Calibration of the energy model of a building is one of the essential tasks required to determine the efficiency of building management systems, and both their own and other systems’ improvement potential. In order to make the building energy model as accurate as possible, it is necessary to collect comprehensive data on its operation and sometimes to assess the missing information. This paper represents the process of developing an energy model for an administrative building and its calibration procedure, using detailed long-term measurement and building management system (BMS) data. Indoor air temperature, CO₂ concentration, and relative humidity were experimentally measured and evaluated separately. Such dual application of data reduces the inaccuracy of the assumptions made and assesses the model’s accuracy. The DesignBuilder software developed the building model. During the development of the model, it was observed that the actual energy consumption needs to be assessed, as the assumptions made during the design about the operation and management of HVAC systems often do not coincide with the actual situation. After integrating BMS information on HVAC management into the building model, the resulting discrepancy between the model results and the actual heat consumption was 6.5%. Such a model can be further used to optimize management decisions and assess energy savings potential.

Air source heat pumps (ASHPs) are becoming an increasingly popular heating source for buildings. The paper presents an evaluation of the experimental data from ASHP operation during the heating season in Lithuania when the problem of the evaporator’s surface freezing is visible. The performance of the air-to-water heat pump is examined using energy and exergy analyses performed by a coefficient of performance (COP), COP_Carnot, exergy efficiency, and primary energy ratio. Analysis results show that the existing difference between the ideal and actual operation of ASHP represents the demand to improve the performance of ASHP evaporator. The actual COP was from 3.5 to 4.7 times lower than the Carnot COP. At 0 °C and 95% humidity, the ASHP’s performance was least favourable, with an average exergy efficiency of 0.21 and a COP of 1.49. Keyword : air source heat pump, thermodynamic analysis, ambient conditions, performance, exergy

For direct investment towards activities that significantly contribute to the achievement of the European Green Deal objectives, the European Union has adopted “Taxonomy Regulation”, which also applies disclosure requirements to financial institutions that finance the construction, renovation, or acquisition of buildings. For this reason, the financial sector needs methodologies and guidelines, adapted to the national situation, to define the primary energy thresholds to be used when assessing sustainability and financing the acquisition of real estate. This paper presents the methodology developed to identify 15% and 30% of the most energy-efficient national building stock in Lithuania based on EPC data. As a result, functional primary energy indicator (FPEI) threshold values are set for 17 distinct categories of existing buildings built by 31 December 2020. The 15% FPEI thresholds range from 81 kWh/m² for warehouse buildings to 228 kWh/m² for swimming pool buildings. Similarly, the 30% FPEI thresholds span from 104 kWh/m² for warehouses to 303 kWh/m² for foodservice buildings. The methodologies and threshold values are compared to other countries’ practice and recommendations are provided.

The mandatory energy performance certification of new buildings or buildings for sale has been introduced in all Member States in order to achieve European Union’s energy efficiency goals. The certification of buildings sets mandatory requirements for higher energy efficiency buildings’ level of airtightness. However, a bigger problem lies in existing older residential buildings, which are energy inefficient and do not require certification. The unused potential for energy savings observed here is related to the airtightness of single and double apartment residential buildings and energy efficiency related to airtightness of them. Therefore, this work analyses the airtightness of energy class D and lower buildings based on actual airtightness measurements and evaluates the possible energy saving potential associated with the application of airtightness measures based on the example of one inefficient single apartment building. The results show that increase of the airtightness in such buildings to 3 h–1 enables to reduce the energy costs related to the airtightness in Lithuania over a period of 10 years by 0.17 TWh per year.

Because of a societal push towards sustainability a problem emerges of adapting the concept to different sectors of the economy and society. The differing complexities of different fields and social structures make it difficult to create a universal sustainability strategy. Higher education institutions (HEIs) consist of a broad range of people, working in various fields of industry, making it an appropriate cross-section of the nation. Adapting sustainability practices in these institutions would allow to screen for successful policies before implementing them more widely, detecting most effective practices, allowing a faster transition towards achieving the Sustainable Development Goals (SDGs). It is hard to decide where to start, as many sustainable practices exist. This article presents the case study of VILNIUS TECH and conducts a comparison with universities in the region, determining best sustainability practices. The Greenhouse gas (GHG) protocol standard was used to form the emission inventory. The university comparison will help identify effective HEIs carbon footprint minimization practices, as well as other implemented policies as an example of where HEIs should start on their road to a more sustainable institution.