1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Active Solar Heating Systems for Energy Efficient Buildings in Greece: A 1 Technical Economic and Environmental Evaluation 2 3 G. Martinopoulos and G. Tsalikis 4 School of Science and Technology, International Hellenic University, 570 01, Thermi- 5 Thessaloniki, Greece, e-mail: g.martinopoulos@ihu.edu.gr , Tel: +302310807533, 6 Fax: +302310474590 7 8 Abstract 9 The purpose of this study is the technical and economic evaluation of a typical solar 10 space and water heating system, utilized in an 88 m 2 detached house that is 11 designed according to the latest Greek Regulation on the Energy Performance of 12 Buildings as a means towards Nearly Zero Energy Buildings (NZEB). The analysis 13 was conducted for each of the four climatic zones designated in the Greek 14 Regulation. A financial analysis was performed and the Net Present Value and the 15 Discounted Payback Period (DPBP) were calculated and correlated with the solar 16 systems collector area and the storage tank volume. Furthermore, the annual 17 avoided emissions from the substituted fossil fuels are estimated for the solar 18 systems considered. The analysis demonstrates that the typical solar space and 19 water heating system can provide a viable solution towards NZEB with solar 20 coverage and DPBP being strongly influenced by the climatic zone of the building 21 and the type of fossil fuel substituted. In all cases the solar system covers at least 22 45% of the total heating loads while the payback period is as low as 4,5 years with an 23 annual abatement of more than 50 t of CO 2 in the worst case scenario. 24