In recent Vietnam, the ownership rate of air-conditioners and the number of units owned has broadly increased in accordance with a rise in standards of living due to economic growth, and the increase in energy used in air-conditioning has become a problem. This study aims to consider ways of living and residences capable of suppressing rising of energy consumption in the future by understanding the current state of cooling and air-conditioning of homes in Vietnam.
Interviews with residents of stand-alone homes built in Haiphong City in northern Vietnam were carried out and room temperatures were taken. The interviews were carried out in August of 2014 and questions were asked about (1) air-conditioner and electric fan usage status, (2) indoor space usage status, and (3) the degree of hotness and coolness indoors. The rooms subjected to temperature measurements were decided from the results of the interview and measurements were carried out in 10 minute intervals in July of 2015.
Three of the four target residences were so called pencil style residences with narrow entranceways, great depth, and three or four floors. The other residence was a single story farmer's residence. All four residences were structures combining reinforced concrete construction with brick walls that were built without insulation.
The three pencil residences had air-conditioners installed in the private rooms of the intermediate floors which were used for approximately 10 total hours for naps and going to sleep at night. The room temperature was maintained at around 28°C and many residents gathered in the cooled room before sleeping and then slept there together. Outside of the cooling period the first floor dining room (or living room) had the lowest natural room temperatures indoors. The residents spend most of their time in this space when not sleeping and carried out various daily activities here such as eating, family socializing, breaks, and receiving visitors. The highest floors on the other hand had exceedingly high temperatures. Consequently, the private rooms on the highest floor are mostly not used during the summer and daily activities on the highest floors are limited to drying laundry.
As stated above, the first floors of pencil residences are the coolest place indoors and are a low priority for air-conditioning while the highest floors are exceedingly hot which leads to the assumption that the air-conditioning efficiency will be poor on the highest floors. Air-conditioners are installed in private rooms on the intermediary floors as a result. Furthermore, along with the phenomenon of there being a persistent high demand for air-conditioning for sleeping periods, little psychological resistance to sleeping with multiple people in the same room, and a poor partitioning between staircases and public spaces such as dining rooms and living rooms which leads to poor air-conditioning efficiency, there is an established way of living where the private rooms on the intermediary floors are cooled and slept in together by the family. The residents of course also consider the heat characteristics of the spaces on each floor at the time of air-conditioner installation and flexibly change where the family stays as necessary. One could say that they have mastered each floor space of the pencil residence.
In the farmer's residence the daytime maximum temperatures are kept low during the day due to the light shielding effect of the plants which cover the garden. In addition, it's also easy to get ventilation since the flat residence is almost like a one room space and there is currently no air-conditioner installed.