Indoor air quality in 24 California residences designed as high-performance homes

Abstract

Today's high performance green homes are reaching previously unheard of levels of airtightness and are using new materials, technologies and strategies, whose impacts on Indoor Air Quality (IAQ) cannot be fully anticipated from prior studies. This research study used pollutant measurements, home inspections, diagnostic testing and occupant surveys to assess IAQ in 24 new or deeply retrofitted homes designed to be high performance green buildings in California. Although the mechanically vented homes were six times as airtight as non-mechanically ventilated homes (medians of 1.1 and 6.1 ACH50, n=11 and n=8, respectively), their use of mechanical ventilation systems and possibly window operation meant their median air exchange rates were almost the same (0.30 versus 0.32 hr -1 , n=8 and n=8, respectively). Pollutant levels were also similar in vented and unvented homes. These similarities were achieved despite numerous observed faults in complex mechanical ventilation systems. More rigorous commissioning is still recommended. Cooking exhaust systems were used inconsistently and several suffered from design flaws. Failure to follow best practices led to IAQ problems in some cases. Ambient nitrogen dioxide standards were exceeded or nearly so in four homes that either used gas ranges with standing pilots, or in Passive House-style homes that used gas cooking burners without venting range hoods. Homes without active particle filtration had particle count concentrations approximately double those in homes with enhanced filtration. The majority of homes reported using low-emitting materials; consistent with this, formaldehyde levels were approximately half those in conventional, new CA homes built before 2008. Emissions of ultrafine particles (with diameters <100 nm) were dramatically lower on induction electric cooktops, compared with either gas or resistance electric models. These results indicate that high performance homes can achieve acceptable and even exceptional IAQ by providing adequate general mechanical ventilation, using low-emitting materials, providing mechanical particle filtration, incorporating well-designed exhaust ventilation for kitchens and bathrooms, and educating occupants to use the kitchen and bath ventilation.3

Results of the C alifornia H ealthy H omes I ndoor A ir Q uality S tudy of 2011–2013: impact of natural gas appliances on air pollutant concentrations

“…Data were collected from 352 homes, including the high‐performance home subsample (Less, ). The overall sample mostly comprised homes with gas appliances in the living space and homes that used gas cooking appliances: 90% of study homes had at least one gas appliance and 82% had gas cooking burners.…”

“…The following factors were considered: frequency of the use of gas cooking burners; which gas appliances were inside the living space or connected spaces and whether they were vented; size of the home; year the home was built (recognizing that newer homes are generally tighter with less infiltration air exchange); household income; and whether the home had been weatherized to increase airtightness. Twenty-four homes constructed or retrofitted for low-energy use were included as part of a supplemental study of IAQ in high-performance homes (Less, 2012;Less et al, 2015). There was intentional sampling of some homes without gas appliances to serve as controls (n = 38).…”

“…Data were collected from 352 homes, including the high-performance home subsample (Less, 2012). The overall sample mostly comprised homes with gas Fig. 1 NO X and NO 2 measured in kitchen and bedroom, and measured or assigned outdoor concentrations, ordered by concentrations in bedroom.…”

Modeling the resiliency of energy-efficient retrofits in low-income multifamily housing

“…Consequently, fans are not fully resilient to heavy smoking when windows are opened across both seasons. The resiliency of exhaust fans could also be affected by inconsistent utilization, lower capture efficiencies associated with certain kitchen exhaust designs and cooking behavior (eg, front versus back burner cooking), or be cost prohibitive to install or keep in good working order in some housing …”

“…In addition to source control policies, operations and maintenance practices and resident education can increase retrofit benefits through proper installation and maintenance of ventilation systems (eg, filter cleaning or replacement) as well as occupant education to improve operation compliance …”