The IVAIRE Project - Ventilation Characteristics of Single Family Homes of Asthmatic Children Followed in an Asthma Clinic

摘要

Background and Aims The IVAIRE study evaluated the impact of improved residential ventilation on IAQ and the frequency of asthma symptoms in children. This paper describes the pre-intervention phase of this study where the ventilation characteristics of the single family homes were analyzed in order to select the homes participating in the ventilation intervention. Methods Between October 2008 and June 2010, 111 children were selected and their homes were visited three times by trained technicians during the heating-season (fall and winter) and summer. During these visits the ventilation rates were measured and the mechanical ventilation system (MVS) and their use were characterized. The measured ventilation parameters were the air changes per hour (ACH) measured with PFT gas, the building airtightness (ACH50) with a blower door, CO2, and relative humidity (RH). Ventilation parameters were compared according to the presence/absence and the type of MVS. Results A MVS was present in 73 of the 111 homes, of which 44 were heat recovery ventilators (HRV) and 29 had mixing boxes. There was no difference in ACH between the homes with (0.22) or without (0.20) a MVS (p=0.53). However, the ACH50 was lower in the homes with a MVS than without (3.1 vs. 4.8, p=＜0.0001) as well as RH (37.6 vs. 42.3%, p=0.0009). Moreover the homes with an HRV had a higher ACH (0.25 vs. 0.18, p=0.003) and a lower RH (35.8 vs. 40.4%, p=0.002) than the homes with a mixing box. Conclusions Even though in the homes with a MVS an HRV seems to be more effective than a mixing box, the ACH remained lower than the ASHRAE recommended guideline of 0.35 h-1. This indicates that the presence of a MVS alone may not guarantee adequate ventilation. Factors such as the capacity of the ventilation unit, proper installation and utilization by occupants need to be investigated to design specific corrective interventions tailored to each home.