The densification of buildings by the recent sudden population and economic growth is significantly higher in the countries of Tropical Asian countries. Additionally, in these countries, it is identified for keeping the indoor temperature in facilities such as office buildings remarkably low. Therefore, it is necessary to elucidate the actual situation of the operation of air conditioning (AC) systems and the indoor environment quality in Tropic Asia, and their influence on the comfort of the residents. To address knowledge gap, this study suggests an appropriate AC system considering actual local situation. In the present study, real conditions of the thermal environment and air leakage were evaluated from actual measurements of the indoor environment of office buildings in five cities (Hong Kong, Taipei, Hanoi, Bangkok, Singapore) from the hot and humid regions of Asia. Based on the questionnaire survey, it was found that an environment with low temperature and low humidity was preferable for office workers. Considering the obtained results, we propose a humidity-controlled external air conditioner as an AC system that can realize an indoor environment as well as meets the preferences of office workers in Southeast Asian countries, while saving energy. The system’s energy conservation performance was verified. The results obtained from the simulation study suggest that the system using the humidity-controlled external air conditioner is expected to reduce energy consumption by 12% to 61% under different temperatures, humidity scenarios, and external skin conditions compared with the conventional system using only a high sensible heat type multi-AC system for buildings. The overall, coefficient of performance of the AC system was approximately 1.7–3.5 in the case of the combined use of humidity control and external AC units. Therefore, it was found that the combined use of external humidity control units has significant advantages in terms of energy consumption reduction and operating efficiency. Broadly, the current study investigated the effect of the external humidity controller based on the actual measurements and simulations in an existing office building without an external humidity controller. Further studies are required to confirm the acceptability of the indoor environment achieved by the proposed system with an external humidity controller to the office workers in the Southeast Asian region.

In this paper, we propose standard office building specifications that can evaluate energy efficiency and conservation performance of medium and large-scale buildings. The results of the study are presented for the maximum air conditioning heat load and primary energy consumption intensity of the standard specifications for these buildings and facilities. Three specifications are proposed for medium-scale office buildings: standard, energy-saving, and ZEB (Net Zero Energy Building). The analysis and evaluation of various methods are conducted for achieving ZEB (energy-saving performance, indoor environment, and air-conditioning heat source load reduction effect). Further, planning methods for each specification, not by the hierarchical approach but back casting, are presented.

The authors are proceeding with a series of studies on corrosion countermeasures for building equipment in water piping systems. In the previous paper (Part1), the authors showed that treatment of tap water with anion exchange resin reduced corrosivity drastically. In practice, carbon steel did not corrode for 720h in the treated water. This paper (Part2) aimed to elucidate the mechanism of this reduction in corrosivity. First, the trajectory of corrosion potential vs. pH over time was discussed on the Pourbaix Diagram. The trajectory indicated that the passive film became tough in the treated water, while it collapsed in untreated water. The corrosion indexes supported this mechanism. Second, the change of water composition before and after the corrosion test was studied. The concentrations of Ca²⁺ and ionic SiO₂, which were thought to be main constituents of the deposits, changed slightly. This indicated that no deposits was formed at the metal surface. From these results, the authors concluded that the key mechanism of corrosion prevention of the treated waters was the sustenance of passive film.