LOW ENERGY HOUSING FOR THE HOT HUMID CLIMATE OF VIETNAM: THE VALUE OF A PASSIVE HOUSE APPROACH

In Vietnam, the climate is such that creating thermal comfort inside building consumes significant energy. Residential buildings are responsible for 35% of electricity consumption and 27% of total energy use in the country. Therefore, in the context of ongoing global warming and energy crises, there is an urgent need to use energy efficiently to create thermal comfort in Vietnamese housing. This study aims to identify a new approach, which is based on the Passive House methodology, as an alternative solution to conventional natural ventilation design and to support the development of more robust dwellings in Vietnam.

This study firstly carried out a thermal comfort investigation to supplement the modest thermal comfort database of Vietnam. The thermal comfort zone of Vietnamese people was found to range 23.7 – 29.6°C, and this was used as an important criterion to evaluate indoor thermal conditions of Vietnamese dwellings.

A field study was undertaken to examine existing conditions of Vietnamese housing. The results indicated a poor thermal performance of existing housing with houses failing to satisfy thermal comfort in the hot season. Based on the data collected from the field study and a complementary survey on household appliances and energy consumption, two typical terraced and detached houses were modelled. The simulations of whole-year thermal performance indicated that a significant amount of energy was required to maintain thermal comfort in the existing housing stock.

To improve the performance of existing housing, passive design techniques were applied. While these techniques significantly reduced the cooling demand, high indoor humidity was a continuing disadvantage of conventional naturally ventilated dwellings and added to other indoor air quality concerns in polluted high-density areas. Consequently, the Passive House approach was proposed as an advance alternative solution for low energy housing in Vietnam.

To investigate the potential of the Passive House approach, the housing models were improved to meet the Passive House standard. The standard was adapted to the hot humid climate of Vietnam with a higher thermal comfort zone, higher humidity limit and lower envelope air tightness. Substantial energy saving of the Passive House dwellings were demonstrated compared to the existing houses.

Subsequently, a parametric simulation, based on key influencing building parameters, was used to calculate opportunities for Passive House dwellings in Vietnam. Based on the simulation outcomes, design guidance for Passive House dwellings was proposed.

A questionnaire survey was carried out with 71 professionals to assess the value of the guidance. The results indicate that the Passive House approach should be further researched and developed in Vietnam, and that the proposed design guidance is a useful document to aid decision making at early stage design.