No abstract

Measurements were taken in new US residences to assess the extent to which ventilation and source control can mitigate formaldehyde exposure. Increasing ventilation consistently lowered indoor formaldehyde concentrations. However, at a reference air exchange rate of 0.35 h -1 , increasing ventilation was up to 60% less effective than would be predicted if the emission rate were constant. This is consistent with formaldehyde emission rates decreasing as air concentrations increase, as observed in chamber studies. In contrast, measurements suggest acetaldehyde emission was independent of ventilation rate. To (OEHHA 2013) may require combining source control with ventilation. Ventilation rates could be increased during the first year after construction when VOC concentrations tend to be highest.

Energy efficiency is an essential component of water heating considerations in the overall efforts to achieve national energy saving goals. Although heat pump water heaters have been around for over three decades, this technology has only matured in recent years, in part because of improved systems and infrastructure as well as emerging energy conservation standards on water heating. The goal of this study is to provide a comprehensive and in-depth review of heat pump water heater research on system energy efficiency and performance topics. The study focuses on laboratory and field (in-situ) experiments and measurements, modeling of energy use and efficiency, technological modifications or upgrades, and control operation strategies; with emphasis on the Coefficient of Performance (COP), reliability, and energy savings. The review shows that while most of current heat pump water heater systems operate in the COP range of 1.8-2.5, there are some potential technological updates that could augment the current systems and increase COP to a range of 2.8-5.5. Issues that could dampen the adoption of these technologies are discussed. The review identified key areas for future studies that are still lacking in support of various changes suggested for increasing heat pump water heaters efficiency and performance.

In order to optimize strategies to remove airborne contaminants in residences, it is necessary to determine how contaminant concentrations respond to changes in the air exchange rate. The impact of air exchange rate on the indoor concentrations of 39 target volatile organic compounds (VOCs) was assessed by measuring air exchange rates and VOC concentrations at three ventilation settings in nine residences. Active sampling methods were used for VOC concentration measurements, and passive perfluorocarbon tracer gas emitters with active sampling were used to determine the overall air exchange rate corresponding to the VOC measurements at each ventilation setting. The concentration levels and emission rates of the target VOCs varied by as much as two orders of magnitude across sites. Aldehyde and terpene compounds were typically the chemical classes with highest concentrations, followed by alkanes, aromatics, and siloxanes. For each home, VOC concentrations tended to decrease as the air exchange rate was increased, however, measurement uncertainty was significant. The indoor concentration was inversely proportional to air exchange rate for most compounds. For a subset of compounds including formaldehyde, however, the indoor concentration exhibited a non-linear dependence on the timescale for air exchange.

Measurements were taken in new US residences to assess the extent to which ventilation and source control can mitigate formaldehyde exposure. Increasing ventilation consistently lowered indoor formaldehyde concentrations. However, at a reference air exchange rate of 0.35 h-1 , increasing ventilation was up to 60% less effective than would be predicted if the emission rate were constant. This is consistent with formaldehyde emission rates decreasing as air concentrations increase, as observed in chamber studies. In contrast, measurements suggest acetaldehyde emission was independent of ventilation rate. To evaluate the effectiveness of source control, formaldehyde concentrations were measured in Leadership in Energy and Environmental Design (LEED) certified/Indoor airPLUS homes constructed with materials certified to have low emission rates of volatile organic compounds (VOC). At a reference air exchange rate of 0.35 h-1 , and adjusting for home age, temperature and relative humidity, formaldehyde concentrations in homes built with low-VOC materials were 42% lower on average than in reference new homes with conventional building materials. Without adjustment, concentrations were 27% lower in the low-VOC homes. The mean and standard deviation of formaldehyde concentration were 33 µg m-3 and 22 µg m-3 for low-VOC homes and 45 µg m-3 and 30 µg m-3 for conventional.