Monitoring air quality indicators and energy consumption in Dalarnas Villa during operation of a demand-controlled exhaust ventilation system

Abstract: A real-world study was undertaken of the indoor air quality in a recently-built single family home in central Sweden, to establish whether demand controlled ventilation provided superior interior conditions, when compared with other air supply strategies, including the standard used by the Swedish buildings regulator. The property was highly airtight, with ventilation achieved using a forced exhaust system. Extraction was possible from all rooms of the house, and using a Renson Healthbox air handling unit, the rates of air flow from each room could be adjusted either according to a time schedule, or under demand control according to the unit’s sensing of the air quality in individual rooms. Five ventilation modes were evaluated, each for a period of 24 hours. Occupancy of the house was standardised, with test participants. Two separate air quality monitors were deployed to verify whether measurements made at the air handling unit were representative of the conditions that occupants experienced. Key measurements were the stable level of carbon dioxide overnight in an occupied double bedroom and the time taken for that room to refresh to background CO2 level the following day. The time taken for a kitchen/living room to similarly refresh was also examined. The study found that demand controlled ventilation achieved indoor air quality – assessed on carbon dioxide concentration – comparable with rates of fixed ventilation far greater than the regulated standard. In doing so, the air volume exchanged over a representative day was 33 % less than that standard, providing for significant energy savings. The parallel monitoring of air quality inside the room and via the air exhaust duct showed noticeable variation, but indicated the air handling unit under demand control would never ventilate insufficiently, based on its internal CO2 sensors.