Housing in Southern Africa October-November 2016

‘as-built’ IBT houses the windows were closed during the data collection process. However, this approach does not reflect the real temperatures in the case of an occupied housewhere openwindows allow for cross ventilation. Cross ven- tilation could possibly improve the indoor comfort, but cannot be plau- sibly determined in this phase of the analysis. Reasons why the relevant IBT houses were not thermally com- fortable were also not established for this investigation.

Conclusion For this investigation, focus was on the thermal performance of IBT houses and whether they complied with the ASHRAE 55 Adaptive model thermal comfort ranges. The poor winter results revealed that more research is required on design of IBT houses for thermal performance in different climate zones. Considering these houses were built before 2011, when the SANS 10400XA standard on energy efficiency requirements came into operation, there is now a better benchmark according to which IBT houses can be designed for ensuring thermal comfort. The question on whether the relevant IBT houses comply with comfort ranges has been addressed, but still need to uncover the rea- sons for the relevant performance. Through the use of a certified energy efficiency software one will be able to complete the modelling of the at least one IBT house falling within the relevant different categories (light weight to heavy weight) to establish the variables that contributed to the performance. The variables that could have had an influence on the thermal comfort can range from issues related to orientation, window position and sizes, thermal mass, insulation, cross ventilation and shading. One can then also ascertain whether radiant temperature would have made a significant difference in the results. The thermal ratings will be avail- able on the newdynamic newNHBRC IBT Database. ■

to prevailing outdoor temperature and defines zones of 80% and 90% satisfaction. The tool’s operative minimum and maximum comfort temperature benchmarks automatically adjust according to the input data, which ranged between approximately 15 ºC and 32 ºC. The operative temperature can be defined as the average of the mean radiant and ambient tempera- tures weighted by their respective heat transfer coefficients. The personal factors and humid- ity are not significant in this method since adaptation is considered, and the only variable is the outdoor temperature. The mean radiant tem- perature of the enclosing surface of a space is determined by the emissiv- ity and temperature of the surfaces. According to Holm and Engelbrecht small floor areas and low ceilings force radiant temperature to be clos- er to the dry-bulb air temperature and therefore for this investigation taken as the same value. The input data for the thermal comfort tool was the real-time data collected from the loggers for the indoor and outdoor temperatures for each house to individually establish whether the temperatures fell within the relevant ASHRAE 55 comfort ranges (benchmarks) for the relevant winter and summer periods. Due to the variables for each house being different, direct com- parisons are not made in this phase of the research. The mean radiant temperature for the first exercise is taken as the indoor dry-bulb air temperature.

Methodology and Analysis For the sampling, calibrated Keytag KTL – 508 Temperature and Humidity data loggers were used, which came with a certificate of compliance. For this phase, two instruments (north and south) were set up per house in peak winter and summer periods for one month. Being part of the first stage of the project some interest- ing deductions were made on this analysis in terms of thermal comfort considering indoor and outdoor temperatures for naturally ventilated buildings according the ASHRAE 55 (2013) Adaptive method. The data was analysed using the web-based tool for thermal comfort calculations according to ASHRAE Standard 55 (2013), developed by the University of California at Berk- ley. The main features of the Adap- tive method, applicable to naturally ventilated buildings, included input variables such as dry-bulb air tem- perature, mean radiant temperature and prevailing mean outdoor tem- perature. The adaptive chart/tool re- lates to indoor comfort temperature

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