DE LAS SIEFORE

In this chapter a brief overview of the GIS analysis results is carried out. As it was concluded in the previous sections, all results concerning solar potential, overall energy performance and CO2 emissions of the building stock sample, show a direct strong connection to the construction typology and the respective density factors. Thus, energy conservation studies and the design of respective policies should be planned in terms of a city scale approach and not, as up to now, on a building unit basis.

5.5.1 Solar potential

Given the higher density in the Municipality of Thessaloniki, shading problems are more intense as far as roof solar suitability is concerned; the buildings’ fraction with potential single-phased systems (1 - 5 kWp) does not exceed 46%, whereas over 50% of the buildings are evaluated as unsuitable for PV installations. On the other hand, higher ratio of built area per building in the city centre leads overall to high electrical consumptions per building. On the contrary, in the Municipality of Kalamaria, where the ratio of built area per building is lower, combined with the predominant detached construction system, the capacity outcomes seem more optimistic for solar applications;

the roof solar suitability for instance increases up to 66% of the overall building stock, whilst the solar electricity fraction per building is noticeably improved. Finally, the total PV potential capacity in Thessaloniki can reach 23.0 MWp, whereas in Kalamaria only 8.7 MWp, given the smaller amount of existing buildings. As a consequence, the aggregated CO2 emissions’ reduction provided by PV roof-top systems can account aggregately for 133,771.35 tnCO2 on an annual basis.

In the same line of thought, the results concerning SWH systems are better compared to PVs, given that an annual solar DHW fraction of 5 to 60% is provided by the 81% of buildings in Municipality of Thessaloniki and 85% in Municipality of Kalamaria. More importantly, in case of large scale retrofit programs, the “60% minimum solar fraction” threshold set by the national Regulation of Energy Efficiency of Buildings can be succeeded by a 10.0% of the existing buildings.

5.5.2 Overall energy balance and CO2 emissions

Overall, the GIS analysis proved that the typical MF - buildings chosen for this large scale analysis are suitable for the typological structure of the broader urban area of Thessaloniki. More specifically, buildings MF1 and MF2 are representative for area of the city centre and buildings MF3 and MF4 are representative for the area of Kalamaria. The link to the respective energy balance profile of each typical building provides us with a comprehensive overall illustration of the city’s energy performance.

As regards the potential in retrofit actions, approximately 4,497,027 m² of available roof areas were calculated according to the GIS maps for the implementation of green roof systems. In addition, by means of retrospective thermal insulation measures, for all buildings constructed before 1980, approximately 9,884,077 m² of vertical and horizontal surfaces were estimated for both municipalities. Moreover, the fact that the Municipality of Thessaloniki consists of more compact buildings, explains the relative low energy consumption, regardless the lack of thermal insulation on the buildings’ envelope. On the other hand, detached MF – buildings domain the Municipality of

Kalamaria and are related to higher energy consumption rates. It is important to underline the obvious agreement between the results of this GIS study and the statistical analysis presented in chapter 3.2.

Furthermore, in terms of economic feasibility, urban density could influence respective retrofit strategies to great extents. In other words, in the case of the city centre, the Municipality of Thessaloniki, the expected costs of intervention works in order to reach the minimum requirements set by KENAK concerning the buildings’ envelope U-values were estimated at a sum of 374,927,130 Euros. Additionally, the expected costs for thermal insulation measures regarding horizontal and vertical opaque surfaces in both municipalities rise up to 460,440,610. It is obvious that if these retrofit actions were to be applied also to buildings constructed after 1980 the costs would rise dramatically. Similarly, if all Municipalities of Thessaloniki’s urban region are taken into consideration as well.

Finally, by means of CO2 emissions, both areas under study present rather high amounts of CO2 emissions, although the percentage of buildings constructed before the implementation of the first Thermal Insulation Regulation (1980) in the Municipality of Kalamaria are lower (47%) compared to the Municipality of Thessaloniki (74%).

5.5.3 General results

“God made the country, and man made the town” said William Cowper in 1785. Given the fact that over 200 years have passed, and the structure of cities has changed dramatically, this saying is more relevant than ever. Over this time, cities grew, expanded in height and width, with less environment friendly materials, less green and more inhabitants. Thus, energy efficiency is now a part of a holistic sustainable management approach for urban environments. Great efforts towards this direction have to be made, whilst single solutions cannot offer the covetable results. The need to connect urban topography, typologies of buildings, indoor air quality and urban free spaces of high quality, within a framework of urban sustainable development, is immense.

This research showed that GIS based assessment tools can significantly contribute to energy efficiency management. Hence, the proposed methodology aims at the systematic collaboration of available data, regarding buildings, occupants, urban topography, climatic conditions and many more, in order to better serve this purpose. In this line of thought, besides the hereby presented research parameters, the proposed scheme allows the further elaboration of information input, concerning shading control in buildings, the estimation of CO2 reduction in the urban built

environment according to various retrofit scenarios as well as the implementation cool materials, the potential of RES on vertical building elements and many more.

Conclusively, GIS – maps can become a powerful mechanism during the process of retrofit policy planning in a city scale and provide vital information as regards urban energy efficiency. The bottom line is, as Ben Stein said, “somewhere there is a map of how it can be done”.