ZEMCH 2015 - International Conference Proceedings | Page 619

Adaptive model Category II, defined in BS EN 15251 (BSI 2007) was considered for thermal comfort evaluations in the case study building. The following overheating criteria defined in CIBSE TM52 (CIBSE 2013) were also used to evaluate the risk of thermal discomfort: 1. C riterion 1: maximum 3% of occupied hours during which indoor operative temperature can exceed the maximum acceptable temperature by 1 K or more (ΔT= Top - Tmax rounded to the nearest number). 2. Criterion 2: daily“weighted exceedance”(We) in any one day should not be more than 6 (degree-hours). 3. Criterion 3: this criterion set the absolute maximum temperature level (Tupp) where the indoor operative temperature should not at any time exceed 4 K above the maximum acceptable adaptive temperature (ΔT <= 4 K). 4. Results of Simulations According to the results, an average indoor operative temperature of around 26 °C would be the ideal comfort temperature in free-running, naturally ventilated buildings in Uganda. It should be noted that due to the rather consistent weather conditions, comfort temperature does not change dramatically throughout the year. The average maximum acceptable indoor temperature was also defined as around 29 °C. In hotter months of the year, however, a maximum indoor temperature of up to 30.8 °C was also found to be acceptable. Table 4 summarises the results of the simulations. The results reveal that the most critical factor affecting occupants’ thermal comfort in naturally ventilated homes in Kampala is the roof construction method/material. The thermal performance of different walling and roofing methods are explained in detail in the following sections. Table 4: Summary of thermal comfort conditions for different construction methods and materials. Criterion 1 (ΔT over 1 K) Criterion 2 (Daily degree-hours over 6) Criterion 3 (times ΔT over 4 K) Adobe & Iron Sheet Roof 8.41% 65 6 Adobe & Thatched Roof 0.57% 3 0 Brick & Iron Sheet Roof 7.95% 56 2 Brick & Thatched Roof 0.84% 5 0 Hollow Concrete Blocks & Iron Sheet Roof 13.69% 148 39 TM 52 Criteria Hollow Concrete Blocks & Thatched Roof 3.24% 15 0 Solid Concrete Blocks & Iron Sheet Roof 7.02% 45 2 Solid Concrete Blocks & Thatched Roof 0.75% 5 0 Stabilised Soil Blocks & Iron Sheet Roof 7.51% 49 2 Stabilised Soil Blocks & Thatched Roof 0.83% 5 0 4.1 Adobe walls with iron sheet/thatched roof Adobe walls with iron sheet roof failed all three TM52 thermal comfort criteria. Regarding the first criterion, the indoor operative temperature was for 8.4% of the occupied periods by 1 K or more above the limiting maximum acceptable temperature. The building also failed criterion 2 (the daily weighted exceedance We) as for 65 days (17.8% of occupied days) We exceeded the limit of 6 degree-hours. As to criterion 3 (ΔT exceeding 4 K), the results reveal that there were six hours during which ΔT exceeded the “upper limit temperature” (Tupp). The situation considerably improved for adobe walls with thatched roof. The building passed both criterion 1 (0.6%, 1 K or more above the Improving thermal comfort in low-income tropical housing: the case of Uganda 617