This is the second edition of Susan Roaf et al"s guide first published in 2001. The general format and organisation of the second edition has changed very little from the first, however, many of the topics covered in the first edition have been updated and expanded.
Eco House 2, like its predecessor, begins by stressing the importance of building ecologically in order to avoid ruining the earth with buildings that are profligate consumers of energy and producers of more than half of all greenhouse gases. According to the authors, the world needs 'a new profession of ecotects, archi-engineers and engi-tects' to design buildings to work passively, use less energy and rely on renewable energy when and where possible. The main aim of Eco House 2 is to provide"'how to' information not well covered in other books” and therefore, should not be seen as an all encompassing guide to energy saving or ecological construction.
The main body of the book presents the reader with wide-ranging and often in-depth advice and technical guidance. The authors own experiences in designing and building their own 'eco houses' are used throughout the book to demonstrate principles and technologies in practice. Susan Roaf's Oxford Ecohouse features extensively throughout the book. For instance, readers can compare thermographic images of the Oxford Ecohouse with a neighbouring 1950's house to see the difference higher levels of insulation and triple glazing make in reducing heat loss. In the chapter on photovoltaics (PVs) the reader is offered a description of how the PV roof tiles have been carefully integrated into the roof structure of the Oxford Ecohouse. Manuel Feuntes uses his house in South America to demonstrate the integration of rock beds in a passive solar design and Stephanie Thomas passes on advice on designing a gale and hurricane proof house. A range of experienced and respected practitioners in the field of ecological design, some of whom appear in BFF, have also lent their expertise to the book.
After taking the reader through the ideas, principles and technologies of ecological design of 'eco houses', the book finishes with case studies of 'eco houses' from around the world, which further illustrate many of the principles and ideas discussed in the main section of the book.
Readers who are familiar with or who have read the first edition of Eco House may be wondering what Eco House 2 has to offer in the way of new material.
Chapter 1 - The form of the house: Building as an Analogy is not significantly different, although readers may be entertained by Mike Humprhies informative dissection of what makes a Hobbit hole so comfortable. Chapter 2 The Environmental Impact of Building Materials is page for page the same as in the first edition.
One of the more expanded and most useful chapters in Eco House 2 is Chapter 3 - Pushing the Building Envelope covers the following: performance and specification of insulation, avoiding cold bridges, condensation, as well as air infiltration and leakage. Readers are told the 'trick' in getting it right with insulation is to"choose the right insulation for the climate and the available local energy sources”. The second edition also highlights issues to be considered in the selection of insulation materials. Does the manufacture of the insulation material contribute to ozone depletion? Is the insulation derived from natural or man-made materials? What is the embodied energy of the material? A new section highlighting methods of dealing with condensation through the use of ventilated cavities, vapour checks and breather membranes is included in Ecohouse 2. With respect to the topics of infiltration and air leakage, the reader is advised to"build tight, ventilate right” and is given practical advice on how to design, build and test for airtightness.
Chapters 4 & 5, Christopher Day's Building in Soul and a chapter on Ventilation, respectively, are virtually unchanged.
Chapter 6 – Health and Happiness in the Home is an encyclopedic listing of health issues to be considered when designing a home. In Ecohouse 2, the section on moulds has grown from less than a page to five pages with input from toxicologist Dr. Dave Anderson. 'Dr. Dave' guides the reader through investigation, understanding and prevention of mould growth in the home. Another notable addition to this chapter, is the new section on timber which will aid the reader in asking the appropriate questions when it comes to sourcing sustainable timber: Endangered species are obviously out, FSC timber is the preferred choice and if that isn't available, look for a chain of custody certificate to ensure timber comes from a sustainably managed forest. Readers are reminded to use their common sense if the suggested criteria are not met and look into local sources of timber. A draft copy award winning Lambeth Counci's guidance on timber specification is included to prove the point that even local authorities 'are going green'.
The underlying physics and principles of passive solar design are explored in Chapter 7. In the second edition readers will find a section called ' The Importance of the Orientation'. This part of the chapter focuses on results from running the Oxford Ecohouse through a modeling program designed to test the performance of passive solar designs. The outcome of the modeling helps emphasise the role appropriate (southerly) orientation plays in ensuring a manageable and comfortable internal environment. I think it would have been interesting to see this modeling used to compare the performance of the Oxford Ecohouse design, for example, but built using methods that employ varying arrangements of thermal mass.
Ideas on integrating PV's into a design are briefly expanded upon in Chapter 8: making use of PVs shading elements; installing PV roof tiles; use of translucent PV's for areas like sunspaces or conservatories.
Chapter 9 in Ecohouse 2 , which deals with solar hot water systems, goes into more detail in describing the differences between open vent, sealed and pressurised and pumped, closed loop systems. The step-by-step approach to solar hot water system design and installation now asks readers to consider how climate might affect collector choice and considering the location of the collector and store for the system. A new step has been added which points out to the reader the importance of an auxillary heat source to prevent bacterial growth, how mixers or automatic bleeding devices are possible ways to avoid the danger of scalding.
In Chapter 10, Using Water Wisely, the case is made for a more positive approach to water conservation based on five categories of water saving measures: water conservation; water sufficiency; water substitution; water reuse. Technologies are shown to play an imporant role in reducing water consumption of household items like WCs, showers, washing machines and taps. There is also a new small section that discusses the impact of rainwater harvesting as well as highlighting the importance of more sustainable approaches to rainwater drainage.
Two 'tools' are presented that assist the reader in analysis of the case studies. Craig Simmonds' explanation of ecological footprinting offers an important reminder that our lifestyle and activities once we are settled in our 'eco house' merits as much attention as the design if we are to truly reduce our environmental impact. Fergus Nicol explains how to use local data on temperature to construct their own 'Nicol Graph', a useful tool in defining optimum temperature for a specific building design.
Three new case study houses are added to bring the total number of case studies to 24 houses. The houses demonstrate a variety of interesting design approaches and many of the case studies offer very useful information on how well certain design ideas and technologies have performed.
One of the main strengths of this book lies in the fact that the authors' own designs are used to demonstrate many of the principles discussed. Contributions by others like Pete Warm, Chris Laughton, Nick Grant, and Steven Szolkay also enhance the quality of the book's content. Much of the detailed information which assists the reader in sizing solar panels or a PV array, for example, is useful on two main levels: as a general overview of important issues to be considered prior to design or installation; and as a 'how-to' manual for those 'hands-on' types. Extensive references at the end of each chapter will be handy for those wishing to learn more about topics covered in the book.
Although Ecohouse 2 explores the importance of designing a relatively compact, well insulated, air tight building with adequate controlled ventilation and low energy demands, prior to considering the use of renewable technologies, I find Roaf's assertion that 'PV's should be an essential feature of a real Ecohouse' somewhat prescriptive. It comes across as an 'eco cliché' (to borrow a phrase from Howard Liddel and Nick Grant's article titled 'Eco Minimalism' in BFF v.12 No.3) because the text focuses solely on PVs and fails to explore with its usual rigour the potential of wind, water or biomass energy systems.
Ecohouse 2 covers a lot of ground and does so in a very readable fashion. Even the more technical sections on PV system design, for example are easy to understand. However, I feel these sections would probably be most useful to the self builder or competent DIYer whereas the book as a whole would be suited to both students and professionals in the construction industry. In conclusion, I would recommend this book as an easily accessible and informative reference source for the professional and an introductory text for students (as well as newcomers to green building) that provides a solid understanding of the main principles of ecological house design.
Eric Parks
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