PhD thesis

Abstract:

The main objective of this research is definition of adequate models for refurbishment of residential building stock in Serbia with the aim of improving its energy performance. Significance of single family housing types was established during previous researches, as well as their highly negative energy performance characteristics. Single family houses built between 1946-1970 represent one of the most common single family housing types, making 35% out of total number of single family buildings, and 31% out of total number of residential buildings. They also represent type of houses which are suitable for a research of diverse energy performance improvement models, due to their expressed homogenous characteristic. Adequatelly defined models for energy performance improvements of buildings represent a significant instrument in planning building stock refurbishment activities. Refurbishment models used in recent researches are uniquely defined for all building types within the building stock, without ajustments to specific characteristics of each type or group of similar types. Inadequacy of certain energy conservation measures within defined models for some housing types was noticed, and a need for inovating methodology for refurbishment model definition by introducing and examining a model which is sensitive to specific characteristics of building types was recognized. Problem of this research is the definition and investigation of a complex refurbishment model, which includes energy conservation measures which are derived from the noted limitations and malfunctions in the buildings’ layout and functional organization. These measures include interventions in the spatial structure of the building and introduction of passive design measures. Noted limitations which are eliminated through the complex refurbishment model definition may represent obstacles for achieving significant energy savings in the process of deep refurbishment of buildings. Energy performance achieved through complex refurbishment model are investigated and compared with the existing energy performance of 5 typical single family housing types built during the analyzed period, and with energy performance resulting from two refurbishment models defined within recent research, which consist only of typical energy conservation measures (standard and ambitious improvement models). Energy performance analysis are conducted using two methods: first is the calculation method defined within current legislation, for assessment of energy need for heating (completely defined quasi-stationary monthly method) and the second is thermal simulation of energy need for heating and cooling, using the “Ecotect” software. By the assessment of energy need for heating using two methods, range of savings is estimated for analyzed models, while the energy need for cooling assessed using the simulation is introduces as an additional parameter which is currently not assessed by domestic regulations, with the aim of assessing its relevance for these housing types. By comparison of investigated models it was concluded that energy performance achieved through the complex refurbishment model lies in range or outcomes the results of ambitious refurbishment scenario, with significant increase of usable floor area, property value and spatial comfort. Even in complex refurbishment models which do not include increase in volume and improvement of geometric characteristics (shape factor), same savings were achieved as in ambitious scenario refurbishment, in spite of lower levels of thermal envelope improvement. This means that by passive measures of energy efficiency improvement (attached sunspaces) and increase of thermal envelope segments towards unheated areas, differences which are related to lower values of thermal envelope upgrade can be balanced. Through investigation of various factors which influence energy need for heating, it is concluded that dominant influence lies in geometric characteristics, which also recommends the complex refurbishment scenario, since it is the only one that can outcome the inherited limitations in geometric characteristics. Through the assessment of energy need for cooling in all investigated models, it was concluded that, compared to energy need for heating, its share within selected building types is almost negligible (below 10%), which is in accordance with the characteristics of investigated housing types, but that both its share and nominal values rise with the improvement of thermal envelope and airtightness through refurbishment.