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Abstract Sustainable building design requires many perspectives; one of these being environmental impact. In order to reduce the environmental impact of a building, care should be taken beyond just energy and global warming measures (Brunklaus et al., 2010). Specifically focusing upon lessening the Eutrophication Potential (EP) and Acidification Potential (AP) impact categories, a range of material related strategies are recommended for contemplation. These strategies are based on a case study of a wooden, low-energy residential building. Even so, given the vast amount of assumptions these are in no sense absolute. The general strategies in order of significance include decreasing building size, constructing with recycled concrete (can reduce EP by 21% and AP by 20%) and building without a basement (can reduce EP and AP by 21 and 18% respectively). Reductions under 5% can be achieved by building a duplex house with two stacked buildings reducing the requirement for any additional concrete, building with recycled wood, selecting local materials, and prefabrication. Chapter 8 of this report provides the specifications of these proposals. Keywords: life cycle assessment, residential dwellings, environmental impact, sustainable

construction, building materials.

Rapportmall Byggnadsfysik och Installationsteknik, LTH

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Preface I would like to express my gratitude to the Eliasson Foundation for their generous sponsorship during my Master degree and also in regards to my attendance of the Life Cycle Management Conference last year in Gothenburg.

Of course my appreciation goes to Ms. Maria Wall, the director of the Master Program, for making this degree a reality for not just me but for many more years of students to come.

This thesis was prepared at the PE International office in Vienna and I am thankful for the welcoming team there. I would like to particularly thank Mr. Adolf Merl for the chance to learn under his supervision and Ms. Therese Daxner for always finding the time to answer my questions.

In regards to their continuous support and specifically the final touches, I would like to acknowledge Mr. Dennis Johansson, Ms. Kaisa Svennberg and Mr. Saqib Javed from Lund University.

Lastly, I would like to thank Future Haus for the permission to include their unique building and the authors Sartori, Hestnes and Kellenberger for being valuable references.

“In dwelling, live close to the ground” - Lao Tzu

Vienna, July 2014

Evian Elzinga


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Table of content Abstract ............................................................................................................. 0 Preface ............................................................................................................... 1 Table of content ................................................................................................. 2 Abbreviations 4 Definitions 5 1 Introduction ............................................................................................... 6 1.1 Motivation 6 1.2 Aim and Scope 7 2 Method ...................................................................................................... 8 2.1 System Boundary 8 2.2 Functional Unit 9 2.3 Selection of Impact Categories 9 3 Literature Review .................................................................................... 11 3.1 Background Information 11 3.2 Life Cycle Phases 12 3.2.1 Materials and Components 12 3.2.2 Transport 16 3.2.3 Construction Method 16 3.2.4 Building Operation 17 3.2.5 Maintenance and Refurbishment 17 3.2.6 Demolition & End of Life Treatment 18 4 The Case Study........................................................................................ 19 4.1 Embodied Materials 20 4.2 Operational Energy 21 5 Standards ................................................................................................. 23 5.1 EN standards 23 5.2 ISO standards 24 5.3 DGNB Certification 24 6 Modelling ................................................................................................ 25 6.1 Software 25 6.2 Limitations 26 6.3 Assumptions 26 7 Primary Results ....................................................................................... 29 7.1 Energy mixes 29 7.2 Phases 30 7.3 Materials 32 8 Derived Strategies ................................................................................... 33 8.1 Size of building 33 8.2 Recycled materials 34 8.3 No Basement 35 8.4 Duplex Building 35 8.5 Local Materials 36 8.6 Prefabrication 36 8.7 Refurbishment 37 8.8 Lifetime of building components 37 8.9 Specific wood species 37


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8.10 Substitution of materials 37 9 Summary Table ....................................................................................... 39 10 Practical Limitations ............................................................................... 41 11 Conclusion ............................................................................................... 43 References ....................................................................................................... 45 Appendix A Materials Specifications .......................................................... 50 Appendix B Material Datasets ..................................................................... 51


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Abbreviations AP Acidification Potential CML Institute of Environmental Sciences, Leiden University CO Carbon monoxide CO2 Carbon dioxide DGNB The German Sustainable Building Council EE Embodied Energy EMS Environmental Management Systems EN European Standard EP Eutrophication Potential EPD Environmental Product Declaration GWP Global Warming Potential HVAC Heating, Ventilation and Air Conditioning system ISO International Organization for Standardization LEED Leadership in Energy and Environmental Design LCA Life Cycle Assessment m2 Square metre m3 Cubic metre NO Nitrogen Oxide ODP Ozone Depletion Potential OSB Oriented Strand Board PED Primary Energy Demand POCP Photochemical ozone creation potential. PV Photovoltaic SED Secondary Energy Demand


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Definitions Embodied Energy The amount of energy embodied in the materials, construction, repair

and maintenance

EU-27 An average European energy mix of energy based upon 27 European countries with weightings according to their relative production.

Futura Haus The Swiss house model that is incorporated as case study

GaBi The software program, version 6

Operational energy

The amount of energy required during the operational phase of the building eg. Heating, cooling, ventilation, hot water, lighting and other electrical appliances (Sartori & Hestnes, 2007)

Primary Energy Demand

The total amount of energy demanded at the source of production in order to compensate for losses.

Secondary Energy Demand

The amount of energy demanded at the building site

U-value Thermal transmittance of a material or set of materials (in W/m2K)


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1 Introduction Progressively the European market is leaning towards low-energy residential buildings (BPIE, 2013). The energy demanded during operation generally provides the largest opportunity to reduce a building’s total energy demand (Sartori & Hestnes, 2007) since this is a recurring factor and over a 50 year lifetime accumulates swiftly. In response, design strategies are focusing upon saving heating and/or cooling demands; the focus is dependent upon the climate of the location. In order to achieve these reductions there is generally a higher level of energy embodied in the building materials and construction for a low-energy building relative to that of a conventional one (Sartori & Hestnes, 2007). Despite the higher embodied energy, it still seems to be a reasonable choice to design low-energy buildings for the building’s long term energy perspective and it is a positive initial step. Perhaps the general analysis tends to discontinue here though (Dodoo, 2011) since the largest energy-saving, and cost-saving, opportunity is met. From an environmental perspective however, several additional indicators should be assessed in order to have a broader view of design choices (Brunklaus et al., 2010). These could include the Global Warming Potential, Eutrophication, Acidification Potential, Ozone Depletion Potential and Photochemical Ozone Creation Potential. This thesis focuses on a case study of a low-energy building from Switzerland in order to discover which additional strategies, other than just reducing the operational energy demand, could be applied to specifically lower these environmental impacts. This may be relevant for particular sites that are sensitive to certain chemicals, such as agricultural land or nature reserves, or for clients and companies that wish to have a more holistic view of their building’s environmental impact.

1.1 Motivation

The motivation behind this project is to extend both my and the reader’s view of a building’s environmental performance beyond Primary Energy Demand (PED) and Global Warming Potential (GWP). Perhaps the idea that embodied energy is relatively insignificant to operational energy (Sartori & Hestnes, 2007) leads building engineers, architects, and other building professionals to also solely focus upon the operational phase of the life cycle. Since the environmental impacts of the operational phase are almost solely reliant on the country’s energy mix it is difficult to influence a change in environmental impact, other than obvious option of designing an energy efficient building. The underlying intention here is to reconsider the other phases of the life cycle and take into account some additional compounds which are not included in PED and GWP; see Figure 1.1 for a quick illustration of this. Perhaps considering more compounds shines some light on which factors contribute the most to environmental impacts such as Eutrophication (EP) and Acidification Potential (AP). It is my intention to provide several environmental reduction strategies that can be applied by building professionals.


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Figure 1.1: Environmental performance as a measure of several impact categories. Source: Öberg (2005).

1.2 Aim and Scope

The aim is to examine the subsequent research questions:

What strategies can reduce the environmental impact (particularly eutrophication and acidification) of a residential building?

Do the strategies always result in a reduction of all environmental impact categories?

Which strategies results in an increase in one environmental impact category while decreasing another?

A base case model is integrated in this study to evaluate the above questions. It is a ‘Futura Haus’ model from Switzerland and the data is sourced from Kellenberger (2010). The case study represents a typical low-energy residential building. It has a prefabricated timber-frame construction and the lifetime of the building is estimated to be 50 years. The sole reason behind the choice of the residential building type is that it is a more consistent and simpler form to model. Even though the software model of the building is quite simplified, the ideas presented in this report hopefully highlight general hotspots in the life cycle and therefore may apply to other residential dwellings also.


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2 Method The transmittance of the desired results, and answers to the thesis questions, are obtained by the subsequent procedure:

1) Identify the factors which contribute to the Primary Energy Demand and environmental impact of buildings in general and establish reasonable assumptions (literature review)

2) Formulate a case study of a typical low-energy residential building.

3) Model the case study building while recognising relevant standards.

4) Produce comparative results for this building by employing six environmental impact categories.

5) Evaluate these results and observe where the significant impacts occur.

6) Propose general guidelines/strategies that reduce the environmental impact of such a building.

2.1 System Boundary

The system boundary is cradle to grave, which corresponds to a complete life cycle assessment (LCA) of a building. The manufacturing of construction materials and components is applied, as much as possible, with standard templates. Other phases taken into consideration include transport, construction, building operation, refurbishment and maintenance, and finally end of life. To specifically view all the stages that are analysed, see Figure 2.1 for a moderately detailed illustration. Both the illustration and software model exclude the plumbing, HVAC system and electrical installations within the building since they are not the focus of this report.

Figure 2.1: All phases in a full building life cycle assessment. Source: Khasreen et al. (2009)


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2.2 Functional Unit

According to the ISO 14040 standard (2006a) a functional unit is defined as the “quantified performance of a product system for use as a reference unit”. The standard identifies that the functional unit should be a clear definition but there are no specific guidelines on how to exactly formulate it. For that reason there has been uncertainty around functional units and it has even been described as an unresolved problem of LCA (Reap, 2008). In response to this problem, a general LCA handbook by the Institute for Environmental and Sustainability was published in 2010 (Joint Research Center) proposing some fundamental aspects to address:

The form of the output - what?

The magnitude - how much?

The performance - how well?

The duration - for how long for?

A (relevant) research paper by Cluzel et al. (2013) reveals the significant amount of variation in the assimilation of these details. While their recommendation is to include all of these elements, another source (Esterman, 2012) recognises the first crucial step to an unyielding functional unit as a verb-noun arrangement. With the basis of these recommendations the functional unit of the building is defined accordingly:

The environmental impact of a newly built, low-energy detached home that provides a

weather sheltering and comfortable environment for one single family for at least 50 years

per m2 of heated floor area.

This relatively detailed functional unit aspires for transparency and comparability.

2.3 Selection of Impact Categories

This section describes six well-established environmental impact categories according to CML (2001). These are direct outputs from the Gabi software, as later described in Section 6.1, and the term ‘Environmental impact’ from here on represents these six impact categories. Primary Energy Demand measured in MJ The Primary Energy Demand (PED) is a common measure of environmental impact and considers the amount of energy required from the source of origin in order to provide the demanded energy at a particular application. It takes into account all forms of energy production that contributed; both fossil and renewable energy sources (Gantner et al., 2012). It should be noted that this value is strongly linked to the country’s energy mix, and this study therefore briefly assesses a variety of countries for comparison. The PED is expressed as a net calorific value, rather than gross calorific, to exclude latent heat and therefore has higher authenticity.


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Global Warming Potential measured in kg CO2-Equiv. Another frequently applied measure is the Global Warming Potential (GWP) of a process. It calculates various compounds such as Carbon Dioxide (CO2), Nitrogen Dioxide (NO2), Methane (CH4), Chlorofluorocarbons (CFCs), Hydro chlorofluorocarbons (HCFCs) and Methyl Bromide (CH3Br) (Khasreen et al., 2009). The impact of these compounds is rated against Carbon Dioxide, and the total is displayed as Carbon Dioxide Equivalents. The time that the gases are present in the atmosphere is computed into the total, and is generally specified as 100 years (Shine et al., 2005).

Acidification Potential measured in kg SO2-Equiv. The Acidification Potential (AP) represents a range of air pollutants that can transform into acids. These include Sulphur Oxides (SOx), Nitrogen Oxides (NOx), Hydrochloric Acid (HCl), Hydrofluoric Acid (HF), and Ammonia (NH4) (Khasreen et al., 2009). Acidification can directly affect the biotic environment through contaminating the soil and waterways (Bayer et al., 2010). The impacts can also extend to damaging building components via rainfall and can cause an increased rate in the corrosion of metals or disintegration of natural stones (Grossi & Brimblecombe, 2002) Eutrophication measured in kg Phosphate-Equiv. The Eutrophication Potential (EP) is based on another range of pollutants. This encloses Phosphate (PO4), Nitrogen Oxide (NO), Nitrogen Dioxide (NO2), Nitrates and Ammonia (NH4) (Khasreen et al., 2009). When these chemicals exceed the optimal level in water the reaction is an increased amount of algae growth. Essentially the sunlight is blocked, limiting the plants on the bottom surface to produce oxygen. Another factor that constricts the amount of oxygen is that the algae consume oxygen (Cloern, 2001). The aquatic animals in the water struggle for oxygen and their death, in the absence of oxygen, results in an excessive amount of naturally occurring compounds being released in the water (Bayer et al., 2010). The result is that the once clear aquatic ecosystem shifts to an alternative state. In terrestrial ecosystems, nitrates are a common source of pollution and they can react into nitrite (Gelfand & Yakir, 2008) which is toxic to humans. Ozone Depletion Potential measured in kg CFC-11-Equiv. An indicator to note is the Ozone Depletion Potential (ODP). Certain anthropogenic emissions that contribute to this effect are Chlorofluorocarbons (CFCs), Hydro chlorofluorocarbons (HCFCs), Halons, and Methyl Bromide (CH3Br) (Khasreen et al., 2009). The damage that these gases cause to the ozone has a long term and partially irreversible effect (Rao & Riahi, 2006). Some of these impacts include the warming of the earth surface, higher levels of Ultraviolet (UV) radiation and a range of detrimental impacts to ecosystems and human health (Caldwell & Flint, 1994). Photochemical Ozone Creation Potential (POCP) measured in kg Ethylene-Equiv. An additional indicator explored in this study is the Photochemical Ozone Creation Potential (POCP) or occasionally referred to as ‘Photochemical smog’. It refers to the reaction of nitrogen oxides and hydrocarbons exposed to sun radiation (Labouze et al., 2003). Research (Labouze et al., 2003) indicates that reactions are most volatile and frequent in areas with conditions similar to a forest (i.e. with less NO and CO).


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3 Literature Review

3.1 Background Information

A study conducted by Brunklaus et al. (2010) compares passive housing with conventional housing. As expected, the energy requirement was typically lower in the passive housing, but controversially almost all the other environmental indicators show higher impact than the conventional housing. Particularly the Eutrophication and Acification Potential (EP and AP) scored higher in the passive housing, this by 48% and 31% respectively. This provided one idea that inspired the theme of this study; to evaluate the environmental impact of housing beyond energy values.

Figure 3.1: Environmental Comparison of Conventional and Passive Housing. Source: Brunklaus et al. (2010)

Another applicable idea presented is that “…as building operational energy use declines, the rising importance of understanding and interpreting the embodied energy and environmental impacts associated with other life cycle stages besides the building use phase is becoming more significant” (Robertson, 2011, p. 125).

148% 131%

0%

100%

200%

Energy GlobalWarmingPotential

(GWP)

EutrophicationPotential (EP)

AcidificationPotential (AP)

PhotochemicalOzone

CreationPotential(POCP)

Land use Radioactivewaste

conventional housing passive housing

Relative difference of passive housing compared with conventional housing


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3.2 Life Cycle Phases

This chapter encompasses the stages of a building life cycle assessment within the mentioned system boundary. It reviews literature sources in order to comprehend reasonable assumptions for the upcoming modeling section.

3.2.1 Materials and Components The actual manufacturing of construction materials and components is based on the standard processes within Germany. The material selection is inspired by the following four ideas:

The choice of wood

The building materials chosen should reflect those of a low-energy wooden house. This study evades the conventional wood versus concrete analysis and instead simply assumes that wood has lower environmental footprint. Excluded from this analysis is the concept of CO2 uptake during the life cycle of concrete. There is emerging research (Andersson et al., 2013) regarding this subject, but intergration of this into the upcoming software calculations is considered too complex for the purpose of this report. According to Robertson (2011), a heavy timbered office building has a lower global warming impact relative to a concrete structure impact by up to 71%. Various environmental impacts can be reduced with the substitution of a laminated timber structure. The exception to this is fossil fuel depletion which is lower in a reinforced concrete building. Fossil fuel depletion is based on the energy intensity of extraction. The results for this are 30 times higher for natural gas (7.80 MJ/kg) relative to coal (0.25 MJ/kg) (Robertson, 2011). The production of concrete and steel is largely based on coal, while natural gas is predominately required during the production of adhesives and bonding agents for the production of laminated timber (Robertson, 2011). Therefore, a wooden construction scores with a higher energy value for fossil fuel depletion than the reinforced concrete office. Depicted in Figure 3.2 are the relative reductions for some equivalent impacts that are assessed here, such as ozone depletion, eutrophication and acidification, but also additional noteworthy impacts such as water intake, human health effects and ecological toxicity.


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Figure 3.2: Environmental Comparison of Concrete and Timber Designed Offices. Source: Robertson (2011)

0% 25% 50% 75% 100%

Fossil Fuel Depletion

Acidification

Smog

Ecological Toxicity

Eutrophication Potential (EP)

Water Intake

Criteria Air Pollutants

Human Health Effects

Ozone Depletion Potential (ODP)

Global Warming Potential (GWP)

Laminated Timber

Reinforced Concrete

Relative difference of laminated timber compared with reinforced concrete


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Maintaining the energy-efficient functionality of the building

Research (Sartori & Hestnes, 2007; Feist, 1996) demonstrates that low energy buildings, in contrast to conventional buildings, can commonly require a higher Embodied Energy (EE). The total energy over a 50 year life span is reduced by building with a more energy intensive set of materials and construction method. This is likely due to the effect of higher insulation properties of the materials and the associated reduction in heating and cooling demand.

To further exemplify this point, six cases studies with various material sets can be graphically viewed in Figure 3.3. It comprises of an ordinary 1984 building, a low energy building, a self-sufficient solar building and a passive house. It is eminent that the low-energy building and the passive buildings especially, have a higher relative (%) and absolute amount of embodied energy (EE) while the overall energy intensity is significantly lower. This implies the idea, which was mentioned in the introduction, that it is fair to invest in slightly more energy demanding materials and construction methods with the intention of reducing the cooling and heating demand. Consequently there is a considerably lower operational energy which is indeed the larger share of the 50 year energy total.

Figure 3.3: Energy balances of four case studies. Source: Feist (1996)

7% 12%

100%

31%

0

4000

8000

12000

16000

20000

24000

Ordinary house1984

Low-energybuilding

Self-sufficient solarbuilding

Passive house (asbuilt)

Operating Energy

Reoccuring EE

Initial EE

Energy use / (kWh/m²)


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The avoidance of steel, concrete and gravel

The base case building is formed to avoid, as much as possible, the integration of steel, concrete and gravel. It is a well-accepted idea that steel and concrete are high contributors to the building’s overall impact to global warming (Gustavsson & Sathre, 2006). The influence of various building materials to the global warming and supplementary environmental impact categories is summarised in Figure 3.4. Concrete and steel are usually predominant sections, while gravel has a very significant contribution to the Human Health (HH) cancer and noncancer categories.

Figure 3.4: Impact of building materials on environmental impact categories. Source: Thiel et al. (2013)

No integration of an active solar system

This project avoids an active solar system for several reasons, but this does not imply that in reality it is not recommended. One motive for avoiding an active solar system is that the base case model in the project should be simple; this is for both time reasons as well as to provide a generic low-energy house model. The second reasoning is that as seen in Figure 3.3 the self-sufficient solar building has a very high initial and refurbishment energy requirement. This would require extensive research on the installing and maintenance of photovoltaic system which is why it is excluded. A third point is that in Figure 3.4 it can be seen that the Photovoltaic (PV) panels and inverters, contribute quite significantly to almost all environmental impact categories. The PV panels are not the focus of this project and including them could shift the focus from the other factors considered. This would be counterproductive to the underlying concept that these factors are vital to consider.

0% 20% 40% 60% 80% 100%

Cumulative Energy Demand

Global Warming Potential (GWP)

Eutrophication Potential (EP)

Acidification Potential (AP)

Ozone Depletion Potential (ODP)

Smog

Exotoxicity

Human Health - Cancer

Human Health - Noncancer

Human Health - Air Pollutants

Natural Resource Depletion

Water IntakeConcrete

Steel

Gravel

Wood Products

Combination ofother materials

PV Panels,Inverters

Relative material contribution


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3.2.2 Transport There are several transport processes that require modelling:

The transfer from the production of materials directly to the construction site. The transfer from the production of materials to prefabrication site. The transfer from the prefabrication site to the construction site. The transfer of repair materials to the construction site. The transfer from the construction site to the incineration site. The transfer from the construction site to the landfill site. The transfer from the construction site to a usage site of the recycled materials.

The distance for each of the transfers is 100 km as derived directly from the default settings in the software. The road selection and vehicle type are also important influences to take into consideration (Sartori & Hestnes, 2007). These are also kept as generic as possible, by assuming a single truck without trailer that can carry up to 17.3 metric tonnes of heavy load for main national/international roads (PE International, 2012) It is said (Sjunnesson, 2005) that transport distances are a main contributor to the environmental impact, in the case of concrete that is but perhaps still relevant, and that it is important to consider various distances to observe if a significant reduction can be accomplished.

3.2.3 Construction Method The construction method that is employed for the case study building model is the prefabrication of materials. The construction method technically involves two separate processes with a transport link between them:

Prefabrication of materials On-site construction

The primary energy required to assemble a wooden building on-site is approximately 50 kWh per m2 ground floor area (Dodoo, 2011; Adalberth, 2000). A reduction of 34% is possible through prefabrication of the materials (Monahan & Powell, 2011). Of course these two statistics are dependent on many assumptions particularly the country of the energy mix; which in the initial observation is from Sweden. Therefore Sweden’s energy mix conversion rate of 1.74 (NorthPass, 2012) is applied to calculate a Secondary Energy Demand of 18.97 kWh/m2. There can be a variation in values between different wooden houses due to materials, construction techniques and size of building (Sartori & Hestnes, 2007). Nonetheless the mentioned values serve as a general rule of thumb for the case study in this report. The case study building is constructed with the intention of lasting 50 years. Perhaps constructing in such a way that would provide for a longer lifetime would be worthwhile in order to reduce the relative environmental impacts per year further.


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3.2.4 Building Operation For the building’s operation phase data is taken directly from the Futura Haus case study (Kellenberger, 2010). The energy requirement can be divided into:

Total electricity consumption Total energy for heating (and cooling if required) Total energy for hot water production.

The data is based on a European mix and the results would vary noticeably with national energy mixes. To place this in perspective, several energy mixes are tested in order to observe the various environmental impacts (see section 7.1).

3.2.5 Maintenance and Refurbishment Adequate maintenance of a building is important to avoid further, more intensive reparations. The various paths of maintenance, repair and a voluntary refurbishment are shown in Figure 3.5. Basically the building can either be adequately maintained, or requires repair due to the lack of maintenance. An optional refurbishment can take place a little over half way during the expected lifetime of the building to allow for a higher performance level of the building. There is no refurbishment modelled for the case study house. The path chosen is sufficient maintenance and there is no sudden end of life scenario considered.

Figure 3.5: Several paths of maintenance and repair. Source: EeBGuide Project (2012a)


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Examples of repair include leaks, cracks and settlement, dampness problems and termites. Many steps can be undertaken in order to prevent repair situations and such maintenance tips can be readily found online (Reardon, 2013). It is assumed that none of these occur during the building’s lifetime. The general repair or replacement rate is highly dependent on the durability of the materials (Landesverband Steiermark und Kärnten, 2006). The expected lifetime of the building materials can be found in Appendix B. The building materials that are assumed to be replaced at some stage during the 50 year life cycle, with significant simplification being involved, only include the cladding panels and the gypsum plaster board.

3.2.6 Demolition & End of Life Treatment The end of life phase of prefabricated house should be accomplished with relative ease compared to a conventional building. As a quick comparison, a low energy building has a recycling ability of 30 to 40% (Thormark, 2002), while proper management of the demolition of a prefabricated building allows for reuse of construction materials to a much higher degree of up to 69.1% (Aye et al., 2012). This share of materials avoids being disposed in landfill or incineration, and also reduces the demand for these virgin materials. Principally it is said to be a major advantage to construct with prefabricated elements as it provides “the ability for construction elements to be disassembled at the end of their useful life and reused in a new building” (Aye et al., 2012, p. 166). Assuming that each recycled materials results in another material not having to be produced, it could be considered as an avoided environmental impact or so called ‘credit’. Hence, it is concluded that recycling would in all cases be the most appropriate way to handle materials after the demolition stage. Nevertheless, the most realistic end of life scenario would for many materials include landfill or incineration (Institut Bauen und Umwelt e.V., 2014). Therefore it is initially modelled in this manner.


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4 The Case Study A case study is included to characterize a low-energy building rather than a typical conventionally-built house. In this study it is analysed with 50 years of useful lifetime, which is unlike the document from which most these upcoming details are obtained (Kellenberger, 2010). In form it is a two storey, single family house with a well-insulated envelope. It has an unheated basement consisting of 100.5 m2, and the heated surfaces account for 201 m2. This is illustrated in Figure 4.1. As formerly mentioned in section 1.2, in this case it is a building with a timber frame support structure. It is a Swiss model so the operational energy demand is dependent on the national climatic conditions.

The specified materials and operational energy are detained directly from the original case to create a realistic base case model. Outlined in this chapter are these specifications.

Figure 4.1: Section of building. Source: Futura Haus (2014)


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4.1 Embodied Materials

The range of materials in the sample house is matched with the materials in the Gabi database. This consists of anhydride cast plaster floor, bituminous, concrete, glass wool, gravel, gypsum plaster board, heat protection glass, larch boards, Oriented Strand Board (OSB) panel, particle board, polystyrene high-resistance foam board, reinforce concrete, rock wool, and various wood products (fiber board, lattice, studs beam and boards). These products and their assumingly equivalent forms in the database can be read in Appendix B. In Appendix A there is the quantification and application of the materials. They are categorized accordingly:

Basement floor Floor (above basement) Floor (above ground) External walls (below ground) External walls (above ground) Flat roof Windows Exterior door Interior walls (not painted)

The materials will not be categorized according to their application in the results chapter however. They are shown individually in order to give the viewer a direct idea from where the environmental impact has originated (see section 0:


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Materials). It is noteworthy to mention that the amount of the material is directly linked to the magnitude of the impact, and therefore Figure 4.2 shows the various contributions.

Figure 4.2: Volume of Materials in case study.

4.2 Operational Energy

As mentioned in the literature review, the operational energy of the building should be divided into electricity demand, energy for heating and energy for hot water production. The studied building employs gas for both the heating demands, and electricity from the grid. The contributions of these can be examined in Figure 4.3.

Timber pine 34%

Reinforced concrete

22%

Mineral wool 12%

Rock wool 8%

Anhydride cast plaster floor

5%

Gravel 3% OSB panel

3%

Polystyrene high-resistance

foam boards 5%

Other 8%

Proportion of total volume


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Figure 4.3: Aggregate demand for Base Case Model. Source: Kellenberger (2010)

The values presented here based on the European mix (Kellenberger, 2014). Since the values are in Primary Energy Demand (PED), the conversion to Secondary Energy Demand (SED) is necessary. The European (EU-27) conversion values are derived from the software (Gabi 6, 2013) and are 2.67 and 1.12 for electricity and gas heating respectively. This resulted in 8.24 kWh/m2 of electricity and 73.21 kWh/m2 of gas heating; both are then multiplied out by the liveable floor area and 50 years. For the initial analysis these specification remain identical.

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20

22

0

20

40

60

80

100

120

Futura model

total electricalconsumption

total energy for hot waterproduction

total energy for heating

Energy use/(kWh/(m²·year))


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5 Standards A range of standard of life cycle related standards are outlined in the following chapter. These are applied throughout the study.

5.1 EN standards

There are two pertinent European standards regarding the life cycle assessment of a building. The EN15804 specifically focussed upon materials and EN15978 is related to whole buildings. The life cycle of the materials and buildings are required to be divided into specific phases. These are displayed in Table 5.1. Table 5.1: Life Cycle Stage Modules. Sources: e.V. (2013), EeBGuide Project (2012b)

Life cycle stage modules Code Description

Product stage A1 Raw material supply

A2 Transport

A3 Manufacturing

Construction process stage A4

Transport

A5 Construction, installation processes-installation-process

Use stage B1 Use

B2 Maintenance

B3 Repair

B4 Replacement

B5 Refurbishment

B6 Operational energy use

B7 Operational water use

End-of-life stage C1 Deconstruction, demolition

C2 Transport

C3 Waste processing

C4 Disposal

Benefits and loads beyond the system boundary

D Reuse, recovery and/or recycling potential

These stages are necessary in order to verify the information of a product as an Environmental Product Declaration (EPD). This is naturally applied to materials in the Gabi database and the building as whole is roughly modelled to synchronise with these modules also. The standards are imperative as it forms the basis of comparison and transparency between several products or buildings.


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5.2 ISO standards

The International Organization for Standardization (ISO) has taken responsibility to encourage Environmental Management Systems (EMS) (Board on Agriculture, 1997). In order to standardise Life Cycle Assessment (LCA), the following standards were produced (Leiden University, 2001):

ISO 14040-2006 Environmental management, LCA, Principles and framework ISO 14044-2006 Environmental management, LCA, Requirements and guidelines

The key principles in these according to USA’s National Research Council (Board on Agriculture, 1997, p. 48) include “a well-defined process for planning, support and commitment of top management, the identification of individuals and procedures to implement plans, the communication of those plans, and a process of review”. The reviewing stage is critical for creating credible and transparent results (Bauman & Tillman, 2004). For the LCA of this building there is no third party review, however this study is reviewed by both university supervisors and a life cycle analysis expert within PE International.

5.3 DGNB Certification

The German Sustainable Building Council, (Deutsche Gesellschaft für Nachhaltiges Bauen) is a non-profit and non-governmental organization that is responsible for the environmental certification system known as DGNB (Olsson et al., 2012). It offers certification for various building types or whole urban districts, for both in or outside of Germany, and for new or existing buildings. The DGNB system has 6 categories with numerous issues that it addresses. Olsson et al. (2012) describes these categories and the percentage of worth as environmental quality (22.5%), technical quality (22.5%), economic quality (22.5%), social-cultural and functional quality (22.5%), process quality (10%) and site quality which is assessed separately. A certain score can be obtained in each category which consequently results in a final rating; the thresholds are 50% for Bronze, 65% for Silver and 80% for Gold. The energy demand is considered in the environmental category. The highest ranking points in this category are the primary energy demand, the percentage of renewable primary energy, global warming potential and risks to the local environment. All in all, the DGNB certification perceives the environmental category as only a fifth of the picture. While other certification systems, such as Leadership in Energy and Environmental Design (LEED), give higher ranking to the environmental category, it is still critical to reflect on other issues when designing a sustainable building.


25

6 Modelling

6.1 Software

The LCA model is created using the GaBi 6 Software. It is a system for life cycle engineering developed by PE International AG. They (PE International, 2014) have described their software as a life cycle inventory for several raw and process materials stored in the database, which was last updated in 2013. The software model is a mathematical algorithm, which covers all potential input and output flows of material and energy for the considered scenarios. Figure 6.1 displays the highest level of plan hierarchy of the building in the software model. The phases shown in this plan can be directly transferred as the dependent variables in one of the result sections (see section 7.2).

Figure 6.1: Screenshot of overall model in Gabi 6 software.


26

6.2 Limitations

There are some limitations which are related to the modeling in the software. In Gabi software the user develops a personalized model and this represents the real world scenario. The overall accuracy and reliability is dependent but not limited to the following variables: User´s choices; depends on time availability, user’s knowledge Data availability; how accurately this represents the data required Reliability of the data; how accurate the underpinning data is to reality System boundary; whether some phases of a life cycle are excluded Sample size; the amount of case studies and level of literature research Third party review; the quality of the final check or the lack thereof As a general rule of thumb, it said that “At least +/- 10% appears to be the minimum overall uncertainty range, even if the model is set up with data of high quality containing few errors. While interpreting the results this must be kept in mind” (PE International, 2014).

6.3 Assumptions

Materials The materials are standard templates and the specific processes for Futura Haus are not

modelled. This is due to a shortage of company process data. Density for materials originate in the database or from Environmental Product

Declarations (EPDs) (Institut Bauen und Umwelt e.V., 2014) The thickness of window glass required is assumed to be 10 mm in total. Concrete and reinforced concrete are aggregated together in the same category for

simplification. Larch boards and timber pine are considered as equivalents since their output from Gabi

is the same. Beams, studs, the roof lattice, larch boards, the insulated door are all considered as pine.

Pine is chosen as a random species of wood. Alternative wood species can be assessed. Materials are loaded in same truck rather than each material having each own transport

method. Again, this is for simplification.

Construction Construction and prefabrication are modeled separately for transport purposes but the

energy demand is modeled collectively (as also mentioned in the Section 3.2.3). The glass and basement materials go directly to site, all other materials are

prefabricated. User Phase Natural gas heating and electricity are based on an average European mix (EU-27). Varying occupant behavior or equipment is unknown in primary energy values.


27

Repair & Maintenance The repair stage is very simplified and not focused upon. Materials that are replaced once during the life cycle are wooden cladding, in the form

of pine, and gypsum plaster boards. End of Life The end of life options are incineration, landfill and recycling. Incineration: No energy credits are included from the incineration process. This is

assumed to be beyond the system boundary (stage D according to EN15804). The materials that are conveyed to incineration include bituminous, OSB panel, particle board, both types of polystyrene foam board, wood fibre board, larch boards and timber pine from both the initial set up and repair stage. The carbon sequestered within the wood products is released back to the atmosphere at the end of life phase. This ensures equilibrium of the amount of carbon being captured and released during the life cycle.

Landfill: The materials directed to landfill are anhydrite cast plaster, glass wool, gypsum plaster board, mineral wool, rock wool and the replacement gypsum plaster board.

Recycling: Recycling only includes the benefit of avoiding landfill or incineration; the avoidance of producing new materials can be included in the subsequent building’s life cycle. The materials that are recycled are gravel, heat protected glass and reinforced concrete.


28


29

7 Primary Results There are three main categories of results shown to provide an overview. They reveal the major critical points and also less significant factors of the case study building. It may be an appropriate time to mention that since numerous assumptions are underlying these results, they may differ from the real ‘Futura Haus’ building. For the discretion of Futura Haus, in all cases the results are shown as norminalised percentages. Since the building is specifically a prefabricated, timber-framed, low-energy building, the proceeding results even as percentages are not conclusive for all other residential buildings.

7.1 Energy mixes

This subsection shows the comparison of various electricity grid mixes. An average European mix (EU-27), a German (DE), an Austrian (AT) and a Swiss (CH) electricity mix are shown in Figure 7.1 with their relative effect on six environmental categories. The average European mix is based upon the various electricity mixes of 27 European countries with higher weightings for intensive energy producers such as France and Germany (EIA, 2011). The selected countries are weighted against the EU-27 mix which is therefore always set to 100%.

Figure 7.1: Environmental impact of electricity mixes to supply electricity in the operational phase1.

Displaying a selection of countries energy mixes alongside one another as in Figure 7.1, highlights the amount of variability. Germany’s (DE) electricity grid has a higher Primary Energy Demand, Global Warming Potential and Eutrophication Potential than the typical European (EU-27) electricity mix. While Germany has a lower Acidification Potential, Ozone Depletion Layer Potential and Photochemical Ozone Creation Potential than

1 Note: the legend and order of bars match in all figures in chapter eight.

0%

20%

40%

60%

80%

100%

120%

140%

Primary energydemand [MJ]

Global WarmingPotential

[kg CO2-Equiv.]

EutrophicationPotential [kg

Phosphate-Equiv.]

AcidificationPotential [kg SO2-

Equiv.]

Ozone LayerDepletion Potential

[kg R11-Equiv.]

Photochem. OzoneCreation Potential[kg Ethene-Equiv.]

EU-27: Electricity grid mix PE DE: Electricity grid mix AT: Electricity grid mix CH: Electricity grid mix

Relative impact of a country's energy mix compared with the European average


30

typically in Europe, both Austria and Switzerland have even smaller environmental impact in these categories and the first three also. The one exception to this is that Switzerland has a relatively high Ozone Layer Depletion Potential but this could also seem this way because the graph displays relativity. The absolute figures of Ozone Layer Depletion Potential are in fact very small. This is only mentioned to take this into consideration and does not imply that the impact of a small mass of compounds in this category cannot cause a significant level of environmental harm however. Simply stated, Austria and Switzerland have electricity mixes that are relatively lower in environmental impact than Germany and the European average (EU-27). Since the composition of electricity is difficult to influence as an individual, particularly in the field of construction, other phases could be focused upon.

7.2 Phases

All phases of the life cycle are assessed in order to determine their share of impact in the six environmental impact categories. Figure 7.2 illustrates that the phases that are largely responsible differ for these various environmental impacts. The composition of phases in the Primary Energy Demand category for instance, do not represent the other impact categories at all, so this alone would not provide a complete overview of environmental impact.

Figure 7.2: Phase contribution to environmental impact.

The various phases of the building life cycle and their contribution to environmental impact can shine a light on where to lay focus. From Figure 7.2, it simply cannot be concluded that only the use phase is enough to consider especially when factoring in the Eutrophication, Acidification, Ozone Layer Depletion and Photochemical Ozone Creation Potential categories. The level of repair and maintenance is somewhat negligible, since it is highly

29% 25% 39% 35%

90%

35%

6% 3%

-9%

67%

58%

41% 54%

10%

52%

16% 13% 7%

-3%

Primary energydemand

[MJ]

Global WarmingPotential

[kg CO2-Equiv.]


Phosphate-Equiv.]

AcidificationPotential

[kg SO2-Equiv.]

Ozone LayerDepletion

Potential [kg R11-Equiv.]

Photochem.Ozone Creation

Potential [kgEthene-Equiv.]

End of Life

Repair &Maintenance

Use Phase

Construction

Materials

Relative Phase Contribution


31

simplified and modeled minimally. The results therefore reflect this as it is barely evident. The construction phase is another generally small share but contributes with 6% and 3% respectively to the Eutrophication and Acidification Potential impacts. The end of life scenario should not be forgotten either, particularly for the Eutrophication, Acidification and Global Warming Potential. To refer back to the aim and scope, it mentioned Eutrophication and Acidification as the two focal parameters, and particularly in these categories the impact of the material selection is evident. In fact in all categories the initial set of construction materials occupies a reasonable share and it is therefore important to evaluate how, from an environmental perspective, the material selection can be improved. The building’s impact on a range of other environmental indicators is also tested, simply out of interest. This is not incorporated in the scope and therefore will not be extensively discussed. However, it could form the basis of further research and it reconfirms a previously mentioned idea. By observing Figure 7.3 it can be confirmed that primary energy demand would give a very unrepresentative view of the overall environmental impact. Additionally the graph indicates the significance of material selection on toxicity measures.

54% 57% 48%

66%

5%

5% 36%

30%

27%

11%

8% 5%

24% 15%

Human ToxicityPotential [kg DCB-

Equiv.]

FreshwaterAquatic

Ecotoxicity Pot.[kg DCB-Equiv.]

Marine AquaticEcotoxicity Pot.[kg DCB-Equiv.]

TerrestricEcotoxicity

Potential [kg DCB-Equiv.]

Relative Phase Contribution for another range of environmental categories

End of Life

Repair &Maintenance

Use Phase

Construction

Materials

Figure 7.3: Phase contribution for a larger range of environmental categories


32

7.3 Materials

The initial construction materials are assessed in terms of their environmental impact. To specify this, Figure 7.4 represents the material phase only and precisely cradle to gate. If a material has attained higher than 9% of the total material contribution to one or more impact categories then they in this instance classified as a ‘hotspot’ or critical point. These materials are displayed separately in the graph, while materials that score below 9% in all categories are grouped together as ‘other materials combined’.

Figure 7.4: Material contribution to environmental impact.

The initial selection of materials seems like a vital focus point. In Figure 7.4, it can be observed that it is a combination of the same four materials that generally cause hotspots in all environmental categories. These materials are anhydride cast plaster floor, OSB panel, polystyrene high-resistance foam board and reinforced concrete. The largest contributor of these, with the exception of this in the Ozone Layer Depletion Potential category, is reinforced concrete. The results thus uphold an earlier comment which said to avoid concrete as much as possible for the environment’s sake. The next most environmentally damaging material typically in all categories is the polystyrene high resistance foam board. The OSB panels seem very high with a 99% contribution to Ozone Layer Depletion but this again due to the fact that those values are minute. The OSB panel should still be highlighted however, since it has a 10% contribution to the total Primary Energy Demand. The Anhydride cast plaster floor is rated as 9% for both the Eutrophication and Acidification Potential indicators. The subsequent chapter particularly focuses on strategies that aim to reduce the environmental impact of these materials.

42%

66%

55% 58% 54%

26%

11%

10% 14% 19%

10%

-7%

99%

8% 9% 9%

19% 20% 16% 18%

Primary energydemand [MJ]

Global WarmingPotential [kg CO2-

Equiv.]


Phosphate-Equiv.]

AcidificationPotential [kg SO2-

Equiv.]

Ozone LayerDepletion

Potential [kg R11-Equiv.]

Photochem.Ozone Creation

Potential [kgEthene-Equiv.]

Other materialscombined

Anhydride castplaster floor

OSB panel

Polystyrene high-resistance foamboardReinforcedconcrete

Relative material contribution


33

8 Derived Strategies The following chapter discusses ten environmental reduction strategies. The strategies are inspired by the knowledge gained throughout the literature study, and when directly possible are applied to Futura Haus model to observe quantified changes. A strategy may result in a significant environmental reduction in one phase, but it has to result in a significant reduction from the whole LCA perspective in order for it to be suggested here as a potentially worthwhile strategy for action. The results are therefore as a percentage of impact on the overall’s building and are only shown if there is a reduction greater than 1% in at least one impact category. A summary can be found in Table 9.1.

8.1 Size of building

Selecting a smaller building size is a simple strategy that can directly reduce the environmental impact. Some changes along the life cycle include initial material requirement, the operational energy demand, the level of materials for maintenance, the energy required for construction, transport loads, and the amount of materials at the end of life. These changes were modelled in Gabi (2013) and the results showed an obvious relationship between the total liveable area and environmental impact (see Figure 8.1). The changes occurred in all impact categories and due to nature of the assumptions it emerged as a proportional linear relationship. The energy required for construction for example was an assumption based on the floor area and therefore if the building size reduced by 10% then so did the environmental impact for this energy requirement. Another example would be that if the building size is reduced by 10%, then 10% less materials are assumed to be required and so 10% less transport via trucks is also implied.

Figure 8.1: Relative environmental impact for various building sizes.

R² = 1

0%

20%

40%

60%

80%

100%

Total livable area / m²

Relative environmental impact


34

According to Figure 8.1, if this building model was reduced to 70% of its original size it would measure 160.80 m² in terms of living space. This decision alone would theoretically reduce all six environmental impact categories to 70% of the original impact. While in reality this curve would not have a perfectly linear correlation, it can still be concluded that the level of environmental reduction can be radically diminished by choosing a smaller building size. This level of reduction would also be dependent on building type, integrated materials and construction method. A similar concept would be design a building form which requires fewer materials relative to the amount of useful floor area to also reduce the environmental impacts.

8.2 Recycled materials

Building with recycled materials is another effective strategy. Each recycled product that is obtained and integrated into the building is assumed to no longer be required as a virgin material. Thus, the environmental reduction comes from the avoidance of producing that product as new. It is important to not count these effects with the previous building’s life cycle because then there is the risk that it is double counted.

The two scenarios tested were the shunned material production for firstly just wooden components and secondly just reinforced concrete.

Building with recycled wooden products results in:

Primary energy demand [MJ] reduced by 3.18% Global Warming Potential [kg CO2-Equiv.] increased by 2.22% 2 Acidification Potential [kg SO2-Equiv.] reduced by 1.37% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 2.22% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.07% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] reduced by 3.53%

Building with recycled concrete, assuming direct reapplication, results in:

Primary energy demand [MJ] reduced by 12.32% Global Warming Potential [kg CO2-Equiv.] reduced by 22.60% Acidification Potential [kg SO2-Equiv.] reduced by 20.37% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 21.35% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.42% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] reduced by 25.25%

If these recycled materials can be collected locally, then this is very sensible option for both reducing the environmental impact but also for economic benefits (U.S. Environmental Protection Agency, 2013).

2 This increase is due to avoided production of new wooden materials and their amount of carbon storage. In this case

recycled materials replace newly built materials, which theoretically would have been incinerated, releasing that same level of

carbon. Therefore this result may be misleading and should not be considered as a weakness.


35

8.3 No Basement

Since the basement is responsible for a large proportion of concrete, the change in environmental impact is remarkable for the model without a basement.

Primary energy demand [MJ] reduced by 11.38% Global Warming Potential [kg CO2-Equiv.] reduced by 17.84 % Acidification Potential [kg SO2-Equiv.] reduced by 18.50% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 21.34% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.37% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] reduced by 12.46%

It could be worthwhile to consider other storage alternatives, perhaps in the attic, rather than constructing a basement.

8.4 Duplex Building

The environmentally destructive impact of concrete was noted earlier, and therefore it is a suggestion to build higher. This does not imply more floor area per family, but instead the suggestion is to accommodate several family houses stacked upon another. In theory this would prevent the need for another concrete slab on the ground. The results presented below exclude the basement in both the initial and comparison case, and all phases are adjusted to provide for the two buildings. It focuses on the reduction of building two family homes stacked rather than two detached family houses. The total percentage change is halved in order to consider the effect per one building.

Primary energy demand [MJ] reduced by 2.10% Global Warming Potential [kg CO2-Equiv.] reduced by 2.92 % Acidification Potential [kg SO2-Equiv.] reduced by 3.18% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 3.64% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.07% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] reduced by 2.37%

The number of stacked houses could be extended beyond two, and would likely indicate environmental benefits of multi-storey building design. Further analysis would be required r to take into account intermediate concrete slabs and the increased foundation required to support a high-rise buildings. However, the idea remains relevant, also from an urban planning perspective where relatively fewer infrastructures are required per family in densely populated cities.


36

8.5 Local Materials

The selection of locally produced materials could reduce the environmental impact through shorter transport distances. It may not be the case that the local materials are produced with the most environmentally friendly procedure, and so the effect of reducing transport may or may not outweigh these impacts. As an example, if the distance from of transport between the producer and construction site decreased from 100 kilometres to 50 kilometres, the results are:

Primary energy demand [MJ] reduced by 0.21% Global Warming Potential [kg CO2-Equiv.] reduced by 0.23% Acidification Potential [kg SO2-Equiv.] reduced by 0.85% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 1.89% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.00% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] increased by 4.10%3

The results for another building may be higher however, since there has been a modeling assumption that all materials have a common transport flow. In reality this could be different since companies may choose to deliver only their products to the site.

8.6 Prefabrication

The process of prefabrication is said to have a significant potential for a building’s energy and waste reduction (Yupeng et al., 2005). It can be noted that a prefabrication site should be within an appropriate distance for these outcomes to have benefit.

Energy reduction

Firstly, the energy reduction for prefabrication instead of complete on-site protection is assumed to result in an energy reduction of 34% during the construction phase. The environmental impact reductions are consequently quite significant in the construction phase. However, since this phase is only a very small share of the total building’s LCA, possibly due to simplifications in modeling, the overall environmental impact reduces only ever so slightly. The results are below 1% in all categories and therefore not displayed.

Waste reduction

The second advantage of prefabrication is that if the building is dismantled correctly there is a potential for recycling and reuse. The avoided production by reusing the materials is not calculated in the below results since this can be considered in the next building’s lifecycle. The avoidance of incineration is calculated for building though, and this alone is advantageous from all considered environmental categories. Under the supposition that all wooden materials are to avoid incineration, the following outcomes are derived:

Primary energy demand [MJ] reduced by 0.07% Global Warming Potential [kg CO2-Equiv.] reduced by 1.46%

3 This is due to nitrogen oxides that are released in the truck transport process that can have negative and positive effects. This

is caused by a reaction between nitrogen oxides and volatile organic compounds which is still under research (PE International, 2014).


37

Acidification Potential [kg SO2-Equiv.] reduced by 0.40% Eutrophication Potential [kg Phosphate-Equiv.] reduced by 0.71% Ozone Layer Depletion Potential [kg R11-Equiv.] reduced by 0.00% Photochem. Ozone Creation Potential [kg Ethene-Equiv.] reduced by 0.28%

In the summary, Table 9.1, the environmental reductions from energy and waste reduction are counted collectively.

8.7 Refurbishment

Instead of building from scratch, a large proportion of environmental impact could be avoided by refurbishing an existing building instead. Even if the environmental impacts from the refurbishment may be equal to or even exceed those of the construction phase of a new building, it could be worthwhile considering that a large sum of materials do not require production. In this case study, the materials alone are responsible for at least 25% of all impact six categories. Additionally if the building contained steel, then the percentage of impact from materials would likely be much higher. Research (Webster, 2004) draws attention to structural elements, such as steel, being responsible for a large proportion of impact and these elements could remain intact during the refurbishment.

8.8 Lifetime of building components

A proposal is to select materials that require little effort, or energy, to construct and/or select those with a longer lifetime. Since the repair and maintenance phase contributes to no more than 1.70% to any of the environmental categories this is not modelled and tested. However, it is suggested that the occupants undertake necessary maintenance steps to prevent major repair situations (Reardon, 2013). These can be readily found online.

8.9 Specific wood species

The type of wood species can also have an impact on the overall LCA. An additional variable to take into account would include thickness of a particular wood species for adequate load bearing. Since timber pine, as the randomly selected wood species in the study, does not indicate a critical point of impact and is assumed to be recycled, it does not represents a large impact. Due to these reasons and the fact that the sourcing of different wood species and their processes would vary heavily on the applied building location, this is not tested and modelled further. There could already be some research on the local timber sources of the relevant location.

8.10 Substitution of materials

Materials with a large share of environmental impact can be substituted with other materials. It should be carefully noted whether the substitution material has at least the same functional properties as the material being replaced. Four main materials are discussed:


38

Aerated concrete

This is particularly applied in the slab on the ground. An alternative solution would be low carbon cement. The comparison is thus between the aerated concrete in the Gabi software and a reference case to Slagstar’s environmental cement. It is said (Slagstar ÖkoBeton, 2014) that 1000 m³ of their low carbon cement saves 200 tonnes of CO2. It is assumed that this is relative to a standard cement case and that the low carbon cement has adequate weight bearing properties for the case building. This would result in an overall reduction of 3.52% to the whole building LCA in the Global Warming Impact category. The other impact categories are not published by the source and no low carbon cement is available in the database so it is not conclusive to say that a low carbon alternative would reduce the overall environmental impact. OSB panel

In the building, the OSB panels are within the walls to support the insulation layer. OSB panels are a fairly standard construction material and could be substituted with any lumber board. Another solution would be to compare various brands of OSB panel. At a brief glance of the datasets in Gabi, the OSB panel seems to score with lower impact in the six analysed environmental categories relative to a typical particle board. There appears to be no outstanding variation between different OSB brands and there is no overall ‘winner’ in all categories. Perhaps the most relevant angle to assess the environmental impact of the OSB panels is by their amount of carbon storage and the amount of energy exerted when incinerated (combustion value). An OSB panel exerts a high amount of energy in a biomass incineration plant and this could be a very suitable end of life option particularly in Austria where these plants are readily available.

Polystyrene high resistance foam board

This material is included in structures as thermal and sound insulation and partially scores highly in environmental impact due to the large quantity required. While other insulation materials can replace polystyrene foam boards, it should be noted that it is an appropriate material from a moisture safety perspective (Tatarka & Cunningham, 1998). Alternatives like particle mineral wool or particle boards do not have the ability to resist moisture as sufficiently. While the Photochemical Ozone Creation Potential can be reduced by substituting with mineral wool, the other five impact categories are actually lower in polystyrene foam board.

Anhydride cast plaster flooring

This type of cast plaster was integrated for indoor flooring purposes. Cement plaster could be another alternative to this for instance. While the cement plaster in Gabi (2013) does not improve the environmental impact at all, it could be worthwhile considering various brands and options. This last strategy has highlighted that there are substitution materials available but they may not necessarily improve the environmental impact. That being said, it cannot always be assumed that the lowest impact materials are already standard practice. After all, the functionality of the building material should remain highest priority.


39

9 Summary Table Table 9.1: Summary table of Environmental Impacts4

4 It is noteworthy to mention that for all the strategies mentioned in Table 9.1 not only does the environmental impact for the assessed categories decrease but for other environmental indicators also. The two exceptions to this are methodological issues.

1.

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Abiotic Depletion (ADP elements) [kg

Sb-Equiv.] -0,1% -22,3% -17,0% -2,8% 0,0% -0,1%

Abiotic Depletion (ADP fossil) [MJ]

-1,0% -12,4% -11,8% -2,3% -0,2% -0,2%

Acidification Potential (AP) [kg SO2-

Equiv.] -1,4% -20,4% -18,5% -3,2% -0,9% -0,7%

Eutrophication Potential (EP) [kg

Phosphate-Equiv.] -2,2% -21,3% -21,3% -3,6% -1,9% -0,9%

Freshwater Aquatic Ecotoxicity Pot.

(FAETP) [kg DCB-Equiv.] -3,3% -18,6% -24,1% -6,1% -1,4% -0,4%

Global Warming Potential (GWP 100

years)[kg CO2-Equiv.] 2,2% -22,6% -17,8% -2,9% -0,2% -1,6%

Global Warming Potential, excl

biogenic carbon (GWP 100 years) [kg

CO2-Equiv.] -0,9% -22,8% -17,7% -2,8% -0,2% -0,6%

Human Toxicity Potential (HTP inf.)

[kg DCB-Equiv.] -1,5% -41,6% -32,1% -6,0% -0,4% -0,9%

Marine Aquatic Ecotoxicity Pot.

(MAETP) [kg DCB-Equiv.] -5,0% -34,1% -25,6% -4,4% -0,1% -2,6%

Ozone Layer Depletion Potential

(ODP) [kg R11-Equiv.] -0,1% -0,4% -0,4% -0,1% 0,0% -0,1%

Photochem. Ozone Creation

Potential (POCP) [kg Ethene-Equiv.]

-3,5% -25,2% -12,5% -2,4% 4,1% -0,5%

Terrestric Ecotoxicity Potential (TETP)

[kg DCB-Equiv.] -1,4% -41,5% -33,6% -6,1% -1,5% -1,0%

Total Primary energy demand [MJ]

-3,2% -12,3% -11,4% -2,1% -0,2% -0,2%

Primary energy from non renewable

resources [MJ] -1,0% -12,6% -11,8% -2,2% -0,2% -0,2%

Primary energy from renewable

resources [MJ] -24,8% -9,6% -7,5% -1,0% -0,1% -0,4%

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arch

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10 Practical Limitations The underlying focus was to consider ecological impact indicators, rather than just primary Energy Demand and Global Warming potential, for the building under study. Some general strategies are previously mentioned in order to accomplish a lower environmental footprint. In regards to these strategies, there are numerous practical implications that could limit the study’s accuracy and require further research. These are noteworthy: Only energy and environmental categories

Environmental impact categories are just one of the many aspects to a sustainable building. Further major categories to consider include economic quality, socio-cultural and functional quality, technical quality and process quality (DGNB, 2014). For instance, it is vital that whilst reducing the environmental impact of a building to not neglect functional specifics such as safety in case of fire, hygiene, health (indoor climate), safety in use, acoustics, durability, robustness, lifetime, usability and architecture (Öberg, 2005). Only six environmental impact categories

The choice of environmental impact categories was limited to only six indicators. Two important environmental considerations that were not fully analysed are toxicology and water consumption for instance (Thiel et al., 2013). The Gabi software could also analyse the subsequent environmental impacts: Abiotic Depletion, Freshwater Aquatic Ecotoxicity, Human Toxicity, Marine Aquatic Ecotoxicity, Radioactive Radiation, Terrestric Ecotoxicity and more (PE International, 2014).

Importance of certain categories and their effect

There is no quantitative method to decide whether one category is of higher importance to another category shown in this study. Decisions ultimately depend on subjectivity; what is personally considered important. Various energy certification rates give specific factors ratings or a weighting (Olsson et al., 2012), but it is still a complex decision whether the decrease of one environmental impact is worthwhile if it increases the environmental impact of another factor. If it is, the next debatable question would be how much the other impact could increase by. There are simply no direct equivalencies between two environmental impact categories as they measure completely different compounds and effects.

Even when evaluating individual categories, such Ozone Depletion Potential, it is difficult to understand the magnitude of effect of a theoretical value.

Only one type of building and construction method

The only building type included is this report is a residential building. For large and complex building forms a customized analysis should be conducted. In fact, for any building a customized model and evaluation should be performed. The building under analysis here is very specific in the sense that it is a timber-frame, prefabricated low-energy home. While the concepts presented here may serve as insight for similar buildings, they are not conclusive since the outputs rely on a vast amount of variables.


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Modelling limitations

The precision of the data depends on assumptions, the comprehensiveness of the considered system and the representativeness of the used data. This study therefore includes all the approximate error factors and assumptions in the previous studies, as well as new assumptions and limitations. Generally a third party review would also be required to ensure that the LCA has been conducted properly. This was not integrated in this case study.

Less developed categories

The categories have different reliability and acceptance levels. Some impact categories, such as global warming, are considered relatively robust regarding completeness of the potential contributing emissions and the degree of impact. Impact categories for toxicity, which were not used in this case, are much less developed (PE International, 2014). Human toxicity is an example of this, since it does not include the harm during the construction phase from paints and glues on the labourers. It is also mentioned (Perming, 2012) that for the ozone depletion potential category nitrous oxide is incorrectly excluded.

Several exclusions

There are numerous additional components that could be modelled in order to produce a more precise picture of the building. These include many minor details that are overlooked, such as “the influence of the ancillary materials is highest for wooden constructions as a lot of screws nails and other connectors are essential” (Kellenberger & Althaus, 2009, p. 818). A major exclusion from this study would be, for instance, that with highly insulated envelopes evolves the requirement of an active ventilation system. Integrating such system has the potential to noticeably increase the embodied energy demand and environmental impact.

Location

The country of study, Switzerland, has an influence on the results. It is possible that since it is a relative clean energy mix that the impact of the operational phase is less significant than in other countries for instance. On the contrary, the energy requirement during the operational phase may be higher for thermal comfort control. These factors should be kept in mind when applying this building’s results to other countries.

Lastly, LCA does indicate where the impact occurs. For Primary Energy Demand, Global Warming, and Ozone Depletion this may not be relevant but it does matter for Eutrophication Potential, Acidification Potential and Photochemical Ozone Creation Potential. The impact on terrestrial, aquatic or atmospheric environments would depend on the vulnerability or stability of that specific location.


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11 Conclusion Life Cycle Analysis has been a vital tool in assessing the environmental impact of the case study building. It gave an insight into the effect of various electricity mixes, life cycle phases and materials. The use phase is recognised as a major proportion of the building’s environmental impact; particularly for Primary Energy Demand and Global Warming Potential. However the focus was to specifically highlight the significance of materials and their effect on the Eutrophication and Acidification Potential. These indicators among many more, which are not analysed here but are still very relevant, can have destructive consequences particular for agricultural land and nature reserves. Ten strategies were developed which hope to serve as a general guide for those who wish to have a more holistic view of their building’s environmental impact. With the exception of some methodological discrepancies, all the quantified strategies resulted in a reduction in the six impact categories assessed. The magnitude of the impact varies and therefore subjective decisions are required to determine which strategies are worthwhile.


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Appendix A Materials Specifications

Table A.1: Material applications and quantification, edited from: (Kellenberger, 2010)

element: material: thickness area /

m2 U-value / (W/m2K)

Basement floor 100,5 0,34

ground slab reinforced concrete 200 mm

thermal insulation polystyrene high-resistance foam board 110 mm

plaster anhydride cast plaster floor 50 mm

Floor (above basement) 100,5

floor slab reinforced concrete 200 mm

thermal insulation polystyrene high-resistance foam board (2 layers) 70 mm

impact sound insulation glass wool 20 mm


Floor above ground floor 100,5

ceiling , wooden beam timber pine 440 mm

particle board 22 mm

thermal insulation polystyrene high-resistance foam board (2 layers) 70 mm

impact sound insulation glass wool 20 mm


External walls (below ground) 92,5

filter slab concrete 70 mm

coating bituminous 2 kg/m2

thermal insulation polystyrene high-resistance foam board, extruded 100 mm

wall construction reinforced concrete, waterproof 200 mm

External walls (above ground) 213 0,22

cladding panels larch boards 21 mm

ventilation spacing 30mm 2 mm

sheeting OSB panel 15 mm

wood frame, studs timber pine 190 mm

thermal insulation mineral wool 160 mm

sheeting OSB panel 15 mm

plaster gypsum plaster board 15 mm

Flat roof 100,5 0,2

roof covering gravel 100 mm

coating bituminous 1.7 kg/m2

sheeting particle board 22 mm

pitch and ventilation timber pine (as lattice) 11.25 mm

wood fiber board 22 mm

wooden beams timber pine 30 mm

thermal insulation rock wool 160 mm

sheeting wood fiber board 27 mm

Windows 32,4 1,5

windows north heat protection glass (double glazed, 4mm air filled, coated) 2,4 m2

windows east heat protection glass (double glazed, 4mm air filled, coated) 1.7 m2

windows south heat protection glass (double glazed, 4mm air filled, coated) 26 m2

windows west heat protection glass (double glazed, 4mm air filled, coated) 4 m2

Exterior door 2 2,6

insulated door timber pine 2 m2

Interior walls (not painted) 99,5


sheeting OSB panels 15 mm

insulation rock wool 60 mm

wooden frame timber pine 100 mm

sheeting OSB panels 15 mm



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Appendix B Material Datasets Table B.1: Material Datasets. Names from (Gabi 6, 2013)

material name dataset in software: lifetime / years

conversion / (kg/m2)

density /

(kg/m3)

area / m2

volume / m3

mass / kg

anhydride cast plaster floor

Floor screed (anhydrite); technology mix; production mix. at plant; (en)

20-40 2.000 15.08 30150.00

bituminous Bitumen sheet v 60; technology mix; production mix. at plant; 5 kg/m2 (en)

40-60 1.7-2.0 355.85

glass wool Glass wool insulation material - ISOVER; technology mix; production mix. at producer; (en)

40-60 32 4.02 128.64

gravel Gravel grain 2-32 mm; technology mix; production mix. at plant; dried (en)

30- 2.400 10.05 24120.00

gypsum plaster board

Dry screed (Gypsum plaster board); technology mix; production mix. at plant; 20 kg/m2 (en)

20-40 20 412 8240.00

heat protection glass (double glazed. 4mm air filled. coated)

Double glazing unit; technology mix; production mix. at plant; (en)

20- 2580 32.4 0.324 835.92

mineral wool Mineral Wool (facades) 40-60 46 34.08 1567.68

OSB panel AGEPAN/Greenline OSB-panel - Glunz; technology mix; production mix; 606 kg/m3 (en)

30-50 606 9.375 5681.25

particle board Particle board; P2 (Standard FPY); production mix. at plant; 7.8% water content (en)

30-50 655 4.42 2896.41

polystyrene high-resistance foam board

Expanded Polystyrene (PS 20); technology mix; production mix. at plant; (en)

30-50 10.4 502.5 5226.00

polystyrene high-resistance foam board. extruded

Extruded polystyrene (XPS); technology mix; production mix. at plant; 32 kg/m3 (en)

30-50 32 9.25 296.00

reinforced concrete

Aerated concrete block element; technology mix; production mix. at plant; average density 500 kg/m3. reinforced (en)

40-60 2400 65.18 156420.00

rock wool Rock wool flat roof plate (100 mm); technology mix; production mix. at plant; (en)

40-60 32 22.05 705.60

wood fiber board Wood fibre board; technology mix; production mix. at plant; (en)

30-50 700 4.92 3447.15

larch boards Timber larch (12% moisture / 10.7% water content); technology mix; production mix. at plant; 661 kg/m3 at 12% moisture (en)

30-50 661 4.47 2956.65

timber pine (as random example of wood species)

Timber pine (12% moisture / 10.7% water content); technology mix; production mix. at plant; (en)

40-60 420 98.99 41573.96

TOTAL MASS: 284601.12

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