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VENTILATION AND INDOOR AIR QUALITY IN NEW HOMES

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Abstract

Concerns have been raised regarding whether homeowners use windows, exhaust fans, and other mechanical ventilation devices enough to remove indoor air contaminants and excess moisture. In a multi-season study of ventilation and indoor air quality of 108 new single-family, detached homes in California, window use, ventilation rates, and air contaminant concentrations were measured. The median 24-hour outdoor air exchange rate was 0.26 air changes per hour; 67 percent of the homes were below the California building code requirement of 0.35 air changes per hour; and 32 percent of the homes did not use their windows. Home-to-garage pressure testing guidelines were exceeded in 65 percent of the homes. The median indoor formaldehyde concentration was 36 micrograms per cubic meter (range of 4.8 to 136 micrograms per cubic meter). Nearly all homes had formaldehyde concentrations that exceeded guidelines for cancer and chronic irritation, while 59 percent exceeded guidelines for acute irritation. In conclusion, new single-family detached homes in California are built relatively airtight, can have very low outdoor air exchange rates, and can often exceed exposure guidelines for air contaminants with indoor sources, such as formaldehyde and some other volatile organic compounds. Mechanical ventilation systems are needed to provide a dependable, continuous supply of outdoor air to new homes, and reductions of various indoor formaldehyde sources are also needed.
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... Traditionally, open windows have made important contributions to residential ventilation, so simply having a tighter envelope does not necessarily translate to lower air-exchange rates. However, recent measurements of ventilation rates in new single-family dwellings in California indicate that low rates are common in that portion of the building stock: 67% of 108 homes monitored had ventilation rates lower than the California building code requirement of 0.35 air changes per hour (Offermann 2009). Lower air-exchange rates would tend to provide improved protection for building occupants against particles of outdoor origin. ...
... A transition is underway in the US housing stock toward more widespread use of mechanical systems to provide ventilation , Offermann 2009, Sherman and Walker 2011. Mechanical systems that provide supply air can be equipped with filters to remove particles. ...
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... 24 The study in California investigated 24 VOCs in 108 newly-built homes and found that formaldehyde concentrations were affected by ventilation type and geographical location of the dwellings. 25 Similar conclusions were drawn in the measurement campaign in 305 dwellings in Sweden. 26 The French Observatory for Indoor Air Quality (IOAQ) measured VOCs in 567 French homes, in which the influence of building characteristics and socioeconomic factors on VOCs was analyzed. ...
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Exposure to elevated levels of certain volatile organic compounds (VOCs) in households has been linked to deleterious health effects. This study presents the first large‐scale investigation of VOC levels in 169 energy‐efficient dwellings in Switzerland. Through a combination of physical measurements and questionnaire surveys, we investigated the influence of diverse building characteristics on indoor VOCs. Among 74 detected compounds, carbonyls, alkanes and alkenes were the most abundant. Median concentration levels of formaldehyde (14 μg/m3), TVOC (212 μg/m3), benzene (< 0.1 μg/m3) and toluene (22 μg/m3) were below the upper exposure limits. Nonetheless, 90% and 50% of dwellings exceeded the chronic exposure limits for formaldehyde (9 μg/m3) and TVOC (200 μg/m3) respectively. There was a strong positive correlation among VOCs that likely originated from common sources. Dwellings built between 1950s and 1990s, and especially those with attached garages had higher TVOC concentrations. Interior thermal retrofit of dwellings and absence of mechanical ventilation system were associated with elevated levels of formaldehyde, aromatics and alkanes. Overall, energy‐renovated homes had higher levels of certain VOCs compared to newly built homes. The results suggest that energy‐efficiency measures in dwellings should be accompanied with actions to mitigate VOC exposures as to avoid adverse health outcomes.
... • Where concentrations of formaldehyde significantly increased as the air change rate fell below 0.5 ACHnat (see Figure 1) when there was no mechanical assistance in a US survey by Offermann (2009). Nearly all houses in this survey failed a 9 µg/m 3 8hour Reference Exposure Level for formaldehyde (Offermann 2009, 5-6). ...
... 22 Despite these regulations, formaldehyde levels exceeded guidelines for chronic and acute respiratory irritations and cancer risks in most California homes tested in a 2007-2008 study. 23 Why? ...
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... In response to changes in building codes, recent studies have evaluated the energy use and other performance aspects of new US homes [6][7][8]. These studies suggest a general trend that new homes are being built tighter in some parts of the US. ...
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A multi-season field study of ventilation and indoor air quality (IAQ) was conducted in 108 new single-family, detached homes in California, to study the elevated concentrations of indoor air contaminants with indoor sources in airtight homes with closed windows. In the study, outdoor air ventilation rates were determined concurrent with the air contaminant measurements using passive perfluorocarbon tracer (PFT) gas measurements. The results show that of the indoor air contaminants measured, only formaldehyde and particulate matter exceeded recommended non-cancer and non-reproductive exposure guidelines. For carbon dioxide, the indoor concentrations exceeded the ASHRAE Standard 62.1 body odor guideline of 700 ppm over outdoors for 9.4 hours per day, with no exceedences for a continuous system. It is recommended that airtight energy-efficient homes be provided with mechanical outdoor ventilation that is at least that prescribed by Standard 62.2. For a 1,764 ft 2.
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