Regarding a comprehensive long term evaluation of thermal comfort quality of specific zones, buildings or space architypes, EN ISO 15251 proposes several homologous me- thods. Appendix F provides three different methods (A – C), which help valuating the quality of measured or calculated indoor thermal comfort in terms of PMV or operative temperature limit exceedance.
In this line, method A, which concentrates on operative temperature limits exceedance qualifies for winter month evaluations. Opposed to method A, procedure B focusses on degree hours as expression of frequency and intensity of overheating. Both methods are eligible for holistic yearly-based comfort evaluation of naturally ventilated spaces, which offer occupants considerable areas of envelope openings for individual control and adaptation.
Since sun spaces typically exclude mechanical ventilation and conditioning and typi- cally do not belong to working spaces, frequencies of hours with limits exceedance allow greater tolerance than in working spaces.
Whereas Appendix H of DIN EN ISO 15251 limits frequencies of limit exceedance to 3 to 5% for working spaces, naturally ventilated sun spaces allow higher frequencies of excee-dance. The fact, that sun space occupants qualify sun space thermal comfort detached from appropriate working productivity conditions, but rather qualify in respect to leisure qualities and are willing to adapt at short notice, widens tolerable limits exceedance to 10 to 15%.
§ 2.9.1
Explanation of method DIN EN ISO 15251, Appendix F or G
DIN EN ISO 15251 exemplifies in Appendix F method A, which evaluates thermal comfort in a comprehensive long term perspective by the calculation of cumulative frequencies of hours with exceedance of lower and upper operative temperature. As limits of operative temperature are defined <18°C, <20°C and >26°C in the con- text of sun spaces and category II. The evaluation distinguishes between entire day inspection and the preferred occupation time investigation.
153 Literature survey and empirical evaluation of thermal comfort in sun spaces
Method B focusses on hours with exceedance of the daily upper limit of operational temperature calculated with the adaptive comfort algorithm based on the daily mean external temperature. Moreover, the intensity of exceedance is weighted.
This is achieved by calculation of the actual difference of the observed operational temperature towards the daily calculated adaptive comfort upper limit Top,up,l of, for example 27,3°C (32,7°C-27,3°C => ΔTup.l = 5,4K). The multiplication of frequency and difference generates degree hours of exceedance. The sum of degree hours within a month interval gives insight in adaptive thermal comfort mismatch.
§ 2.9.2
Winter month evaluation according DIN EN ISO 15251, App. F : method A
Figure 2.68 shows a 100%, respectively 96%, frequency of hours with operative temperature lower than 18°C for January and December respectively in a 24h day perspective for the south flank. That means, that operative temperature is for almost all the time in question below 18°C between December and January. Especially in December the frequency of hours raises to 97 in the preferred occupational time between 5 to 10 PM.
The results of the west flank equals the results of the south flank. In February 117 hours of in total 130 hours represent operative temperature below 20°C during 5 to 10 PM in the south flank.
This equals 90%, whereas 2 hours are identified to with temperature above 26°C. In the west flank even 94% of all observed hours between 5 to 10 PM encounter less than 20°C indoor temperature.
Further, also in March more than the half of observed hours, precisely 60% of hours between 5 to 10 PM, showed operative temperature less than 20°C in both the south and west flank. Opposed to that benefits the south flank of 465 instead of 481 hours as the west flank of temperature below 20°C in entire day perspective.
On the contrary, hours with operational temperature below 20°C between 5 to 10 PM occur with a frequency of solely 19 and 20% respectively. Thus, 80% of all observed hours in April provided sufficient thermal comfort temperature in the sun space. Nonetheless, the hours with operational temperature above 26°C accounted with frequencies of 25 to 27 between 5 to 10 PM and 61 to 46 hours for the entire day. In November, the frequency of hours with temperature below 20°C assesses for more than 95% in south and west flank in the preferred evening hours, while the frequencies in entire day perspective slightly improve to 95 to 93%. Operational temperature <18°C accounts for 85 to 90% of observed time, either entire day or 5 to 10 PM inspection period.
Summary
The midwinter months November, December, January and February encounter signi- ficant frequencies of hours which represent operational temperature either below 20°C or even below 18°C. Thus we can conclude, that despite marginal additional distribution of heating energy by façade integrated solar thermal collectors, passive solar gains and floor heating do in terms of 85 to 90% of observed hours not manage to provide considerable frequencies of hours with sufficient operational indoor temperature. Consequently, the evaluation of indoor thermal comfort is between November until end of February demonstrably unsatisfactory.
Thermal comfort slightly improves in March towards 40% of hours representing ther- mal comfort. Solely in April, up to 80% of observed hours provide satisfactory thermal comfort. Although evaluation of south and west flank equals, the south flank results overrun for slightly 1%.
Further it is to emphasize, that in particular the south flank suffers from significant frequencies of hours with operational temperature higher than 26°C April. Hence, be- side 19% of hours with dissatisfying resulting temperature, overheating for more 27 and 61 hours respectively becomes significant.
155 Literature survey and empirical evaluation of thermal comfort in sun spaces
§ 2.9.3
Summer month evaluation according DIN EN ISO 15251, App. F : method B
Figure 2.69 illustrates, that for May 35% and 30% respectively of hours between 5 to 10 PM represent operational temperature, that exceed the calculated upper limit. Absolutely, thermal comfort mismatch accounts in the south and west flank for 249 and 216 degree hours. An entire day inspection reveal 1.031 and 1.042 degree hours exclusively in May.
In June the number of degree hours nearly triples in the south flank, whereas it lowers to 179 in the west flank. On entire day basis, degree hours raises to 1.736 for the south and to 1.694 hours for the west flank. In July, the number of degree hours lowers to 466 during evening hours in the south flank and to 219 in the west flank, what equals the number calculated for May. Similarly, degree hours in entire day perspective approximates that level of May with 1.039 in the south flank and 934 for the west respectively. Opposed to that, in August can be recognized the maximum number of degree hours both for the 5 to 10 PM interval and for the entire day interval. Seven hundred sixty five hours in the evening for south and mostly one third 267 hours for the west flank account for August. Notwithstanding, in entire day context the cumulative numbers raise to maximum with 1.622 and 1.481 hours respectively.
FIGURE 2.69 Weighted degree hours of as deviation from lower and upper limit generated with the daily mean of external temperature
A demonstrably decrease in degree hours for the preferred evening occupation time is ob-served in September in the south flank. Rarely 55 degree hours cause no worth mentioning mismatch of thermal comfort in the south flank, whereas still 195 degree hours in the west flank quadruplicate the account of the south equivalent. From entire day perspective the amount of degree hours are with 957 and 1.059 significantly high and especially for the west flank outnumber the comparative result for May.
Summarizing, in particular for the south flank the number of degree hours during evening hours is the lowest ever calculated for all summer month, but from entire day perspectives it outruns the level of May.
Contradictive, in October the number of degree hours raises to 232 and 480 in the west flank respectively from 5 to 10 PM in particular. Moreover, 1.787 and 1.872 hours account in an entire day inspection context. That means, that the west flank encounters the highest number of degree hours within summer month especially in the October evening time. The number is 2,7 times higher than compared to the equivalent of June and double the calculated number of degree hours for the entire day of July. With respect to the south flank, the second lowest number of degree hours within the summer period is calculated for the evening hours with 232 hours.
§ 2.9.3.1
Cumulative frequencies of hours with exceeding of category III
Additionally to degree hour calculations, this section calculates analogous to winter months the frequencies of hours with daily upper limit exceedance for the summer period. This calculation accessorily helps to identify significant months, when thermal comfort beside adaptive control facilities even outruns PMV levels of + 0,7 and more than 20% of occupants disclaim unsatisfactory thermal comfort. This limits equals adaptive comfort category III of DIN EN ISO 7730 A.1, Tab. A.1.
Figure 2.70 expressively demonstrates, that in the south and west flank based on an entire day perspective from May to September mostly 50 to 57% of hours exceed comfort category III.
Opposed to that, for more than 74% of all observed hours in October the operational temperature in sun space flank south result in more than 20% of predicted dissatisfied occupant and thus exceedance of comfort category III. In case of the west flank, even 77% of observed hours represent operational temperature exceeding the daily calculated upper limit. In terms of the preferred evening occupational time interval between 5 to 10 PM the table in Figure 79 illustrates the highest cumulative frequency
157 Literature survey and empirical evaluation of thermal comfort in sun spaces
of exceedance for August with both 90% of hours in south and west flank. In July, as midsummer month similar to August, three of four observed hours between 5 to 10 PM represent limit exceedance (73%). Both months are followed by June and October, when approximately 54 to 60%, every second or three of five hours encounter unsatisfactory thermal comfort.
FIGURE 2.70 Cumulative frequencies of hours with exceeding of category III
On the contrary, especially September and May show cumulative frequencies of observed hours with 21 and 26% respectively, and 49 and 45% of hours with limit exceedance. Thus we can summarize, that all summer month show at least 50% and in particular October more than 74% cumulative frequencies with exceedance of category III on entire day basis. The west flank does not differ significantly from the south flank. On the other hand, are frequencies of hours with limit exceedance comparably low in the evening hours in September, which account for solely one of five or one of four hours. Opposed to that, the frequencies of hours with category III exceeded con- siderably outnumber the level of midsummer months from entire day perspective during evenings in July and August. In this case between 70 to 90% of hours provide no tolerable thermal comfort between 5 to 10 PM.
Summary
While most degree hours between 5 to 10 PM could have been calculated for the south flank in June and August, the most degree hours in the west flank for evening hours could have been detected in October. Whereas the south flank suffers from 736 to 756 degree hours in midsummer, the west flank encounters with 480 maximum demonstrably less in October. Both the south and west flank encounter fewest degree hours during evening in September. Similar to the evening period account degree hours on entire day perspective most intensive in June, August and with maximum in October. All months encounter more than 1.480 degree hours, which maximum relocate during midsummer to autumn from south to the west flank.
Parallel, category III is homogenously exceeded for at least 50% of all entire day hours from May to September, even for more than 73% in October. From 5 to 10 PM perspective, the results differ significantly.
Fewest category III exceedance and thus most frequent satisfying thermal comfort is calculated for September evenings, whereas October evenings encounter 30% more hours with unsatisfying thermal comfort from overheating. Finally, July and August suffer considerably from overheating, when 70 to 90% of hours do not meet any comfort category.