The growing popularity of buildings with integrated sub-systems requires a review of methods to optimize the preheating of ventilation air. An integrated system permits using geothermal heat storage parallel to the direct outdoor air intake with additional treatment in the mechanical room as a part of building an automatic control system. The earth–air heat exchanger (EAHX) has many advantages but also has many unanswered questions. Some of the drawbacks are: A possible entry of radon gas, high humidity in the shoulder seasons, and the need for two different air intake sources with a choice that depends on the actual weather conditions. In winter the EAHX may be used continuously to ensure thermal comfort, while in other seasons its operation must be automatically controlled. To generate missing information about EAHX technology we examined two nearly identical EAHX systems, one placed in the ground next to a building and the other under the basement slab. In another project, we reinforced the ground storage action by having a heat exchanger placed on the return pipes of the hydronic heating system. The information provided in this paper shows advantages of merging both these approaches, while the EAHX could be placed under the house or near the basement foundation that is using an exterior basement insulation.

Introducing integrated, automatic control to buildings operating with the environmental quality management (EQM) system, we found that existing energy models are not suitable for use in integrated control systems as they poorly represent the real time, interacting, and transient effects that occur under field conditions. We needed another high-precision estimator for energy efficiency and indoor environment and to this end we examined artificial neural networks (ANNs). This paper presents a road map for design and evaluation of ANN-based estimators of the given performance aspect in a complex interacting environment. It demonstrates that in creating a precise representation of a mathematical relationship one must evaluate the stability and fitness under randomly changing initial conditions. It also shows that ANN systems designed in this manner may have a high precision in characterizing the response of the building exposed to the variable outdoor climatic conditions. The absolute value of the relative errors ( $MaxARE$ ) being less than 1.4% for each stage of the ANN development proves that our objective of monitoring and EQM characterization can be reached.

This is an overview of a Key Note lecture; the quote for this lecture is from T.S. Eliot: “We must not cease from exploration and at the end of all our exploring will be to arrive, where we began, and, to know the place for the first time”. This quote highlights that the process of scientific development goes in circles, yet each of them goes above the previous circle, building up the ladder of knowledge. Closing one circle and opening the next may be either be a quiet, unnoticeable event or a roaring loud, scientific revolution. Building science (physics) was started about 100 years ago, but only now are we closing its second circle. Perhaps, because of building physics’ role in the fourth industrial revolution, this discipline itself is undergoing a scientific revolution The first industrial revolution was based on steam generated by burning coal, the second was based on petroleum, and the third on electricity and concentrated electricity production. The current one, i.e., the fourth, is based on distributed energy sources combined with information technology.

Protests during the 2021 Climate Conference in Glasgow exemplified our dilemma. The establishment perpetuates old thinking, while young people demand a new approach to mitigate the impact of climate change. The authors agree with the young people, and as a solution we propose to replace the current fragmentary approach with a new holistic one. The passive house approach that was conceptualized by the University of Illinois and built in Canada in 1977 showed us that energy consumption can be reduced about half of that used in the traditional design. Seventeen years later, a European passive house was built in Darmstadt. In 2008, a demonstration house in Syracuse, NY, showed that integrated passive measures produced energy use by about half of the NY state code for 2004. At the same time, some advanced houses in the USA showed total energy use of about 70 kWh/(m²∙y). In 2008, at the first Building Enclosure Science and Technology Conference, two equally important objectives for 2030 were proposed by the Lawrence Berkeley National Laboratory: (1) a 90% reduction of energy use in new buildings and (2) 50% for the retrofitting of existing buildings, i.e., to the level achieved in the 1980s. The first objective has recently been achieved in small buildings while the large residential buildings remain on the level obtained in the 2000s. Yet, the retrofitting of existing buildings (the second objective) has been a dismal failure. This paper acknowledges progress in hydronic heating and cooling involving electric heat pumps and hybrid solar panels, building automatics used for operation of HVAC, and modification of air distribution systems that comes from experience with the SARS-CoV-2 pandemic. Furthermore, it highlights that to accelerate energy efficiency and carbon emission reductions, there must be broad public-private educational programs with demonstrations of a new generation of retrofitting. Economically and ecologically retrofitted buildings will create a new approach to real estate investment.

One of the ways to improve the energy balance of buildings is through the use of local, renewable energy sources, for example, ground air heat exchanger. This article continues the study on improving energy efficiency of an EAHX working in cooperation with a ventilation unit. In the previously reported study (Romańska-Zapała et al., 2017), performed during the summer of 2016, it was found that in the summer, the continuous operation of these exchangers is not optimal. Furthermore, there is a need for dynamic control of the ventilation unit's fresh air source. This is due to changes in the exchanger's operating status between heating and cooling, as a result of external temperature fluctuations. This article presents the results of in situ measurements of the horizontal, tubular EAHX which supports maintaining the desired temperature in a building by preheating or precooling the inlet air of the cooperating ventilation unit during transitional seasons of the climatic conditions of southern Poland. In particular, this article provides details on the experimental verification of the 2017 thesis regarding the ineffective work of an EAHX during transitional seasons. The influence of the exchanger on changes in the ventilation unit's inlet air temperature is presented. Numerous, unfavorable changes were registered in the state of the exchanger's work, either heating or cooling the flowing air, depending on the relation of outside air temperature to the achieved output air temperature. This indicated that the work of the exchanger was ineffective for buildings. The key to optimal, energy efficient EAHX – ventilation unit system operation during transitional seasons is the dynamic selection of a fresh air source depending on external conditions and the required output air temperature of the ventilation unit (air supplied to rooms), accounting for the increase of electric energy consumption for the fan drive during EAHX operation.

Renewable energy sources have a significant impact on improving a building's energy balance. These sources are increasingly used in modern construction. One such source is a ground air heat exchanger (earth-air heat exchanger – EAHX), which is used in a building's mechanical ventilation system. This solution allows for the initial preparation of inlet air in a ventilation unit prior to the exhaust air energy recovery process (recuperation). As a result, the solution reduces the energy demand for the heating or cooling of rooms. This article expands upon a previous study on the possibilities of improving energy efficiency of a horizontal earth-air heat exchanger (EAHX) working in cooperation with a ventilation unit. This study adds to the knowledge gained in the previous study (Romańska-Zapała et al., 2017) performed during the summer of 2016. This previous study found that, in the summer, the continuous operation of these exchangers is not optimal; therefore, there is a need for dynamic control of the ventilation unit's fresh air source. This is due to changes in the exchanger's operating status between heating and cooling, as a result of external temperature fluctuations. The thesis statement of this previous paper emphasized that this relationship is not only appropriate on an annual basis for the transitional seasons (spring and autumn), but also on individual days during the potentially most favorable seasons of exchanger work (summer and winter). This article presents the results of in situ measurements of the horizontal, tubular ground air heat exchanger which supports building heating by preheating the inlet air of the cooperating ventilation unit in the winter season, in southern Polish climatic conditions. In particular, this article provides details on the experimental verification of the previous paper's thesis regarding the possibility of sub-optimal performance of an EAHX exchanger subject to continuous operation during the winter season. The experiment in this paper was performed using a ventilation unit (intake – exhaust) connected to three independent fresh air sources: a direct external air intake located on the wall, and two air intakes located outside of the building that directs air into the pipes of two earth-air heat exchangers. This article illustrates how the exchanger's work changes the ventilation unit's inlet air temperature. For a majority of the experiment, the exchanger – ventilation unit system was working optimally. Therefore, the system did not require intervention of the control system. However, due to several temporary increases in outdoor temperature, the occasional cooling state operation of the EAHX exchanger was also recorded. Even before the occurrence of these undesirable states, an exchanger should be switched off and a bypass should be used to directly collect external air and reduce the unnecessary load of electric fan drives. Considering the results of this study, it can be concluded that in the winter, it is favorable to automatically control the selection of a ventilation unit's fresh air source depending on external conditions. However, in the winter, the energy effect of the control is comparatively lower than in the summer.