Assessing the “sufficient ventilation” requirement for Austrian buildings: development of a Monte Carlo based spreadsheet calculation to estimate airing intervals and mould risk in window ventilated buildings

Figures & data

Figure 1. Examples of probability density functions based on beta distributions used to define variability of input parameters. Left: airtightness value for standard new constructions [1/h], Center: room area for bedrooms [m²], Right: window tightness class for old buildings (is consequently rounded to integer value).

Table 1. Summary of all relevant input parameters and the corresponding number of defined probability density functions (PDFs) and what the selection of the PDF depends on {in curly brackets}.

Building and room parameters	No. PDFs {dependency}	Parameters for mould risk assessment	No. PDFs {dependency}
Location	–	Thermal bridges (fRSI)	5 {bld. standard}
Building type	–	Total humidity load (l/d)	–
n50-value (1/h)	5 {bld. standard}	Emi. rate occupancy (g/(h m²))	1 {hum. load}
Room type	–	Emi. rate occupancy (g/(h per))	1 {hum. load}
Room area (m²)	9 {room type}	Emi. rate absence (g/(h m²))	1 {hum. load}
Room height (m)	9 {room type}	Dwelling area (m²)	4 {bld. type}
Window area (m²)	9 {room type}	No. of person	4 {bld. type}
Window airing AER (1/h)	2 {bld. type}	Window airing AER (1/h)	2 {bld. type}
Window airing dura. (min)	2 {bld. type}	Window airing dura. (min)	2 {bld. type}
Window class (EN12207)	5 {bld. standard}	Temperature avg. (°C)	5 {bld. standard}
Terrain class (wind)	15 {location}	Temperature min. (°C)	5 {bld. standard}
Shielding class (wind)	15 {location}	Temperature abs. (°C)	5 {bld. standard}
Occupancy parameters	No. PDFs {dependency}	“Hidden” parameters (not shown in entry mask)	No. PDFs {dependency}
No. adults	9 {room type}	Factor n50 bld. vs. n50 room	1 {–}
Activity adults (met)	9 {room type}	Factor leakage distribution	2 {}
No. children	9 {room type}	Building height (m)	6 {bld. type}
Activity children (met)	9 {room type}	Rel. stack eff. height (–)	6 {bld. type}
Avg. age children (a)	9 {room type}	Rel. wind press. height (–)	6 {bld. type}

Table 2. Assumptions of reasonable time interval between occupant intervention.

Room type	Time interval
Bedroom	480 min
Living room, office	120 min
Meeting room	60 min
Classrooms	45 min

Figure 2. Window airing requirement for the bedroom of a new multifamily building (see text). Left: Evolution of time average of CO₂ concentration without and with airing for the median case, and for selected percentiles without airing. Right: Histogram of window airing interval if Austrian limit value is not to be exceeded.

Figure 3. Window airing requirement for a 50 m² living room of a new multifamily building (see text). Left: Evolution of time average of CO₂ concentration without and with airing for the median case, and for selected percentiles without airing. Right: Histogram of window airing interval if Austrian limit value is not to be exceeded.

Figure 4. Histogram for number of cases with different water activity results. Values >0.8 correspond to cases with substantial mould risk. Left: Result for standard newly constructed multifamily building in Vienna. The remaining parameters are defined by the stored PDFs. Right: Results for newly constructed multifamily building in Vienna with minimal thermal bridges (Passive House standard) and low humidity load assumption.