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Multi-attribute analysis for the eco-energetic assessment of the building life cycle/ Pastato gyvavimo ciklo daugiakriterine analize ekoenergetiniu poziuriu.

1. Introduction

A great number of factors can be used to valuate a building. Factors' selection depends on a purpose of this assessment (e.g. Norris and Marshall 1995). It can be: select the best building component, select the best residence, or select the best building location and others (Fig. 1).

These selections are based on the analysis of many attributes and their hierarchy. This paper aims to make an eco-energetic estimation of a building that is characterized by groups of the factors presented on Fig. 1. Firstly, environmental impacts will be defined and analyzed. The estimation regards materials and building installations. The choice of appropriate materials is very important, because production of building materials, construction of building structures and their further use constitutes, in general terms, a source of detrimental effects on the environment. The eco-energetic assessment requires taking into consideration a building life-cycle. The knowledge on the ecological assessment of a building life cycle should be utilised while making a decision on the selection of types of materials available, production technologies, selection of material, structural and utilisation solutions in buildings by the designer and, most importantly, by the investor. Such choices, regarding the designer and investor, are obviously influenced by regulations, standards, competition etc., whereas the investor-user relationship is affected by the social awareness of the necessity to observe the rules of sustainable development, project economics spread all over the building life cycle, and regulations being introduced, related, for example, to energy certification of buildings. There is, hence, a demand for a simple tool to design and decide the solutions for buildings to meet the relevant requirements.

The detrimental environmental impacts can be assessed and determined with a variety of methods. One of them being LCA--Life Cycle Assessment. This method allows harmful environmental factors to be identified together with the points of strongest effect on the environment throughout the entire life cycle, and to compare alternative products and production technologies.

One of the issues of the strategy of sustainable development, also as regards the building sector, is to minimise energy consumption during the production of building materials, erection of buildings and during their life cycle. According to the analysis of harmful environmental factors present during the production and use of the products (e.g. buildings), the majority of them are the derivatives of energy acquired from combustion of fossil fuels (greenhouse effect, acidification, toxicity etc.). Although this is the greenhouse effect that prevails during the building utilisation stage, the other factors, identified as the environmental impact categories, prevail during the production stage (toxicity).

[FIGURE 1 OMITTED]

The concept of supporting the decision-making during the design stage, and while deciding an optimum solution, as presented in this paper, is based on the LCA method and on the multi-criteria optimisation based on the Baas-Kwakernaak method (Bass and Kwakernaak 1977). As an example, it has been utilised to evaluate material solutions of a single-family house. Single-family buildings have a considerable share in the general building production and are of critical influence on the degradation of environment. More than 40% of Polish citizens live in single-family houses, and use fossil fuels for heating (coal, gas). In the multicriteria analysis, the environmental impact categories have been adopted as the optimisation criteria, related to the consumption of energy generated by combusting fossil fuels.

2. Subject of studies in view of literature

In the view of the literature two problems are considered: the application of multi-attribute analysis for investigations and valuation of building questions and a problem of eco-energetic valuation of buildings--how do they influence environment in dependence on the implemented constructional solutions.

For instance, multi-attribute decision analysis methods (MADA) for evaluating buildings and building systems are presented in a voluminous publication (Norris and Marshal 1995). This report reviews 14 classes of methods for performing MADA. It summarizes their usefulness for screening, ranking, and choosing among projects; their data input requirements; and how each method scores project alternatives. Two methods: the analytical hierarchy process (AHP) and non-traditional capital investment criteria (NCIC) are described in detail. Assumptions, procedures, strengths, and limitations are described for each. Detailed descriptions of some typical building-related decisions--choosing among office buildings, residences, building components, and building materials-provide additional examples of possible MADA applications. A list of 15 building-related attributes with complete definitions helps decision makers customize a MADA model for making a building choice. Although the report focuses on buildings, MADA methods apply equally to the evaluation of non-building capital budgeting decisions.

The multi-attribute analysis in building is useful for investigation and solving different types of questions--more or less particular. It is being employed for examination and decision-making in building construction projects (Zavadskas et al. 2007; Zavadskas et al. 2008; Ginevicius et al. 2008), building objects' localization (Zagorskas and Turskis 2006), as well as for building implementation management. Many works present an application of the multi-attribute analysis for investment risk estimation in construction (e.g. Shevchenko et al. 2008), estimation and choice contractors (Turskis 2008; Turskis et al. 2009; Zavadskas and Vilutiene 2006; Jaselskis and Russell 1992; Zavadskas et al. 2008).

In multi-attribute analysis different computational methods are used and developed, starting with these generally known, as ELECTRE, AHP (Saaty 1988), up to the newest--Clara and Saw (Shevchenko et al. 2008), and many others (Bass and Kwakernaak 1977; Trzaskalik 2008).

In this paper the problem of influence of a building object for environment is analyzed with the multi-attribute analysis. This influence means emitting a lot of toxic compounds arising during building materials production, and especially caused by heating. Related to this problem is defining and rating criteria for ecologic and energetic evaluation of the building. There is an extensive literature concerning different aspects of "building objectversus-environment" relation.

We can mark out some groups of examined problems:

--Examination and analysis of environment's encumbrance caused by raw and building materials in life-cycle (Gorzynski and Piasecki 2002; ISO 14040^42; European Environment Agency 1997).

--Rankings of materials, considering environment's encumbrance (The Handbook ... 1996).

--Studies on selected elements, structures and buildings, according to toxic compounds emitting (Seo and Hwang 2001; Piasecki 2003; Stachniewicz 2006; Giergiczny 2008; Stephan and Wilhelm 2006; Odeen et al. 1996).

--Projecting of energy-saving and passive buildings to minimize fossil-fuel energy consuming, during exploring them as a warmth providers (Brandt 2005; Sarosiek and Sadowska 2006; Stachniewicz 2006; Szczechowiak 2008).

--An energetic validation of buildings (EPBD 2003).

The studies indicate that, bearing in mind the building life cycle, the greatest environmental impact in most categories is present during the period of building use, due to the need for heating in winter in our climate and in most EU countries. Therefore, the development of energy-saving and environment-friendly building technologies is supported by the EU directives and relevant regulations, e.g. CPD--Council Directive 89/106/EEC (CDP 1989) and EPBD--Parliament and Council Directive 2002/91/EC (EPBD 2003), on the energy performance of buildings.

The CPD Directive is the basic document relating to the construction products and building industry in the European Union. It introduces, among others, the assessment of suitability of construction products for the intended use. The Directive sets out the requirements regarding the materials and products used in terms of: (1) load-carrying capacity and stability, (2) fire safety, (3) health and hygiene, (4) safety of use, (5) noise protection, (6) energy saving and thermal protection in properly designed and constructed buildings (additional new requirement relating to environmental protection according to the sustainable development principle).

The EPBD Directive introduces the requirement of an obligatory energy-certification of buildings, which should be designed and constructed in such a manner that the energy required for their use is kept at a low level, taking into consideration the local climatic conditions and needs of the residents. The energy-quality of a building should also include the quality of the internal environment and economic efficiency. Provisions of the Directive are supposed to come into force in the EU states in 2009 the latest. The mentioned directives support the development of low-energy and passive buildings and as a consequence lead to significant decrease of environmental degradation by building production and usage.

3. Research methodology

With a variety of producers of building materials, indoor system solution (heating, water heating, ventilation heat recovery system), building erection technologies, it is possible to design and construct different variants of buildings. They are of varied impact on the environment along their entire life cycle, and the relevant knowledge should be used on the design stage, while making decision on the choice of a given material and construction solution for the building. The building design is expected to meet the requirements related to the environmental protection and of both, the investor and user. Fig. 2 presents the concept of the IT system supporting designing of buildings of various material, construction and indoor systems solutions, their valuation from the point of view of the environmental impact categories, namely the emission of pollution, and finding with the multi-criteria analyses an optimum solution meeting the minimisation criteria adopted. The decision as to the choice of a given variant analysed throughout the entire life cycle should also take into consideration the advance in technology and its scenarios during prolonged use of the building.

The proposed method is, therefore, based on the determination of ecological and energetic characteristics of a structure of improved inherent energy economy and energy delivered. In this method for designing buildings, taking into consideration their influence on the environment, the decision is made after the completion of three stages of the research and design work:

--Determining the environmental impact of the building with the LCA method.

--Select and choice attributes to multi-criteria analysis.

--Drawing up an optimisation balance

--Choice variant and possibly re-designing the chosen variant into a building of low energy demand (green house).

Stage 1 involves designing the version of a building, so-called "basic", and other versions using database on materials and their influence on the environment. Proposed variants with selected plumbing and heating systems are subjected to assessment with the determined/calculated vectors of environmental impact, according to the LCA method.

The LCA method is described in the ISO 14040/42 standards. The method defines and evaluates a set of inputs and outputs of the product system, and its influence on the environment throughout the entire life cycle. The streams of inputs and outputs, and their material and energy balance, determine arduousness of the product to the environment. The LCA analysis involves a selection of the "environmental impact categories" which determine the influence of substances polluting the environment. The obtained data on the emission, consumption of resources and others, are grouped according to their categories, and then subjected to aggregation for easier interpretation of the results. The result of the study is an environmental characteristics of the product in a form of a multi-dimensional vector of environmental impacts [OMEGA]. The method for calculation the [OMEGA] vector is described in ISO 14040.

[FIGURE 2 OMITTED]

An equivalent emission of pollution in a given category can be expressed with the general formula (Gorzynski and Piasecki 2002):

[OMEGA].sub.x] = [SIGMA].sup.n.sub.j=1] [b.sub.j][m.sub.j], (1)

where: [b.sub.j]--an equivalent environmental impact for an [i.sup.th] reference substance, [m.sub.j]--mass of the [i.sup.th] substance released to the environment in the discussed group of pollutants kg subst./kg, n--number of substances in a given impact category included in the analysis, x--denotes given criterion.

To each material contained in the product, a set of equivalent cumulated environmental impacts [[OMEGA].sub.i] can be assigned, including impacts in individual categories in a form of a k-dimensional vector:

[[OMEGA].sup.T.sub.i] = [[OMEGA].sub.e], [[OMEGA].sub.z], [[OMEGA].sub.w], [[OMEGA].sub.b], [[OMEGA].sub.c], [[OMEGA].sub.a], [[OMEGA].sub.f], [[OMEGA].sub.eu], [[OMEGA].sub.l], [[OMEGA].sub.htp], [[OMEGA].sub.htw], [[OMEGA].sub.s], [[OMEGA].sub.t]], (2)

where: e--cumulated consumption of primary energy, z--cumulated consumption of nonenergy resources, w--cumulated water consumption, b--index of cumulated emission of greenhouse gases, c--index of cumulated emission influencing the atmospheric ozone, a--index of cumulated acidifying emission, f--index of cumulated emission triggering photochemical oxidisation, eu--index of cumulated emission of eutrophic action, i--eco-toxicity, htp, htw--indexes of cumulated toxic emission in ambient air and in water surrounding, s--generation of solid waste, t--transport.

Each environmental impact category is described by a set of equivalent emissions of substances causing a given environmental effect. One type of pollutant can influence several impact categories with various equivalents. Most units used in the environmental criteria are of equivalent character, for example:

--Greenhouse effect [kg C[O.sub.2] eq./100 l] refers to the emission, in a 100-year period, of carbon dioxide and other substances affecting the greenhouse effect, "transformed" into C[O.sub.2]. These are the methane, nitrogen suboxide, sulphur hexafluoride and others;

--reduction of the ozone layer [kg CFC11eq.] caused by substances acting on the atmospheric ozone;

--acidification [kg S[O.sub.2] eq.] with sulphur dioxide and nitrogen oxides, ammonia and other acidifying substances;

--toxicity to human--air [kg tox.] refers to the emission of kgs of toxic substances: acetone, acetylene, aromatic hydrocarbons, carbon benzenoxide, dioxins, ethane, heavy metals, nitrogen oxides, sulphur dioxide, xylenes and a number of other toxic substances in ambient air;

--toxicity to human--water [kg tox.] refers to the emission of kgs of toxic substances in water: aliphatic and aromatic hydrocarbons, heavy metals, pesticides and others;

--photochemical smog [kg ethene eq.] caused by ehtene, acetone, acetylene, butanols, benzene, ethane, formaldehyde, glycols, propane, toluene, xylenes and many other compounds resulting in photochemical oxidisation per one kg ethane;

--eco-toxicity [[m.sup.3]] refers to air pollution by 1 mg of toxic substances such as: heavy metals, dioxins, pesticides, others;

--eutrophisation [kg P[O.sub.4] eq.] caused by phosphate and nitrogen suboxide, ammonia, nitrates and orthophosphates ions etc. released to water, expressed in kg P[O.sub.4].

Impact vectors for building materials which are analysed in this paper, based on the data obtained from the Building Research Institute, professional literature and building materials producers. Bearing in mind the data, regarding the emission of individual materials and products for a specific building design, it should be transformed into a unit of a component, in relation to the entire life cycle (production, construction, use and disposal).

The LCA method does not assume further aggregation of individual environmental impact categories for a given product, yet attempts are also made to prioritise individual criteria, in order to find the best (optimum) solution. The necessity of such actions results from the difficulties in interpretation of data obtained from the LCA analysis. It is, therefore, necessary to carry out a multi-criteria comparison analysis, in order to choose the proper solution. Such analysis, along with the selection of poly-optimisation criteria, is the second and thirty stage of the studies involved in the concept of design support. The task involves poly-optimisation activity, the criteria of which are the chosen environmental impact factors (categories). Presenting the results in a single number, expressing the environmental impact according to the criteria adopted allows solution variants to the compared according to such criteria and to find a compromise between them. In the proposed system for the selection of an optimum solution, various poly-optimisation methods can be adopted, e.g. the traditional ones: Weighted Objectives Method, Utility Function Method, or the modern ones using evolutionary algorithms (Jaskowski and Sobotka 2004). In the example discussed, the Baas and Kwakernaak (Nikiel 2004) method using fuzzy assessment has been utilised due to the fact that some of the assessments in the model have the properties of fuzzy values (example of mass--see 4.2).

4. Application example

4.1. Calculating the environmental impact vectors

The proposed methodology for designing and selection of the material and construction variant of the building is presented based on an example of a design of a single-family house and selection of an optimum solution from the point of view of minimisation of the environmental pollution throughout the entire life cycle.

This section covers the results of studies of a building designed in four material and structural variants (Table 1). The data collected and calculations performed allow creating considerably a greater number of variants, yet the studies were limited to typical solutions. The basis for the elaboration of the variants, is the design of a one-storey, single-family house with partial basement, of gross covered area 195.0 [m.sup.2], heated area of 200 [m.sup.2], heated cubage of 568 [m.sup.3], A/V index = 0.35 kW * h/[m.sup.3] year, and the seasonal heat demand 53.1 kW * h/[m.sup.3] year (150.9 kW * h/[m.sup.2] year), here referred to as the basic variant. The building has an unheated, glazed veranda on the north side, serving as an entrance enclosure, and a timber terrace and cellar on the southern side. The heat transfer coefficient for the walls of the building in the basic variant (and others) is 0.29 W/([m.sup.2] K). In all building versions tested, an identical heating system has been adopted.

The assessment involves the comparison of the environmental impacts of the individual components and of the building as a whole. The following parts were assessed: external walls, ceiling above the ground floor, roof covering, windows. Other components were categorised in individual material groups and calculated in relation to the entire building.

The environmental impacts were studied in the following sequence:

--collecting data on the environmental impact vectors [OMEGA] regarding the unit quantities of individual materials built-in the structure;

--calculating values of the environmental impact vectors in individual and in the entire life cycle of the building per 1 [m.sup.2] of a wall (see Table 2), floor, roof and window (see Table 3);

--calculating the environmental impact vectors for the life cycle of the building (see Table 4);

--analysing the results and conclusions (assessment of building variants).

The analysis involves the following stages of the building life cycle: 1--building, comprising stages: acquisition of raw materials, production of products, leaving the factory, transport from the factory to the building site, construction of the building, 2--use of the building (component), 3--demolition. The basic assumptions of the calculations:

--averaged industrial data on the emission and other environmental impacts were adopted;

--according to the LCA methodology, in the analysis from material acquisition to the completion of construction, the influence of partition components below 2% of its mass was omitted (paint, nails etc.);

--masses of components were assumed based on the producers' data or the PN-82/B 02001 standard;

--the building is located in the 3rd climatic zone (Krakow, latitude 50[degrees]);

--the transport work, including delivery of the material from manufacturers to the construction site, were adopted pro rata to the partition mass (around 2 tons/km in case of wall partitions (Piasecki 2003);

--during the construction phase the following was assumed: a concrete mixer capacity 250 l to prepare masonry and plaster mortars, motor power rating 1.1 kW; a hoist lifting capacity 0.5 t for vertical transport; (1.1 kW); delivery of material to the site--close to the place of use;

--the work of people is considered as environment-friendly (no harm to the environment);

--while analysing the utilisation phase of the building, the emission from a dual-function gas boiler (heating and tap water) was assumed: energy loss for heating, based on the seasonal heat demand, and for heating tap water of 5387.04 kWh (19393.344 MJ) was calculated with KOLEKTOREK software, electric energy consumption 6000 kWh per annum. The energy loss for heating was established based on the calculations of seasonal demand for heat with a detailed method (PN-B-02025--Calculating seasonal heat demand for heating residential buildings);

--in the wall operation phase, for the entire life cycle, the heat loss resulting from the penetration of heat flux through a partition was considered, taking into consideration the efficiency of the gas boiler;

--the following repair works were included in the 60-year operation period assumed for the house: replacement of the insulation courses in case of double-leaf walls--once, facade painting--6 times; painting walls and ceilings--12 times, exchange of the external sheathing and thermal insulation in the wall partition of the timber structure--once, replacement of window joinery--twice; environmental impact related to the transport of the waste to the waste dump is already covered;

--during the demolition phase, the environmental impact of transport of 20 tons is included, as required to transport the waste to the waste dump, similarly to the transport of building materials from the factory to the construction site.

In the studies carried out, impact categories were covered mostly based on the assessment of the product life cycle (Gorzynski 2002; Gorzynski and Piasecki 2002; Piasecki 2003). There are 14 such categories including the cost. Tables 2 and 3 present the calculated values of the environmental impact vectors in the whole life cycle of the variants of individual components of the building, and Table 4 gives the values for the entire building. The results presented in Table 5 illustrate the per cent share of the environmental impacts in individual phases of the life cycle of the basic variant.

Based on the analysis of the results obtained, the following conclusions can be drawn:

--the cellular concrete partition, in the basic version, has the best eco-properties regarding environment acidification, toxicity of airborne substances to human, eco-toxicity, eutrophisation and water consumption, and good properties as regards: smog, utilisation of primary energy, consumption of materials, wastes and transport;

--the utilisation of ceramic material in the walls results in the worst influence on the environment, as compared to other material solutions tested;

--a three-leaf partition made of cellular concrete exhibits the worst influence on the environment as compared to other types of partitions, as regards the reduction of ozone layer and toxicity of substances contained in water to human;

--the solution based on timber has less effect on the environment in the following categories: the greenhouse effect, impact on the ozone layer, photochemical smog, utilisation of primary energy, utilisation of minerals, transport and waster, yet it uses more water;

--the construction cost is the lowest for three-leaf cellular concrete walls.

According to the analysis of the environmental impacts due to the floors:

--the least harmful solution of a floor partition is the timber floor; such solution exhibits a negative balance as regards the greenhouse effect; the use of timber reduces the environmental influence of other products in this category,

--the floor made of ceramic material has the worst influence on the environment, except for the toxicity of substances contained in water to human and water consumption,

--reinforced concrete floor is more than the others harmful to the environment, as regards: toxicity of substances contained in water to human and water consumption.

The analysis of roofing materials indicates greater environmental impact of the ceramic roof tiles than that of the lightweight sheet metal roofing, moreover the cost of such roof is around 50% higher.

According to the comparison of the environmental impact vectors of windows, the impacts are similar for the PVC and wood-aluminium joinery, where the arguments that speak for the wood-aluminium window refer to the categories: greenhouse effect and primary energy, whereas for the PVC windows: toxicity to human--air, eco-toxicity, water consumption and transport; the cost of a PVC window is around 50% below that made of wood.

The values of the environmental impact vectors of the entire buildings throughout their life cycles are given in Table 4 together with graphic presentation. Environmental impacts differ along the individual phases of the building life cycle. The greatest impacts have been found during the phases of building use and the production of materials. In the other phases, the impacts are considerably less significant in almost all categories (see Table 5).

By analysing the data provided in table 4, the following conclusions can be drawn:

--the building of the ceramic material has the strongest effect on the environment considerably in most categories, except for the influence on the ozone layer and water consumption;

--the timber building is the most efficient technical solution, except for the categories: water consumption,

--the building in its basic variant exhibits the best environmental properties in the following categories: toxicity of substances contained in water to human and water consumption, and good properties as regards: the greenhouse effect, acidification of the environment, primary energy consumption, utilisation of minerals, waste and transport; and worse as regards reduction of ozone, photochemical smog, toxicity of airborne substances, eco-toxicity, eutrophisation,

--building of cellular concrete exhibits good environmental effects in the categories: environment acidification, toxicity of airborne substances to human, photochemical smog, eco-toxicity and eutrophisation; and worse properties as regards: the greenhouse effect, ozone reduction, primary energy consumption, toxicity of substances contained in water to human, utilisation of minerals, water consumption, waste and transport,

--the lowest construction cost is involved in the timber building and slightly higher cost results for cellular concrete solutions; higher construction cost is involved while using the YTONG and ceramic components, which results mainly from the prices of wall materials.

4.2. Multi-criteria optimisation

The choice of the best solution, having the least impact on the environment is possible with the multi-criteria optimisation, or--more appropriately--the multi-criteria analysis. In the example presented as the optimisation criteria such environmental impact categories (factors) are adopted that involve the cumulated energy consumption of the building, environmental pollution and costs. These are: greenhouse effect, acidification, toxicity to human--airborne, primary energy, eco-toxicity, eutrophisation, mineral use, water, cost of 1 [m.sup.2] (or total per building) [PLN] (Table 6).

With the above criteria a separate optimisation of material solution variants was performed for individual components of the building (walls, structural floors, roofing material, window joinery) and for four versions of buildings that are made of the mentioned materials as well.

The Baas--Kwakernaak method was utilised for the optimisation, which is based on the method of weighted criteria and is shown in (Baas and Kwakernak 1977 and Nikiel 2004). In this method it is assumed that weightings and values of criteria are fuzzy numbers.

The method adopted involves the selection of an optimum solution from a finite set of acceptable solutions A (variants) A = {[A.sub.1], [A.sub.2], ..., [A.sub.k], ..., [A.sub.N]}; k = 1, 2, ..., N with the set of criteria K(A) = { [K.sub.i](A)}; i = 1, 2, ..., M.

Due to the deterministic character of the assessments of optimisation criteria and their different units (results of the authors' research--see Table 3, 4 and 5), for the next calculation criteria estimates were changed to point estimates (1-9 scale). Finally, the estimation of individual criteria was adopted as fuzzy numbers.

After having determined the set of feasible solutions, criteria and point scales to the assessment of solutions (alternatives) and significance of the criteria by experts (Table 6), Saaty matrices for all experts were created and, for each of them, coordinates of own vectors were created, respectively to the greatest own values. Further, the coordinates of own vectors were normalised for the matrices of criteria weighting, and coordinates characteristic for the plots of function of belonging were set. Finally, the summarised Zr assessment for a material solution (variant) was derived from the dependency:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.] (3)

where: [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.], [K.sub.i]--assessments of the weighting and value of an [i.sup.th] criterion.

Table 7 presents the results of the multi-criteria analysis of the studied single-family houses and building components of various material and structural solutions, taking into consideration selected optimisation criteria, their values and significance. The calculations were executed by means program PoliOpt (Nikiel 2004).

4.3. Analysing the results

By analysing the results obtained from poly-optimisation, according to the criteria studied, the following conclusions can be drawn: 1) buildings:

--building solutions using timber (D) appear to be most beneficial. The timber building is least harmful to the environment, as results directly from the studies, and has an attractive price;

--the lowest grade received the building in which ceramic components prevail (C); this involves more expensive solutions--the lowest grades to all criteria;

--buildings and building components of cellular concrete are assessed relatively well, both in the basic version (P)(YTONG) and with the three-leaf walls (G);

2) walls:

--walls of YTONG (P) cellular concrete blocks received the highest grades, for environmental impacts; Ytong walls (single-leaf) received a better grade as compared to the three-leaf cellular concrete walls (G), despite higher cost;

--two-leaf walls of ceramic (C) components are the least favourable solution;

3) structural floors:

--similarly to other timber components, the timber floor, again, received the best grade;

--ceramic floor received worse grade than reinforced concrete floor, it is more expensive and less environmentally-friendly;

4) roof covering of roof ceramic tiles is more expensive and--as other ceramic components--has greater impact on the environment, which results in a lower grade (1.000), as compared to lightweight covering of pantile sheathing (2.1936);

5) PVC windows were graded higher than the wood-aluminium windows, as regards the criteria considered, they are much cheaper and less toxic to human and cause less acidification to the environment throughout the life cycle.

5. Summary

The studies carried, we succeeded in identifying the differences as to the environmental impacts of various materials and structures made of such materials and designed buildings. Such impacts are measured with a variety of factors (in the LCA method grouped in so-called vectors--thirteen vectors in the example). It is, hence, feasible to undertake the optimisation of a building design in terms of minimising such impacts, taking into consideration numerous criteria, i.e. to perform a multi-criteria analysis and to select the least harmful building.

However, the studies indicate that, bearing in mind the building life cycle, the greatest environmental impact in most categories is present during the period of building use (Table 7), due to the need for heating in winter in our climate and in most EU countries. Therefore, the development of energy-saving and environmentally-friendly building technologies is supported by the EU directives and relevant regulations.

Promotion of the assessment of environmental impacts in the entire life cycle, polyoptimisation methods and comprehensive product information, will allow the design and selection of such solutions which are both environment-friendly and least costly. It is essential to provide the designers of energy-saving and passive buildings with expert DSS systems to enhance the variant-based design process and optimisation balance (including e.g. computeraided systems for simulative modelling of energy flow in a building).

doi: 10.3846/1392-8619.2009.15.593-611

Received 1 April 2009; accepted 30 October 2009

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Reference to this paper should be made as follows: Sobotka, A.; Rolak, Z. 2009. Multi-attribute analysis for the eco-energetic assessment of the building life cycle, Technological and Economic Development of Economy 15(4): 593-611.

Anna SOBOTKA. DSc. (Eng), Assoc. Prof., Department of Geomechanics, Construction and Geotechnics Faculty of Mining and Geoengineering, AGH University of Science and Technology in Cracow, Poland. Graduate Warsaw University of Technology. Academic degrees: PhD in construction from Warsaw University of Technology and D.Sc. from Poznan University of Technology (2001). Author of about 150 scientific articles. Research interests: construction technology and organisation, project management, construction logistics management and sustainable development in construction, properties management.

Zbigniew ROLAK. MSc (Eng). Graduate of University of Technology in Lublin, Poland (2007). Employed in University of Physical Education in Warsaw, Faculty in Biala Podlaska as chief engineer. Professional powers (1999) in design, management and supervision of construction works. Author 4 scientific articles. Researches interests: power-consuming and sustainable development of construction.

Anna Sobotka (1), Zbigniew Rolak (2)

(1) GH University of Science and Technology, Al. Mickiewicza 30, 30-059 Cracow, Poland (2) University of Physical Education in Warsaw, Faculty of Physical Education in Biala Podlaska, Akademicka 2, 21-500 Biala Podlaska, Poland E-mail: (1) sobotka@agh.edu.pl, (2) rolak@onet.pl
Table 1. The list of residential building variants

Variant Description

P--basic external walls of YTONG cellular concrete blocks,
 timber floor, ceramic roof tiles, wood

C--ceramic double-leaf walls of MAX hollow bricks, insulation
 with lightweight wet method with Styrofoam, CERAM
 45 rib-and-slab floor, ceramic roof tiles PVC
 window joinery.

G--cellular three-leaf walls of cellular concrete 600, insulated
concrete blocks with rockwool, solid reinforced concrete floor,
 sheet metal tile roofing, wooden window joinery--as
 in in the basic

D--timber walls--timber framework, wooden sheathing, with
 rockwool filling, timber floor as in the basic
 version, sheeet metal tile roofing, wooden window
 joinery.

Table 2. Values of environmental impact vectors in the whole life
cycle of a wall per 1[m.sup.2]

Environmental impact Variants of walls
categories
 P C G
Greenhouse effect, kg 389 544 425
C[O.sup.2] eq./ 100
year/unit

Reduction of the ozone 7.48E-05 7.43E-05 7.75E-05
layer, kg CFC11 eq./unit

Acidification, kg 0.62 1.67 0.73
S[O.sup.2] eq./unit

Toxicity to human--airborne, 2.04 3.20 2.26
kg toks./unit

Photochemical smog, 0.12 0.29 0.14
kg etene eq./unit

Primary energy, 13,682 14,984 13,936
MJ/unit

Toxicity to human--water, 0.064 0.061 0.075
kg tox./unit

Eco-toxicity,
[m.sup.3]/unit 9,452 54,869 9,717

Eutrophisation, kg 0.090 0.422 0.109
P[O.sub.4] eq./unit

Mineral use, kg/unit 304 711 490

Water, l/unit 4,513 5,081 4,667

Waste, t/unit 6.33 7.22 6.62

Transport, t *
km/unit 7.05 21.44 12.56

Cost * of 1 [m.sup.2] 984 1 088 744
component-wall, [PLN]

Environmental impact Variants of
categories walls
 D
Greenhouse effect, kg 223
C[O.sup.2] eq./ 100
year/unit

Reduction of the ozone 7.41E-05
layer, kg CFC11 eq./unit

Acidification, kg 0.80
S[O.sup.2] eq./unit

Toxicity to human--airborne, 2.28
kg toks./unit

Photochemical smog, 0.10
kg etene eq./unit

Primary energy, 13,659
MJ/unit

Toxicity to human--water, 0.050
kg tox./unit

Eco-toxicity,
[m.sup.3]/unit 27,197

Eutrophisation, kg 0.104
P[O.sub.4] eq./unit

Mineral use, kg/unit 138

Water, l/unit 5,113

Waste, t/unit 6.06

Transport, t *
km/unit 5.08

Cost * of 1 [m.sup.2] 942
component-wall, [PLN]

* own estimating (according to Polish Standards of Construction Works
Cost Estimating 2005), it inclusive whole-life cost (WLC).

Table 3. Values of environmental impact vectors in the whole life
cycle of a floor, roof and windows per 1[m.sup.2]

 Variants floors

Environmental
impact categories reinforced
 timber ceramic concrete

Greenhouse effect, -91 136 105
kg C[O.sub.2]eq./100year/
unit

Reduction of the 3.24E-06 3.49E-06 3.25E-06
ozone layer, kg
CFC11 eq./unit

Acidification, kg 0.35 0.89 0.56
S[O.sub.2] eq./unit

Toxicity to 0.86 1.39 0.97
human--airborne, kg
toks./unit

Photochemical 0.026 0.125 0.050
smog, kg etene
eq./unit

Toxicity to human 0.006 0.170 0.317
water, kg tox./unit

Eco-toxicity, 475 12,938 691
[m.sup.3]/unit

Eutrophisation, kg 0.034 0.199 0.073
P[O.sub.4] eq./unit

Mineral use, kg/unit 132 615 552

Water, l/unit 818 892 1,185

Waste, t/unit 0.243 1.183 1.055

Transport, t-km/unit 5,597 17,772 14,051

Cost (WLC) of 1 [m.sup.2] 1,173 1,413 1,184
component, [PLN]

 Variants roofs

Environmental sheet
impact categories ceramic metal
 roof tiles roof tiles

Greenhouse effect, -49 -29
kg C[O.sub.2]eq./100year/
unit

Reduction of the 9.57E-08 6.42E-10
ozone layer, kg
CFC11 eq./unit

Acidification, kg 0.29 0.10
S[O.sub.2] eq./unit

Toxicity to 0.38 0.08
human--airborne, kg
toks./unit

Photochemical 0.043 0.008
smog, kg etene
eq./unit

Toxicity to human 0.001 0.089
water, kg tox./unit

Eco-toxicity, 5,354 13
[m.sup.3]/unit

Eutrophisation, kg 0.066 0.008
P[O.sub.4] eq./unit

Mineral use, kg/unit 76 2

Water, l/unit 396 335

Waste, t/unit 0.148 0.008

Transport, t-km/unit 4,280 0.921

Cost (WLC) of 1 [m.sup.2] 481 335
component, [PLN]

 Variants windows

 wood-
Environmental aluminum PVC
impact categories window window
 joinery joinery

Greenhouse effect, 899 947
kg C[O.sub.2]eq./100year/
unit

Reduction of the 0.92 0.91
ozone layer, kg
CFC11 eq./unit

Acidification, kg 2.22 1.18
S[O.sub.2] eq./unit

Toxicity to 3.65 0.96
human--airborne, kg
toks./unit

Photochemical 0.700 0.785
smog, kg etene
eq./unit

Toxicity to human 2,717 3,568
water, kg tox./unit

Eco-toxicity, 40 26
[m.sup.3]/unit

Eutrophisation, kg 0.348 0.328
P[O.sub.4] eq./unit

Mineral use, kg/unit 0 110

Water, l/unit 11,804 10,595

Waste, t/unit 13,560 13,560

Transport, t-km/unit 53,754 45,385

Cost (WLC) of 1 [m.sup.2] 2,154 1,608
component, [PLN]

Table 4. Values of environmental impact vectors in the whole life cycle
of buildings

 Building
Environmental impact categories
 P-Basic C-Ceramic

Greenhouse effect, 670118 720043
kg C[O.sub.2] eq./ 100 year
Reduction of the ozone 2726 2726
layer, kg CFC11 q.
Acidification, kg S[O.sub.2] eq. 47,763,631 47,763,793
Toxicity to human--airborne, 3780 3872
kg toks.
Photochemical smog, kg etene eq. 1329 1372
Primary energy, MJ 14,806,648 15,289,610
Toxicity to human--water, kg tox. 28598 28661
Eco-toxicity, [m.sup.3] 128490 134041
Eutrophisation, kg PO4 eq. 12,695,557 12,695,626
Mineral use, kg 493790 611951
Water, l 89,367,386 89,391,219
Waste, t 65,217,161 65,217,391
Transport, t-km 80,216,676 80,219,919
Cost (WLC), PLN 1,393,000 1,427,000

 Building
Environmental impact categories
 G-Cellurar
 concrete D-Timber
 blocks

Greenhouse effect, 699088 647739
kg C[O.sub.2] eq./ 100 year
Reduction of the ozone 2726 2726
layer, kg CFC11 q.
Acidification, kg S[O.sub.2] eq. 47,763,629 47,763,622
Toxicity to human--airborne, 3766 3759
kg toks.
Photochemical smog, kg etene eq. 1328 1319
Primary energy, MJ 14,859,911 14,766,717
Toxicity to human--water, kg tox. 28648 28613
Eco-toxicity, [m.sup.3] 127486 127382
Eutrophisation, kg PO4 eq. 12,695,553 12,695,549
Mineral use, kg 550061 452762
Water, l 89,410,933 89,452,309
Waste, t 65,217,257 65,217,092
Transport, t-km 80,217,718 80,215,698
Cost (WLC), PLN 1,346,000 1,329,000

Table 5. Per cent share of the environmental impacts in individual
phases of the life cycle

Environmental impact categories Based variant of building

 production transport build

Greenhouse effect 6.16 0.46 1.53
Reduction of the ozone layer 98.15 0 0
Acidification 99.96 0 0
Toxicity to human--airborne 6.26 0.88 1.97
Photochemical smog 4.09 0.36 3.32
Primary energy 0.74 0.22 0.45
Toxicity to human--water 99.25 0 0
Eco-toxicity, 8.75 0 3.19
Eutrophisation 100.00 0 0
Mineral use 11.41 0 2.40
Water 50.21 0 1.71
Waste 99.96 0 0
Transport 100.00 0 0

Environmental impact categories Based variant of building

 operation waste transport

Greenhouse effect 91.39 0.46
Reduction of the ozone layer 1.85 0
Acidification 0.04 0
Toxicity to human--airborne 90.00 0.88
Photochemical smog 91.88 0.36
Primary energy 98.37 0.22
Toxicity to human--water 0.75 0
Eco-toxicity, 88.06 0
Eutrophisation 0 0
Mineral use 86.19 0
Water 48.08 0
Waste 0.04 0
Transport 0 0

100% values in the table result from rounding to two decimal places;
trace amounts occur in other phases.

Table 6. The point estimate of criteria weighting

 Experts
Criteria estimate

 E1 E2 E3

K1--greenhouse effect 9 8 8
K2--acidification 3 3 4
K3--toxicity to 6 6 5
human-airborne
K4--primary energy 7 5 6
K5--eco-toxicity 6 6 5
K6--eutrophisation 2 2 3
K7--mineral use 4 4 3
K8--water 6 4 5
K9--cost 9 8 9
(Whole-Life Cost)

Table 7. The final assessment list of solutions

Building Estimate Wall Estimate Floor Estimate

 P 1.397 P 2.169 timber 2.120
 C 1.000 C 1.000 ceramic 1.000
 G 1.389 G 1.989 reinforced 1.639
 D 1.593 D 1.900 concrete

Building Estimate Roof Estimate Windows Estimate

 P 2.120 ceramic roof 1.000 PCV 1.210
 C 1.000 tiles
 G 1.639 sheet metal 1.801 wood- 1.000
 D tiles aluminum
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Publication:Technological and Economic Development of Economy
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Date:Dec 1, 2009
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