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In this paper, presented is the state-of-the-art of energy Efficiency of residential buildings in Serbia. Special attention is paid to energy efficiency in already existing buildings. The average energy consumption in residential buildings in Serbia is over 150 kWhm -2 per year, while in developed European countries it is about 50 kWm -2 per year. In this paper examined is the contribution of ventilation losses, through the windows of low quality, regardless whether they are poorly made, or made from bad materials, or with no adequate glass. Besides ventilation losses, which are of major importance in our buildings, special attention is paid to transmission losses, which are consequence of the quality and energy efficiency of the facade. All of the above statements are proved by measurements obtained on a representative building of the Block 34 in New Belgrade, built in the eighties of the last century. In addition to measurements performed the calculation of energy consumption for heating during winter has been made. The results of two different methods of calculation of energy consumption for heating are compared with the values obtained by measuring.

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Energy system in Serbia, in the whole energy chain, from exploitation of primary energy sources, transformations in electric power plants and district heating plants, energy (electric and heat) transmission and distribution to final users, and up to final energy consumption, is faced with a number of irrational and inefficient behavior and processes. In order to fight with such situation National Energy Efficiency Program, financed by the Ministry of Science and Environmental Protection has been founded in 2001. Basic facts about status of energy sector in Serbia, with special emphasis on the energy efficiency and use of renewable energy sources have been given in the review paper published in the issue No. 2, 2006 of this journal. In present paper new strategy and priorities of the National Energy Efficiency Program for the future period from 2006 to 2008, and beyond, is presented. This strategy and priorities are mainly based on the same concept and principles as previous, but new reality and new and more simulative economic and financial environment in energy sector made by the Energy low (accepted by Parliament in 2004) and Strategy of Development of Energy Sector in Republic Serbia up to 2015 (accepted by the Parliament in May 2005), have been taken into account. Also, responsibilities that are formulated in the Energy Community Treaty signed by the South-East European countries, and also coming from documents and directives of the European Community and Kyoto Protocol are included in new strategy. Once again necessity of legislative framework and influence of regulations and standards, as well as of the governmental support, has been pointed out if increased energy efficiency and increased use of renewable energy sources are expected. .

In Sijarinska spa, there are some 15 mineral and thermomineral springs, that are already being used for therapeutic purposes. For the exploitation of heat energy boring B-4 is very interesting. It is a boring of a closed type, with the water temperature of about 78?C and a flow rate of about 33 l/s. Waters with the flow rate of about 6 l/s are currently used for heating of the Gejzer hotel, and waters of the flow rate of about 0,121 l/s for the pilot drying plant. The paper presents this pilot plant. .

In this paper we have examined the effect of variable frequency electromagnetic field generated with a homemade device on deposit formation in installations with geothermal water from Sijarinjska Spa. The frequency alteration of the electromagnetic field in time was made by means of the sinusoidal and saw-tooth function. In laboratory conditions, with the flow of geothermal water at 0.015 l/s and temperature of 60 °C for 6 hours through a zig-zag glass pipe, a multiple decrease of total deposit has been achieved. By applying the saw-tooth and sinusoidal function, the decrease in contents of calcium and deposit has been achieved by 8 and 6 times, respectively. A device was also used on geothermal water installation in Sijarinjska Spa (Serbia), with the water flow through a 1'' diameter non-magnetic prochrome pipe at 0.15 l/s and temperature of 75 °C in a ten-day period. A significant decrease in total deposit and calcium in the deposit has also been achieved

The hygrothermal properties related to rockwool insulation material structure with different additives are presented using rockwool insulation products obtained from row material of southern Serbia (Vranje region) in the wide range of reference temperatures (10?C to 70?C). The hygrothermal properties of basic sample (without additives) are compared to two samples with different additives for two sets of rockwool insulation samples namely: light-soft-panels (LSP) with density of 50 kg/m3, and middle-weight-panels (MWP) with density of 80 kg/m3. It is shown that there is significant (approximately 10%) improvement of thermal conductivity for additives based on zeolite. Also, correlation of thermal conductivity and sorption properties of selected samples are presented.

On construction with dimensions 15 x 5 x 2 m, conditions of temperature transmission and vegetables growth are examined. We have been cultivating pepper, cucumber, small cucumber, tomato, and lattice. Over ground heating has been used, consisting of one bent pipe with radius of 10 mm, in the shape of hairpin along the both sides of the construction. Underground heating consists of six pipes with radius of 20 mm on the depth of 350-400 mm. There have been measured the temperature inside construction, the temperature outside construction, the waterflow, and water temperature flowing into and out of the construction. The approximate heating flow factor K is determined by both the equation: heating balance equation and basic equation for temperature transmition. Vegetable growth has been watching during the period of time from March to November 2005.