thermal bridges make only 3 % of overall heat losses through envelopes, it is 122 kWh/m² per year. According to results of the analyse general specifications were made for designing building envelopes of "A" energy efficient class: _ The building of "A" class can be designed using ordinary solutions of linear thermal bridges, bigger heat losses through thermal bridges can be covered by increasing thickness of thermal insulating layers and using windows of better thermal behaviour but as a result the costs of building house increase too._ When effective solutions of linear thermal bridges are used, the same energy efficiency of the building can be reached using less thermal insulating layers, windows and doors of less thermal behaviour if the building of better energy characteristics is designed.
Drain water heat exchangers worldwide are used since the end of the twentieth century. Different drain water heat exchangers have been installed in Lithuania in last five years. Performance of these systems varies depending on the type of energy users, equipment and design of the systems, as well as their maintenance. The aim of this paper was to analyze different types of drain water heat exchangers and operational systems from the perspective of energy saving and temperature effectiveness. One drain water heat exchanger system in Lithuania was selected for the analysis. Calculation of temperature effectiveness showed that in most cases it is possible to save energy for hot water preparation.
Recently, the construction of external walls of various blocks, which are externally insulated with mineral wool thermal insulation layer, with ventilated air gap and external finishing (ventilated wall structures) is becoming popular for public and office buildings. These blocks are used without internal rendering because they have a good interior surface, stable dimensions, and various filling of masonry joints provide an attractive architectural appearance. This reduces the cost and duration of construction work, however, problems with airtightness of such walls often occur. The air can penetrate through blocks or their joints, and the thermal insulation and wind protection layer does not usually provide the required air tightness of the wall. Currently, there are no standard methods to predict the air tightness of such wall, in practice, samples of particular walls are produced and their air permeability is measured at the laboratories. This is a costly job, which is only suitable for a combination of particular building materials. For the broader use of results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from blocks, made of ceramic, expanded clay and aerated concrete with various joints, were used for the research; mineral wool boards of various air permeability were used for thermal insulation and wind protection layer. After measuring the air resistance of masonry units, thermal insulation and wind protection boards, the air flow resistances of the walls of different construction were calculated. The comparison of calculated and measured air permeability of wall samples showed that in cases where the nature of air movement (laminar to turbulent) through a single material remains similar with the nature of air movement through the product incorporated in the structure, the calculation and measurement data differ no more than 12-15%. In structures with building products with very different air permeability properties, especially at high thicknesses of air permeable thermal insulation products, air movement parameters change occurs and calculated and measured results have larger differences.
Recently, the construction of external ventilated walls has become popular for public and office buildings. These blocks are used without internal rendering because of their good interior surface, stable dimensions and various filling of masonry joints, which provide an attractive architectural appearance. However, problems with the airtightness of such walls often occur. Currently, there are no standard methods to predict the airtightness of such wall. In practice, samples of particular walls are produced, and their air permeability is measured at laboratories. For the broader use of the results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from various blocks were used for the research; mineral wool boards of various air permeability were used for thermal insulation and the wind protection layer. After measuring the air resistance of the samples, the air flow resistances of walls of different construction were calculated. This study compared the calculated and measured air permeability values of different wall masonry samples and evaluated the suitability of created calculation method for prediction of the airtightness of insulated block masonry wall.
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