This paper evaluates the energy performance of ground-source variable refrigerant flow (VRF) systems to condition office buildings located in various U.S. climates. Specifically, the performance of the ground-source VRF systems was determined and evaluated against that achieved by conventional space heating and cooling systems, including packaged terminal air-conditioners (PTACs), water-source heat pumps (WSHPs), ground-source heat pumps (GSHPs), and water-source VRF systems. A comparative analysis shows that ground-source VRF systems require significantly lower source energy uses than other heating and cooling systems in all U.S. climates, ranging from 21% to 50% for PTACs, from 36% to 52% for WSHPs, from 22% to 49% for GSHPs, and from 4% to 19% for water-source VRFs. These results indicate that ground-source VRFs can be suitable heating and cooling systems for all U.S. climates when designing high-energy-performance commercial buildings.
Building air-tightness has been increased to make energy efficient buildings. However, various indoor air quality issues can be caused by high building air-tightness because it allows low air and moisture transmission through building envelop. In order to solve and prevent these issues, mechanical ventilation systems can be used to control the indoor humidity level. The purpose of this paper is to evaluate the performances of the Relative Humidity (RH)-sensor based auto-controlled centralized exhaust ventilation systems to manage indoor air quality and thermal comfort of multi-family residential buildings in South Korea. A series of field tests were performed for different target zones and for various moisture source scenarios. As a result, it was found that the auto-controlled centralized exhaust ventilation systems were able to control indoor air quality and to maintain the zones thermal comfort faster than the baseline cases that did not operate exhaust vents. The results presented in this paper can show the potential and the feasibility of the auto-controlled centralized exhaust ventilation systems for multi-family residential buildings in South Korea. It is expected that the results presented in this paper would be useful for building owners, engineers, and architects when designing building systems.
A transient three-dimensional numerical solution is developed to analyze the thermal performance of thermo-active foundations used to heat and cool commercial buildings. Using laboratory testing data, the numerical solution is validated and used to carry out a sensitivity analysis to assess the most important design and operating parameters that affect the thermal performance of thermo-active foundations. It is found that the foundation depth, the shank space, the fluid flow rate, and the number of U-tube loops in each foundation pile are the main parameters that affect the thermal performance of a thermo-active foundation system. Based on the validated numerical solution, thermal response factors for a thermo-active foundation are developed, and implemented into a detailed building energy simulation program. These thermal response factors are then used to estimate the impact of installing thermo-active foundations on the total energy use of typical office buildings in representative US climates.
The purposes of this study were to overview the building-energy policy and regulations in South Korea to achieve energy-efficient multifamily residential buildings and analyze the effects of strengthening the building design requirements on their energy performances. The building energy demand intensity showed a linear relationship with the area-weighted average U-values of the building envelope. However, improving the thermal properties of the building envelope was limited to reducing the building-energy demand intensity. In this study, the effects of various energy conservation measures (ECMs) on the building-energy performance were compared. Among the various ECMs, improving the boiler efficiency was found to be the most efficient measure for reducing the building-energy consumption in comparison to other ECMs, whereas the building envelope showed the least impact, because the current U-values are low. However, in terms of the primary energy consumption, the most efficient ECM was the lighting power density because of the different energy sources used by various ECMs and the different conversion factors used to calculate the primary energy consumption based on the source type. This study showed a direction for updating the building-energy policy and regulations, as well as the potential of implementing ECMs, to improve the energy performances of Korean multifamily residential buildings.
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