• Energy Research

The IPCC 2021 report predicts rising global temperatures and more frequent extreme weather events in the future, which will have different effects on the regional climate and concentrations of ambient air pollutants. Consequently, changes in heat and mass transfer between the inside and outside of buildings will also have an increasing impact on indoor air quality. It is therefore surprising that indoor spaces and occupant well-being still play a subordinate role in the studies of climate change. To increase awareness for this topic, the Indoor Air Quality Climate Change (IAQCC) model system was developed, which allows short and long-term predictions of the indoor climate with respect to outdoor conditions. The IAQCC is a holistic model that combines different scenarios in the form of submodels: building physics, indoor emissions, chemical-physical reaction and transformation, mold growth, and indoor exposure. IAQCC allows simulation of indoor gas and particle concentrations with outdoor influences, indoor materials and activity emissions, particle deposition and coagulation, gas reactions, and SVOC partitioning. These key processes are fundamentally linked to temperature and relative humidity. With the aid of the building physics model, the indoor temperature and humidity, and pollutant transport in building zones can be simulated. The exposure model refers to the calculated concentrations and provides evaluations of indoor thermal comfort and exposure to gaseous, particulate, and microbial pollutants.

In electrical grids with a high renewable percentage, weather conditions have a greater impact on power generation. This can lead to the overproduction of electricity during periods of substantial wind power generation, resulting in shutoffs of wind turbines. To reduce such shutoffs and to bridge periods of lower electricity production, three thermal energy storage systems (TESs) have been developed for space heating and domestic hot water. These include a water-based thermal system (WBTS), a thermally activated building system (TABS), and a high-temperature stone storage system (HTSS). The paper explains the development of computer models used to simulate the systems and their successful verification using field measurements. Target values to cover about 90% of building heating demand with excess electricity were found to be achievable, with performance ratios depending on storage size, particularly for WBTS and HTSS. The TABS’ storage capacity is limited by building geometry and the available inner ceilings and walls.

Abstract Much research has been focused on maintaining stable humidity conditions in buildings housing heritage collections while reducing energy use. Moisture buffering by collections themselves can have a marked effect on the stabilisation of relative humidity (RH), the key parameter for preservation. Modelling of moisture transport using COMSOL Multiphysics was applied to transform three-dimensional paper and wooden objects into their one-dimensional representations, without changing the moisture uptake and release characteristics. The results were coupled to the modelling of indoor microclimate and energy consumption in collection storage spaces with the use of WUFI ® Plus software. The study revealed the crucial impact of air exchange rate of the building on the stability of indoor RH and the humidification and dehumidification loads required to maintain it. In the adequately air-tight library store, a sizeable paper collection was found to reduce the RH fluctuations from ±9% to ±6% around the yearly average and the energy consumption due to the humidification and dehumidification load by 38% when compared with the empty space, for a high-quality climate control scenario. In turn, a wooden collection, occupying a realistic fraction of a museum store was not large enough to significantly narrow down the RH variations and reduce the energy consumption.

Abstract The paper presents the experimental measurements and numerical simulation of a ground source heat exchanger operating at a cold climate for a passive house ventilation system. The investigated passive house is a detached single-family house without a basement, occupied by a four head family, located in the South of Poland. The measurements cover over one year period and CFD (Computational Fluid Dynamics) simulations are reported for February when system operates at typical for this period and location cold climate conditions. The calculations were made with the CFD ANSYS FLUENT software package. The house and its components are fitted with a data acquisition system that is operational from 2011 and records 139 points at an interval of 1 min. The data reported in the paper were recorded during winter in the year 2011/2012 by an onside located meteorological station and temperature sensors placed at different depths in the ground and at the outlet of the ground heat exchanger.

Abstract Solar energy gains are among the most important aspects in the design of very low energy buildings like passive houses. An optimization of solar gains reduces the required heating demand, however too high solar gains can lead to overheating issues. Most methods for building energy ratings and building energy certificates use a monthly balance based calculation procedure. Also the current methodology for passive house assessment and certification is a monthly balance based one. To incorporate shading by fixed elements as an influence on solar gains into those methods, some simplifications are necessary. This paper discusses the current implementation of the shading calculation in the passive house verification method. Based on comparison tests of the current method with an advanced shading calculation method shortcomings of the existing method are discussed. It is shown that the current algorithms for static calculation sometimes give erroneous and unreliable results. The impact on the different assessment criteria, energy demand and loads as well as overheating, exceeds acceptable margins of error.

Abstract The authors assume that determining temperature distribution and heat flux directions in the ground beneath a greenhouse can help to establish the role of ground in its thermal management and explain how soil temperature of cultivated plants is shaped. Measurements of temperature distribution in the ground and in the air were conducted in a greenhouse situated in the south of Poland. Both the foundation as well as the floor has not been thermally insulated. The greenhouse has been adjusted to biennial flower cultivation. Results of air and ground temperature measurements along the vertical and horizontal measurement planes are presented in a graphic form. The observed temperatures and directions of heat transfer in the ground helps to explain the mechanism of heat flows to and from greenhouse during the whole year. In particular heat losses in winter and stabilizing of inner air temperature through heat buffering in summer periods and during intermittent heating in cold periods. Estimated heat exchange with the ground is very small in comparison with heat flows through transparent thermal envelope and does not essentially influence thermal balance of the greenhouse.

AbstractMit steigenden Anforderungen an die thermische Hülle von Gebäuden werden zu deren Design vermehrt dynamische Simulationsverfahren eingesetzt. Im Gegensatz zu Bilanzverfahren werden bei der dynamischen Simulation Wärmebrücken oft nicht berücksichtigt. Gerade eine Kombination von hygrothermischer Gebäudesimulation mit der Simulation von Wärmebrücken würde erlauben, den dynamischen Einfluss von Wärmebrücken auf den Energiebedarf des Gebäudes, aber auch ein mögliches Risiko für Schimmelpilzwachstum zu ermitteln.Dieser Artikel stellt die Grundlagen der Simulationsverfahren für die dynamische hygrothermische Gebäudesimulation und die Wärmebrückenberechnung sowie die Kopplung beider Module vor. Nach der Validierung des Wärmebrückenmoduls, das die normgerechte Umsetzung der Wärmebrückenberechnung sicherstellt, wird für einen exemplarischen Anwendungsfall das gemeinsame Simulationswerkzeug angewendet. Wenn bei nebeneinander liegenden Wohnungen nachträglich eine der Wohnungen innen gedämmt wird, treten in der Praxis häufig Schimmelpilzprobleme in der nicht gedämmten Wohnung auf, in der vorher keine Schäden zu finden waren. Es wird gezeigt, wie sich die Temperaturverläufe in der Außenwand durch die teilweise Innendämmmaßnahme verändern. Der Einfluss von Raumlufttemperatur, Feuchteproduktion im Raum, Luftwechsel und Dämmstärke auf die relative Feuchte an der kältesten Stelle wird untersucht. Die Teilsanierung verursacht höhere und zum Teil kritische Feuchten an der Anschlussstelle zwischen Wohnungstrennwand und Außenwand.Zusammenfassend wird eine hygrothermische Gebäudesimulation mit gekoppelter dreidimensionaler dynamischer Wärmebrückenberechnung vorgestellt. Das Wärmebrückenmodell wird erfolgreich validiert und die kombinierte Software für einen Praxisfall angewandt.Coupling of dynamic thermal bridge and hygrothermal building simulation. With increasing requirements on the thermal envelope of buildings dynamic building simulation is used more and more often for the design. Contrary to balance methods thermal bridges are often not accounted for in dynamic simulation. Especially the combination of a hygrothermal building simulation with the simulation of thermal bridges would allow assessing the dynamic influence of thermal bridges on the building energy demand, but also allow analyzing a possible risk for mould growth.This article presents the simulation methods for hygrothermal whole building simulation and thermal bridge simulation as well as their coupling. After validation of the thermal bridge module, which ensures a standard‐conform implementation, an exemplary application case for the new simulation software is shown. Mould growth is sometimes found in the non‐insulated and before damage free apartment, in cases where one of two side‐by‐side apartments is retrofitted with interior insulation. It is shown, how the temperature distribution in the exterior wall is changed due to the partial interior insulation measure. The influence of room temperature, moisture production, room ventilation and insulation thickness on the relative humidity on the coldest spot in the corner is analyzed. The partial retrofit causes higher and sometimes critical moisture conditions on the connection between exterior wall and party wall.In summary a hygrothermal whole building simulation software with coupled three dimensional dynamic thermal bridge simulation is presented. The thermal bridge module is successfully validated and the combined software applied to a practical case.

This article presents the results of experimental research on energy consumption of a prefabricated lightweight passive house located in the south of Poland. The key design parameters of the building were as follows: orientation maximizing heat gains from solar radiation, high thermal insulation of partitions, heat provided by ground source heat pump, and mechanical ventilation system with the heat exchanger. The measurements were performed in normal operating conditions in an inhabited building, throughout the years 2011–2019. For the year 2012, the article also presents the detailed structure of electricity used for particular devices. The objective of the research was to verify whether, in the long term, the building fulfils the energy consumption requirements for passive buildings. The measurements showed that energy consumption for heating was 50% lower than the value required from passive buildings. However, primary energy consumption for the entire building was exceeded already in the second year of research. This was caused by two factors: human behaviors and the type of primary energy source. The research concludes that the maintenance of passive house standard is vulnerable to human impact and difficult in the case of power source characterized by high index of expenditure on non-renewable primary energy. The article also presents recommendations on how to restore the passive house standard in the building.