Vesna Zegarac Leskovar

Vesna Zegarac Leskovar (2011), Development of Design Approach for the Optimal Model of an Energy-Efficient Timber House, Institute of Urbanism; 1st reviewer: Grigor Doytchinov, 2nd reviewer: Miroslav Premov; 120 pages, English.

The present times, characterized by specific circumstances in the sphere of climate change, witness an intensive focus of the sciences of civil engineering and architecture on searching for ecological solutions and construction methods that would allow for greater energy efficiency and, consequently, for a reduced environmental burden. Being a natural raw material, timber represents one of the best choices for energy efficient construction since it also functions as a material with good thermal transmittance properties if compared to other construction materials, plays an important role in the reduction of CO2 emissions (Natterer, 2009), has good mechanical properties and ensures a comfortable indoor living climate. The latter statements accord well with the statements of Joseph and Tretsiakova-McNally (2010) who declare that the use of timber in construction gains more and more support, especially in the regions with vast forest resources, because it can reduce both the energy demands of the buildings and the concentration of GHG in the atmosphere. Respecting all these facts the energy-efficient properties of prefabricated timber buildings are, in comparison with other types of buildings, excellent but not only because they use less energy for heating, which is environmentally friendly, but also due to the extremely positive feelings that homeowners have when living in such houses. Additionally the use of glazing surfaces in timber structures is becoming an important issue of energy-efficient construction. Over a number of years of development glazing manufacturers have improved their products’ thermal-insulation and strength properties as well as their coefficient of permeability of total solar radiation energy and thus enabled the use of large glazing surfaces not only to illuminate indoor areas but also to ensure passive solar heating. The features listed above make prefabricated timber structures suitable for the construction of energy efficient houses of various classes where an increased proportion and a suitable orientation of the glazing surfaces play an important part due to solar heat gains. It follows that timber construction along with the use of suitable and correctly oriented glazing surfaces represents a great potential in residential and public building construction, which is also the main point of the presented research. The current research is generally based on a case study of a two-storey prefabricated timber house. In the first part of the thesis a deep parametric analysis of an increased-proportion-of-the-glazing-surfaces impact, taking the climate data for Ljubljana into consideration, is performed. The analysis is carried out on different exterior prefabricated timber wall elements having different thermal properties, i.e. different thermal transmittance coefficients, while the rest of the parameters, such as the ground plan of the model as well as the active systems, roof and floor slab assemblies remain constant. It is important to underline that the presented research is limited to timber construction only, which is also termed as lightweight construction, since the influence of the different thermal capacities of the materials as well as the thermal mass of the building were not taken into consideration. The graphical presentation includes figures showing the annual energy demand for heating and cooling dependant on the proportion of the glazing area in relation to the total surface area of the south-oriented façade. The comparative analysis results can nevertheless serve as a good frame of reference to civil engineers and architects in an approximate estimation of energy demand accompanying the different positioning and proportion of glazing surfaces while using various prefabricated timber wall elements as well as serving some basic practical and very useful principles regarding the energy efficient refurbishment of old timber buildings.

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