Scholarly article on topic 'Multi-criteria Decision-making for Sustainable Wall Paints and Coatings Using Analytic Hierarchy Process'

Multi-criteria Decision-making for Sustainable Wall Paints and Coatings Using Analytic Hierarchy Process Academic research paper on "Civil engineering"

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Abstract of research paper on Civil engineering, author of scientific article — Mariia Rochikashvili, Jan C. Bongaerts

Abstract To which extent do potential users of construction products take sustainability into account during their decision-making process? How well could they align themselves in all the legislation frameworks and calculation tools for the sustainable construction products? In accordance with the Environmental Product Declaration (EPD) [1], determining of ecological properties of construction products could be accomplished with applying life cycle assessment (LCA). There is a number of tools and frameworks for evaluating the sustainability of construction products for the European experts, which may be used in such a decision-making process. However, for a non-expert user, this could be quite complex. Therefor, the assumption here is that environmental and human health safety are prior in contrast to the market prices when it comes to choosing a decorative paint or coating. In the framework of herein research, an Analytic Hierarchy/Network Process model was designed involving four major merits of the Analytic Hierarchy Process: Benefits, Opportunities, Costs, and Risks [2]. The model which is based on the major characteristics of a decorative wall paint helps emphasising the best alternative with respect to given priorities: low risk of environmental and human health damage, quality, market price, repairability. The model shows values for all the criteria and alternatives with respect to pairwise comparisons. In a future research step, this model will be validated with a questionnaire survey targeting non-expert users, i.e. average consumers, on the construction market in Germany.

Academic research paper on topic "Multi-criteria Decision-making for Sustainable Wall Paints and Coatings Using Analytic Hierarchy Process"

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Energy Procedía 96 (2016) 923 - 933

SBE16 Tallinn and Helsinki Conference; Build Green and Renovate Deep, 5-7 October 2016,

Tallinn and Helsinki

Multi-criteria decision-making for sustainable wall paints and coatings using Analytic Hierarchy Process

Mariia Rochikashvilia*, Jan C. Bongaertsb

aPhD Candidate, TU Bergakademie Freiberg, Schlossplatz 1, Freiberg, 09599, Germany bProfessor, Head of the Chair International Management of Resources and Environment, TU Bergakademie Freiberg,Schlossplatz 1, Freiberg,

09599, Germany

Abstract

To which extent do potential users of construction products take sustainability into account during their decision-making process? How well could they align themselves in all the legislation frameworks and calculation tools for the sustainable construction products? In accordance with the Environmental Product Declaration (EPD) [1], determining of ecological properties of construction products could be accomplished with applying life cycle assessment (LCA). There is a number of tools and frameworks for evaluating the sustainability of construction products for the European experts, which may be used in such a decision-making process. However, for a non-expert user, this could be quite complex. Therefor, the assumption here is that environmental and human health safety are prior in contrast to the market prices when it comes to choosing a decorative paint or coating. In the framework of herein research, an Analytic Hierarchy/Network Process model was designed involving four major merits of the Analytic Hierarchy Process: Benefits, Opportunities, Costs, and Risks [2]. The model which is based on the major characteristics of a decorative wall paint helps emphasising the best alternative with respect to given priorities: low risk of environmental and human health damage, quality, market price, repairability. The model shows values for all the criteria and alternatives with respect to pairwise comparisons. In a future research step, this model will be validated with a questionnaire survey targeting non-expert users, i.e. average consumers, on the construction market in Germany.

© 2016 The Authors. Publishedby ElsevierLtd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of the SBE16 Tallinn and Helsinki Conference.

Keywords: Sustainability; Construction products; Life cycle assessment; Wall paints; Analytic Hierarchy Process; Analytic Network Process

* Corresponding author. Tel.: +49-176-456-81821. E-mail address: mariia.rochikashvili@bwl.tu-freiberg.de

1876-6102 © 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of the SBE16 Tallinn and Helsinki Conference. doi:10.1016/j.egypro.2016.09.167

1. Introduction

Choices of a construction product according to the sustainability objectives require basic expert knowledge. This involves reading not only instructions provided on the product packaging, but also material safety data sheets. This research is prepared for the construction market in Germany approaching the Analytic Hierarchy Process [2] within the Super Decisions Software. The outcome of the research is a model of potential user behaviour for choosing decorative wall paint. The model will be further tested with the help of a questionnaire survey for the non-expert users, i.e. average consumers. The main purpose of this research consists in identifying the relative importance of sustainability characteristics in selecting construction products. Particularly, decorative wall paints are considered to be chosen. For this purpose, with an assumption that environmental and health safety is of a high priority, an AHP/ANP model is used for a comparison ofthree alternative decorative wall paints and coatings.

Nomenclature

AHP analytic hierarchy process

ANP analytic network process

BWR basic work requirements for construction works

B Benefits

C Costs

CPD Construction Products Directive (EU) No 89/106/EEC [3]

CPR Construction Products Regulation (EU) No 305/2011 [4]

EN European standard

EPD Environmental product declaration

kt kiloton

LCA life cycle assessment

MSDS material safety data sheet

O Opportunities

ppm part per million

R Risks

VOC volatile organic compound

2. Legislation and literature review

There is a wealth of European legislative standards and directives for building in general and construction products in particular, including legislative regulations for decorative paints that are commonly produced, sold and used on the territory of the European Union. These regulations define sustainable construction products and life cycle assessment, set the limit values for hazardous emissions into the environment caused by using decorative paints and coatings, which contain organic solvent. Literature review includes the brightest examples of the decision-making process with respect to construction products.

2.1. Legislation/or building and construction products

In accordance with the Environmental Product Declaration (EPD) [1], determining ecological properties of construction products could be accomplished with applying of life cycle assessment (LCA). The difference between ecological and non-ecological construction products could be based on the environmental parameters, such as Abiotic Depletion Potential, Ozone Depletion Potential, Acidification Potential, Global Warming Potential, Eutrophication Potential, and Photochemical Ozone Formation Potential [1], but also from the factors of eco-toxicity and human toxicity over their entire life cycle. All the categories are in good agreement with European standards. There are numerous tools and frameworks for evaluating sustainability of construction products for European users, which may

be used in such a decision-making process. Annex31 IEA [5], REGENER [6], PRESCO [7], ENSLIC Building [8], IMPRO-Building [9], eLCA [10], and LoRe-LCA [11] are among them. Together with European standards on construction products and works, such as EN 15804 [12] and EN 15978 [13], there are labelling and certification schemes on sustainable building, such as BREEAM (UK) [14], LEED (USA) [15], CASBEE (Japan) [16], Green Star (Australia) [17], from the world and European practices, and DGNB in Germany [18].

Fig. 1 shows the relation between the main frameworks, Environmental Product Declaration (EPD), LCA projects on sustainable building, and certification schemes. LCA serves as a basis for assessing a product and particularly EPD [19]. This helps forming a data base for building estimation while designing the labelling and certification schemes.

Fig. 1. European situation with respect to EPD and projects on LCA for the buildings [19].

The definitions of LCA basis given in standards and the ILCD Handbook [20] are not consistent and even conflicting to some extent. Hence, different approaches for calculation exist. The Construction Products Regulation (CPR 2011) provides additional Basic Work Requirements (BWR), i.e. the additional information added concerning the environmental issues, such as at BWR 3 - Hygiene and health, and BWR 7 - Sustainable use of natural resources [4]. European standards EN 15804 [12] and EN 15978 [13] have definitions for general framework as well as calculation methods for LCA ofbuilding and products. These are based on the international standards ISO 14040:2 0 0 6 [21] and ISO 14044:200 6 [22].

EeBguide is the Europen project for energy-efficient buildings [19], which covers the legislation issues for sustainable building as well as use of sustainable construction materials in Europe. According to the EeBguide, the European ECO EPD program as well as national EPD program might refer to EN 15804 [12], but have different sets of rules. The sustainable building council and labelling schemes contain different sets of calculation LCA rules, according to the labelling scheme. They might refer to the European standard EN 15978. In general, referring to the EeBguide, LCA calculation rules and guidelines in Europe are not in a harmony, which might be a barrier for the potential end user of a construction product in a process of estimation of its environmental parameters. Also, the connection between EPD data source and LCA projects on buildings and products seems to be less well arranged. Nevertheless, there is a project SBA Common Metrics aiming on development of the common rules [23]. These rules are primarily used by experts, such as architects and construction engineers, and are common in Europe as well as in Germany. The framework called eLCA is highly used in Germany [10]. It contains a great database of construction products. However, such LCA tools are quite comprehensive for the experts, which makes decision-making for construction products a very difficult task for a non-expert user.

2.2. Legislation for decorative paints

According to the European Directive 2004/42/EC [24], "VOC means any organic compound having an initial boiling point less than or equal to 250°C measured at a standard pressure of 101.3 kPa". In 2000 the VOC-emissions approximated to ca. 580 kt p.a. based on using decorative paints and varnished coatings in the EU-member states [24]. Furthermore, the European Directive 2004/42/EC of the European Parliament and of the European Council on the limitation of VOC due to the use of organic solvents in certain paint and varnishes, is aiming to improve the VOC Solvent Emissions Directive 1999/13/EC [25]. The main objectives of the Directive 2004/42/EC are monitoring, controlling and minimizing the negative effects caused by VOC exposed from paints and varnishes. The Directive is limiting the VOC content in certain products, focusing on decorative paints, varnishes, and vehicle re finishing products. Table 1 shows the maximum limit values for the VOC amount in the interior and exterior wall paints as well as for wood coatings. The type of coating varies from a water-borne to solvent-borne. The adjustment of a paint viscosity happens due to the use of water for a water-borne paint, and due to the use of organic solvent for a solventborne paint, respectively [25]. From the beginning of 2010 the limit values ofVOC have been reduced dramatically, especially for the matt coatings for interior walls.

Table 1. The VOC maximum limit values according to the Directive 2004/42/EC.

Subcategory of product Type of coating Phase I, g/l, ready to use, (01.01.2007) Phase II, g/l, ready to use, (01.01.2010)

1a Matt coatings for interior walls, gloss Water-borne 75 30

< 25@60° Solvent-borne 400 30

2a Interior/exterior trim and cladding Water-borne 150 130

paints for wood and metal Solvent-borne 400 300

3a Interior/exterior trim varnishes and Water-borne 150 130

woodstain, incl. opaque woodstains Solvent-borne 500 400

The implementation of the EU Solvent Directive 1999/13/EC in Germany was fulfilled by the means of the Ordinance for implementation of Directive 1999/13/EC aiming to reduce the amount of VOC emissions [26] from the use of organic solvents in specific installations, including industrial activities involving painting, varnishing, as well as paints, varnishes, adhesives and some more. It is available on the web-resource of the Federal Ministry for the Environment, Nature, Conservation, Building and Nuclear Safety [27].

Furthermore, some decorative paints and coatings could contain VOC, particularly formaldehyde. Formaldehyde can irritate eyes and the respiratory system in low air concentrations. It can cause nasal cancer and could even contribute to leukaemia. More symptoms can be caused at higher air exposures that cannot occur in the indoor environment. Formaldehyde has C1B class carcinogen in Europe. Moreover, the recent reports of the independent agencies claim that formaldehyde in the air concentration below 124 ^g/m3, which is equivalent to 0.1 ppm, cannot cause cancer [28]. According to the Euro-Class, the content of volatile aromatic substances shall not exceed 0.2% (m/m) ofthe product [29], and the proportion of preservatives in the total product must not exceed 0.1%.

Association of German Industry for Paints and Varnishes (in German: Verband der deutschen Lack- und Druckfarbenindustrie e.V.) published guidelines [29] for European regulations on hazardous compounds in paints and varnishes, implemented in Germany. These guidelines were developed by the technical working group (Technischer Arbeitskreis Bautenanstrichstoffe, or TBK) ofthe Association ofGerman Industry for Paints and Varnishes e.V. (VdL) for decorative paints and coatings. The guidelines serve the potential users to identify the ingredients of specific product groups of decorative paints and give an overview on terminology, definitions, and abbreviations. With this information, the user of decorative paints and coatings should have the opportunity to better assess the products used. It is available only in German language.

2.3. Literature review on decision-making for construction products

Material-selection tools for expert users, such as architects and construction engineers, are nowadays commonly applied worldwide. For instance, Ogunkah et al. (2012) presented a study with the AHP model of selection of local

and recycled building materials in the decision-making process [30]. The study is aiming to collect the information regarding the essential factors or variables that influence the experts decision-making for the construction materials . The authors designed a toolkit as a result of the expert poll, including accredited experts of LEED, CASBEE, and BREEAM. The AHP model for potential material-selection factors/variables for the building material performance/service-life is a result of the study.

Analogously, Wahlström et al. (2014) described the legislation criteria influencing the selection of construction products in Europe within the EU legislation framework in the final report for the project called "Sustainable construction products and materials for renovation" [31]. In this report, the harmonized standard methods for the indoor emissions measurements were applied in order to find a way to include the data from these tests into a broader assessment of environmental sustainability, in LCA and EPD.

The report contained an overview of current and future legislations that influences the construction products. In the project, the characterization factors for calculation of toxicity in LCA in European-member states were reviewed. Moreover, the project reveals the guidance on using release data in LCA. Wahlström et al. proposed approaches of including recycling in the EPD, as well as generic scenarios for granular materials in civil engineering works. However, the project can be primarily referred to the experts in construction works, mostly to the civil and construction engineers.

Similarly to Wahlström et al., Dirlich (2011) compared various sustainability assessment schemes for construction products in the world praxis as well as in Germany [32]. Dirlich made an overview of criteria for traditional building and use of traditional construction products in Germany. Moreover, an assessment of benefits and drawbacks of a traditional building for refurbishment works and new building was applied. The major focus was made on the refurbishment of a 360 years old house using traditional sustainable construction products.

The mentioned material selection tools and assessment schemes do not reflect the frameworks for selecting a building product oriented on a non-expert user, i.e. average consumer. Hence, selecting tools for the experts are complex enough, containing lots of detailed criteria, which could become complicated when an average consumer is taken into consideration.

3. Objectives

The research objective is developing a decision-making model which could characterise the behaviour of the potential users of sustainable construction products with regard to the sustainable decorative wall paints. In the research methodology, the life cycle assessment principles are not taken into consideration, since the possibility that non-expert users take them into consideration for their decision-making for construction products is very low. However, the issue emphasising to which extent LCA is involved in decision-making process will be embedded into the future research, a questionnaire survey. The research focuses on decorative wall paints and varnishes with respect to its properties regarding safety criteria for environment and human health. All the criteria that could be considered in the decision-making process of a consumer are rated in accordance with the importance priority. There is the assumption that environmental and health safety is at the highest priority for people, far above the price of a product. For that purpose, the alternatives that are less risky for the environment and human health as well as less costly, rather than alternatives rated with the best protection function and as the most durable, are chosen. As for the chosen alternatives, the decision-making model is focused on the decorative paints and varnishes, since this art ofconstruction products could be more likely used by an average consumer.

4. Research methodology

For developing a decision-making model, the Analytic Hierarchy/Network Process [2] was chosen as the best way to find the most appropriate alternative to the chosen criteria. This methodology helps determining the main criteria involved in the decision-making process. The AHP/ANP model explaining a user behaviour is developed in accordance with available literature and legislation documents with respect to the decorative paints and coatings in Germany. Three different alternatives for a paint product were chosen: Acrylic no-VOC paint which is safe for the allergic people. Another alternative is old-fashioned milk paint which does not contain any chemical compounds, it is classified to DIN EN 71-3 [33] and could be used for producing children toys and cooking surfaces. Similarly, Tung tree oil does not contain any solvents, making it completely biodegradable. Tung oil is also known as Danish oil, since

it evolves the traditional minimalistic Scandinavian style for interior works with a very low sheen, which was so popular in the second half of the twentieth century. Tung oil also meets the requirements of a DIN EN 71-3 [33] and could be used for the kitchen cabinet and cooking surfaces.

4.1. Analytic Hierarchy Process

Analytic Hierarchy Process [2] was created by the American mathematician Thomas L. Saaty in 1980s. It is based on the judgements made according to each criterion determining its importance, likelihood or preference. These criteria should be compared pairwise, scales could be derived form the paired comparisons in order to get a positive reciprocal matrix, which includes a set ofall judgements. The alternatives should be compared pairwise as well: As a result, a positive reciprocal matrix for the alternatives should be designed. All the judgements over the criteria and alternatives have to be consistent. This means that inconsistency index for the each of the reciprocal matrices should not exceed 0.1. The judgements are made in accordance with the fundamental scale of absolute numbers, suggest by Thomas L. Saaty. Intensity of importance is applied within the numbers from 1 to 9. The numbers have specific relation to the judgements: (1) equal importance, (2) weak or slight, (3) moderate importance, (4) moderate plus, (5) strong importance, (6) strong plus, (7) very strong or demonstrated importance, (8) very, very strong, (9) extreme [2].

4.2. Analytic Network Process

Analytic Network Process [34] is used for decision-making with dependence of all of the criteria and subcriteria and feedback within clusters and between them. This decision-making tool was designed by Thomas L. Saaty in 1990s and is a generalisation of the Analytic Hierarchy Process. ANP is approaching four merits: (i) Benefits, (ii) Opportunities, (iii) Costs, and (iv) Risks. The process was implemented in the Super Decisions Software, which is not complicated to use. It is possible to design a Benefits (B) model, an Opportunities (O) model, a Costs (C) model, a Risks (R) model, as well as a combined (BOCR) model in this software in accordance with the principle of a network with the inner and outer dependence between all the clusters: goal, criteria, alternatives [34]. (i) The Benefits cluster includes alternatives, that would be the most beneficial for the decision-making. (ii) The Opportunities cluster is also beneficial and has the alternatives with the greatest potential. Both clusters have positive value as applied in the resulting formula. (iii) The Costs cluster determines the costliest alternative, meaning not only the market price of a product or service. This cluster has a negative value for the result formula as well as a (iv) the Risks cluster, which reveals the alternative with the highest potential risk.

5. Data analysis

In the herein presented research, a combined BOCR model is applied.

Fig. 2. Network ofthe combined BOCR model with weighting values.

All the four criteria clusters are in the hierarchical relation with the main goal and the alternatives. The model was designed with the help of the Super Decisions Software. Fig. 2 shows the network of the combined BOCR model for the decorative paints and coatings available on the construction market in Germany. It consists of Goal as a major cluster. This cluster has a direct connection to the lower hierarchical level, criteria. There are four general criteria: (i) Benefits, (ii) Opportunities, (iii) Costs, and (iv) Risks. Then, each of the criterion has its subcriteria, aligned according to the characteristics and purpose of the research methodology. The Alternatives cluster has the lowest position in the hierarchy. After all the pairwise comparisons were made, each criterion has its value, that could be seen on Fig. 2. The values are taken from the Limit matrices, which contain the final priorities. This means that Limit matrix is the final supermatrix with the final answers. These values serve the input data for the result calculations in the supermatrices using additional and multiplicative formulas.

5.1. Goal

The Goal cluster has the highest position in the hierarchy, it defines the purpose of the designed model. It is the main cluster for the whole model that aims at choosing the best decorative wall coating with respect to its environmental and human health criteria, which are high above its market price and protection properties.

5.2. Criteria

There are four criteria which are related to the goal cluster: (i) Benefits, (ii) Opportunities, (iii) Costs, and (iv) Risks. Each control criterion helps to create a network of influences in order to ascertain the priorities for each of the alternatives, which are sufficient to make a decision. Each criterion includes several subcriteria, which allows to get the more detailed and precise model structure.

5.3. Subcriteria

According to the quality characteristics of a decorative paint or coating, the most important are its protection functions, durability, aesthetics, and easy application. All these characteristics belong to the (i) Benefits cluster and serve as subcriteria for the whole network.

Similarly, (ii) Opportunities cluster includes future benefits of using a decorative paint or coating, such as ease of its reapplication, low repair bills, and its long durability of using a paint over its life-span. These subcriteria have a positive value.

At the same time, there are two other criteria with the negative value. First one, (iii) Costs, includes initial cost, repair cost, and a reliability cost. Initial cost is a purchase price of a wall paint, while repair cost is a price of repurchasing a paint. And last but not least, reliability cost, involves an estimated complexity due to paint fading or cracking and necessity of its reapplication. The less costly alternative should result out of the cluster supermatrix.

The second criterion with a negative value is (iv) Risks. It includes likelihood of environmental harm while maintaining a wall paint or coating, such as air pollution, and damage of water or soil if it gets into the sewage. Next to it, there are likelihood of human health damaging and durability failure. Hence, (iv) the Risks criterion is the most important for the objective of the herein research - of choosing the best alternative of a decorative paint or coating prior to its environmental and human health safety. Therefor, the less risky alternative should be found.

5.4. Alternatives

There are three alternatives for a decorative coating for the indoor application. These is an acrylic paint which does not contain VOC, such as formaldehydes, a milk paint, and a Tung oil. All the necessary information is used in accordance with the Material and Safety Data Sheets (MSDS) to such products, paying attention to the sections 2 (ingredients), 3 (health hazards), 5 (fire and explosion data), and 11 (toxicological properties).

5.4.1. Acrylic no-VOC

Acrylic paint free of VOC, such as formaldehydes, serves as the first alternative in the BOCR model. An example of such paint could be Alpina Naturaweiss, which is safe for people with asthma and other types of respiration diseases. According to its MSDS, it is a dispersion-based interior paint free from preservatives, solvents, softener, and harmful emissions [35]. VOC concentration is 0%, which is less than 1 g/l here, responds the Directive 2004/42/EC [24]. The paint is produced in accordance with the DIN EN 71-3 and could be used for children toys [34]. Moreover, the paint is pollutant and allergy-controlled and works well for living and working environments. So, it is low-toxic (less than 2,000 mg/kg) and non-combustible. Furthermore, the paint is not fully biodegradable, but it can be recycled. It has low sheen, which means it could be easily reapplied. Only one coat is enough for a proper protection. In Germany, its average market price lies at 1.33 €/m2. Such paint is widely represented on the market all over Germany.

5.4.2. Milk paint

Milk paint is all-natural and consists ofmilk protein (casein) and Calcium Hydroxide (lime) in a granular powder. It could also contain natural pigments and salts. Milk paint is free of solvents, VOC or any hazardous compounds. The paint is easy in its application and does not crack, a slight fading could appear over time [36]. It is absolutely matt, which makes its repair easy. It is non-toxic, does not cause irritation. This kind of paint is fully biodegradable and non-combustible. One coat for application of milk paint is not enough, it requires at least two coats of paint. Milk paint is very pricey. The average market price is 4 €/m2. However, it would be difficult to buy milk paint on the local market for construction products, but much easier to purchase it online. Examples of products ofa kind ofmilk paint could be Old Fashioned Milk Paint and Mustard Seed Milk Paint. There are three retailers whose sell Mustard Seed Milk Paint in stores.

5.4.3. Tung oil

Tung oil is a decorative and protection coating used primarily for wooden surfaces. Tung oil is produced from a vegetable oil ofa Tung tree. It contains a thinner, but no solvent, such as white spirit. Tung oil is produced with respect to DIN EN 71-3 [34]. It is safe for toys and kitchen surfaces. Dry product contains pure Tung oil and no artificial varnish or resins. Tung oil is completely biodegradable and non-hazardous to marine life [37]. For example, Bestwood Danish Oil contains de-aromatized white spirit, which is less irritating when dry as a traditional solvent [38]. However, it is combustible when liquid. The finish is low sheen, which makes its repair easier. Tung oil is formulated to penetrate deep into the timber. It has protecting and nourishing functions and is dirt resistant. However, 3 to 5 coats are essential Its average market price is 0.87 €/m2, which is less in comparison with other alternatives. Nevertheless, as its direct drawback, Tung oil could be hardly ever found in stores for construction products. It could be rather purchased online.

6. Development of the BOCR model

After all the judgements and comparisons of the criteria as well as of the alternatives were made, weighted, unweighted, and limit supermatrices [34] for each of the criterion were calculated. Synthesizing the results gives priority vectors to all the alternatives. Then, the sensitivity analysis which gives a visual overview of the priorities for each of the alternatives is also possible. Inconsistency indices for each pairwise comparison did not exceed 0.06948, which is well below the recommended critical value of 0.1 [34]. Inconsistency targets at measuring the inconsistency of the judgements made.

6.1. Supermatrix and calculating results

Overall synthesized priorities for all the alternatives are shown in the Table 2. Results are combined in the toplevel network in two ways: First, results were calculated with the multiplicative formula. Second, results were calculated with the additive negative formula. Multiplicative formula is the original formula for (bB*oO)/(cC*rR).

Small letters in the formula mean eigenvectors, while capital letters mean eigenvalues in each of the supermatrices for each cluster respectively.

The alternative values from the subcriteria of (i) Benefits and (ii) Opportunities were multiplied. The result was divided by the alternative values of the subcriteria of (iii) Costs and (iv) Risks, as shown in formula (1). This formula is of a marginal utility type and gives a result for a short term.

$SmartAlt(Benefits)* [invert $SmartAlt(Costs)]*$SmartAlt(Opportunities)*[invert $SmartAlt(Risks)] (1)

Table 2. Overall synthesized priorities for all the alternatives combined in the top-level network in two ways.

Benefits Opportunities Costs Risks (bB*oO)/(cC*rR) multiplicative formula bB+oO-cC-rR additive neg. formula

Acrylic no-VOC paint 0.200 0.105 0.100 0.277 0.506 0.408

Milk paint 0.133 0.144 0.316 0.081 0.029 0.138

Tung oil 0.167 0.252 0.083 0.142 0.464 0.454

According to the multiplicative formula, the best alternative for the stated objective is acrylic paint free of VOC with the highest value of 0.506.

As for the additive negative formula, where un-inverted alternative values from the subcriteria of (i) Benefits and (ii) Opportunities were added to the inverted alternative values from the subcriteria of (iii) Costs and (iv) Risks, as shown in formula (2):

$NormalNet(Benefits)*$SmartAlt(Benefits)+$NormalNet(Costs)*$SmartInvAlt(Costs)+ +$NormalNet(Opportunities)*$SmartAlt(Opportunities)+$NormalNet(Risks)*$SmartInvAlt(Risks) (2)

Additive negative formula gives a result for a long term. The best alternative for the whole model using additive negative formula is Tung oil with the highest value of 0.454.

7. Conclusion

The AHP/ANP model was designed under the assumption that a user would rather prefer a wall paint giving the priority to safety and quality over its price. Moreover, judgements were obtained from the secondary literature sources, such as MSDS. Having an opportunity to start it over, quality and price could be prioritized higher than product safety, since all of the given alternatives respond the requirements of a sustainable product. The outcome of the AHP/ANP model is based on the hypothesis that environmental and health safety scores high above product prices. Hence, adding outcomes from a survey about the actual assessment of these characteristics by non-experts, i.e. average consumers, would lead to a better understanding of the decision-making process. Results involving kinds of paints used in the herein research, such as milk paint and Tung oil, could differ from the real world, since milk paints as well as Tung oil are not presented widely on the German market. However, these products were taken into consideration equally, independent of their availability on the market.

The outcome ofthe presented research is overview ofthe LCA tools, which can be used in decision-making process for expert users of construction products. However, such tools are comprehensive for a non-expert user, i.e. average consumer. There is a lack of information about ignorance of LCA frameworks by non-expert users, as well as how knowledge of LCA could influence their decision-making. Therefor, this research question will be involved in the questionnaire survey for average consumers on the construction market in Germany.

Designing an AHP/ANP model with a high priority of the sustainability characteristics of construction products, in particular wall paints, leads to a meaningful comparison of alternative products. The AHP/ANP model will be extended by real world assessments ofthese priorities by average consumers as non-experts. In the further research,

this model is expected to be applied within the framework of a study for a German construction market: A survey, for which a questionnaire will be developed and validated through the communication with users ofconstruction products. The main objective of the study is to determine to which priority average consumers take environmental and human health safety in the decision-making involving decorative paints and varnishes. Results of this study are supposed to be analysed with the AHP/ANP methodology. Results involving kinds of paints used in the herein research, such as milk paint and Tung oil, could differ from the suggested BOCR model, since milk paints as well as Tung oil are not presented widely on the German market. However, such a drawback could not be applied to the acrylic paints free of VOC.

Acknowledgements

This research is supported by the Ministry of Science and Art of Free State of Saxony, Germany (in German: Sächsisches Ministerium für Wissenschaft und Kunst - SMWK).

References

[1] Environmental Product Declarataion. ISO 14025: Environmental labels and declarations - Type III environmental declarations - Principles and procedures. ISO - International Organization for Standardization. Geneva: ISO 2006.

[2] Saaty TL. Decision making with the analytic hierarchy process. Pittsburg: Int. J. Services Sciences, Vol. 1, No. 1; 2008. p. 83-98

[3] Construction Product Directive 89/106/EEC of 21 December 1988 on the approximation of laws, regulations and administrative provisions of the Member States relating to construction products. Official Journal L 040; 1989. p. 12-26.

[4] European Union: Regulation (EU) No 305/2011 of the European Parliament and the Council of 9 March 2011 laying down harmonised conditions for the marketing of building products and repealing Council Directive 89/106/EEC. (CPR) (Official Journal of the European Union) Brussels: 2011.

[5] Annex31: http://www.iisbe.or g/annex31/index.html

[6] Life Cycle Analysis of Buildings: The European Project REGENER: http://www-cep.ensmp.fr/

[7] PRESCO: http://www.etn- presco.net/

[8] ENSLIG Building: Energy conservation by promoting the assessment ofthe life cycle of buildings. Bulgaria: http://circe.cps.unizar.es/enslic/index.htm

[9] IMPRO-Building: Environmental Improvement Potentials ofResidential Buildings; http://circe.cps.unizar.es/enslic/index.html

[10] Okobau.dat (Germany) http://www.nachhaltigesbauen.de/baustoff-und- gebaeudedaten/oekobaudat.html

[11] LoRe-LCA: Low Resource consumption buildings and constructions by use of LCA in design and decision-making, European project (FP7), 2011, deliverables available online: http://www.sintef.no/ Projectweb/LoRe-LCA/Training/

[12] EN 15804: Sustainability ofconstruction works - Environmental product declarations - Core rules for the product category ofbuilding products. CEN - European Committee for Standardization. Brussels: CEN - CENELEC 2011.

[13] EN 15978: Sustainability ofconstruction works - Sustainability assessment of buildings - calculation method. CEN - European Committee for Standardization. Brussels: CEN - CENELEC 2010.

[14] BREEAM (British system for the labelling ofbuildings): http://www.breeam.org/

[15] LEED (USsystem for the labelling of buildings): http://www.leed.net

[16] CASBEE (Japanese system for the labelling ofbuildings): http://www.ibec.or.jp/CASBEE/english/

[17] Green Star (Australian system for the labelling of buildings): https://www.gbca.org.au/green-star/

[18] DGNB (German system for the labelling of buildings): http ://www.dgnb.de/dgnb-ev/de/

[19] Wittstock B, Gantner J, Lenz K, Saunders T, Anderson, Carter C, Gyetvai Z, Kreißig J, Braune A, Lasvaux S, Bosdevigie B, Bazz ana M, Schiopu N, Jayr E, Nibe S, Chevalie J, Hans J, Fullana-i-Palmer P , Gazulla C, Mundy M, Barrow-Williams T, Sjöström C. EeBguide Guidance Document Part A: Products - Operational guidance for Life Cycle Assessment studies of the Energy Efficient Buildings Initiative. Stuttgart: Fraunhofer Institute for Building Physics; EeB.ENV. 3.1.5-2; 2011. p. 1-297.

[20] European Commission - Joint Research Centre - Institute for Environment and Sustainability (Ed.): ILCD Handbook. General guide for life cycle assessment: detailed guidance. First edition. Luxembourg: Publications Office of the European Union 2010. ISBN: 978-92-7919092-6.

[21] ISO 14044: Environmental management - Life cycle assessment - Requirements and guidelines. ISO - International Organization for Standardization. Geneva: ISO 2006.

[22] ISO 14040: Environmental management - Life cycle assessment - Principles and framework. ISO - International Organization for Standardization. Geneva: ISO 2006.

[23] SBA Common Metrics: http://www.sballiance.org/our-work/news/piloting-sba-common-metrics/

[24] Directive 2004/42/CE of the European Parliament and of the Councilof 21 April 2004 on the limitation of emissions of volatile organic compounds due to the use of organic solvents in certain paints and varnishes and vehicle refinishing products and amending Directive 1999/13/EC. Official Journal L 143; 2004. p. 87-96.

[25] Council Directive 1999/13/EC of 11 March 1999 on the limitation of emissions of volatile organic compounds due to the use of organic

solvents in certain activities and installations. Official Journal L 85; 1999. p. 1-22.

[26] Verordnung zur Umsetzung der Richtlinie 1999/13/EGüber die Begrenzung von Emissionen flüchtiger organischer Verbindungen, BGBl. I, No. 44. p. 2180.

[27] Federal Ministry for the Environment, Nature, Conservation, Building and Nuclear Safety on Germany; http://www.bmu.de

[28] DIN EN 13300: Paint and varnishes. Water-borne coating materials and coating systems for interior walls and ceilings. Classification; German version EN 13300:2002

[29] VdL-RL 01 (4. Revision) - Richtlinie zur Deklaration von Inhaltstoffen in Bautenlacken, Bautenfarben und verwandten Produkten. Frankfurt am Main: Verband der deutschen Lack- und Druckfarbenindustrie e.V. 2013. p. 1 -12

[30] Ogunkah I, Yang J. Investigating factors affecting material selection: The impacts on green vernacular building materials in the design-decision making process. Buildings 2012; 2. p. 1 -32.

[31] Wahlström M, Laine-Zlijoki J, Järnström H, Kaartinen T, Erlandsson M, Cousins AP, Wik O, Suer P, Oberender A, Hjelmar O, Birgisdottir H, Butera S, Astrup TF, J0rgensen A. Environmentally sustainable construction products and materials - assessment ofrelease and emissions. Nordic Innovation Publication 2014; 3. p. 171.

[32] Dirlich, S. Integration der Bestandsqualität in die Zertifizierung von Gebäuden. Dresden: IÖR Schriften Band 55; 2012. p. 1-220.

[33] DIN EN 71-3: Safety of toys - Part 3: Migration of certain elements; German version EN 71-3:2013.

[34] Saaty TL. Relative measurement and ist generalization in decision-making - Why pairwise comparisons are central in mathematics for the measurement of intangible factor - The Analytic Hierarchy/Network Process. Vol. 102 (2). Spain: RACSAM; 2008. p.251-318.

[35] Sicherheitsdatenblatt - Material Safety Data Sheet. Alpina Naturaweiss; 2015. p. 1 -12.

[36] Material Safety Data Sheet. Old Fashioned Milk Paint. 2008. p. 1-4.

[37] Material Safety Data Sheet. Bestwood Pure Tung Oil; 2012. p.1 -3.

[38] Material Safety Data Sheet. Bestwood Danish Oil; 2012. p.1-5.