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This study investigated cooling capacity concerns in 2-pipe economy fan coil units used in Korea, prompted by frequent field replacement claims and HVAC design engineer feedback. Comprehensive field testing of approximately 100 economy FCUs revealed significant performance discrepancies. KS B 6377 certified models (n=49) performed 6.9% below ratings, while uncertified models (n=54) averaged 9.0% below rated airflow specifications. Detailed in-situ evaluation of selected models showed uncertified units achieving only 68% of rated airflow at maximum fan speed, whereas certified models delivered 138% of rated airflow. Laboratory testing of certified models revealed internal inconsistencies, with cooling capacity ranging from 85.4% to 118.2% of rated capacity as a result of varying airflow rates despite meeting NC-40 acoustic criteria. Reduced cooling capacity results from intentionally diminished airflow rates used for noise mitigation—a concerning compromise of thermal comfort for acoustic compliance. Recommendations include implementing advanced low-noise fan technologies and specifying precise fan flowrate conditions in KS B 6377 certification standards.

New functions and requirements of high performance building (HPB) being added and several regulations and certification conditions being reinforced steadily make it harder for designers to decide HPB designs alone. Although many designers wish to rely on HPB consultants for advice, not all projects can afford consultants. We expect that, in the near future, computer aids such as design expert systems can help designers by providing the role of HPB consultants. The effectiveness and success or failure of the solution offered by the expert system must be affected by the quality, systemic structure, resilience, and applicability of expert knowledge. This study aims to set the problem definition and category required for existing HPB designs, and to find the knowledge acquisition and representation methods that are the most suitable to the design expert system based on the literature review. The HPB design literature from the past 10 years revealed that the greatest features of knowledge acquisition and representation are the increasing proportion of computer-based data analytics using machine learning algorithms, whereas rules, frames, and cognitive maps that are derived from heuristics are conventional representation formalisms of traditional expert systems. Moreover, data analytics are applied to not only literally raw data from observations and measurement, but also discrete processed data as the results of simulations or composite rules in order to derive latent rule, hidden pattern, and trends. Furthermore, there is a clear trend that designers prefer the method that decision support tools propose a solution directly as optimizer does. This is due to the lack of resources and time for designers to execute performance evaluation and analysis of alternatives by themselves, even if they have sufficient experience on the HPB. However, because the risk and responsibility for the final design should be taken by designers solely, they are afraid of convenient black box decision making provided by machines. If the process of using the primary knowledge in which frame to reach the solution and how the solution is derived are transparently open to the designers, the solution made by the design expert system will be able to obtain more trust from designers. This transparent decision support process would comply with the requirement specified in a recent design study that designers prefer flexible design environments that give more creative control and freedom over design options, when compared to an automated optimization approach.

Energy Efficient Building (EEB) design decisions that have traditionally been made in the later stages of the design process now often need to be made as early as the feasibility analysis stage. However, at this very early stage, the design frame does not yet provide sufficient details for accurate simulations to be run. In addition, even if the decision-makers consider an exhaustive list of options, the selected design may not be optimal, or carefully considered decisions may later need to be rolled back. At this stage, design exploration is much more important than evaluating the performance of alternatives, thus a more transparent and interpretable design support model is more advantageous for design decision-making. In the present study, we develop an EEB design decision-support model constructed by a transparent meta-model algorithm of simulations that provides reasonable accuracy, whereas most of the literature used opaque algorithms. The conditional inference tree (CIT) algorithm exhibits superior interpretability and reasonable classification accuracy in estimating performance, when compared to other decision trees (classification and regression tree, random forest, and conditional inference forest) and clustering (hierarchical clustering, k-means, self-organizing map, and Gaussian mixture model) algorithms.

To design a High-Performance Building (HPB), a performance goal should be clearly set from very early design phases, and then a decision path of what performance measures have been chosen in the past stages and shall be chosen in a later stage should be visible. In particular, for small- and mid-sized HPBs that are constructed with a smaller budget, if applicable performance measures are subjective to change, supplementary design costs can increase due to intermittent performance evaluations. To help this situation, we are developing a design expert system for small- and mid-sized buildings that pursues a balance between economic value and energy performance. The economy rule base suggests the most economic building volumetry and form in view of the site context, while the energy rule base suggests a series of energy-sensitive design variables and their options. Based on these rule bases, the expert system presents multiple design decision paths. The design decision support model of the inference engine helps stakeholders choose a preferred design path out of multiple paths, compare the paths, trace back the paths, and effectively revoke past decisions. An actual small retail and office construction project was chosen as a test case to compare the utility and robustness of the pilot system against the conventional design practice. In case of a rather risky design change scenario, the decision-making using the pilot expert system outperforms the conventional practice in terms of selecting designs with a good balance between economic value and energy performance. In addition, it was easier for users of the pilot system to forecast risks upon critical design changes and, in turn, to identify reasonable alternatives.

While many school retrofits in Korea tend to focus on energy savings, some school operation practices and policies in the field may cause indoor air quality issues. This study aims to analyze the indoor air quality impact when selected measures of the energy retrofit package are applied to classrooms in a real operation context with actual airflow and contaminant transport characteristics. The selected measures included replacement of envelope windows/doors/hallway-side windows, more airtight enclosures as a byproduct of adding envelope insulation, ventilation systems and air purifiers under various operating conditions, and natural ventilation. Actual classrooms with the ages of 10, 20, and 80 years were selected. Their CONTAM base models were calibrated with the measured airflow and contaminant transport variables per American Society for Testing and Materials (ASTM) D5157. The near-open-air hallways and frequent door opening made ambient PM2.5 in the hallways, which initially originated from outdoors, flow into the classrooms. Therefore, the infiltrations and penetrations from hallways to classrooms should also be secured along with those via the envelope. When the enclosures’ airtightness is enhanced, mechanical ventilation and filtration should be in operation. Specifically, they should operate independently from school energy demand reduction policy. Installing a high-efficiency filter can help a situation when mechanical ventilation needs to run at a reduced volume. Natural ventilation, as intended for energy savings, should be introduced only when the outdoor conditions are desirable and should be supplemented with a high-capacity air purifier to maintain stable indoor concentrations.

We propose an integrated geothermal system that consists of air-conditioning and hot water service ground source heat pumps, both of which share a ground water loop. The proposed system increases the COP of the service hot water ground source heat pump by recovering the condensation heat of the air-conditioning ground source heat pump as an evaporator heat source for the hot water service ground source heat pump. Eventually this integration expands the scope and capacity of the evaporator source in addition to the underground water of heat exchangers, which also leads to increase the COP of the air-conditioning ground source heat pump. The integrated geothermal heat pump system was installed in a hotel, and then data were measured for a limited period due to the hotel’s ongoing business activities. A TRNSYS simulation model has been developed as a baseline, and the baseline has been calibrated with the measured data. By running one-year simulations, it turns out that the annual electricity use for heating and cooling, and service hot water was reduced by 19.1% in the cooling season, and by 9.6% in the heating season, with respect to the conventional configuration in which the air-conditioning heat pump and hot water service heat pump work individually on their own ground loops.

An integrated geothermal system in which heat pumps for air conditioning and hot water both share the same ground loop was proposed in our previous study. Although this system produced electricity savings of 15% compared to a conventional system in which the two heat pumps operated on their own ground loop, practical requirements regarding further lowering the operation cost of the integrated geothermal system and the possibility of the energy savings being low during winter initiated further investigation into potential energy conservation measures at no initial cost increase, if possible. Outdoor reset control for hot water supply and sequential heat pump operation, both of which could be included at no extra cost, were subsequently targeted as potential measures for greater electricity savings and economic feasibility. When these measures were incorporated into the integrated geothermal system, electricity savings of approximately 25% during the heating season compared to the conventional system were predicted. Eventually it led to annual electricity savings of about 25% compared to the conventional system, which is up to 9.6 million South Korean won a year at today’s rates. Additionally, it reached the break-even point earlier than one year after installation.

School retrofitting should aim to not only improve its energy performance, but also maintain a good IAQ. An optimal combination of retrofitting measures must be selected by considering the transient state changes of the outdoor and built environments. Although a simulation is an effective platform to evaluate a combination of the retrofitting measure candidates, there is a general lack of practical methods for practitioners to collect the field data and prepare a reliable IAQ baseline model within a project timeline. This study suggests a suite of tools to generate a classroom IAQ baseline, which includes standardized diagnostic scenarios based on common retrofitting practices and measurement protocols of classroom IAQs; the diagnostic scenarios intend to quantify the dilution and filtration capabilities of classrooms through deposition, infiltration, and natural/mechanical ventilations when a high concentration is observed; the first principle model is developed to normalize the measurement, which is fitted against the measurement by adjusting its parameter values. In order to save time and effort for practitioners, automated and semi-automated calibrations that run in a short time are also developed. While the automated calibrations performed better in some cases, the semi-automated calibrations performed better than the automated ones in many cases, the CV-RMSE were smaller, by between −7% and −0.5%. Meanwhile, it took a comparably larger effort and longer time (>1 h for the worst cases) for the heuristic calibrations to have a similar accuracy with the machine-driven calibrations. If the model structure suffers a problem with the measurement, the modeler must intervene in the calibrations. In this case, semi-automation can be a diagnostic tool for a practitioner to intuitively determine from which variables to start the calibration.

Portable air flow meters are widely used for measuring air flow rates in the field. To cover broad range of flow rates, multi nozzles are generally used. If ASHRAE standard for installing nozzles is applied, the device gets large and heavy, and becomes difficult for compact siting and handling. In order to overcome this problem, computational fluid dynamic(CFD) simulations were performed to identify the factors that can make the size of the air flow meter smaller. With help of numerical simulation of which the accuracy was verified by the experiment, the necessary area for multi nozzle installation can be reduced by 47%. Based on the modeling of CFD, a portable air flow meter was manufactured and compared with an air flow measurement device that is compliant with ANSI/ASHRAE 51-1999. Nozzles and dampers which affect the length and cross-sectional size of an air flow meter were selected and improved to suit the portable type. A portable small scale multi nozzle flow meter with exit pressure control that was developed in this study has advantages of small size and acceptable accuracy in the field measurement which showed an error of 0.93%.

Most domestic modern buildings from the early 1900s have been constructed as heavy mass, and for many years have relied on passive measures for climate control. Since effective passive measures eventually reduce the heating and cooling loads, thus also reducing the system size, passive and hybrid measures are the most preferred Energy Conservation Measures (ECMs). In addition, the domestic situation and climate are additional constraints in energy retrofit decision making, such as a shorter budget and time, poor maintenance history, and uncertainties in vernacular lifestyle. For this reason, the performance improvement and side-effects prior to installing ECMs should be predictable, particularly in case the originality can be damaged. This complexity confirms that simulation-based Measurement and Verification (M&V) would better suit the energy retrofit of domestic historic buildings. However, many domestic investors still believe re-construction has a larger economic value than restoration. Therefore, they are even unwilling to invest in more time than a preset audit period—typically less than a week. Although simulation-based M&V is theoretically favored for retrofit decision making, its process including collecting data, modeling and analysis, and evaluating and designing ECMs could still be too demanding to domestic practitioners. While some manual, repetitive, error-prone works exist in the conventional retrofit process and simulation-based M&V, it is proposed here that enhanced Building Information Technology (BIT) is able to simplify, automate, and objectify, at least the critical steps of the retrofit project. The aim of this study is to find an efficient and effective energy retrofit strategy for domestic historic buildings that appeals to both domestic investors and practitioners by testing selective BIT tools on an actual historic building. This study concludes with the suggestion that software vendors are asked to develop enhanced features to resolve users’ pending demands. It is also suggested that, in the domestic context, how the current practice for each process of the energy retrofit of historic buildings needs to shift to take a full advantage of BIT.