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Despite the tightening of energy performance standards for buildings in various countries and the increased use of efficient and renewable energy technologies, it is clear that the sector needs to change more rapidly to meet the Net Zero Emissions (NZE) scenario by 2050. One of the problems that have been analyzed intensively in recent years is that buildings in operation use much more energy than they were designed to. This problem, known as the energy performance gap, is found in many countries and buildings and is often attributed to the poor management of building energy systems. The application of Artificial Intelligence (AI) to Building Energy Management Systems (BEMS) has untapped potential to address this problem and lead to more sustainable buildings. This paper reviews different AI-based models that have been proposed for different applications and different buildings with the intention to reduce energy consumption. It compares the performance of the different AI-based models evaluated in the reviewed papers by presenting the accuracy and error rates of model performance and identifies where the greatest potential for energy savings could be achieved, and to what extent. The review showed that offices have the greatest potential for energy savings (up to 37%) when they employ AI models for HVAC control and optimization. In residential and educational buildings, the lower intelligence of the existing BEMS results in smaller energy savings (up to 23% and 21%, respectively).

Air-to-air heat pumps are used in today’s ventilation systems increasingly often as they provide heating and cooling for buildings. The energy transformation modes of these units are subject to constant change due to the varying outdoor air state, including temperature and humidity. When choosing how to operate and control energy transformers, it is important to be able to adapt effectively to the changing outside air conditions. Nowadays, modern commercial heat pumps offer two levels of control flexibility: a compressor with a variable speed and an electronic expansion valve. This combination of control elements has boosted the seasonal energy efficiency of heat pumps. For a long time, cycle control possibilities have been dominated by electronic controls. The authors of this paper aim to present an additional element to the traditional heat pump controls, which provides a third level of control over the cycle. To achieve the objective, experimental investigations of a heat pump integrated into a ventilation unit have been carried out under real-life conditions. The experiments involved varying the operating modes of the unit by adjusting the compressor speed, the position of the expansion valve, and the volume of the system loop. The study examined the performance characteristics of the heat pump and found that the performance of a variable-volume heat pump is comparable to that of a conventionally operated typical constant-volume heat pump system. In addition, the study found that by adding a third level of volume control to the active heating circuit, in combination with conventional controls, the heat pump’s heat output range could be extended by 69.62%. The study determined the variation of the heat pump cycle in the p-h diagram with the variation of the loop volume. The benefits and drawbacks of a heat pump with a variable-volume loop are discussed in this study.

Climate change and its consequences pose an existential threat to Europe and the world, where more than 75% of the European Union’s greenhouse gas emissions come from energy production. For this reason, it is very important to increase the energy efficiency of buildings, as the building sector is one of the biggest energy consumers with an impact on the still untapped potential for energy savings. Although buildings are constructed and certified as energy efficient, their in-use consumption is often significantly higher than expected. Especially significant in energy consumption between design and actual consumption are found in office buildings. The higher energy consumption is due to factors related to the design and operation phases. Researchers often emphasize the management of a building’s engineering systems as one of the key factors influencing a building’s energy consumption. The article analyses the existing office building and evaluates the efficiency of its energy using systems’ management based on long-term monitoring data. After identifying which systems are managed inefficiently, several management strategies have been proposed and evaluated. It was found that with simple management strategies heating energy reduction is about 20% per year. Article in Lithuanian. Administracinio pastato sistemų valdymo efektyvumo vertinimas remiantis ilgalaike stebėsena Santrauka Klimato kaita ir su tuo susiję padariniai kelia egzistencinę grėsmę Europai ir pasauliui, o daugiau kaip 75 % Europos Sąjungoje išmetamo šiltnamio efektą sukeliančių dujų kiekio susidaro gaminant ir naudojant energiją. Dėl šios priežasties labai svarbu didinti energijos vartojimo efektyvumą pastatuose, nes pastatų sektorius yra vienas iš didžiausių energijos vartotojų ir turi didelį vis dar neišnaudotą energijos taupymo potencialą. Nors pastatai statomi ir sertifikuojami kaip energiškai efektyvūs, dažnai eksploatacijos metu suvartojimai būna daug didesni, nei prognozuota. Dideliais energijos suvartojimo skirtumais, lyginant su projektiniais, ypač išsiskiria administracinės paskirties pastatai. Didesnį energijos vartojimą lemia įvairūs veiksniai, apimantys projektavimo, statybos ir eksploatavimo etapus. Mokslininkai dažnai išskiria pastato inžinerinių sistemų valdymą kaip vieną iš pagrindinių veiksnių, darančių įtaką pastato energijos suvartojimui. Straipsnyje analizuojamas realus administracinis pastatas ir vertinamas jo valdymo efektyvumas, remiantis ilgalaikės stebėsenos duomenimis. Identifikavus, kurios sistemos yra valdomos neefektyviai, buvo pasiūlytos ir įvertintos kelios valdymo strategijos, kurios leistų sutaupyti apie 20 % šilumos per metus. Reikšminiai žodžiai: mikroklimatas, stebėsena, administracinis pastatas, energinis efektyvumas, pastato valdymas.

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. Article in Lithuanian. Eksploatuojamų gyvenamosios vieno ar dviejų butų paskirties pastatų sandarumo matavimų analizė Santrauka Siekiant Europos Sąjungos (ES) energijos vartojimo efektyvumo tikslų visose šalyse narėse yra įvestas privalomas naujai statomų ar parduodamų pastatų energinio naudingumo sertifikavimas. Sertifikuojant pastatus yra nustatyti reikalavimai aukštesnio energinio efektyvumo pastatams išlaikyti tam tikrą sandarumo rodiklį. Tačiau didesnė problema slypi esamuose senesnės statybos gyvenamuosiuose pastatuose, kurie yra energetiškai neefektyvūs ir jiems sertifikavimas neprivalomas. Čia pastebėtas nepanaudotas energijos taupymo potencialas susijęs su vienbučių ir dvibučių gyvenamųjų namų sandarumu ir su juo susijusiu energijos efektyvumu. Todėl šiame darbe yra analizuojamas D ir žemesnės energinio naudingumo klasės pastatų sandarumas, remiantis faktiniais sandarumo matavimais, ir vertinamas galimas energijos taupymo potencialas, susijęs su sandarumo didinimo priemonių taikymu, remiantis vieno neefektyvaus vienbučio namo pavyzdžiu. Rezultatai rodo, kad tokiuose pastatuose sandarumą padidinus iki 3 h–1, galima būtų energijos sąnaudas, susijusias su sandarumu, Lietuvos mastu 10 metų laikotarpiu sumažinti 0,17 TWh per metus. Reikšminiai žodžiai: energijos taupymo potencialas, gyvenamieji vieno ar dviejų butų paskirties pastatai, oro infiltracija, pastatų sandarumas.

Technologies that use renewable energy sources (RES) are crucial to achieving decarbonization goals, but a significant number of studies show their relatively high environmental impact during the production phase. Therefore, technologies need to be compared in terms of their life-cycle environmental impact. The life cycle analysis (LCA) methodology is well known and widely employed. However, problems related to the methodological choices prevent taking full advantage of the LCA, as the results of numerous studies are often incomparable. The presented review aims to critically compare the impact of different energy generation technologies—RES (as well as non-RES) energy generators and co-generators. The numeric results are structured and analyzed in terms of the global warming potential (GWP) and non-RES primary energy consumption. The results show that RES technologies are superior compared to conventional fossil-fuel-based systems in most cases, and the high impact during the production and installation phases is compensated in the operational phase. The high variations in GWP from similar technologies result from different methodological choices, but they also show that the wrong choice of the technology in a certain location might cause serious environmental drawbacks when the impact of the RES technology exceeds the impact of fossil fuel-based technologies. Cogeneration technologies using waste as a fuel may even have a negative GWP impact, thus showing even higher potential for decarbonization than RES technologies.

During the building design phase, a lot of attention is paid to the thermal properties of the external envelopes. New regulations are introduced to improve energy efficiency of a building and impose a reduction of the overall heat transfer coefficient; meanwhile, this efficiency is more influenced by the efficiency of the heating system and the type of fuels used. This article presents a complex analysis including the impact of: heat transfer coefficient of the envelope, efficiency of building service systems, the type of energy source, and the fuel. The analysis was based on the results of simulation tests obtained for an exemplary multi-family residential building located in Poland that is not equipped with a cooling system. The conducted calculations gave quantitative evaluation of the influence of particular parameters on building energy performance and showed that the decrease of heat transfer coefficient of building boundaries, in accordance to the Polish regulation for 2017 and 2021, gave only 11% of reduction on usable energy demand index. On the other hand, it was found that modification of the heating system and heat source can significantly influence the values of the final and primary energy consumption at the level of 70%. The application of heat pumps has a greater influence on the final and primary energy consumption for heating indices than other parameters, such as the building’s envelopes.

As literature shows, energy efficient and even sustainable buildings show the difference between predicted and actual energy consumption, when buildings consume 1.5−2.5 times more energy than predicted. The behavior of occupants in buildings is distinguished as one of the 6 factors that determine the energy demand of the building, and a number of studies show that the occupants behavior, both passive and active, has a major impact on the actual energy consumption. In this work, surveys were carried out to determine indoor climate sensations of the occupants of two sustainable office buildings seeking to find out: how much their emotional state determines the sensation, what are their knowledge on energy saving measures in the building. The results showed that during the summer, consumers are not satisfied with the room temperature and the number of unsatisfied does not meet the normative requirements. There was also a clear dependency between the employee’s salary, his emotions and his satisfaction with the indoor climate − the less a person earns, the more he experiences negative emotions, which leads to greater dissatisfaction with the comfort of the premises. Santrauka Kaip rodo tyrimai, energiškai efektyviuose ir net darniuose pastatuose atsiranda prognozuojamų ir realių energijos sąnaudų skirtumų, kai realiai pastatai suvartoja 1,5−2,5 karto daugiau energijos, nei buvo numatoma projektuojant. Žmonių elgsena pastatuose išskiriama kaip vieną iš šešių energijos poreikius pastate lemiančių veiksnių ir nemažai tyrimų rodo, kad labai didelę įtaką realiam pastato energijos suvartojimui daro būtent vartotojų elgsena, tiek pasyvi, tiek aktyvi. Šiame darbe buvo atliekamos apklausos, siekiant nustatyti, kaip jaučiasi dviejų darnių biurų pastatų vartotojai, kiek jų emocinė būklė lemia mikroklimato pojūčius ir kokios yra jų žinios apie energijos taupymo priemones pastate. Rezultatai parodė, kad vasarą vartotojai nepatenkinti patalpų temperatūra ir tokių vartotojų skaičius neatitinka norminių reikalavimų. Taip pat buvo nustatytas akivaizdus ryšys tarp darbuotojo darbo užmokesčio, jo emocijų ir pasitenkinimo mikroklimatu – kuo mažiau žmogus uždirba, tuo didesnis nepasitenkinimas patalpų komfortu. Reikšminiai žodžiai: vartotojų elgsena, emocijos, energijos poreikiai, apklausa, pasyvi ir aktyvi elgsena.

Despite increasing energy efficiency requirements, the full potential of energy efficiency is still unlocked; many buildings in the EU tend to consume more energy than predicted. Gathering data and developing models to predict occupants’ behaviour is seen as the next frontier in sustainable design. Measurements in the analysed open-space office showed accordingly 3.5 and 2.7 times lower occupancy compared to the ones given by DesignBuilder’s and EN 16798-1. This proves that proposed occupancy patterns are only suitable for typical open-space offices. The results of the previous studies and proposed occupancy prediction models have limited applications and limited accuracies. In this paper, the hybrid differential evolution online sequential extreme learning machine (DE-OSELM) model was applied for building occupants’ presence prediction in open-space office. The model was not previously applied in this area of research. It was found that prediction using experimentally gained indoor and outdoor parameters for the whole analysed period resulted in a correlation coefficient R2 = 0.72. The best correlation was found with indoor CO2 concentration—R2 = 0.71 for the analysed period. It was concluded that a 4 week measurement period was sufficient for the prediction of the building’s occupancy and that DE-OSELM is a fast and reliable model suitable for this purpose.

Increasing the energy efficiency of buildings, heat losses through envelope and infiltration become very low, therefore, the proportion of the heat gains in the heat balance of the building increases. Due to their abundance of computer equipment, intensive lighting and the abundance of employees the information technologies’ (IT) staff offices are characterized by high internal heat gains. Formally, such offices are not distinguished when designing the building and its energy performance, values of internal heat gains are the same as for usual offices. Insufficient attention to the detailed differentiation of the heat gains may lead to the inadequate assessment of the energy performance of the building, insufficient design power of the cooling system. The aim of this work is to determine the influence of internal heat gains on the heat balance of a existing IT office. The heat gains are initially determined experimentally and compared with the values calculated in accordance with STR 2.01.02:2016, the room model is calibrated in the IDA ICE software, which is used to analyze building’s annual energy demand sensitivity to internal heat gains. It was defined that in the case of maximum heat gains, the experimental internal heat gain are 63–81% higher than the ones, calculated in accordance with norms. The annual heating demand is 31% lower, and the cooling demand is 56% higher according to the experimental simulation compared to standardized simulation results. Santrauka Didinant pastatų energinį naudingumą, šilumos nuostoliai per atitvaras ir dėl infiltracijos tampa nykstamai maži, todėl pastato šilumos balanse didėja vidiniams šilumos pritekiams tenkanti dalis. Dideliais vidiniais šilumos pritekiais pasižymi informacinių technologijų (IT) personalo biurai dėl juose gausiai naudojamos kompiuterinės įrangos, intensyvaus apšvietimo bei darbuotojų gausos. Formaliai tokie biurai, projektuojant pastatą ir jo energinį naudingumą, nėra išskiriami, jiems taikomos tokios pačios vidinių pritekių vertės kaip ir įprastiems biurams. Nepakankamas dėmesys išsamesniam šilumos pritekių diferencijavimui gali lemti tai, kad pastato naudingumas bus įvertintas netinkamai, vėsinimo sistemos bus suprojektuotos nepakankamos galios (projektinei šildymo galiai šilumos pritekiai įtakos neturi). Šio darbo tikslas yra nustatyti vidinių šilumos pritekių įtaką realaus IT biuro patalpos šilumos balansui. Šilumos pritekiai pradžioje nustatomi eksperimentiniu būdu ir lyginami su dydžiais, apskaičiuotais pagal STR 2.01.02:2016 standartą, patalpos modelis kalibruojamas IDA ICE programoje, kurioje atliekama pastato metinių energijos poreikių priklausomybės nuo vidinių šilumos pritekių parametrinė analizė. Nustatyta, kad maksimalūs paros eksperimentiniai vidiniai pritekiai yra 63–81 % didesni nei apskaičiuoti pagal reglamentą, metiniai šildymo poreikiai pagal eksperimentinius duomenis yra 31 % mažesni, o vėsinimo poreikiai 56 % didesni lyginant su gautais taikant normines pritekių vertes. Reikšminiai žodžiai: IT biuras, vidiniai šilumos pritekiai, eksperimentinis tyrimas, modeliavimas, IDA ICE.

To make reasonable solutions concerning integration of PV into the façade, complex assessment must be performed at the design stage of the building, taking into account all benefits and losses. The paper presents multi-criteria analysis of semi-transparent BIPV. It is based on 4 criteria: energy, ecology, economy, comfort – 3e+c. Results show that because of twice lower solar heat gains, PV window enables to save almost half of cooling energy, it also significantly improves thermal comfort. Total primary energy demand of the office after application of PV drops from 171 kWh/m2 to 96 kWh/m2. Multi-criteria analysis shows that office with BIPV is more sustainable than the one with transparent window.

The aim of this study is to show the critical aspects of a completely glazed high rise office building from an energy efficiency point of view in different European climates. The achievable consumptions and the most influential parameters such as glazing U-value, VT/SHGC and shading and their optimal values were investigated. The study has been carried out for a theoretical office building in Italy and Lithuania, representatively of a southern and northern EU climate. The building chosen is representative of all the glazed-simple shape buildings and the analysis of the entirety of the building enables a clear and im-mediate outcome of global consumptions. Number of DesignBuilder simulations were performed and the annual consumptions are summed with the primary energy criteria. Results show the critical aspects of 100% WWR buildings: in the coldest climate the main problem is the huge surface of relatively high glass U-value compared with standard walls, while in the warmer one the main efforts need to be done to avoid the summer overheating caused by incoming solar radiation. Finally, it is shown that it is difficult to lower the overall primary energy consumptions below 130 and 140 kWh/m2a for North-Italy and Lithuania locations respectively. The analysis is focused only in the envelope parameter, thus it is not included renewable energy systems, which can generate higher energy efficiencies. Santrauka Straipsnyje pateikiamo tyrimo tikslas – parodyti kritinius daugiaaukščių administracinių pastatų su dideliais įstiklinimo plotais atitvarų charakteristikų aspektus energinio efektyvumo požiūriu esant skirtingam klimatui. Buvo tiriami labiausiai įtaką energiniam efektyvumui darantys parametrai – šilumos perdavimo koeficientai U, šviesos ir visuminio saulės energijos praleisties koeficientų santykis VT/SHGC bei apsaugos nuo saulės priemonės ir optimalūs jų dydžiai. Buvo atliekama teorinio administracinio pastato Italijoje ir Lietuvoje analizė. Šios vietovės buvo parinktos Europos pietiniam ir šiauriniam klimatui reprezentuoti. Parinktas pastatas yra tipinės nesudėtingos formos, su visiškai įstiklintais fasadais. Pastato charakteristikų įtaka vertinama kompleksiškai modeliuojant pastato metinius energijos poreikius taikant DesignBuilder programą, vertinimo kriterijus – metiniai pirminės energijos poreikiai. Rezultatai parodė, kad pastatui su 100 % fasado įstiklinimo plotu nustatyti kritiniai aspektai yra: esant šaltam klimatui pagrindinė problema yra dideli atitvarų plotai, kuriems būdingas sąlygiškai didelis šilumos perdavimo koeficientas, lyginant su neskaidriomis atitvaromis, o esant šiltam klimatui reikia dėti pastangas, kad būtų sumažinti milžiniški šilumos pritėkiai, atsirandantys dėl saulės. Straipsnyje parodyta, kad vien optimizuojant atitvarų charakteristikas sudėtinga pasiekti metinius pirminės energijos poreikius, mažesnius nei 130 ir 140 kWh/m2, esant Italijos ir Lietuvos klimatui atitinkamai. Tyrime nevertinamas atsinaujinančios energijos išteklių panaudojimas, kuris gali itin padidinti pastato energinį naudingumą. Reikšminiai žodžiai: administracinis pastatas; klimatas; energinis efektyvumas; atitvaros; stiklinis fasadas; apsauga nuo saulės.

There are a lot of methodologies and simulation tools in the world to assess the energy demand of a building. The results of simulation tools often differ, but the causes are not analysed in more detail. The article compares the results of two most widely used dynamic energy simulation tools – DesignBuilder and IES-VE, when simulation of identical building model with the same assumptions in both programs is performed. In addition, for comparison, calculations are performed with the PHPP program, as well as using STR2.09.04:2008 methodology. The tools compare the heating, cooling capacity, energy consumption of the building for heating and cooling the building during the simulation. Following differences comparing energy demands gained with two different simulation tools are defined: ventilation – up to 11%, cooling – up to 9%, heating – up to 5%. Santrauka Šiuo metu pasaulyje yra daugybė metodikų ir modeliavimo priemonių, skirtų pastato energijos poreikiams įvertinti. Modeliavimo priemonių rezultatai dažnai skiriasi, o to priežastys detaliau nepakankamai analizuojamos. Straipsnyje lyginamos dvi pasaulyje populiarios tarpusavyje konkuruojančios dinaminio energinio modeliavimo programos – DesignBuilder ir IES-VE, rezultatai, kai abiejose programose sukuriamas identiškas pastato modelis ir daromos tos pačios prielaidos. Papildomai palyginimui atliekami skaičiavimai taikant PHPP programą ir remiantis STR2.09.04:2008 metodika. Įrankiuose palyginamos modeliuojant gaunamos pastato šildymo, vėsinimo galios, energijos sąnaudos pastatui šildyti bei vėsinti. Atlikus pastato dinaminį energinį modeliavimą gauti atitinkami poreikių skirtumai modeliuojant dviem programomis: vėdinimo – iki 11 %, vėsinimo – iki 9 %, šildymo – iki 5 %. Reikšminiai žodžiai: dinaminis energinis modeliavimas; pastato energijos poreikiai; IES-VE; DesignBuilder; PHPP.

In the buildings with large glazed areas the biggest problem is the space overheating during the warm season. This causes increased energy demand for cooling. The survey was carried out during the warm and cold seasons in two office buildings with large glazed areas. The methodology was prepared for evaluating indoor climate parameters using objective and subjective evaluation. The measurements have shown that there are problems with lighting in workplaces of both buildings during both the warm and cold seasons. The biggest problem is too dry air during the cold period, an acceptable temperature is also not always in the building No. 2. The survey has shown that some employees are dissatisfied with the indoor climate in the workplace, the bigger dissatisfaction is in building No. 2. Assessing according to the O. Fanger methodology was obtained that the number of PPD is in the normal range during the cold period, whereas close to the limit when the building can not be operated in the warm period. Santrauka Lietuvoje ir kitose šalyse, siekiant skaidrumo įspūdžio, vis dar nemaža statomų visuomeninės paskirties pastatų dalis pasižymi dideliais fasado įstiklinimo plotais. Dėl to pastatuose ne visada pavyksta užtikrinti tinkamas komforto sąlygas. Šiame straipsnyje pateikiamas dviejų administracinių pastatų su dideliais įstiklinimo plotais mikroklimato tyrimas šiltuoju ir šaltuoju metų laikotarpiu taikant dvi metodikas: objektyviąją (matavimai) ir subjektyviąją (apklausa). Matavimai rodo, kad tiek šiltuoju, tiek šaltuoju metų laikotarpiu abiejuose pastatuose kyla problemų dėl apšvietos darbo vietose. Šaltuoju metų laikotarpiu taip pat didelė problema – per sausas oras. Iš apklausos matyti, kad dalis darbuotojų nepatenkinti mikroklimato sąlygomis darbo vietoje, šis nepasitenkinimas didesnis pastate Nr. 2. Šaltuoju metų laiku PPD skaičius neviršija normos ribų, o šiltuoju yra arti ribos, kai pastato negalima eksploatuoti. Reikšminiai žodžiai: administraciniai pastatai; apklausa; apšvieta; įstiklinimo plotas; komfortas; šiluminė aplinka.

Buildings are significant contributors to energy-related sustainability challenges and a sustainable future. Practice shows—that the traditional building design process is becoming ineffective and will no longer be able to meet the determined requirements and standards of low energy architecture. The aim of this research is to introduce and validate the newly developed technology of building design concept, which integrates Quality Function Deployment (QFD) and Axiomatic Design (AD) methods. The proposed technology eliminates the traditional building design problems, ensures a smooth Integrated Building Design (IBD) process and matches the needs of the customer and the whole building design team. The new technology also provides a quicker and more effective way to find a sustainable and customer-orientated solution. Validation of the technology on the case study has shown that the energy functionality of the building proved to be superior to buildings, created during traditional building design process.

The paper presents experimental study of apartment buildings' ventilation parameters which was carried out during the heating season. The results show that the existing apartment buildings often don‘t guarantee the hygienic conditions that are directly related to the indoor air ventilation. Also article contains an analysis of possibilities to upgrade the ventilation systems of apartment buildings. Four ventilation systems‘ upgrade options were examined. The economic analysis showed that according to the economic aspect the best solution for mechanical ventilation in the typical apartment houses is a centralized ventilation system which operates in combination with ground heat pump when supply ducts are mounted on the building facade, and extraction takes place at existing natural ventilation system channels. Santrauka Straipsnyje pateikiami daugiabučių gyvenamųjų namų vėdinimo parametrų eksperimentiniai tyrimai, kurie buvo atlikti šildymo sezono metu. Tyrimų rezultatai rodo, kad esamuose daugiabučiuose namuose dažniausiai nėra užtikrinamos higieninės sąlygos, kurios yra tiesiogiai susijusios su šių namų vėdinimu. Taip pat straipsnyje pateikiama daugiabučio vėdinimo sistemų atnaujinimo galimybių analizė. Ekonomiškai išnagrinėti keturi vėdinimo sistemų atnaujinimo variantai. Atlikus ekonominę analizę, nustatyta, jog ekonominiu aspektu geriausias mechaninio vėdinimo sprendimas tipiniame daugiabučiame name yra centralizuota vėdinimo sistema, veikianti kombinuotai su gruntiniu šilumos siurbliu, kai tiekiamieji ortakiai montuojami ant pastato fasadų, o ištraukimas vyksta esamais natūralios vėdinimo sistemos kanalais. Raktiniai žodžiai: daugiabučiai gyvenamieji namai, vėdinimas, oro parametrų tyrimas, ekonominė analizė.

One of the most popular wind driven ventilation devices is a turbine ventilator. Its main construction components usually are air suction duct and impeller. However, there are many different configurations of such devices – different shape of vanes and ratios between main dimensions. In order to develop turbine ventilators there is demand for deeper fundamental researches. Major part of previous experimental investigations compares turbine ventilators performance. The aim of presented experimental investigation is to understand key parameters affecting wind driven ventilators performance. For this purpose, straight and curved vane devices under 4 different test conditions are tested. All tests are performed in modified wind tunnel based on the following methodology: 1) testing devices under normal operation conditions; 2) testing without impeller; 3) testing while impeller is stopped; 4) testing while air suction duct is sealed. Experimental results have shown that the biggest part of extracted air flow rate is impacted due to ejection of wind and air suction duct interaction process. A slight increase in performance of turbine ventilators compared to open duct column has been confirmed. Experiments also revealed differences between tested turbine ventilators rotational speed trends. Presented empirical equations of experiments could be used for design of turbine ventilators or other researches purposes.

Ventilation systems using renewable energy enable to reduce electricity demand. However, their operation directly depends on the stability of the renewable energy source. In this study, the wind driven roof turbine ventilator (RTV) is analysed. As a rule, this equipment is selected based only on the average annual wind speed and there exists a lack of date related to functionality of RTV. The case study presented in the paper seeks to assess functional operation of the RTV within the whole year. Simulations, performed with TRNSYS software, are based on the empirical equation for the ventilation flow rate extracted by the tested turbine ventilator. Results provide the number of RTV operational hours and share (%) of the time, when the RTV operates. Most of the time RTV operates at partial required load, however, there are periods when air flow rates are excessive and this should be considered as storage potential. The presented results could help to determine more accurately functional operation of RTV in the selected room/building and estimate demand for additional ventilation solutions as well energy storage potential.

The paper analyses the influence of the solar wall (unglazed transpired solar collector) on the external envelope during heating and non-heating seasons. Experiments were performed in two rooms – the one with a solar wall and without it. Based on experimental data, the analysis of the influence of the solar wall on the external envelope was done for two cases: employing air by-pass and refusing it. Also, the numerical simulation of the solar wall employing “COMSOL Multiphysics” software was performed. 8 different alternatives were simulated thus seeking to define the ways to decrease a negative and increase a positive influence of the solar wall on the external envelope of the building both in heating and non-heating seasons. The obtained results have shown that the solar wall makes a negative influence on the envelope during the non-heating season if air by-pass is not used. Heat gains increase by 8–12.2%, compared to the case without the solar wall. It has been also defined that the solar wall protects the envelope from heat gains if air by-pass is applied. During the heating season, the solar wall may decrease heat losses by 25.5%, compared to the case without the wall. Santrauka Straipsnyje nagrinėjama saulės sienos (neįstiklinto pratakaus saulės kolektoriaus) įtaka išorinei atitvarai šiltuoju ir šaltuoju metų laiku. Eksperimentinis tyrimas buvo atliktas dviejose patalpose: vienoje – išorinė atitvara dengta, o kitoje – nedengta saulės siena. Remiantis gautais eksperimentiniais ir meteorologiniais duomenimis atlikta saulės sienos poveikio atitvarai ir jos priklausomybės nuo saulės spinduliuotės intensyvumo su oro apeiga ir be jos analizė. Saulės siena modeliuota su „COMSOL Multiphysics“ programa. Sumodeliuoti aštuoni skirtingi atitvaros su saulės siena variantai, siekiant nustatyti būdus, kaip sumažinti neigiamą ir padidinti teigiamą įtaką atitvarai šiltuoju ir šaltuoju metų laiku. Nustatyta, kad saulės siena šiltuoju metų laiku, kai oras joje nejuda, daro neigiamą įtaką atitvarai – šilumos pritėkiai padidėja 8–12,2 %, lyginant su nedengta atitvara. Analizė parodė, kad saulės siena apsaugo atitvarą nuo tiesioginės saulės spinduliuotės, jei oras ištraukiamas per apėjimo ortakį. Šaltuoju metų laiku saulės siena šilumos nuostolius sumažina 25,5 %, lyginant su nedengta išorine atitvara. Reikšminiai žodžiai: „COMSOL Multiphysics“; eksperimentas; įtaka atitvaroms; modeliavimas; saulės siena.

Currently, such topics as improvement of energy efficiency of buildings and energy systems, development of sustainable building concepts, and promotion of renewable energy sources are in the focus of attention. The energy efficiency targets of the European Union are based on information regarding energy consumed by buildings. The amount of energy consumed by buildings depends on the main influencing factors (namely, climate parameters, building envelope, energy systems, building operation and maintenance, activities and behaviour of occupants), which have to be considered in order to identify energy efficiency potentials and opportunities. The article aims to investigate the total amount of energy consumed by a low energy house, built in Lithuania, using a combination of energy consumption data received from a simulation and measured energy consumption data. The energy performance analysis in the low energy house revealed some factors that have the main influence on the total figures of energy consumed by the house. The identified significant factors were used to find the optimal solutions for the design of low energy buildings.

The paper explains the results of a detailed energy audit of the buildings of Vilnius Gediminas Technical University. Energy audits were performed with reference to the international scientific project. The article presents the methodology and results of detailed measurements of energy balance characteristics. Santrauka Nuo 2009 metų VGTU dalyvauja tarptautiniame Europos mokslo projekte USE Efficiency. Pagal šį projektą Pastatų energetikos katedros jaunieji tyrėjai, naudodami Civilinės inžinerijos mokslo centro matavimo įrangą, atliko detalius universiteto pastatų energinius auditus. Straipsnyje pateikiami šių auditų atlikimo metodai, matavimų priemonės ir rezultatai bei jų analizė. Raktiniai žodžiai: energinis auditas; pastatai; energijos efektyvumas; matavimai

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. Santrauka Pastaraisiais metais Lietuvoje ir kaimyninese šalyse daugeja administracines paskirties pastatu, kuriu dauguma išoriniu atitvaru yra skaidrios. Didesnis istiklinimo plotas lemia mažesnius energijos poreikius apšvietimui, tačiau didina šildymo ir vesinimo sistemu energijos poreikius, sukelia šilumini bei vizualini diskomforta. Neigiamai dideliu skaidriu atitvaru itakai sumažinti naudojami tamsinti ir kitu specialiu charakteristiku stiklai, tačiau tai savo ruožtu didina energijos poreiki apšvietimui. Todel, priimant sprendimus del pastato istiklinimo, svarbu prieš tai kompleksiškai išnagrineti konkretaus sprendimo itaka pastato energijos poreikiams. Straipsnyje pateikiama modeliuojant gautu rezultatu analize. Rezultatai parode, kad vesaus klimato šalyse, kurioms priklauso ir Lietuva, kondicionuojamu administraciniu pastatu fasadu, kai nenaudojamos apsaugos nuo saules priemones, energiškai efektyviausias istiklinimas yra i šiaures puse. Energiškai efektyviausias santykinis fasado istiklinimo plotas pietines, rytines ir vakarines orientacijos fasadams yra 20 %, o šiaurines ‐ 20–40 %. Tačiau tokie istiklinimo plotai neatitinka norminiu natūralaus apšvietimo reikalavimu. Reikšminiai žodžiai: administracinis pastatas, istiklinimas, šildymas, vesinimas, apšvietimas, energijos poreikiai, mode‐liavimas