design is refined to optimise its performance in reality.

Alongside the design process you will have a whole lot of other constraints you have to manage and integrate into the design process including:

• The budget: Keep checking that your design is affordable at every stage of the project to avoid incurring extra cost re-tracing your steps to rationalise the design when you find you are moving outside your financial comfort zone. No one wants unaffordable debt in the economic turmoil of the twenty-first century so do leave aside a decent provision for the small things at the end such as door handles, light fittings and bath taps that can be surprisingly expensive.

• The programme: Get a clear project programme from day one and try and stick to it to avoid extra cost.

• Site surveys: Getting an accurate site survey can make or break a project. Full checks on the legal and social constraints on the site should be made – and make friends with your new neighbours to help smooth the way through the planning process.

• Procurement route / selecting the team: Get expert advice if possible on how you should engage your design and build team and what contracts to use. Stick to that advice for dear life. Be careful about using family or friends to design for you, and don’t fall into the cheap / friendly architect or builder pitfalls. Always try and get three people to tender and ask for three references for each from previous clients to get a feel for what they are really like to work with. If you want an amusing read on the subject of designer–builder–client relationships go back to the 1920s for advice in The Honeywood File.³ You do need to work with a design professional to get a watertight specification for the build, the right contract signed and a clear and reasonable build programme to avoid litigation and overspend. A good working relationship with the Building Regulations Office of the council helps too as they will have to sign off the project after ‘completion’ of the build, enabling yo...