Selection of low-e windows in retrofit of public buildings by applying multiple criteria method COPRAS: A Lithuanian case Arturas Kaklauskas, Edmundas Kazimieras Zavadskas * , Saulius Raslanas, Romualdas Ginevicius, Arunas Komka, Pranas Malinauskas Faculty of Civil Engineering, Vilnius Gediminas Technical University, Sauletekio al. 11, LT-10223 Vilnius 40, Lithuania Received 30 May 2005; received in revised form 21 July 2005; accepted 5 August 2005 Abstract Calculations of building retrofit effectiveness have shown that the replacement of original windows with new ones is not as effective in terms of heat energy saving as are the insulation of a roof, walls and other improvements because the investments are large and take a long time to be repaid. However, in addition to energy saving, window replacement improves the indoor climate of the building, its interior and architectural appearance as well as its market value. The sequence of building operations determines when the replacement of windows should be done. When financial resources are limited, managers of public buildings often begin the renovation of a building’s envelope with the replacement of windows. The client faces some problems in choosing among the great variety of windows to satisfy his/her needs, especially with respect to the cost-quality relationship. The method of multiple criteria complex proportional assessment (COPRAS) developed by the authors aims at solving the above- mentioned problems. The solutions based on multicriteria analysis allow for a more rational and realistic assessment of customer’s needs as well as cutting down window renewal costs. In this paper, practical example (key-case) of selecting a contractor for the replacement of windows in the main building of Vilnius Gediminas Technical University (VGTU) is presented as a part of its retrofit multivariant design. # 2005 Elsevier B.V. All rights reserved. Keywords: Public building; Retrofit; COPRAS 1. Introduction The authors of this paper are participating in the project Framework 6 ‘‘Bringing Retrofit Innovation to the Application of Public Buildings’’ (BRITA in PuBs) (see http://www.brita-in- pubs.com). Public buildings may be of different types, such as colleges, cultural centers, nurseries, student halls of residence, and churches, etc. Public buildings are most suitable for achieving the market’s penetration of innovative and effective retrofit solutions to improve energy efficiency and implement renewables, with moderate additional costs. With their help it will be easier to reach groups of differing age and social origin. Public buildings can also be used as engines to heighten awareness and sensitize society on energy conservation. In all European countries it can be observed that general opinion on the realization of energy saving measures differs greatly between residential and non-residential buildings as well as between new and existing buildings. Most European countries have succeeded in reducing their energy consumption in new dwellings by more than 50% without increasing the building cost and, therefore, energy efficiency concept has reached greater acceptance by the building’s owners. Development is quite different for the non-residential buildings. Energy consumption problems are secondary to the improvement of comfort. Decisions to retrofit a building are often made because of dissatisfaction regarding the comfort level. Therefore, the primary goal is to improve these comfort conditions. Decision makers are often skeptical about measures that aim to reduce energy consumption because they are afraid that these measures could limit the effect of improving the indoor climate and increase costs. The improvement of comfort as the primary aim can be achieved alongside energy saving. It is, therefore, particularly important to demonstrate the effective solutions of public building retrofit and to make them visible to the wider public. One such project that represents the renovation of a main building at VGTU is considered in this paper. www.elsevier.com/locate/enbuild Energy and Buildings 38 (2006) 454–462 * Corresponding author. Tel.: +370 5 274 50 02; fax: +370 5 270 01 14. E-mail address: edmundas.zavadskas@adm.vtu.lt (E.K. Zavadskas). 0378-7788/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.enbuild.2005.08.005