Results

The occupancy profiles age and gender

The subjects were all Vietnam nationals in the age group 24-55 years who had worked in the offices for longer than three months. A total of 244 responded in two period times:

108 male, 103 female.

The average age of occupants was 30.2 yrs. Most of occupancy age is 30 to 39 yrs in all office, whereas the ages over 40 was found less than 20%. However, the gender and age is similar in both summer and winter surveys time. The age and the gender profile of the subject sample is shown in Figure 3.30 and 3.31

Figure 3.30 Gender profile

Figure 3.31 Age profile

The overall clothing rate was calculated by the estimated formula by ISO9920 as following;

Where:

Icl: Total clothing amount

Iclu: clothing amount for each cloth

From the answering of question about clothing include tops; bottom and shoes, the value of clothing insulation [Iclu] were summed of occupants responded. Iclu of inner is standardized as 0.093 for man, 0.060 for woman.

Figure 3.32 Total clothing rate

Average clothing insulation is 0.652 clo in summer, and 0.707 clo in winter. Divided this into men and women, average on only men is 0.70 clo in summer and 0.791 clo in winter, while 0.60 clo in summer and 0.63 clo in winter for women. Figure 3.32 shows cumulative frequency of overall clothing amount. The signification value vary from 0.4 clo to 0.7 clo is very frequent in both season; 71.9% in summer and 63.0% in winter.

Table 3.5-4 Overall clothing rate measurement

Overall clothing rate Male Female Average frequency

Summer 0.698 0.604 0.653 71.9%

Winter 0.792 0.634 0.707 63.0%

Thermal environment conditioning Outdoor conditions:

During the survey period, the outdoor daily mean temperature in Hanoi varied from 24.3 to 36.8 ˚C in summer time and 14.1 to 19.5 ˚C in winter time. While daily mean relative humidity varied from 47.4% to 86%. with a wider range of daily mean relative humidity and temperature, summer season has the highest level of discomfort in outside condition, winters during the survey period were very mild.

Figure 3.33 Correlation air temperature and humidity ratio during the period surveys

Figure 3.34 Indoor air temperature and operative temperature in summer days Indoor conditions:

Indoor temperature during investigation time is show in figure 3.34. The valued data is 8:00 AM to 5:00PM as working time. All of this time the indoor environment has air-conditioning model, the straight line shown the operative temperature and the dot-line shown the air-temperature. It is interesting to note that, the mean air temperature between five case study had distinct differences from 24.5 to 27.2 ˚C in summer and 21.6 to 25.2

˚C in winter. Similar outdoor condition, the humidity in winter drier summer, the

humidity ratio of indoor has over 0.012g/g in all case. In summer time, the mean operative temperature varied between 29.1 to 30.37 ˚C, it mean value hovered around 29

˚C. Only case study CA has very stable between air temperature and operative temperature.

Thermal sensations vote

The thermal sensation (TS) is an important psychological expression relating to the feeling warmth or coolth. It is estimate from the response to a direct question “how do you fell the present temperature of this room?” Figure 3.35, 3.36 and 3.37 shown the distribution of thermal sensation, preference and acceptability votes.

Proportion voting within the comfort neutral on the sensation scale was about 64.7% in winter and 47.8% in summer. Cold discomfort was noticeable in both season.

For example, 38.2% occupants voted on the cooler side in summer time, while only 2.94% occupants felt cold discomfort (voting: - 2 and - 3) in winter time. This is a significant observation that displays indoor air distribution debacles with the HVAC systems. In warmer side, the voting is similar rate with 5.9% in winter and 4.2% in summer of occupancy felt warm discomfort (voting: 2 and 3).

Figure 3.35 Frequency distribution of Thermal sensation in summer and winter

The thermal preference (TP) were measured with question “how would you preference to fell?”. Figure 3.36 shows the distribution of the thermal preference doe. A preference for neutral was about 63.2% in winter and 55.4% in summer. A preference for cooler environments was evident throughout the survey. Interestingly, about 10.6% of the subjects preferred still neutral or comfortable while voting on the cooler side of

discomfort on the sensation scale and similarly about 6.2% desired still neutral environments even while feeling a warm discomfort sensation.

Figure 3.36 Frequency distribution of Thermal preference in summer and winter

Figure 3.37 Frequency distribution of Thermal acceptability in summer and winter Thermal acceptability (TA) relates to very important psychological dimension of thermal comfort perception. It reflects a several aspects pertaining to the occupant comfort:

indoor and outdoor thermal conditions, access and use of control, thermal history, air quality, etc. This surveys collected with question “Do you accept the present indoor conditions?” to all the occupants to ascertain the thermal acceptability. Figure 3.37 show the result in winter and summer, the response are similar in both season. There were around 63% and 65% has accepted the present conditions in respectively winter time and summer time.

Trend to feel cool and comfortable is often seen from response. However, we noticed lower acceptability in general. This in our opinion is due to poor indoor air distribution due to the HVAC system, lack of air movement, and fluctuations of indoor temperature leading to discomfort sometime.

Further analyzing the subject’s skin moisture (SM) and its influence on thermal acceptability. Skin moisture was measured on a four points scale (none = 0; slight = 1;

moderate = 2; and profuse = 3). People complained litter of sweating when the AC is on in both season, more so in summer. A higher percentage of people voted the environment acceptable even while sweating. Figure 3.38 show a relationship between thermal acceptance and skin moisture during two times investigation.

This is further corroborated by the correlation between TA and SM. Hanoi being a humid climate as shown in section 2.2, the occupants considered sweating natural and acceptable. In this surveys had not conducted with outdoor questionnaire. According to other reaches has done in hot and humid climate, for example M. Indraganti, 2013 conducted a survey in Chennai with 25% occupants sweating profusely accepted the environment. In this study, there are 14.9% of occupants sweating slight accepted the environment with office indoor in AC mode. This enabled considering in terms of thermal adaptation, thereby increasing thermal acceptability.

Figure 3.38 Frequency distribution of skin moisture

On the other hand, we measured humid sensation HS. The subjective feeling of dryness, wetness or neutral is measured using on three point scale (dry = - 1; neutral = 0; wet = 1). It is interesting to noticed that a higher percentage of occupants vote the feeling of dryness. Figure 3.39 show frequency distribution of rate voting. It was slight higher in winter. Comparison in both indoor and outdoor conditioning show on Figure 3.33, its may because of the influence of the natural environment impact on the sense of human adaptation in the indoor enclose environment

Figure 3.39 Frequency distribution of Humid sensation HS

Figure 3.40 (a,b) shown a correlation between feelings of dryness/wetness and indoor absolute humidity compared with thermal criterial by ASHRAE standard in limitation of water vapor ratio below 0.012 g water per dry air. Its indicated that the thermal adaptive of humidity of occupants in Hanoi can be higher than the limit index. There are over 47% occupants has constantly feeling of dryness in under 47% relative humidity.

Figure 3.40 a;b Correlation between absolute humidity and humid sensation Comfort temperature

Linear regression analysis is a well known method to analysis the thermal comfort field data to examine the change in thermal sensation with indoor temperature and to evaluate the comfort temperature of an occupants. By examining the mean response of an occupants over a wide range of temperature, its can predict the comfort temperature.

Thus on regression of the measured thermal sensation with the indoor globe temperature

Figure 3.41 Correlation between TSV and globe temperature in summer time