Low Impact Building

Housing using Renewable Materials

Tom Woolley

• Publisher: Wiley-Blackwell
• Year: 2013
• ISBN:
  9781118524190
• Edition: 1
• Topic: Architecture
• Subtopic: Architecture Design

This guide to the designs, technologies and materials that really make green buildings work will help architects, specifiers and clients make informed choices, based on reliable technical information.

Low Impact Building: Housing using Renewable Materials is about changing the way we build houses to reduce their 'carbon' footprint and to minimise environmental damage. One of the ways this can be done is by reducing the energy and environmental impact of the materials and resources used to construct buildings by choosing alternative products and systems. In particular, we need to recognise the potential for using natural and renewable construction materials as a way to reduce both carbon emissions but also build in a more benign and healthy way. This book is an account of some attempts to introduce this into mainstream house construction and the problems and obstacles that need to be overcome to gain wider acceptance of genuinely environmental construction methods.

The book explores the nature of renewable materials in depth: where do they come from, what are they made of and how do they get into the construction supply chain? The difference between artisan and self-build materials like earth and straw, and more highly processed and manufactured products such as wood fibre insulation boards is explored.

The author then gives an account of the Renewable House Programme in the UK explaining how it came about and how it was funded and managed by Government agencies. He analyses 12 case studies of projects from the Programme, setting out the design and methods of construction, buildability, environmental assessment tools used in the design, performance in terms of energy, air tightness, carbon footprint and post-occupancy issues.

The policy context of energy and sustainability in the UK, Europe andthe rest of the worldis subjected to a critical examination to show how this affects the use of natural and renewable materials in the market for insulation and other construction materials. The debate over energy usage and embodied energy is discussed, as this is central to the reason why even many environmentally progressive people ignore the case for natural and renewable materials.

The book offers a discussion of building physics and science, considering energy performance, moisture, durability, health and similar issues. A critical evaluation of assessment, accreditation and labelling of materials and green buildings is central to this as well as a review of some of the key research in the field.

1. Renewable and non-renewable materials

…many of us feel motivated to choose environmentally friendly products, even if they cost a little bit more. We know that products can be made from rare natural resources or from renewable raw materials, with or without unfair labour, with chemical input or from organic agriculture, with more or less energy based emissions. This is not a question of income but one of willingness.

(Welteke-Fabricius 2011)

In order to understand why natural and renewable materials are beneficial in mainstream building construction it is necessary in this chapter to explain what these materials consist of and to compare them with more conventional products. This book focuses largely on timber frame construction, insulation and board and panel materials. From these materials it is possible to construct many buildings that are required by society, even some multi-storey buildings. Environmental issues related to steel and concrete are not discussed in any detail here though they will be touched on in Chapter 6.

For many practitioners of natural building around the world, this would be quite a narrow perspective, as natural builders will use a wide range of resources, local green timber, earth, straw, bamboo and whatever else is to hand. This approach was covered in another book (Woolley 2006), and there are many organisations offering services, training and advice on natural building in the UK and throughout the world. In this book, the aim is to concentrate on natural materials being used in mainstream construction rather than handmade /self-build structures.

Natural and renewable materials can be made from biological sources such as hemp, flax, wood, straw, sheep’s wool and so on. They can also be combined with benign or low impact materials such as lime and earth into composites. However, some natural materials also include synthetic additives that are intended to improve performance. A key issue here is the reasons for selecting such materials and also the reasons given for not selecting them. There is a great deal of prejudice against natural or unusual materials and in conversation 90% of people also say that such materials are ‘too expensive’, even though this is not always the case and is usually based on ignorance. Many people also fear that such materials are not robust and long lasting.

However, there are many people, professionals and builders who overcome these prejudices and have been willing to give natural and renewable materials a chance, in preference to manmade synthetic products, even when they do cost a little more. This is even the case in projects where there are cost constraints, such as social housing. One key to selection is the level of commitment to doing the right thing for the environment.

Synthetic, manmade materials

Most construction materials used today involve a great deal of energy and much environmental damage to produce. They must be quarried, processed, subjected to heat or treated with a range of chemicals. Very often they are derived directly or indirectly from petrochemical sources, and polluting emissions are frequently a by-product of the manufacturing process. For the purposes of this book, these materials will be referred to as synthetic materials. Often such products are also referred to as ‘manmade’, but this is confusing as some of the natural renewable materials discussed here are also manmade. The word synthetic is used to contrast with the word natural, but as with so much in the English language there are problems of definition. Mineral wool insulation, for instance, is sometimes referred to as a natural product as it is made from naturally occurring rock. However, the process of melting the rock and then binding it with chemical glues is far from natural and can safely be referred to as synthetic. On the other hand, many natural insulation materials such as sheep’s wool or hemp may also have manmade glues and binders and other chemicals added to them to make them perform better. However, many natural materials use natural glues, resins and binders or simply water. Other terms such as ecological and bio-based are also used to describe natural renewable materials.

There is also a growing body of materials made from recycled materials such as glass and plastic that many regard as environmentally acceptable. These recycled materials are even referred to as renewable as there seem to be unlimited amounts of waste materials in our throwaway society. However, some recycled materials require significant amounts of heat and chemical processes to convert them. An environmental judgement, based on scientific evidence and independent certification, when this is available, has to be made about the impact of these processes before deciding whether such materials are acceptable. In order to understand the distinctive characteristics of natural, renewable materials, we first have to understand the limitations of synthetic products.

Limitations of synthetic materials

The key difference between natural and synthetic materials is the concept of renewability. Once a load of rock has been melted and spun into mineral wool insulation it cannot easily be returned to the earth and certainly cannot be grown again so it cannot be renewed, and its CO₂ emissions, from manufacturing, cannot be recovered.

However, many companies make strong environmental claims in favour of non-renewable products. For instance Rockwool says that its stone-based insulation product is ‘sustainable’.

Rockwool is an environmentally conscious company with a long track-record of producing, according to independent assessments, one of the most sustainable insulation products available. During its long lifetime, a typical Rockwool insulation product saves more than 100 times the energy invested in its manufacture, transport and ultimate disposal. Therefore, Rockwool insulation is one of the most practical, cost-effective and environmentally efficient ways that homeowners and organisations can reduce their energy consumption and improve their carbon footprint. Created from natural and recycled products, Stone wool is made by melting naturally occurring volcanic diabase rock and recycled briquettes, made with carefully selected by-products from our own and other industries. Our high-tech production process employs filters, pre-heaters, after-burners and other cleaning collection systems to ensure an environmentally responsible approach. (emphasis added)

(Rockwool 2011)

There is little doubt that stone based insulations can be useful products, particularly because of their fire safety characteristics, though many natural renewable products also have good fire resistance performance. The aim here is not to suggest that they should never be used, as they might be the best material for a particular job. However, the specifier is confronted with a simple choice when considering the use of renewable or synthetic products and needs to question some of the sustainability claims for such products. For instance Rockwool states on its website; ‘Rockwool is 97% recyclable’, though it is not clear what happens to the mysterious 3% that is not recyclable. It also states correctly that something being recyclable does not mean that it is actually recycled.

Stating that rock wool is one of the most sustainable products available is based on a flawed definition of sustainability. In order to be sustainable, based on the Brundtland definition (Brundtland 1987), requires human activity not to compromise future generations, so non-renewable materials (that use a great deal of fossil fuel energy for manufacture, and resources that cannot be renewed) should not be referred to as sustainable. Stone wool insulation may help with energy efficiency but it is the energy used in the short term, to manufacture the material, that is doing the greater damage to the environment. To be regarded as sustainable, materials should be largely free of added toxic chemicals and be able to be disposed of safely. Stone wool products may not meet this standard. There may be an argument for the use of high embodied energy or petrochemical based products used in small quantities, such as aluminium or plastics, when nothing else will do the job. This is a social policy or political decision, but if a manufacturer like Rockwool says its product is the ‘most sustainable’, the average specifier seems to believe it, without investigating the claim any further.

It is possible that stone wool products can be recycled if the building containing the materials is carefully dismantled so that the insulation can be taken out and reused, but this rarely happens in practice. Synthetic fibre insulations often become dirty and damp and fall apart if disturbed and this makes reuse almost impossible. More commonly, synthetic insulations end up as waste in landfill. Mineral fibres do not biodegrade into the earth. Also, the off-cuts and general mess on building sites can lead to a significant amount of new insulation material going to waste and landfill.

Questioning claims about recycling

Most of the manufacturers of synthetic insulation materials make claims about the role of recycled content in their materials to claim a good environmental performance. They state that they can recycle all recovered material in their factory but never give figures, so it makes one suspect that these claims may be misleading. There are a few synthetic products that are largely made from recycled materials but it is often hard to distinguish these from other products where perhaps only a tiny proportion of the material is from recycled sources.

Black Mountain Ltd, one of the leading UK manufacturers of natural insulations, claimed on its website in 2011, that mineral fibre insulation was not recycled and that manufacturers of these products were wrong to claim that this was the case.

Sheep’s wool is biodegradable and therefore can be composted into the ground to enrich the soil and remain part of the earth’s natural cycle. Sheep’s wool insulation can be recycled or incinerated to produce additional energy, whereas man-made mineral fibre materials currently have no practical recycling system in place and can only be properly disposed of into landfill sites.

(Black Mountain 2011)

A complaint was made about this to the Advertising Standards Authority (ASA) by the Mineral Wool Insulation Manufacturers Association (MIMA) but the ASA found in favour of Black Mountain, as they said that MIMA did not provide any solid evidence of recycling.

The Mineral Wool Insulation Manufacturers Association (MIMA) challenged whether the claim was misleading and could be substantiated, because they understood that mineral wool insulation could be recycled. We noted that the MMMF (Man Made Mineral Fibre) manufacturers website MIMA referred to, stated that the manufacturer encouraged the return of their product for recycling where it was in the form of construction off-cuts or reclaimed from refurbishment or demolition work. However, we considered that that statement did not in itself constitute evidence that that particular manufacturer recycled significant quantities of end of life MMMF, nor that there was a generally used system in place for...

Table of contents

• Cover
• Title page
• Copyright page
• Dedication
• Acknowledgements
• Figure credits
• Introduction
• 1 Renewable and non-renewable materials
• 2 Case Studies: twelve projects in the Renewable House Programme
• 3 The Renewable House Programme: a strange procurement!
• 4 Analysis of issues arising from the case studies
• 5 Attitudes to renewable materials, energy issues and the policy context
• 6 Building physics, natural materials and policy issues
• 7 Other solutions for low energy housing
• 8 A future for renewable materials?
• Glossary/Abbreviations
• Index
• Other Books Available from Wiley-Blackwell
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