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1.1 Multizone option is missing
Paragraph 6.4.3.1 now explicitly limits the application of the calculation methods described in the standard to single zone conditions. Here, a multi-zone option needs to be added, and the relevant equations added to 6.4.3.9. As a basis, the conclusions from the COMIS workshop (COMIS fundamentals) and IEA-EBC Annex 23 ‘multizone air flow modeling’ will be used. Additionally, the reference material from the AIRNET/CONTAM code can be used to fill in gaps. This may require a new structure for the standard.
1.2 Louvres and other ventilative cooling components are not considered
Louvres or other ventilative cooling components can be included in the calculation procedure in chapter 6 ( Calculation of air flow rates due to window openings) by specifying a method to determine the “opening free area” of louvres or ventilative cooling components.
One possible approach is to use the ratio of the louvre discharge coefficient and the discharge coefficient of an ideal window (similarly as in 6.4.3.5.2 for Aw,i):
- Louvre opening free area AL ,i = CD;L/CD;w ⋅ AL;max ,i
where AL;max ,i is the rough louvre area (excluding the frame or flanges), where CD;L = (CE+CD)/2 is determined from CE and CD measured according to EN 13030 and where CD;w=0.67 (Table D.1).
Once the free area is determined, the calculation procedure in chapter 6 can be straightforwardly applied for combinations of windows, louvres, or other ventilative cooling components (provided the discharge coefficient can determined).
1.3 Thermal stack effect is underestimated in case of multiple openings
In chapter 6.4.3.5 (Airflow due to windows opening), formula (45) - (48): A fixed coefficient Cst (Table 11) is used for the calculation of the thermal stack effect in both case with (1) one opening or (2) multiple openings. In cases with multiple openings (2) the coefficient Cst can be much higher because there is no interfacial mixing of supply and exhaust flows (Alloca 1999).
1.4 No Cross-ventilation for roof windows possible
Now there is no cross-ventilation possible because the difference in wind pressure coefficient ΔCp is always zero for roof windows. Formula (45) - (48) can be refined w.r.t. calculation of cross-ventilation for roof windows or a minimum difference in wind
pressure coefficient could be used for roof windows that are not in the same roof plane.
1.5 Calculation of airflow due to window opening not possible (6.4.3.5.2)
In the current standard, it is not possible to calculate the airflow due to window opening. R_W;arg,i as a function of angle βw,i is not defined. An approximation for R_W;arg,i as a function of βw,i is missing (see EN 15242:2007 equation (15)).
1.6 Values for fctrl are too unspecific for energy calculations (Table A.8 resp. B.4)
The value of fctrl depends on the quality of the sensors and the implementation of the automation strategy (e.g. location of sensors and control devices in relation to occupancy and pollutant levels in the various rooms in the zone, hysteresis control, set values, supply air/exhaust air compensation, etc.). In the current standard, values for fctrl are too general. Switzerland’s approach in their national annex should be considered.
Reģistrācijas numurs (WIID)
83814
Darbības sfēra
1.1 Multizone option is missing
Paragraph 6.4.3.1 now explicitly limits the application of the calculation methods described in the standard to single zone conditions. Here, a multi-zone option needs to be added, and the relevant equations added to 6.4.3.9. As a basis, the conclusions from the COMIS workshop (COMIS fundamentals) and IEA-EBC Annex 23 ‘multizone air flow modeling’ will be used. Additionally, the reference material from the AIRNET/CONTAM code can be used to fill in gaps. This may require a new structure for the standard.
1.2 Louvres and other ventilative cooling components are not considered
Louvres or other ventilative cooling components can be included in the calculation procedure in chapter 6 ( Calculation of air flow rates due to window openings) by specifying a method to determine the “opening free area” of louvres or ventilative cooling components.
One possible approach is to use the ratio of the louvre discharge coefficient and the discharge coefficient of an ideal window (similarly as in 6.4.3.5.2 for Aw,i):
- Louvre opening free area AL ,i = CD;L/CD;w ⋅ AL;max ,i
where AL;max ,i is the rough louvre area (excluding the frame or flanges), where CD;L = (CE+CD)/2 is determined from CE and CD measured according to EN 13030 and where CD;w=0.67 (Table D.1).
Once the free area is determined, the calculation procedure in chapter 6 can be straightforwardly applied for combinations of windows, louvres, or other ventilative cooling components (provided the discharge coefficient can determined).
1.3 Thermal stack effect is underestimated in case of multiple openings
In chapter 6.4.3.5 (Airflow due to windows opening), formula (45) - (48): A fixed coefficient Cst (Table 11) is used for the calculation of the thermal stack effect in both case with (1) one opening or (2) multiple openings. In cases with multiple openings (2) the coefficient Cst can be much higher because there is no interfacial mixing of supply and exhaust flows (Alloca 1999).
1.4 No Cross-ventilation for roof windows possible
Now there is no cross-ventilation possible because the difference in wind pressure coefficient ΔCp is always zero for roof windows. Formula (45) - (48) can be refined w.r.t. calculation of cross-ventilation for roof windows or a minimum difference in wind
pressure coefficient could be used for roof windows that are not in the same roof plane.
1.5 Calculation of airflow due to window opening not possible (6.4.3.5.2)
In the current standard, it is not possible to calculate the airflow due to window opening. R_W;arg,i as a function of angle βw,i is not defined. An approximation for R_W;arg,i as a function of βw,i is missing (see EN 15242:2007 equation (15)).
1.6 Values for fctrl are too unspecific for energy calculations (Table A.8 resp. B.4)
The value of fctrl depends on the quality of the sensors and the implementation of the automation strategy (e.g. location of sensors and control devices in relation to occupancy and pollutant levels in the various rooms in the zone, hysteresis control, set values, supply air/exhaust air compensation, etc.). In the current standard, values for fctrl are too general. Switzerland’s approach in their national annex should be considered.
