Abstract. The number of office buildings with highly fenestrated facades is currently increasing in Lithuania and neighboring countries. Highly fenestrated facades reduce energy consumption for lighting and simultaneously increase energy consumption for heating, cooling, air conveying and may cause thermal and visual discomfort. Pursuing to reduce negative effects of the highly glazed facade, special glasses are frequently used. However, such windows usually increase demand for lighting energy. Therefore, when making early decisions about glazing the building, it is important to have a complex evaluation of energy demand related to the specific case. The paper presents the results of analysis made using energy simulation tools. The obtained results have shown that when shading is not applied, the north is the most energy efficient orientation to glazing for an air conditioned office building in cool climate zones like Lithuania. The most energy efficient window-to-wall ratios (WWR) for the south, east and west oriented façade are 20%, whereas for the north it makes 20-40%. However, such WWR values do not satisfy standard requirements for day lighting.
Measurements of the airtightness of blocks of flats in Lithuania were carried out between 1995 and 1997 to assess the effectiveness of energy saving measures. At that time there was no real data on the airtightness of such dwellings available. The aim of the measurements was to evaluate how much heat could be saved by diminishing the air change rate. Since there are no thermostats installed in the dwellings, ‘tightening’ becomes the only measure available to increase indoor temperature. Unfortunately, the results show that the popular expectation that energy was being wasted are not well grounded. We conclude that there is no real possibility for saving heat in small dwellings without contravention of health requirements except in isolated cases. The mean air change rate was found to be approximately 1.5 h–1 and further steps to tighten the building envelopes could only save energy in some large dwellings of three and more rooms.
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