Abstract
In general, new Finnish apartment buildings are equipped with mechanical balanced demand-based ventilation. The airflow rate in the kitchen hood is boosted on demand to improve pollutant extraction during cooking. However, in practice, it has been found that the system does not work as desired. The focus of the paper was to present the simulation results from a case building equipped with a ventilation system that is commonly used in Finland. In the analysis, the airflow rates are calculated for the room, apartment, and air handling unit (AHU) levels for various ventilation mode scenarios. A significant imbalance of over 10% between the supply and exhaust airflows at the room and apartment levels was observed in the boosting mode. This imbalance creates a pressure difference over the building envelope, particularly in small studio apartments. The calculated pressure difference for future buildings with high airtightness were at the warning level of 40 Pa below atmospheric level. The kitchen hood exhaust system showed a 28% lower airflow rate in certain scenarios. A new solution to guarantee the designed airflow rates was proposed and assessed. The new solution consists of replacing the apartment level flow control damper and a new balancing method for the kitchen hood exhaust branch. The proposed design was able to stay within 10% of the designed airflow rates in all operation modes.
Highlights
The general purpose of residential ventilation is to provide a sufficient amount of fresh and clean air to the occupants with an acceptable level of energy consumption [1]
In Finland, recommendations toward the ventilation and building construction of the residential building stock are given by the Ministry of Environment [5,6,7], requiring the minimum airflow rate to be set at 0.5 1/h
Some ventilation systems have several operation modes with variable airflow rates, providing purging features based on the dwelling occupancy level using the variable-air-volume (VAV) system design [16]
Summary
The general purpose of residential ventilation is to provide a sufficient amount of fresh and clean air to the occupants with an acceptable level of energy consumption [1]. Some ventilation systems have several operation modes with variable airflow rates, providing purging features based on the dwelling occupancy level using the variable-air-volume (VAV) system design [16]. In Finland, most newly built apartment buildings are equipped with demand-based mechanical balanced ventilation with a heat recovery of at least 67% efficiency [27]. The novelty of the paper comes from the performance analysis of the demand-based mechanical balanced ventilation system with kitchen exhaust boosting, implemented in the apartment building with a high airtightness level. This type of system, unlike common modern ventilation systems, has not been assessed or simulated. The main research question is to assess whether a ventilation system with a kitchen hood boosting mode works as designed, what are the possible shortcomings and how they can be addressed
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