Indoor air quality impacts of residential mechanical ventilation system retrofits in existing homes in Chicago, IL

Insung Kang; Anna McCreery; Parham Azimi; Amanda Gramigna; Griselda Baca; Kari Abromitis; Mingyu Wang; Yicheng Zeng; Rachel Scheu; Tim Crowder; Anne Evens; Brent Stephens

doi:10.1016/j.scitotenv.2021.150129

Indoor air quality impacts of residential mechanical ventilation system retrofits in existing homes in Chicago, IL

Sci Total Environ. 2022 Jan 15:804:150129. doi: 10.1016/j.scitotenv.2021.150129. Epub 2021 Sep 8.

Authors

Affiliations

¹ Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology, Chicago, IL, USA.
² Elevate, Chicago, IL, USA.
³ Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA.
⁴ Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology, Chicago, IL, USA. Electronic address: brent@iit.edu.

PMID: 34798726
DOI: 10.1016/j.scitotenv.2021.150129

Abstract

Mechanical ventilation systems are used in residences to introduce ventilation air and dilute indoor-generated pollutants. A variety of ventilation system types can be used in home retrofits, influencing indoor air quality (IAQ) in different ways. Here we describe the Breathe Easy Project, a >2-year longitudinal, pseudo-randomized, crossover study designed to assess IAQ and adult asthma outcomes before and after installing residential mechanical ventilation systems in 40 existing homes in Chicago, IL. Each home received one of three types of ventilation systems: continuous exhaust-only, intermittent powered central-fan-integrated-supply (CFIS), or continuous balanced system with an energy recovery ventilator (ERV). Homes with central heating and/or cooling systems also received MERV 10 filter replacements. Approximately weeklong field measurements were conducted at each home on a quarterly basis throughout the study to monitor environmental conditions, ventilation operation, and indoor and outdoor pollutants, including size-resolved particles (0.3-10 μm), ozone (O₃), nitrogen dioxide (NO₂), carbon dioxide (CO₂), carbon monoxide (CO), and indoor formaldehyde (HCHO). Mean reductions in indoor/outdoor (I/O) ratios across all systems after the intervention were approximately 12% (p = 0.001), 10% (p = 0.008), 42% (p < 0.001), 39% (p = 0.002), and 33% (p = 0.007), for CO₂, NO₂, and estimated PM₁, PM_2.5, and PM₁₀, respectively. There was a reduction in I/O ratios for all measured constituents with each type of system, on average, but with varying magnitude and levels of statistical significance. The magnitudes of mean differences in I/O pollutant concentrations ratios were generally largest for most pollutants in the homes that received continuous balanced with ERV and smallest in the homes that received intermittent CFIS systems, with apparent benefits to providing ventilation continuously rather than intermittently. All ventilation system types maintained similar indoor temperatures during pre- and post-intervention periods.

Keywords: Field measurements; Indoor air quality; Infiltration; Residential mechanical ventilation.

Publication types

Randomized Controlled Trial

MeSH terms

Adult
Air Pollutants* / analysis
Air Pollution, Indoor* / analysis
Chicago
Cross-Over Studies
Humans
Respiration, Artificial

Substances

Air Pollutants