# Performance Analysis of the Demand-Based Ventilation in a Nordic Apartment Building
## 4 Conclusions  
In Nordic Europe, energy efficiency requirements and a cold climate led to the utilization of balanced mechanical ventilation with heat recovery in apartment buildings. Starting from 2018, the building code requires to boost the airflow rate in the kitchen during cooking gas as it is the primary source of indoor pollutants in modern residential buildings.  
Figure 7: Airflow rates of the 2-room and studio apartments in boosting and normal modes with two position dampers installed and with two positions dampers and an improved balancing method.  
This paper assesses the performance of the centralized demand-based ventilation system with kitchen airflow rate boosting in a modern Finnish apartment building with high airtightness level. In the paper, the performance of the standard design was assessed and analyzed.  
Based on the conducted simulation, the standard design is unable to reach the design values in boosting mode with increased airflow rates. The kitchen hood exhaust was 28% lower than the target values in all apartments in the case of simultaneous apartment boosting. The studio apartments have a significant (24 %) exhaust and supply airflow rate imbalance in the boosting mode. The two-, three- and four-room apartments have about 14% higher airflow rates in the exhaust than in the supply, and in the bathroom this difference is 40%. The imbalance of the airflow rates leads to a 15 Pa negative to atmospheric pressure with existing building airtightness levels. In the very energy-efficient building, the pressure difference increased to over \(-\)40 Pa.  
To improve the performance, a new design of apartment airflow control devices and a new balancing strategy were proposed. The concept addresses changes to the overall design approach for the future apartment residential building with high airtightness level in Finland. With the improved design, the performance of the ventilation system enhanced significantly, and the maximum difference of apartment supply and exhaust airflow rates were under 10%. Furthermore, the kitchen hood operation matched the designed values of 25 L/s and provided the required pollutant extraction in the boosting mode. The average error of the standard measuring devices is around 10-15%, which in practice significantly increases the pressure over the building envelope in modern airtight buildings. Thus, this indicates that the accuracy of measuring devices is also required to be improved, and the target of the measurement devices should be 5 % to be able to prevent high pressure differences over the building envelope.  
Conceptualization: I.K., R.K. and S.K. Data curation: I.K. Formal analysis: I.K. Methodology: I.K. Investigation: I.K. Supervision: R.K. and S.K. Writing--original draft: I.K. Writing--review and editing: R.K. and S.K. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
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The authors would like to thank [PERSON] from the Halton Group for providing the Heat Balance toolset and technical support for the simulation.  
The authors declare no conflict of interest.