In partnership with Livable Housing, Inc., ROCIS offered two webinars on assessing and installing bathroom fans. This page provides access to those two webinars as well as additional guidance documents to support you as you determine whether your bathroom fan is doing its part in providing a healthy home for you and everyone in your family.

Background

By Tom Phillips

Residential bathrooms can have significant sources of various indoor pollutants from consumer products, cleaning products, and bathing and showering that present increased risks for asthma, cancer, immune responses, and mucosal irritation (Wang et al., 2026; Tang, 2026; Adcock et al., 2026; Salonen et al., 2024; EWG, 2023). Estimated bathroom exposures to VOCs from consumer and cleaning products can exceed acute health hazard criteria (Nazaroff et al., 2006). In addition, indoor VOCs can produce toxic or irritant compounds and secondary organic aerosols from reactions with ozone or nitrate radicals (Wang et al., 2026). The bathroom was also a hot spot for molecular diversity and chemically transformed compounds on the surfaces of a Texas test home (Aksenov et al., 2022).

Bathroom exhaust fans have been used as local exhaust for bathrooms and for whole house ventilation in new and existing homes. Bathroom exhaust fans running continuously have substantially reduced indoor levels of indoor Total VOCs, radon, formaldehyde, and moisture balance in older, weatherized single family homes in Illinois and Indiana (Francisco et al., 2016). The bath fans were also significantly more effective that natural ventilation. Both supply and exhaust fans helped reduce levels of some indoor air pollutants, but supply fans were more effective in reducing indoor PM2.5 levels in existing single-family homes in Illinois (Francisco et al., 2025). As with most mechanical ventilation systems, the real-world, life cycle effectiveness depends on the proper installation, operation and maintenance of the system.

A few studies have examined the question of which mechanical exhaust ventilation methods are most effective in reducing levels of indoor pollutants in bathrooms and in improving health.

For example:

Kim, O. & Yang, J. H. (2016). On the Design to Improve the Bathroom Exhaust Performance in Multi-Unit Residential Building. Journal of Asian Architecture and Building Engineering, 15(2), 349–356

Field measurements in different floors of a multifamily building in Korea were conducted to determine if the bathroom exhaust fans met the 8 air change/hour criteria. The installed fans did not meet the ventilation criteria, and most occupant complaints were due to odor and mold problems. Fan performance problems were due to excessive duct length, air leaks in the exhaust duct, variable proficiency of the fan installers, and lack of fan testing, adjusting, and balancing. Fan run time was also inadequate: after a 10 minute shower, a fan run time of 70 minutes was needed to control moisture sufficiently. In addition, laboratory tests were conducted to offer a design standard of the fan′s components and a standard installation method for the fans.

Recommended solutions included limiting the exhaust duct length to no more than 1,500 mm, commissioning of the fan flow, installing the fan at the bottom of the shower stall partition. The air flow calculations also need to be adjusted for pressure drops from different diffuser type, the fan and duct work, and the manufacture’s pressure-flow curves.

Kang, I., et al. (2025). Effects of Residential Ventilation and Filtration Interventions on Adult Asthma Outcomes. Building and Environment, 285B.
News item: Breathing room: UTA study clears the air on asthma (UT Arlington, 2025).

Researchers installed one of three types of ventilation systems in homes of 51 adult asthma patients in Chicago: upgraded bathroom exhaust fans that run continuously to draw air in from the outside; a supply fan connected to the central heating and cooling system set that ran intermittently to push air into the home; or an energy recovery ventilator (ERV) that continuously exchanged indoor and outdoor air. The supply and balanced systems circulated and filtered air, while the ERVs also conserved heating and cooling energy. Several homes with upgraded bathroom exhaust fans did not initially have a bath exhaust fan, a functioning fan, or one in every bathroom.

After adjustment for demographic factors and seasonality, all three systems led to measurable and significant improvements in indoor air quality and asthma outcomes during the study’s second year, when ventilation was activated. Greater improvements in asthma control were observed with ERV systems (8.4%), followed by CFIS (7.1%) and exhaust-only systems (3.8%), and these improvements gradually increased over the year. Reduced indoor NO₂ levels were significantly associated with improved asthma control and marginally associated with reduced indoor CO₂ levels. Asthma improvements were significantly greater in participants’ ≥ 45 years, Black, White, or with incomes
< $75K.

Webinar 1: Assessing Your Bathroom Exhaust Fan

December 11, 1:00–2:30 p.m.

This session will offer a rationale for having a bathroom exhaust fan, an explanation of the basic components of a bathroom exhaust system, a step by step process for determining how well an existing fan is working with specific details on how much air it is moving, the options for switching the fan on and off, required maintenance and the viability of the ductwork and outlet.

Learning objectives:

Webinar attendees will be able to:

1. Identify the three basic components of a bathroom exhaust fan system. Learners will examine their bathroom fan and identify the connection to electrical power, the method for switching the fan on and off, and the duct system that controls the exhaust air.
2. Measure and evaluate airflow and ventilation effectiveness. Learners will be able to perform the tissue test to assess airflow and approximate the amount of air flow in cubic feet per minute (CFM).
3. Inspect exhaust fan components for optimal performance. Learners will be able to locate, and inspect, components (grille, duct, damper, and exterior vent termination), identifying issues such as dust buildup, obstructions or defects in the ductwork system, or faulty outlets that reduce efficiency or prevent the exhausted air from reaching the outdoors.

Webinar 2: Installing or Replacing a Bathroom Exhaust Fan

December 18, 1:00–2:30 p.m.

This webinar is designed to help you choose an appropriate bathroom exhaust fan, considering both your household’s need for bathroom and/or whole house ventilation, and the construction of your bathroom. We will provide information on replacing an existing fan and installing a new fan from scratch. We will also compare the options of either doing a DYI installation or hiring a contractor.

Learning objectives:

Webinar attendees will be able to:

1. Identify proper fan placement. Learners will be able to determine the optimal mounting location for their new bathroom exhaust fan.
2. Identify appropriate exhaust fan system specifications and select a specific bathroom exhaust fan. Learners will be to select the appropriate exhaust fan features and other exhaust system components for their bathroom based on manufacturers installation requirements and research-based guidance on exhaust fan system performance (CFM rating, noise level, energy efficiency, incorporated light, switching and time delay options and ductwork).
3. Install or engage a contractor to install the bathroom exhaust fan system. Learners will be able to locate the manufacturer’s installation instructions for all the system components, understand the standard steps in the process and asses their capacity to do the work, and either install the fan themselves or hire a competent contractor.

Presented by Armand Magnelli

Senior Consultant and Trainer
Livable Housing, Inc.

Armand Magnelli has over 40 years of experience in affordable housing and community development. As a consultant and trainer, Armand had a 12-year tenure with Enterprise Community Partners, and 19 years of independent work as a principal of Livable Housing, Inc. As a practitioner, Armand has managed production of a city-wide owner-occupied rehab program, and housing development for two Community Development Corporations, including six years as an Executive Director.

Working with nonprofits and city governments, he provides training and technical assistance on Community Development, Affordable Housing Production, Disaster Preparedness and Recovery, Organizational Development, Volunteer Training and Management, and Healthy, Green, Resilient and Sustainable approaches to all of the above.

His training and technical assistance work in the Gulf Coast (Katrina/Ike), in NJ and NY (Sandy), in Houston (Harvey), in US Virgin Islands (Irma/Maria) and in Columbia SC (Joaquin), has provided him with invaluable experience in preparedness, recovery and resilient design.

Armand authored significant portions of NeighborWorks America’s curriculum on addressing vacant and foreclosed housing and he has developed localized Green specifications for housing rehabilitation programs in multiple cities nation wide.

He developed a set of toolkit document templates available on the HUD Exchange website: Health@HOME High-Performance Housing Rehabilitation Guidelines, a Housing Rehabilitation Standard, and a library of Housing Rehabilitation Specifications and an Inspection Checklist. Armand is also an owner and subject matter expert for the Housing Developer Pro® software application, an automated specification writing, cost estimating and construction management tool.