Thermal Performance of Contemporary Earth

Célia Macedo | September 2009

Thermal Performance of Contemporary Earth Architecture in Portugal

Submitted in partial fulfilment of the MSc degree in Energy Efficient and Sustainable Building Oxford Brookes University - 2009

MSc EESB | Thermal Performance of Contemporary Earth Architecture in Portugal

ABSTRACT

The earth as a building material has been used for many centuries in vernacular and traditional architecture throughout the world. It served not only the purpose of providing shelter but also comfort to occupants, simply by responding to local climatic conditions. The immense cultural legacy of earth construction techniques enhanced by thousands of years of tradition allied by today’s knowledge is contributing to the significant increase of its use all across the globe. This dissertation aims to investigate the thermal performance of earthen buildings, focusing on three case studies located in the Low-Alentejo, a region located in the south of Portugal. The literature review on the subject provided a background which informed the remaining research work; subsequently, the methodology utilized combined real data collection from three case studies with thermal model simulations. The latter allowed for a comparison between various building materials regarding their thermal performance. Moreover, the research was complemented with occupancy surveys in order to assess the users’ perception of the internal environment of the case study buildings, thus focusing on both quantifiable data from the temperature measurements, and qualitative information gathered from the surveys. The findings from this research work led to the conclusion that rammed earth, when used with no insulation, although it shows a very effective thermal behaviour during the summer fails to provide comfortable thermal conditions during the coldest periods of the year. However, this problem can be overcome when insulation is used, thus providing thermal comfort both during the winter and during the summer. Based on these premises, it can be stated that the building material earth used as part of a passive design building strategy possesses a good potential in terms of providing thermal comfort, having therefore the properties of a material which can contribute towards a more sustainable future.

Célia Macedo | 2009

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ACKNOWLEDGEMENTS

I would like to honestly express my gratitude to the people who contributed in many ways towards this work, whether by providing moral support or valuable information for the research. To Bruno, for the constant love and support and for making this stage of my life possible; To the authors and occupants of the case studies, architect Henrique Schreck, architect Alexandre Bastos and architect Graça Jalles, for the immediate decision and availability to take part in this project; To my friend Helena Arguelles, for accompanying me during several visits to the case studies and for the motivation provided in these most difficult times; To my friend Mariana Correia for being an inspiration and an excellent role model; To Ashley Burns for proofreading and support; To Smita Chandiwala and Paola Sassi, for a very helpful supervision and support throughout the making of this dissertation; and finally, To everyone who contributed somehow towards this work. Thank you very much.


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CONTENTS

Abstract............................................................................................................

i

Acknowledgements........................................................................................

ii

Contents............................................................................................................

iii

List of Illustrations..........................................................................................

v

Introduction ....................................................................................................

10

Aims and Objectives...........................................................................

12

Scope and Methodology.....................................................................

12

Limitations...........................................................................................

14

Dissertation outline..............................................................................

14

Chapter 1 | Sustainable Building...................................................................

16

1.1

Human Impact and Global Warming..........................................

17

1.2

Sustainability for the architect....................................................

18

1.3

New Building Paradigm..............................................................

19

1.3.1

Materials.......................................................................

19

1.3.2

Different approaches to sustainable buildings..............

23

1.3.3

Visual and Comfort aspects..........................................

24

Chapter 2 | Earth construction.......................................................................

26

2.1 Historical Background.................................................................

27

Earth as a building material........................................................

29

2.2.1

Thermal Properties........................................................

29

2.2.2

Environmental Impact and Embodied Energy................

31

2.2.3

Cost................................................................................

32

Earth Construction in Portugal...................................................

34

2.3.1

Historical Note................................................................

34

2.3.2

Present and Future........................................................

35

Description of techniques used in Portugal................................

38

2.4.1

Rammed Earth...............................................................

39

2.4.2 Adobe.............................................................................

42

2.2

2.3

2.4


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2.4.3 Wattle-and-daub............................................................

44

2.4.4 CEB...............................................................................

45

Chapter 3 | Case Studies...............................................................................

48

3.1

Methodoly of Analysis...............................................................

49

3.2

Global analysis, background information..................................

50

3.3

Case Studies.............................................................................

54

3.3.1 Case Study 1.................................................................

54

3.3.2 Case Study 2.................................................................

58

3.3.3 Case Study 3.................................................................

62

Thermal Comfort.......................................................................

66

3.4.1 Occupancy satisfaction survey......................................

67

Chapter Conclusions.................................................................

70

Chapter 4 | Thermal Modelling......................................................................

72

4.1

Intention....................................................................................

73

4.2

Comparison between options ...................................................

76

4.2.1 Embodied Energy..........................................................

76

4.2.2 Thermal Performance....................................................

77

4.2.3 Comparison between rammed earth options................

80

Chapter Conclusions.................................................................

81

Conclusions...................................................................................................

82

References......................................................................................................

87

Appendices.....................................................................................................

94

3.4 3.5

4.3


iv


LIST OF ILLUSTRATIONS FIGURES Chapter 1 1.1 – Three perspectives on sustainable design © Brian Edwards Chapter 2 2.1 – Distribution of earthen buildings in the world 2.2 – The Great Mosque, Mali © Kathleen Cohen 2.3 – The Old City, Yemen © Kathleen Cohen 2.4 – Relation between density and conductivity in earthen materials 2.5 – Life cycle of a rammed earth wall 2.6 – Ruin of an old rammed earth wall 2.7 – Ruin of an old rammed earth wall 2.8 – Geographical distribution of earthen building techniques in Portugal 2.9 – Manual rammers 2.10 – Mechanical rammers 2.11 – Pneumatic rammers 2.12 – Vibrating rammer 2.13 – Ramming process 2.14 – Ramming process © Pedro Abreu 2.15 – Rammed earth construction site © Pedro Abreu 2.16 – Adobe mould 2.17 – Internal adobe wall 2.18 - House in Zanzibari, Africa © Kathleen Cohen 2.19 - House in Zanzibari, Africa © Kathleen Cohen 2.20 – House in York, UK © Kathleen Cohen 2.21 – CEB stored 2.22 – CEB wall


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2.23 – CEB mechanical press 2.24 – CEB wall, detail Chapter 3 3.1 - Map of Europe. © Central Intelligence Agency 3.2 - Map of Continental Portugal. © Central Intelligence Agency 3.3 - Average annual temperature and precipitation in Continental Portugal (19611990). © Instituto de Meteorologia Portugal 3.4 – Case study 1 – wall detail 3.5 – Case study 1 – interior 3.6 – Case study 1 – main façade 3.7 – Case study 1 – I-buttons’ location 3.8 – Case Study 2 - Entrance 3.9 – Case Study 2 – Internal wall 3.10 - Case Study 2 – Main façade 3.11 - Case study 2 – I-buttons’ location 3.12 - Case Study 3 – Interior 3.13 - Case Study 3 – Winter garden area 3.14 - Case Study 3 – External slate wall 3.15 - Case study 3 – I-buttons’ location

Chapter 4 4.1 – Image of the building model produced in the IES simulation environment


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GRAPHS Chapter 1 1.1 - EU-27 Greenhouse Gas Emissions by pollutant, 2006. © European Communities, 2008 1.2 - EU-27 Greenhouse Gas Emissions per sector, 2006. © European Communities, 2008 1.3 – Embodied Energy of selected materials Chapter 3 3.1 – Nicol Graph for Odemira, Alentejo 3.2 – Total energy consumption by Sector, Portugal 3.3 – Typical Energy consumption in a house 3.4 – Case study 1 - Internal temperatures: 1-15 January 2009 3.5 - Case study 1 - Internal temperatures: 9 January 2009 3.6 - Case study 1 - Internal temperatures: 17-31 July 2009 3.7 - Case study 1 - Internal temperatures: 20 July 2009 3.8 - Case study 2 - Internal temperatures: 1-15 January 2009 3.9 - Case study 2 - Internal temperatures: 9 January 2009 3.10 - Case study 2 - Internal temperatures: 17-31 July 2009 3.11 - Case study 1 - Internal temperatures: 20 July 2009 3.12 - Case study 3 - Internal temperatures: 1-15 January 2009 3.13 - Case study 3 - Internal temperatures: 9 January 2009 3.14 - Case study 3 - Internal temperatures: 17-31 July 2009 3.15 - Case study 3 - Internal temperatures: 20 July 2009 Chapter 4 4.1 – Comparison between construction types. Simulation 11-17 January 4.2 – Comparison between construction types. Simulation 16 January 4.3 – Comparison between construction types. Simulation 5-11 July 4.4 - Comparison between construction types. Simulation 11 July 4.5 - Comparison between rammed earth options. Simulation 16 July


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4.6 - Comparison between rammed earth options. Simulation 11 July

TABLES Chapter 1 1.1 – Environmental profile of selected building materials Chapter 2 2.1 – Properties of selected materials 2.2 – Life Cycle Assessment of the building material Earth Chapter 3 3.1 – Case study 1: information 3.2 – Case study 2: information 3.3 – Case study 3: information 3.4 – Case study 1: Summary of results of occupancy survey 3.5 – Case study2: Summary of results of occupancy survey 3.6 – Case study 3: Summary of results of occupancy survey Chapter 4 4.1 – Simulation conditions and variables 4.2 – Embodied energy of the different options


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INTRODUCTION

“It is necessary to study building as a kind of doing called Architecture. Not merely is Architecture made at the drafting board, but Architecture in all of its aspects is to be studied as environment, as the nature of materials to be used, as the forms and proportions of Nature itself in all her forms – sequences and consequences. Nature is the great teacher – man can only receive and respond to her teaching.” Frank Lloyd Wright (1954) The Natural House. USA: Horizon Press Inc.


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INTRODUCTION According to scientists and researchers the human impact on global warming is now a given fact. Moreover, the greenhouse emissions resulting from the burning of fossil fuels and other processes are deeply affecting the planet at a global scale. (Smith, 2007) The building sector alone accounts for more than half of the primary energy consumption globally and consequently for the same portion of greenhouse gas emissions. (Roaf et al., 2007) There is hence an urgent need to tackle this serious problem and contribute towards a more sustainable world. The belief that earth as a building material can play a key role in a new more environmentally conscious building paradigm is currently being supported by numerous experts who point out its environmental, cultural and economical advantages when compared to other, more commonly used building materials. This is a material that has been present throughout the human kind history, since man first started to gather in primitive villages almost 10,000 ago (Dethier, 1983) and still today an estimate of 30% of the world population dwells in earthen houses. (Houben & Guillaud, 1994). The literature acknowledging the good qualities of this building material go as far back as the 1st century BC and, adding to this, its wide use across the globe constitutes a proof of an immense flexibility when it comes to adapt successfully to different environments and contexts. Although the thermal properties and low environmental impact of this millenary building material apparently make it a suitable choice for today’s demanding building industry, where the need for sustainable buildings is growing, there are still various obstacles to overcome in order to make the material competitive with other current solutions.


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Aims and Objectives The main objectives of this research are: a) Analyse the thermal performance of the building material earth: Measure internal temperatures of case studies during certain periods of the year; Compare thermal performance of earth with various construction solutions. b) Analyse Environmental Impact of the building material earth: Embodied Energy analysis; Life Cycle Assessment. Scope and Methodology This study looks at evaluating the thermal performance of contemporary rammed earth houses in a particular area of Portugal. This was based on literature review and analysis of three case studies, which were selected based on their main building material, their location and receptivity of the occupants towards this study. Real monitored performance data within the case studies was collected during January/February and July/August. This information is further supported with IES modelling of different construction types. Moreover, additional data was collected during 3 field study visits - December, June and August - and interviews with the occupants. The flow chart and bullet points below illustrate the methodology followed in order to conduct this study and achieve the objectives described earlier. Literature review on the subject

Identify case studies

IES - thermal simulation of case study

Comparison with conventional contruction Results: thermal performance

Collect information (drawings, photos, etc.)


Field study: visits, notes, photos

I-buttons and occupancy questionnaires – real data

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1 | Literature survey to investigate current state of earth architecture and its sustainability qualities The literature review focuses on both sustainable architecture and earth architecture as concepts, specifically in what concerns the environmental impact of materials and embodied energy. 2 | Case study of 3 rammed earth buildings including temperature monitoring, questionnaire surveys and interviews In order to select the case studies several aspects were taken into consideration, such as: (a) The material used to build the walls – Earth; (b) The location – All three buildings should be located within close distance of each other so that the external conditions can be similar; (c) The acceptance and collaboration of the occupants towards the study. In order to conduct the analysis of the case study’s internal thermal conditions two different methods were used: Data loggers were used to record the internal air temperature and occupancy surveys undertaken to determine the occupants’ perception of the space in terms of thermal comfort. 3 | IES modelling to compare performance of different construction types One of the case studies was used as a reference to design a thermal model in IES-VE. The objective was to compare the building material earth with other construction materials in terms of their thermal performance. Expected Outcomes It is expected that the outcomes of this research work will contribute to the existing knowledge base regarding the characteristics of earth as a building material. It can do so by contributing with information about earth’s potential as a low environmental impact building material, capable of providing thermal comfort passively to the occupants of buildings.


13


Limitations The complete accurateness of the findings within this research may have been affected due to limitations beyond the author’s control. Such was the case of the weather data utilised to illustrate the external conditions of the case studies’ location. In the absence of equipment to monitor the external temperature on the exact place, the weather data used was obtained from the closest possible weather station and provided by the Portuguese meteorological institute. Also, there was no available weather data integrated in the IES-VE software for the exact location of the case studies, therefore the closest weather station in the software database was again selected. This climatic data may differ slightly from the one provided by the meteorological institute, nonetheless it does not affect the final results. The physical distance between the author and the case studies may be considered an obstacle, as it made difficult to visit them as often as it would have been desirable. This fact required extra work in terms of organisation and planning.

DISSERTATION OUTLINE Regarding the structure, this dissertation adopts a ‘general to particular’ strategy, hence commencing with an introductory approach to broad concepts related with sustainability, and progressively narrows the subject throughout the chapters until it concludes with the analysis of a thermal model simulation. A brief summary of each chapter is provided below. Chapter 1 This chapter touches the emerging problem of global warming and climate change. It then continues by approaching concepts such as Sustainability, Embodied Energy and Environmental Impact. This section intends to provide the reader with background information regarding the way architecture and the built environment are being affected by the intention of reducing the dependency of fossil fuels in order to counter the threat posed by climate change.


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Chapter 2 This chapter is exclusively dedicated to the aspects of earth construction. It approaches the global historical background as well as the characteristics of earth as a building material. Moreover, it also focuses on the use of this material within the particular context of Portugal by analysing both its distribution within the territory and the main earthen building techniques used. Chapter 3 This chapter consists on the analysis of the three earthen building case studies, focusing on their thermal performance and the users’ perception of their internal environment. The chapter also comprises some information about Portugal, namely the climate, typical levels of energy consumption and CO2 emissions. Chapter 4 This chapter provides the outcomes of the thermal model developed using the IES-VE software. The intention of this model is to compare the thermal performance of earth with other materials and construction methods.


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CHAPTER 1 |SUSTAINABLE BUILDING

In order to introduce the subject which inspired this research, it is appropriate to briefly touch on one of the most important discussions of our time: What is sustainability and how does it influence architecture? A special focus will be attributed towards the role of materials in sustainable buildings, and a general approach through the concepts of Embodied Energy, Environmental Impact or Life Cycle Assessment, among others, will contribute to a better understanding of the following chapters where the building material earth is analysed in detail.


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1.1 | HUMAN IMPACT AND GLOBAL WARMING The influence of human activities on the phenomenon of climate change is now a given fact. Scientists and researchers have been showing the world that the emissions of greenhouse gases from fossil fuels, industrial processes and changes in land-use are deeply affecting the planet at a global scale, which will result in major economic and social consequences. (Smith, 2007) Carbon Dioxide (CO2) is considered the most

EU-27 Greenhouse Gas Emissions by Pollutant - 2006 1%

damaging greenhouse gas, and it accounts

8% 8%

for about 83% of the global warming potential of all the EU-27 in 2006. The main source of CO2 is from the burning of fossil

83%

fuels. Within the EU-27 territory, the weight of the

Carbon Dioxide Nitrous Oxide

Methane F-Gases

building sector in terms of greenhouse gas emissions per sector is relatively high, as revealed in the information released by

EU-27 Greenhouse Gas Emissions per sector - 2006 3%

Eurostat (2008), which confirms that in 2006

9%

about 15% were attributed to fuel combustion

8%

from households ‘Other (Energy)’ and 13 % to

15%

fuel combustion of manufacturing industries and construction. The emissions from the other

sectors

may

also

be

indirectly

associated with the building sector. (Eurostat - European Comission, 2008)

31%

13% 2%

19%

Fuel Combustion of Energy Industries Fuel Combustion of Manufacturing Industries and Construction Fuel Combustion in Transport Fugitive Emissions from Fuels

Graph 1.1 – (top) EU-27 Greenhouse Gas Emissions by pollutant, 2006 Graph 1.2 – (bottom) EU-27 Greenhouse Gas Emissions per sector, 2006


Other (Energy) Industrial Processes Agriculture Waste

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1.2 | SUSTAINABILITY FOR THE ARCHITECT The 1970s were fertile in terms of ideas and concepts concerning the relationship between buildings and their impact on the environment. Labels such as ‘green’, ‘ecological’ and ‘environmental’ can be traced to this decade. In fact, they became part of a wide strategy oriented towards designing with the intention of reducing the reliance on fossil fuels, from which also emerged terms like ‘low energy’, ‘solar’ and ‘passive’. (Williams et al., 2003) In 1987, the World Commission on the Environment provided a definition for what constitutes ‘Sustainable Development’. According to the Brundtland Report it can be described as: “meeting the needs of the present without compromising the ability of future generations to meet their own needs”. This definition is still often used today. (World Comission on Environment and Development, 1987) Since then, the concept of Sustainability has been suffering a considerable evolution throughout various congresses, international declarations, and other plans of action. It is also worth mentioning the Earth Summit held in Rio de Janeiro, Brazil in 1992, since it marked an important turning point for architecture in particular. Although various important agreements emerged from the Earth Summit, two of them have direct implications in sustainable architecture: The Agenda 21 and The Framework Convention on Climate Change. The first sets up a series of objectives aimed at improving the social, economic and environmental quality of human settlements as well as the living and working environment of people; while the latter aims to slow down or bring to an end changes on climate which are directly or indirectly attributed to human activity. This may have a considerable effect on the design of buildings, as they are large contributors to CO2 and other green house gas emissions, as previously stated. (Williams et al., 2003) Furthermore, sustainability holds a particularly important meaning for architects, since nowadays the built environment has a great influence in our day to day lives as we seem to spend most of our time in direct or indirect contact with it. Not only do we live in houses, but we also work in buildings and spend our free time going to the cinema,


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theatre, pubs, shops, and so on. Modern day society has grown dependant on an industry which is probably one of the least sustainable in the world. (Edwards, 2005) Sustainability has now left the apparently simple initial approach from the 1980s and has embraced a whole new network of complex systems involving social, economic and environmental impacts. According to Edwards (2005, p.3), “designing sustainably is to do with addressing global warming through energy conservation and using techniques such as life-cycle assessment to maintain a balance between capital cost and long-term asset value. However, designing sustainably is also about creating spaces that are healthy, economically viable and sensitive to local needs. It is concerned with respecting natural systems and learning from ecological processes.” . 1.3 | NEW BUILDING PARADIGM 1.3.1 | Materials Embodied Energy According to Harris & Borer (2005, p.94), embodied energy can be defined as “the primary energy used in all the different stages of materials processing” from the extraction of the raw materials until the demolition and disposal. The same authors continue by saying that when the energy is produced from renewable sources it can be discounted from the embodied energy calculations. Moreover, the energy saving measures incorporated into any stage of the process can be considered as credits. (Harris & Borer, 2005) Determining the embodied energy of a given building material is very useful when assessing its environmental impact. As stated by Baird et al. (1997) there are three main methods of embodied energy analysis: 1) Statistical analysis, 2) Input- Output analysis, and 3) Process analysis. The authors believe that by using a hybrid process, which would incorporate the most useful features of the three, the end result would not


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only be achieved more quickly but it would also be more accurate when compared to the other methods used individually. Furthermore, Baird et al. (1997) points out the fact that the energy coefficient of most materials tend to reduce with time due to the improvement in the manufacturing and energy efficiency. The graph 1.3 illustrates some

Embodied Energy of selected materials

examples of materials and their

Aluminium, virgin

Embodied Energy. The subject

LDPE(low density polyethelene)

103

HDPE(high density polyethelene)

103

will be approached later on when discussing the properties of the building material earth.

191

polyurethane

74

Carpet

72.4

Copper

70.6

PVC

Environmental Impact As

stated

polypropylene

64

polyester

53.7

the

Zinc

51

building industry is amongst the

Bitumen

44.1

most

previously,

70

unsustainable

on

the

planet. Figures tell us that over

Steel, virgin, general

32

Glass - toughened

26.2

Glass - laminated

16.3

half of the energy consumed

Glass - float

15.9

globally is taking place within the

Steel, recycled

building sector, which makes

Aluminium, recycled

8.1

Cement

7.8

brick, glazed

7.2

buildings also responsible for more than half of the world’s

Asphalt (paving)

greenhouse emissions. (Roaf et

brick

al., 2007) The residential sector

concrete pre-cast

10.1

3.4 2.5 2

alone accounted for 15 % of the

Concrete brick

0.97

Concrete block

0.94

world energy consumption in

Raw Earth - rammed soil cement

2006.

(Energy

Information

Administration,

2009).

Moreover, the building industry is

currently

biggest

considered

consumer


of

the raw

0.8

Adobe block, straw stabilised

0.47

Raw Earth - pressed block

0.42

Adobe, cement stabilised

0.42

Adobe, bitumen stabilised

0.29

MJ/Kg

Graph 1.3: Embodied energy of selected materials. Source: (Baird et al., 1997)

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materials, right after the food production industry; hence Berge (2000) remarks on the need to drastically reduce the use of raw materials in construction as a way to reduce environmental impact of buildings. The subject of Environmental Impact has been widely approached by several authors recently. The book The Ecology of Building Materials (Berge, 2000) is one example. It consists of a very complete tool designed to provide what the author designates as the ‘Environmental Profile’ of materials, which takes into account factors such as Effects on Resources, Effects of Pollution and Ecological Potential. The materials are rated from 1 to 3; where 1 is considered the best option and 3 the worst. Some examples taken from

Vertical Structures

Horizontal Structures

Aluminium beams (50% recycling)

Local production

Re-use and recycling

As waste

In the building

Building site

Material

Ecological Potential

Effects on pollution Extraction and production

Water

Energy

Materials

Effects on resources

Environmental Profile

this publication are shown in the table below.

3

3

3

1

2

2

2

3

2

2

2

3

3

2

1

2

2

2

2

3

1

2

1

2

1

1

1

1

1

1

1

1

Aluminium studwork, 50% recycling

3

2

3

3

1

2

2

3

Concrete blockwork (inclusive of reinforcement)

2

2

2

3

1

2

1

2

Earth, without fibres added

1

1

1

1

2

1

1

1

In situ concrete Precast concrete Hardwood beams

Table 1.1 – Environmental Profile of selected building materials. Source: (Berge, 2000)

Kimmis et al., in the Green Building Handbook (1997) stress the importance of evaluating the environmental impact of all the constituent parts of a building, while Anderson et al. (2009, p.12) alerts one to the fact that “the impact of the construction process and the associated impact from materials extraction and manufacture in terms


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of energy and resource use or level of emissions on global could be identified as a major ‘indirect’ environmental hazard”. There is the eminent need to guarantee that the use of products and materials will not increase the environmental problems associated with the construction sector. It is therefore necessary to manage their use and disposal. Roaf (2004, p.353), identifies four main ecological impacts associated with materials: “1 - The energy and water used in these products - to make, transport, run and dispose of them; 2 - Their toxicity in production, use and disposal; 3 - The waste implications in relation to their disposal and landfill; and, 4 - The use of finite reserves of raw materials”.

Environmental Assessment Tools There are various tools currently available which are capable of addressing and assess the environmental impact of materials. The Life Cycle Assessment (LCA) is the most commonly used to determine the environment impact of building materials. This method was first used in the 1970s and was afterwards normalized by the ISO 1040 standard, followed by ISO 1401, 1402 and 1403. In order to achieve a result, it takes into account the full life cycle of the material being analysed, thus adopting a ‘cradle to grave’ approach, which begins with the extraction of the raw material and finishes with the end of its life, including all the stages in between (manufacturing, transportation and consuming). (Graz et al., 2008) (Andreson et al., 2009) Although the LCA can indeed be considered a very thorough and useful tool to determine the overall sustainability of a building, some experts have the opinion that it fails to consider aspects such as soil and water pollution as well as the possible effect that materials can have on human’s health, prioritizing the impact of energetic consummation on the environment. (Graz et al., 2008)


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1.3.2 | Different approaches to Sustainable Building There are currently many labels attributed to sustainable buildings, which makes the task of finding a clear definition for what sustainability in architecture stands for very difficult to obtain. In the Green Building Handbook, Kimmis et al. (1997) points out the fact that words like ‘green’, ‘sustainable’, ‘environmental’ or ‘ecological’ are in fact interchangeable and that “the nuances of their use depend on the context and the audience”. There are in fact various approaches to what architecture and the built environment should represent when aiming for an environmentally conscious end result. Roaf (2007), for instance, refers the new vernacular concept. The author believes that all buildings should be based onto three principles: “- design for a climate; - design for the physical and social environment; - design for time, be it day or night, a season or the lifetime of a building and design a building that will adapt to time” The author continues by stating that the knowledge to create such buildings already exists, as people survived for millions of years without having to rely on oil or gas and that these skills can be learnt from traditional buildings. Moreover, the author reminds us of the importance of maintaining the knowledge hold by the old masters which mixed with new techniques and renewable energy can result in the appearance of a new vernacular approach and help reducing the environmental impact of buildings. Others assume Nature as a guideline and believe that natural buildings give more attention to the social and environmental sustainability. It relies on simple and easy-tolearn construction techniques leaving behind the capital, high-technology and specialized skills to focus on creativity. Moreover, natural building claims to have a low environmental impact and promote a healthy building, free from toxic components and materials. (Kennedy et al., 2002)


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1.3.3 | Visual and Comfort aspects Aesthetics The concept of aesthetics is still poorly understood

when

associated

with

sustainable architecture. Edwards (2005) states that the ecological design will be better accepted if it is regarded by the society

as

beautiful.

Furthermore,

by

embracing this new challenge of creating beautiful buildings with less intervention, the architects will allow for a new movement to emerge, placing sustainability into a cultural

Fig 1.1 – Three perspectives on Sustainable design. Source (Edwards, 2005)

context and not only a technological one. This new “eco-aesthetics” reinforces the idea that sustainability should be connected with the social, economic and social worlds. (Edwards, 2005) Thermal Comfort Thermal comfort is defined by Roaf (2004) as “the relationship between a person’s sensation of warmth or cold and the thermal conditions that create that sensation”. The definition goes on describing that people are more likely to feel thermal comfort by its absence, which is actually a feeling of thermal discomfort instead. (Roaf, 2004) The human thermal comfort is an important factor that has a direct influence in the overall perception of buildings. The indoor temperatures are closely related to the satisfaction of the buildings’ occupants and the buildings’ energy consumption. (Nicol, 1993) This mostly occurs due to the use of auxiliary heating or cooling systems in order to achieve some kind of thermal satisfaction. Such knowledge can aid a project during its design stage, hence contributing to a development of strategies towards the design of more energy efficient buildings.


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People perceive their environment in a complex and dynamic way and, to complicate things even further, that will also differ depending on factors such as the season, climate, social, cultural and economic context, and so on. Moreover, recent studies point to the fact that a variable standard in thermal comfort should be assumed instead of a stable one, as imposed by the HVAC industry, which can actually supply such a stable environment, whilst consuming high levels of energy but ignoring people’s real comfort needs. (Nicol, 1993). On the other hand adopting a dynamic standard, conscious of changeable factors can bring new light to the way buildings are designed, allowing them to change according to the wills of the occupants, so that their environment can adapt to different conditions. Nicol (1993) states that a variable standard could actually contribute to considerably diminishing energy requirements, as the indoor-outdoor temperature difference would be reduced. Testing real situations in the real world, and not in chambers where variable conditions do not usually occur, allows for the true nature of people’s interaction with their natural environment to be accessed. Conducting a field study should be considered. Having a clear idea of what the subject is, i.e. what is going to be measured, the group of people being used as subjects and the method used are all important factors in the making of a successful thermal satisfaction survey. The user satisfaction can be obtained through surveys, which, according to Nicol (1993) can be divided into three different levels, which can be chosen depending on the level of information and required when inquiring the occupants of a certain building. This subject will be approached again when applied to the case study buildings, in Chapter 4.


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CHAPTER 2 | EARTH CONSTRUCTION

The subject of earth construction will be approached within this chapter as an introduction to Chapter 3, where the earth buildings selected as case studies are presented and analysed. This chapter intends to briefly provide technical and historical background information concerning the use of earth as construction material. The outcomes are mostly based on research carried out through different sources. These sources would be predominately published literature on the subject, such as books, papers, magazines and so on. Additionally research ran in parallel with attending seminars and conferences on earth architecture, interviews with experts and the author’s own experience. The history and context of earthen buildings initiates the chapter followed by an approach towards the general characteristics of earth as a building material. To conclude the chapter a description of the main techniques in Portugal will provide an insight into the range of earthen techniques used as part of the building process in the Portuguese context.


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2.1 | HISTORICAL BACKGROUND Earth used as a building material has been present throughout human kind history. It played a key role by providing shelter when man first started to gather in primitive villages almost 10,000 years back. (Dethier, 1983) Its potential is still being explored today, as proof, 30% of the world’s population dwell in houses built with unbaked earth. Experts state that roughly 50% of developing countries’ population (most of its rural populations) and about 20% of urban and suburban populations live in earthen houses. Although these numbers are mentioned many times, there is the idea that they can underestimate the real present situation, since surveys and reports coming from several countries seem to actually point a higher percentage of people living in earth houses. (Houben & Guillaud, 1994) Throughout the course of history, many civilizations learnt to take advantage of this widely available material awarding it different uses, such as the provision of shelter, the building of strong defence walls, amongst others. The unbaked earth was used in Mesopotamia and Egypt, Romans and Muslims followed this example and adapted their techniques through Europe, Africa and the Middle East. Its reputation also reached other continents, such as America, where earth was being used by the Indians, the Toltecs and Aztecs in the Southern area of the continent. The Spanish transferred the European earthen building methods after conquering America, and transformed them into an established building tradition still present in the territory today. (Dethier, 1983) This is one of the most widely-used building materials and is probably present throughout all the inhabited continents. In literature, this fact is extensively registered throughout the writings of some of history’s most influential personalities with regard to history and science of architecture. Following Herodotus, known as the ‘Father of History’, many authors acknowledged the qualities and potential of the building material earth: In the 1st century BC, Vitruvius wrote about it in his treaty ‘De Arquitectura’ (Graz et al., 2008), later, in the 1st century AD Plinys the Elder reinforced the same idea in his encyclopedic work ‘Naturalis


27


Historia’ where he stated that the earth walls last for centuries and are capable of resisting natural elements. Moreover, Plinys also defended earth as superior in terms of solidity to any cement. (Pliny, 1857) Furthermore, in the Renaissance period Alberti followed by other Italian authors in the 16th and 17th centuries are part of a long list of Masters who recognized the importance of this building material. (Graz et al., 2008) The extensive use of earth not only reflects its wide availability but also its immense flexibility in terms of adaptation to different construction techniques, applications and the most diverse of contexts, regardless of social, economic and cultural aspects.

Fig 2.1 (top) – Distribution of earthen buildings in the world. Source: (Reeves et al., 2006) Fig. 2.2 (bottom left) – The Great Mosque, Mali. Source: http://worldart.sjsu.edu/ Fig. 2.3 (bottom right) – Yemen, the Old city. Source: http://worldart.sjsu.edu/


28


2.2 | EARTH AS BUILDING MATERIAL 2.2.1 | Thermal Properties The subject of thermal performance when associated with the building material earth constitutes many times a source of debate. It is common to witness the occupants of traditional earthen buildings reporting a high degree of thermal comfort, which, according to Morton (2008, p.80) “appears to contradict simple calculations of thermal resistance”. The responsibility for this comfort is attributed to the high thermal mass present in this building material. Hence, the thick walls of earthen buildings provide comfort to the occupants and maintain the interior at a relatively stable and comfortable temperature, regardless of the external conditions. In fact, earthen buildings are considered to be cool during the summer and warm during the winter, thus providing protection against the extremes of the climate. (Dethier, 1983) Nevertheless, earth is a material of poor insulation qualities. For instance, a solid wall of rammed earth and a solid wall of fired bricks have similar insulating properties. Although there are ways to improve the insulating properties of this material, such as adding light aggregates (fibres, straw, or woodchips) to the mixture (Minke, 2006), this results in creating a light-weight and not very robust construction material, which usually

requires

large

dimensions

to

maintain a good working strength. Moreover, thermal conductivity and density values are related, therefore the less dense the earth is the lower its conductivity is going to be. Common earthen techniques usually have high density values and therefore a high conductivity. (Morton,

Fig. 2.4 – Relation between density and conductivity. Source (Minke, 2006)

2008)


29


Material Wool Burned brick Basalt Slate Cork board Pine Plywood Cellular concrete Dense, reinforced concrete Rammed earth

Thermal conductivity (W/mK) 0.038 0.75 3.49 1.44 0.04 0.12 0.12 0.16 1.9 0.6 - 1.60

3

Density(Kg/m ) 140 1300 2880 1600 160 510 540 480 2300 1400 - 2000

Table 2.1: Properties of selected materials. Sources: (Walker et al., 2005), (Chartered Institution of Building Services Engineers, 2006)

The thermal performance of an earthen building will depend on the overall project, and not only on the material itself, i.e. the technique utilised or the thickness of the walls. It is therefore necessary to consider factors such as the external climatic conditions, the orientation and several architectural elements that may or not be included in the project, such as overhangs, number and dimensions of windows and so on. In addition to this, there are also studies considering the colour applied on the walls as an influence to the thermal performance process. (Neves, 2005) The greater demand of building regulations, particularly in regard to energy conservation, will pose an extra challenge to earthen buildings. In order to comply with regulations it is most likely that the buildings will have to include insulation as an added element to the walls. According to Simões (2006) the use of insulation materials on the outside is not as important as it would be in a conventional concrete frame construction, since in the case of earthen buildings the insulation will not have to serve the purpose of covering thermal bridges, which are common in the concrete-framed type of construction. Moreover, the same author claims that although the insulation can indeed be placed on the internal face of the walls, the building will perform better when the insulation is placed on the outside, as the thermal mass is in direct contact with the interior.


30


The thermal performance can be measured in several ways; the most commonly used are the Thermal Storage (Specific Heat), the Thermal Resistance (R-Value) (R and the Thermal Transmittance (U--value). (Maniatidis et al., 2003) .2 | Environmental Impact and Embodied Energy 2.2.2 Earth building is considered to have a low environmental impact compared to conventional construction techniques. The raw-material raw material to be used in the construction is usually dug from the site, and even ifi some mechanised system is required to dig, mix or place the earth, the construction process still has a lower embodied energy than a similar construction in brick, concrete or steel. (Kimmis et al., 1997). 1997) Berge (2000) reinforces this idea and remarks that, in the context of the locally built houses, there is no other construction technique that can compete with the earthen ones in terms of its low environmental impact. The end of the life of an earth e building can originate a new ew one. In fact, when demolished, the unbaked earth can melt down back to nature, as its physical and chemical constitution is still in its original form. Hence, in theory it can be used infinitely, whether as a building material or to grow vegetation. Simply ply removing the roof will allow for the rain to wash the walls away naturally. (Berge, 2000) (Rael, 2009) The chart below illustrates the lifecycle of a rammed earth wall while the figures show examples of ruins of old rammed earth houses in which the earth is slowly returning to its original form.

Fig. 2.5 – Life cycle of a rammed earth wall


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Figs. 2.6 & 2.7 - Ruins of old rammed earth walls returning to nature

According to a life cycle analysis, carried out by Roaf et al. (2007), which included embodied energy and emissions, it was determined that a house built from rammed earth and local timber has “a lifetime energy impact in the region of 20% less than a house built using medium-density concrete blocks.” (Roaf et al., 2007) The same authors suggest a mix of high thermal mass and timber-framed construction as an interesting and effective strategy for housing, both in terms of low impact and comfort.

2.2.3 | Cost The literature review focused on this particular subject reveals that opinions regarding the real cost of earth buildings are divided. There are those who consider that this construction method is indeed cheaper while others support the theory that depending on the earth technique used, the overall cost may even be higher than conventional construction, mainly due to high labour expenses. (Lourenço, 2005) The weighting of the labour rate as a main contributor to the overall cost attributed to the earth constructions is a factor which is also pointed out by the Portuguese architect Miguel Mendes, vice-president of a national association dedicated to the study of earth construction. He states that the material earth may be acquired for free, however it


32


carries extra labour costs when compared with conventional construction. Mendes, M. cited by (Carvalho, 2006) Although the lack of documentation such as price lists and cost analysis can indeed enhance this indecision concerning the actual cost of an earthen house and may even marginalise earthen materials (Graz et al., 2008), the majority of estimations fall on the low-cost opportunities attributed to the use of earth as building material. The Egyptian architect Hassan Fathy, for instance, who persistently defended the cheapness of earthen materials saw it as an opportunity to provide good quality housing for the poor, stated that “an ordinary mud brick, dried in the sun, is perfectly adequate for building an ordinary house, and can in Egypt be made for next to nothing”. (Fathy, 1973, p.133) More recent studies have shown that the savings associated with these techniques are due to the source of the material; not only is it available for free, but it also excludes transportation costs, since it is usually extracted from the construction site itself. (Minke, 2006). González (2006) remarks the importance of the use of earthen techniques in developing countries, instead of importing high cost material from developed countries, which results in accumulation of unnecessary debts. The same opinion is shared by Graz et al. (2008, p.98) who state that “The earthen construction remains the least expensive and the most accessible solution for developing countries”.


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2.3 | EARTH CONSTRUCTION IN PORTUGAL 2.3.1 | Historical Note Portugal is one of the European countries where earthen architecture is present and evenly spread across the territory since a very early period. It is estimated that approximately 2 million earthen buildings exist, where 15% are homes and 10% national heritage buildings and housing. (Graz et al., 2008) The development of earth construction in Portugal reflects the history of the country itself, where several occupations took place and thus a diversity of cultures and traditions were assimilated. Furthermore, due to the country’s strategic geographic location by the Mediterranean Sea, which acted as a link to Europe, great civilizations from the East exported their knowledge, inevitably influencing the local customs. (Pinheiro, 1991) During the Iron Age (8th to 2nd centuries B.C.) Portugal was continuously open to cultural influences from the eastern Mediterranean, namely the Phoenicians, Greeks and Carthaginians. (Gomes, 2005) It is actually believed that the Phoenicians brought the rammed earth and other formworks techniques in the 8th century B.C., while occupying the southern areas of the Iberian Peninsula (Graz et al., 2008). It is actually frequent to find elements in common between the Carthaginian architecture in the south of the Iberian Peninsula and North of Africa. During the Greek occupation in the 6th century B.C. another technique, the adobe (sun dried earth bricks) is believed to have been imported into the region. However it is known that this particular technique was already established, far from the colonized areas, when the Greek occupation occurred, suggesting perhaps an earlier influence. (Graz et al., 2008) Archaeological studies place the use of adobe bricks in dwellings since the Calcolithic period in the Portuguese territory. After that, many uses were given to the material for the likes of dams, where the stone coexisted with compacted clay or even for defensive structures, where earth sometimes coexisted with stone and wood. (Gomes, 2005)


34


Depending on the location and cultural influence, the development of earthen constructions originated in the Iberian Peninsula was quite diverse in terms of its type. Nevertheless the techniques used remained very similar. (Graz et al., 2008). With time, construction techniques were refined and eventually spread throughout the country. Soil types and the availability of other natural materials such as stone ended up dictating the expansion of earthen buildings. Generally it can be observed that its range of influence includes the area towards the South: a vast part of the Algarve, nearly the total area of the Alentejo; in the centre: the area of Ribatejo; and further North an area that turns into coast which includes the region of Aveiro. (Pinheiro, 1991) At the end of the 19th and beginning of the 20th century, the earthen houses were part of the vernacular building traditions of a profoundly rural country. Until the 1950s, they were mostly perceived as being poor and undesirable, reflecting low economical and social conditions. It was during the 1960s, when a thorough study focusing on Portuguese traditional architecture and its characteristics was finally carried out, that the true importance and variety of applications of the unbaked earth within the traditional building context were pointed out and acknowledged. Those references would remain practically unaltered until the 1980s, when attention was then devoted to heritage, archaeology and architecture of the country. This had as a consequence further interest in the importance of the earth master builders’ know-how and also in the real social and cultural extension implicated within the use of the material. (Prista, 2005)

2.3.2 | Present and Future The global awareness of the current environmental situation, which owes much to the misconception of buildings and their consequent excessive energy consumption, have been contributing greatly towards a shift in the way built environment is perceived. The situation in Portugal is in no way different from that of other countries where the change of mindset is already taking place and the main goal of achieving a more energy efficient built environment has been established.


35


The recent revival of earthen building techniques has been preceded by a century of contradictory opinions regarding the use of earth as a building material and, although some efforts have been made towards the reintroduction of earth in the contemporary building environment, there are still many obstacles to overcome in order to have this material playing a competitive role as a product in the construction industry’s market. (Prista, 2005) The developments that have taken place within the international construction sector, particularly since the last century, have also had a direct influence in the way architecture was produced in Portugal. In many cases, the use of new construction materials was uncontrolled and even seen today as inappropriate, considering the context. Some authors believe that the areas outside the large cities were particularly affected. Moreover, borders which were naturally created from the existence of individual regional architectural features were losing their significance due to the introduction of a style that lacked integration and character. (Pinheiro, 1993) The group of people most interested in exploring the potential of earthen constructions, comprised mainly by researchers and professionals from the building sector, has been increasing throughout the world. Portugal started following their footsteps since the 1980s, and already there is the idea that in order to plan a future for this building material it is necessary to preserve the existing earthen heritage as well as the knowledge and know-how of the past. (Correia, 2007) Despite these efforts, the traditional building techniques are still being abandoned while other more modern materials, such as concrete or hollow burnt industrial brick, are preferred instead. The houses, especially in the area of Alentejo and the Algarve where the difference between night and day’s temperatures is considerable, which were historically

known for their good adaptation to the local climate and for having

extremely good thermal performance, now require auxiliary heating or cooling systems in order to provide comfort because inadequate materials are being selected. Consequently, not only is energy consumption rising but also the internal air quality is decreasing, which can carry significant problems to human health. (Correia, 2007)


36


Many clients are taking the challenge and choosing earth as building material for the walls of their houses. According to some architects involved in such projects, most of these clients are originally from the country’s largest cities, such as Lisbon. Amongst the reasons for their choice is the awareness of the delicate environmental situation, the search for a healthier house away from the stress of an urban life (Correia, 2007), and also some kind of willingness to preserve the local traditions, although a few also choose to have an earthen house with a modern design. However, many local people do not regard earthen houses as buildings they would want to dwell in, probably because they still associate them with a poor social status and look at the buildings in the big cities as a sign of progress. Consequently, at the moment there is this duality, where on the one hand the building material earth is regarded as a sustainable and viable option for the future and on the other hand it is still somehow associated with lowest layers of society and poverty, thus indicating the opposite of modernity and development. Regarding the use of this material in the context of the future built environment in Portugal, according to Mendes (cited in (Carvalho, 2006)) it is essential that earthen constructions can be seen as just architecture, and the building material earth has to be seen beyond its environmental and ecological qualities as simply another construction material. Furthermore, in order to compete with modern materials and techniques it has to go through some important changes of production, to make the construction process faster and easier. For examples of contemporary earth buildings in Portugal, please refer to Appendix 2.


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2.4 | DESCRIPTION OF EARTH BUILDING TECHNIQUES USED IN PORTUGAL The distribution of the earthen building techniques in the Portuguese territory owes much to natural restrictions, such as the geography, geology or climatic features. Ribeiro (1961) mentions the opposition present between the use of stone and earth in buildings, attributing the first material to the North, where the mountains are predominant and the stones available and the latter to the South, where the climate is drier and the lands flatter. The abundance of the clay is also in the origin of the designation of clay civilization when characterizing the South of Portugal. (Ribeiro, 1961) The main construction techniques existing in Portugal are rammed earth, adobe and wattle and daub. More recently another technique has gained some followers, the Compressed Earth Block or CEB. The image below, published in 2005 (Fernandes & Correia, 2005), is the result of an ongoing survey and illustrates the distribution of the main techniques used in Portugal.

Fig. 2.8 – Geographical distribution of earthen building techniques. (Fernandes & Correia, 2005)


38


Although the case studies presented later are rammed earth buildings, a brief description of the most common techniques used in Portugal is provided below. 2.4.1 | Rammed Earth When a study was carried out in 1961 (Ribeiro) rammed earth was considered the most common technique in the southern region of Portugal and was found that not only houses’ walls but also as external walls to divide rural properties, protecting cultivated areas were made using this technique. The term Taipa - rammed earth in Portuguese - is used to describe both the construction technique and the material itself. Basically, the process consists of compacting, using a rammer, portions of earth between movable formwork in order to erect load-bearing walls. (Rocha, 2005) The mature soils are not suitable for rammed earth since they may contain organic material. The ideal soil should be extracted from the subsoil, where organic material is absent. Soil/Mixture Achieving a good quality rammed earth structure will depend on several factors, such as a good soil selection and a correct mixture. The most appropriate soils should have a high sand content with just enough clay to act as a binder, according to Keable (1996) “50-70% fine gravel and sand, 15 to 30% clay”. (Keable, 1996) In case the earth to be used is poor, some elements may be added to improve the material’s performance such as cement or lime. Furthermore, in order to prevent shrinkage, small pieces of ceramic, tile or brick are occasionally added to the mixture. (Graz et al., 2008) Formwork Although the formwork has been receiving some developments in the last years it seems to still follow the concept of the traditional technique. It consists of a dismountable structure that when together resembles a box without top or bottom. It is generally composed of two large panels – shutters - vertically placed in parallel, two other smaller panels - end stops - placed at the ends of the formwork and other parts -


39


ties or bolts and spacers - which can hold the box firmly together and keep the panels fixed in the desired position, depending on the dimension of the walls being rammed. It should be strong, light and easy to assemble and disband. (Keable, 1996) In the traditional shuttering system the spacers pierce thought the walls, while the ramming process is taking place. This causes openings that will have to be filled in after the formwork is removed. Because the holes can sometimes be considered a disadvantage spacers-free systems have been already developed. (Minke, 2006) Tools The earth can be stamped manual or mechanically. The type of rammer varies and depends on the work required. The manual process can take time while the mechanical ramming reduces construction time. Although it can be stated the mechanical rammers can reduce the overall cost of the building, some investment in machinery is required firstly. (Houben & Guillaud, 1994) Furthermore, the use of mechanical tools will also increase the general embodied energy of the building. Process The process of producing rammed earth basically consists of pouring the mixture into a mounted formwork and spreading it until it forms a layer approximately 100 to 200 mm thick. The mixture is then uniformly compacted with rammers (fig. 2.9 – 2.12) until it reaches its compaction limit (when the layer is dense and hard). The ramming takes place, layer after layer, until the formwork is filled and mounted again to form another ‘block’. The process is then repeated successively in order to erect walls according to the geometry of the project. (Graz et al., 2008)


40


Fig. 2.9 (left) – Manual rammers (Houben & Guillaud, 1994) Fig 2.10 - Middle: Mechanical rammers. (Houben & Guillaud, 1994) Fig 2.11 - Top right: Pneumatic rammer (Minke, 2006) Fig 2.12 - bottom left: Vibrating rammer. (Minke, 2006)

Fig. 2.13 (left) - ramming process ; Fig. 2.14 (middle) – ramming process ; Fig.2.15 (right) – rammed earth construction site


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2.4.2 | Adobe This technique, which essentially consists of throwing earth mixed with water into a small mould, has different designations: adobe, mud bricks or sundried earth blocks. (Minke, 2006). The word adobe has Arabic origins (‘ottob’), which was related to the Egyptian word for sun-dried brick ‘thobe’. It was then adopted in Spain as ‘adobe’ and afterwards in the Americas, as the technique spread across those countries. (Dethier, 1983) (Houben & Guillaud, 1994) Adobe is the most international of all the earthen techniques. Buildings bearing this construction method can be found all over the world. Adobe can be attributed to various construction elements, such as arches, vaults, walls or even floors. (Fernandes, 2005) Soil/Mixture The most suitable soils to use for the production of adobe are considered to be the ones with a substantial percentage of fine elements (silts and sand) and a controlled quantity of clay. The addition of water in the correct amount plays a key role in the making of these moulded bricks, it is usually requires a large quantity of water in order to guarantee a balanced drying of the adobe bricks. (Fernandes & Correia, 2005) The mixture for adobe blocks should have the right percentage of clay to create sufficient binding forces in order to allow for the adobe to be handled and enough coarse sand to allow them to have high porosity. (Minke, 2006) Tools The adobe blocks can be produced using diverse formworks and can therefore have slightly different shapes. The most common are the parallel piped shaped bricks, which size can range from 200 X 110 X 500 mm up to 600 X 300 X 100 mm and weight from 2kg up to 3 kg. (Houben & Guillaud, 1994) The formworks are usually made of wood and can produce a single block or several in one go.


42


Process The quality of compaction and dry strength will depend on the energy with which the mixture is thrown into the mould; the greater it is, a better quality block will result. As far as quantity is concerned, it is possible for one person to fabricate about 300 blocks in a day and that includes the whole process beginning with the preparation of the mix and finishing with the transportation and stacking. In the case of India, where it is common to use double moulds this number can rise up to 500 bricks a day. (Minke, 2006). After a four week period of drying out in the sun, these blocks will be resistant enough to erect walls through successive overlapping. (Pinheiro, 1991)

Fig 2.16 – Adobe mould; Fig 2.17 – Internal adobe wall. The adobe blocks were moulded using the formwork shown on the left.


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2.4.3 | Wattle-and-Daub Wattle-and-daub is a sub-category of the daubed earth techniques. This is one of the oldest known construction techniques, and experts state that it is one of the most widely used in the world. Dwellings built with wattle-and-daub require regular care it receives and its quality and durability will depend on the maintenance and degree of care throughout the period of their life. (Houben & Guillaud, 1994, p.189) Process This is classified as an infill technique, which basically consists of throwing the earth, in a very clayey state, into a mesh of bamboo, twigs, wood or similar. Straw or vegetable fibres are sometimes added to the mixture. Furthermore in order to extend the lifetime of the wattle-and-daub buildings, in some areas, the water in the mixture is replaced with horse urine, which seems to have very positive results. Although the technique may vary slightly, depending on the kind of load-bearing structure and wattles selected, the basic concept remains the same. (Houben & Guillaud, 1994) Wattle-and-daub buildings are usually light, as the infill does not cover up the framework elements, hence the thickness of the walls will depend on the thickness of the framework, which generates quite thin walls. (Doat et al., 1991) There are some problems associated with this technique, such as the occurrence of shrinkage cracks, experts are developing methods to avoid this situation, for instance spraying simultaneously, but from a separate nozzle, thin loam mixture with saw dust, where both sprays mix before hitting the wall. (Minke, 2006) Furthermore, Insects can live inside wattle and daub walls; the Chagas disease comes from insects that live inside these walls. (Minke, 2006, p.18) Some efforts are also being made towards the adaptation of this ancient technique to modern times. For instance in Peru, easy-to-assemble panels are being developed. (Houben & Guillaud, 1994, p.189)


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2.4.4 | Compressed Earth Block - CEB The Compressed Earth Brick can be considered the modern version of the sun-dried earth brick or adobe. Although it is referred as an innovative technique in many occasions, the concept of earth compacted into moulds in order to improve the quality of blocks, is not actually new. Wooden tampers preceded the mechanical presses and are still today used in many parts of the world. (Guillaud et al., 1985) The first mechanical press, the ‘crecise’, was created in France in the beginning of the 19th century by François Cointeraux and was inspired by the wine press. Nevertheless, it was thanks to ‘CINVA-RAM’ press, invented in Colombia around the 1950s, that compressed earth blocks began to take part in building process and assumed importance in an architectural context. (Guillaud et al., 1985) With time and technological progress, the process of CEB production has gained sophistication while a whole industry has developed around this material. Moreover, the process has grown from small presses into massive, semi-industrialized plants and it is now common to manufacture thousands of bricks per day. (Dethier, 1983), (Rael, 2009) Process Although this technique is considered an evolution from ancient adobe bricks, its mixture differs from the one used in the production of adobe, as it should have more sand. Furthermore, the moisture content is also closer to the one used rammed earth technique. (Graz et al., 2008) The exact content of the mixture can vary, however there are recommendations regarding the percentage of each component: 10 – 30% clay, 15 – 25% silt, 15 – 35% fine sand, 15 – 35 % coarse sand and 10 – 70 % fine gravel. (Energy and resources Institute, Institut Català d'Energia and Asia Urbs Programme, 2004) In addition to these components, a percentage of stabiliser, which can be portland cement, emulsified asphalt or lime, needs to be included. A percentage varying between 4 to 8% will guarantee a high compressive strength, which would be lower than common adobe bricks without the stabiliser, as well as good resistance to climatic elements. (Minke, 2006) (Rael, 2009) Even though the addition of stabilisers can be sometimes seen as a disadvantage, as it might increase the embodied energy of the material and reduce its ecological


45


character, the truth is that CEB has contributed to the social image of earth architecture. Because of the manufacturing process, this has become a standard material, which can easily be compared to other materials such as the fired brick or the cement block. Builders appreciate its regular shape and people in general trust more in the material’s performance. (Guillaud et al., 1985) Mali represents an interesting example of the acceptance of this material in a developing country. It is not legal to build a school out of adobe bricks, however that is not the case with the CEBs, as this material is not only welcomed and encouraged, but also regarded as superior. (Rael, 2009)


46


Fig 2.18 (left up) – house in Zanzibari, Africa Fig. 2.19 - house in Zanzibari, Africa Fig 2.20 - (right) – house in York, UK.

Fig 2.21 (left up): CEB stored; Fig 2.22 (left down): CEB wall; Fig 2.23 (right up): mechanical press; Fig 2.24 (left down): CEB wall - detail


47


CHAPTER 3 | CASE STUDIES


48


3.1 | METHODOLOGY OF ANALYSIS The analysis of the case study buildings followed the general guidelines provided below: Global: Background Information – General information regarding aspects of Portugal were investigated. This information is further explored in Appendix 2; Climatic conditions – The external temperatures included in the thermal performance’s graphs were provided by the Portuguese Meteorological Institute (Instituto de Meteorologia, IP Portugal). Site analysis - Field visits combined with architectural drawings allowed for an examination of the general characteristics of the site, including location and exterior landscape. Local: The buildings’ environmental design – Building observation, interviews with authors, examination of the building architectural drawings; Materials - In order to determine the main materials used in these buildings, field visits, local observation and interviews with the authors and occupants were conducted; Indoor: Internal air temperature - In order to provide a general understanding of the buildings’ thermal performance, appropriate equipment (i-buttons) was strategically installed in different points within the buildings to measure air temperature. Furthermore these measurements aimed to record samples of winter and summer conditions and were taken every hour. This data was afterwards combined with external temperature information.


49


Thermal comfort – The occupant’s perception of the internal environment was assessed through occupancy questionnaires, which focus mostly on the occupants’ satisfaction but also aimed at determining whether the occupants were using heating or cooling during the time of assessment.

3.2 | GLOBAL ANALYSIS – BACKGROUND INFORMATION ABOUT PORTUGAL For further information refer to Appendix 3

Geography Located in the Southwest end of the European continent, approximately between the latitudes of 37º N and 42ºN and longitudes 9,5º W and 6,5ºW, continental Portugal has two boarders on its territory, one natural towards the West, the Atlantic Ocean and a political boarder on the East side with its neighbouring country Spain. (Instituto de Meteorologia, 2005) It covers a total land area of approximately 89 000 Km2 and has a rough perimeter of 2.75 thousand km of which almost half is coast line. The case studies are located in the Low-Alentejo area, marked with a brown circle in Fig. 3.2. For a more precise location please refer to Appendix 4.

Fig. 3.1 – Map of Europe. Source: https://www.cia.gov/library/publications/the-worldfactbook/geos/PO.html# Célia Macedo | 2009

Fig. 3.2 – Map of continental Portugal. The brown circle marks the case studies’ approximate location. Adapted from: https://www.cia.gov/library/publications/the-worldfactbook/geos/PO.html# 50


Climate The Climate in Continental Portugal can be very

irregular,

whether

in

terms

of

temperature or rainfall. Episodes of intense drought, which can be focused on one particular region or throughout the country, intercalate with periods of high levels of rainfall (especially in the autumn) due to the passage of cold fronts. (Brito, n.d.) The Low-Alentejo region, where all the case studies are located, is characterised by

having

low

precipitation

levels

throughout the year, specially from June to September, which is also the warmest period

of

the

year,

where

average

maximum temperature can rise up to 32ºC - 34ºC. The winters are typically mild and the coldest months are usually December and January.

Fig. 3.3 - Average annual temperature and precipitation (1961-1990). Source: (Instituto de Meteorologia, 2005)

According to a recent study, the average

Nicol Graph 30

increase at a rate of 0.5ºC/decade during

25

th

the 20 century. The same study estimated that by the end of the 21st century the temperature will increase by 3ºC in the coastal areas and above 7ºC in the interior of the territory. Furthermore, the heat waves will also rise in intensity and frequency. (Miranda et al., 2006)

Temperature ºC

temperature in Portugal has suffered an

20 15 10 5 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ta (Tmean)

Tc

Tmax

Tmin

Graph 3.1 - Nicol Graph for Odemira, Portugal


51


Nicol Graph In

order

to

determine

the

comfort

temperature for every period of the year, a Nicol

Graph

was

plotted

based

Total Energy Consumption by Sector in Portugal 2%

1%

on 12%

information obtained from local climatic conditions (Graph 3.1). This information will be used as reference later when analysing

28% 17%

the internal temperatures measured inside the case study buildings. Moreover, it is

4%

possible to observe the typical monthly 36%

temperatures for this region in the Nicol Graph.

Agriculture fishing Extractive Industries

Energy and CO2 Emissions In

the

last

few

years

Transforming Industries

the

energy

Construction and Public Works

consumption has been rising significantly in

Transports

Portugal.

Domestic

According to DGEG (2007), the percentage

Services

of total energy consumption attributed to buildings is about 29% (17% domestic + 12% services). Considering the consumption of electric

Graph 3.2 (top): Total energy consumption by sector in Portugal. Source: (DGEG, 2007) Graph 3.3 (down): Typical energy consumption in a house. Source (Gonçalves et al., 2002 cited in (Mateus, 2004))

energy in the previous 10 years, the annual average per person rose by about 1.5 thousand KWh and it is now at 7,755.3 KWh.

This

translates

into

an

Typical Energy Consumption Residential

increase in consumption by about 16 billion

25%

KWh.

50%

Contributing for this is the rise on the number residential

Sanitary hot water

overall

of

consumers,

construction

and

enterprises, also

25%

Heating/ Cooling Lighting/ Appliances

an

increase in the number of households.


52


Furthermore, in 2006, the highest consumption of electricity took place within the industrial sector (around 38%), however the residential sector was responsible for approximately 28%. (INE, 2008). As far as the CO2 emissions are concerned, the average is about 6.3 tonne per person, a reasonably low figure when compared to other European countries – see Appendix 3. (United Nations, 2009)


53


3.3 | CASE STUDIES 3.3.1 | Case Study 1 – Art Studio Figs. 3.4, 3.5, 3.6

Year

1993

Building type

Art studio; new building Materials (general) Windows: Single glazing, steel frame Floor: burnt clay tile, perforated steel (mezzanine) Ceiling: timber joists Roof: clay tile (insulation- polystyrene)

Walls

External walls: Non insulated rammed earth, 4.4% hydrated lime added to the mixture (500mm) Internal walls: rammed earth, Finishes: earth left exposed, lime plaster in small areas (internal and external)

Foundations

Raised foundations, cyclopic concrete

Source of earth

Site

Passive design

Orientation, solar gain, local materials, thermal mass

features Occupancy

6 to 8 hours inside (weekdays and weekends)

Heating/ cooling

No cooling; heating:4-6 weeks during the winter season (wood burning stove). Not used during the period of this study.

Note

Refer to Appendix 4 for further information

Table 3.1 - Information based on occupancy questionnaires, observation and interviews.


54


Internal Environment i-buttons location:

Mezzanine Painting room Entrance area Fig. 3.7

Winter: 1-15 January, 2009 – Graph 3.4 18

120

16

Temperature ºC

12

80

10 8

60

6 40

4 2

Relative Humidity%

100

14

20

0 -2 1

2

3

Painting room

4

5

6

Mezzanine

7

8

9

Entrance area

10

11

12

13

External Temp.

14

15

0

Ext. Rel. Humidity

14

90 80 70 60 50 40 30 20 10 0

Temperature ºC

12 10 8 6 4 2 0

Painting room


Mezzanine

Entrance area

External Temp.

Relative Humidity %

Detail: 9 January, 2009 – Graph 3.5

Ext. Rel. Humidity

55


35

120

30

100

25

80

20

60

15

40

10

20

5

Relative Humidity %

Temperature ºC

Summer: 17 - 31 July, 2009 – Graph 3.6

0 17

18

19

20

painting room

21

22

23

mezzanine

24

25

26

entrance area

27

28

29

ext. temp.

30

31 ext. RH

Detail: 20 July, 2009 – Graph 3.7 80

35

Temperature ºC

60 50

25

40

20

30 20

15

Relative Humidity

70 30

10 10

0

painting room

mezzanine

entrance area

ext. temp.

ext. RH

Comments: Winter - No auxiliary heating system is used during this period. Although the temperatures can reach quite low figures (minimum of 8.5ºC), it is probably worth mentioning that the internal gains are minimal, basically limited to passive solar gain, 1 occupant, artificial lighting and a stereo. Moreover the type of glazing used also allows for a higher rate of heat loss. Despite of all these factors, the internal temperatures


56


maintain a relatively regular behaviour, having an amplitude of about 4ºC throughout a typical day. Summer - Much like what happens during the previous period, the internal temperatures recorded throughout the summer were very regular, regardless of the external conditions. As can be observed in the detail graph, the thermal delay due to the use of thermal mass is more obvious during the summer period. Although the highest value for the external temperature is registered at around 11am, it is during the evening and night that the internal temperatures actually rise to the highest point. This fact may be an indication that the building material earth is better suited for warmer climates. Note: Full January and July monitoring under Appendix 4.7


57


3.3.2 | Case Study 2 – Private house Figs. 3.8, 3.9, 3.10

s

Year

1998

Building type

House; refurbishment and new building Materials (general) Windows: Single glazing, timber frame Floor: burnt clay tile Ceiling: timber joists Roof: clay tile (insulation- cork)

Walls

External walls: non insulated rammed earth; fired brick and stone in part of the refurbished areas (0.5m) Internal walls: rammed earth Finishes: earth left exposed, lime plaster in small areas (internal and external)

Foundations


Source of earth

Site

Passive design

Thermal mass, local and natural materials, local workmanship.

features Occupancy

3 occupants, spend 10-12 hours inside on a typical day (week and weekend)

Heating/ cooling

No cooling; heating: used throughout November, December and January (fireplace, gas heater, electrical heater)

Note:




58


Internal Environment i-buttons location:

Not built

Bedroom Living room Kitchen Fig. 3.11

Loft

Winter: 1-15 January, 2009 – Graph 3.8

23

100

18

80

13

60

8

40

3

20

-2 1

2 3 4 Living room ºC Bedroom ºC

5

6

7

8 9 10 Kitchen ºC External Temp.

11

12

13

Relative Humidity %

120

Temperature ºC

28

0 14 15 Loft ºC Ext. Relative humidity

Detail: 9 January, 2009 – Graph 3.9 90

20

Temperature ºC

70 60

10

50 40

5

30 20

0

Relative Humidity %

80 15

10 -5

0 Living room ºC


Kitchen ºC

Loft ºC

Bedroom ºC

External Temp.

Ext. Relative humidity

59


Summer: 17 - 31 July, 2009 – Graph 3.10 35

120 100 Relative Humidity %

Temperature ºC

30

80 25

60 20

40 15

20 0

10 17

18

19

Living room

20

21

22

Kitchen

23 Loft

24

25

26

Bedroom

27

28

29

Ext. temp.

30

31

Ext. Rel. Humidity


35

Temperature ºC

60 25

50

20

40 30

15

20 10

Relative Humidity %

70

30

10

5

0

Living room

Kitchen

Loft

Bedroom

Ext. temp.

Ext. Rel. Humidity

Comments: Winter – During the winter period, temperatures range from approximately 11ºC to 23ºC. These values tend to be higher during the evening period, both due to the effect of the thermal mass but, in this case, also because the occupants use an auxiliary heating system to increase the internal temperatures and thus their comfort. According to the occupants, no heating is ever used in the bedroom, fact that


60


constitutes a good indication on how the house would perform during the winter with no heating at all – constant internal temperatures throughout the day and night, even though the difference between the daily and nightly external temperatures is quite considerable. Summer – The summer readings sample reveal a weakness in the design of the house. A poorly insulated roof in the loft area – 2 cm of cork board – which allows the internal temperatures to rise higher than the average temperature of the remaining rooms. Moreover, like the case study presented previously, the effect of thermal delay provided by the thermal mass is especially obvious. According to the detail graph, the external temperature begins its descendent phase at around 11am, while the temperature inside the house only does so after approximately 9 hours later, at 8pm. Note: Full January and July monitoring under Appendix 4.7


61


3.3.3 | Case Study 3 – Private house Figs. 3.12, 3.13, 3.14

Year

2003

Building type

House, new building Materials (general): Windows: single glazing, timber frame Floor: burnt clay tile and stone Ceiling: timber joists, timber ceiling Roof: clay tile; insulation- cork

Walls

External walls: non-insulated rammed earth and slate for the winter garden (500mm) Internal walls: rammed earth, adobe blocks and slate (roughly 200mm) Wall finishes: earth left exposed, lime plaster in small areas

Foundations


Source of earth

site

Passive design

Winter garden to enhance solar gain in the winter; thermal mass;

features Occupancy

1 occupant, spends more than 14 hours/day inside (typical week and weekend)

Heating/cooling

No cooling; heating: 6-8 weeks during the winter season (wood burning stove)

Note




62


Internal Environment Fig. 3.15

i-buttons location:

Living room Office Winter Garden Bedroom

Winter: 1-15 January, 2009 – Graph 3.12 120

16

100

13

80

10

60

7 40

4

20

1 -2 1

Relative Humidity %

Temperature ºC

19

2

3

4

5

6

Living room ºC Winter garden ºC

7

8

9

10

Office ºC External Temp.

11

12

13

14

15

0

Bedroom ºC Ext. Relative humidity

90

12

80

10

70

Temperature ºC

14

60

8

50

6

40

4

30

2

20

0

10

-2

0 Living room ºC Winter garden ºC


Office ºC External Temp.

Relative Humidity %

Detail: 9th January, 2009 – Graph 3.13

Bedroom ºC Ext. Relative humidity

63


35

120

30

100

25

80

20

60

15

40

10

20

5

Relative Humidity %

Temperature ºC

Summer: 17 - 31 July, 2009 – Graph 3.14

0 17

18

19

20

21

22

23

Living room winter garden

24

25

Office Ext. temp.

26

27

28

29

30

31

Bedroom Ext. Rel. Humidity


80

Temperature ºC

60 50

25

40

20

30 20

15

Relative Humidity %

70

30

10

10

0

Living room winter garden

Office Ext. temp.

Bedroom Ext. Rel. Humidity

Comments: Winter - Generally speaking, the internal temperatures are relatively low, although they maintain a stable pattern throughout the day. According to the occupant, the window frames in the winter garden area were failing and leaking air. This could explain the low temperatures felt during the winter.


64


Summer – The problems within the window frames are apparently influencing the general performance of the house. Thanks to the excessive solar gain and infiltration, the temperatures in this area go above 30ºC most days. The bedroom and the office, which have the lowest temperatures during the summer sample, are the only areas separated with doors from the rest of the house. This can give an idea of how the house could eventually perform when the winter garden area had the infiltration problem rectified. Note: Full January and July monitoring under Appendix 4.7


65


3.4 | THERMAL COMFORT The thermal comfort has been part of this study as a method to establish a direct connection between the thermal performance of the case studies and their occupants, thus bringing up the so often omitted role of the occupants, and their influence on performance. It does not intend to be a statistical analysis of any kind, as the subjects fall short of the required numbers to represent a statistical sample for the occupants of earthen houses in Portugal. Moreover, the main purpose was solely to determine whether the occupants were comfortable in their houses or not and, in case they were not, which strategies could be used in order to improve their comfort and thus their satisfaction with the building. The benefit of thermal mass in buildings has been pointed out frequently as a positive feature, as well as giving the occupants’ thermal satisfaction. For this reason it was decided to combine both parameters in the same study Thermal comfort applied to the case studies The method used as a reference in order to determine the thermal satisfaction of the occupants of the buildings analysed as case studies was the one described by Nicol (1993). Following the guidelines, a mix between Level I and Level II survey was performed (see Appendix 5). Face to face interviews during two field visits were complemented with weekly occupation questionnaires filled out by the occupants during a period when data loggers were also taking the indoor temperatures. The questionnaires, enclosed under Appendix 4, covered the air temperature, which included a question to determine the use of auxiliary heating or cooling systems and air quality. A specific time or location inside the building was not prescribed to fill in the questionnaires, instead the occupants were to follow the instructions to fill them in once a week, choosing the day and location themselves but always clearly indicating the two parameters.


66


3.4.1 - Occupancy satisfaction survey and temperature measurements – Summary of results CASE STUDY 1 Range of internal comfort conditions

Winter: Comfort >=13ºC

according to occupants

Summer: Comfort =23.5ºC 35%

the occupant’s comfort conditions

Use of heating/ cooling Air quality Internal humidity Occupant’s strategy to achieve comfortable conditions

= 20ºC Range of internal comfort conditions according to occupants

Occupant 2(mother) - Comfort >= 17ºC Occupant 3(daughter) - Comfort >= 17.5ºC Summer: All occupants – No desire to change internal conditions felt, although slightly warm from 23.5ºC Winter: from 19/12/2008 to 28/02/2009

Classification of total internal

>=17ºC 30%

temperature readings according to the occupant’s comfort conditions

=23.5ºC 46% =12.5ºC

according to occupant

Summer: Comfort