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Mechanical Ventilation for Attached Garage

Scope

Installing a garage exhaust fan is one important step in keeping auto exhaust and other pollutants out of the home
Installing a garage exhaust fan is one important step in keeping auto exhaust and other pollutants out of the home

Install an exhaust fan in an attached garage to pull fumes out of the garage and to depressurize the garage with reference to the home.

  • Select an energy-efficient garage fan. Look for ENERGY STAR-certified models.
  • Select an installation location on an exterior wall that is located away from the home’s doors, windows, and any ventilation air intakes.
  • Integrate the fan with the water and air barrier layers in the exterior wall and properly flash around the opening for the fan.
  • Install a motion sensor and timer with the fan.

Description

Garages can contain several airborne pollutants. Car exhaust contains combustion pollutants such as carbon monoxide and benzene; even if the garage door is open, some of these fumes can accumulate in the garage when starting or parking the car. An added concern are the keyless fobs that now come with many cars as they offer the potential to accidentally remotely start the car while it is parked in a closed garage. Garages are often used as storage areas for household cleaning products, fertilizers, pesticides, and gasoline for mowers and snow blowers. They are also used as workshop areas for projects involving hazardous chemicals, such as paints, solvents, and glues, which may continuously off-gas into the garage space. Water from rain or snow melt dripping off cars can encourage the growth of mold, another source of potential pollution in the garage. Without proper isolation and ventilation, these pollutants can accumulate in the garage space and may leak into the living areas of the home.  See Figure 1.

Installing a garage exhaust fan is one important step in keeping auto exhaust and other pollutants out of the home
Figure 1 - Installing a garage exhaust fan is one important step in keeping auto exhaust and other pollutants out of the home. (Source: EPA Indoor airPLUS 2014)

The most effective way to keep garage pollutants from entering the home is to design the home with a detached garage. Smaller lot dimensions are making that option less feasible but consideration should still be given in design selection to minimizing the number of shared walls and ceilings between the garage and living space. Any walls and ceilings that are shared between the garage and the home should be thoroughly air sealed and steps should be taken to ensure that the home is not depressurized with respect to the garage.

There are several types of appliances in the home that can cause the home to be depressurized because they pull air out of the home while operating, for example, exhaust fans, range hood fans, clothes dryers, central vacuum cleaners, fireplaces, atmospherically vented water heaters or furnaces, and HVAC supply registers located in a garage or unconditioned basement. If the home does not have a fresh air intake or a balanced ventilation system that brings in fresh air while exhausting stale air, such as an ERV, HRV, or central fan-integrated ventilation system, the home can become depressurized and could draw in outside air from other less desirable places, like the attic, crawlspace, or attached garage.

Recognizing this concern, the U.S. Environmental Protection Agency’s Indoor airPLUS requires homes in the program that rely on exhaust-only ventilation to either have a garage exhaust fan installed or have a blower door test conducted to test the air barrier between the house and the garage. An exhaust fan will remove exhaust and other fumes from the garage and slightly depressurize the garage with reference to the house, significantly decreasing the likelihood that garage air will be pulled into the house. The EPA program requires that the fan be wired for continuous operation or with automatic fan controls such as a motion detector that will activate the fan whenever the garage is occupied and for at least one hour after the garage has been vacated. The exhaust fan should have a minimum installed capacity of 70 cfm and it should be vented directly outdoors, either through the wall or via a duct through the roof. EPA recommends using an ENERGY STAR-labeled exhaust fan. See the Compliance tab for more information.

There are several additional steps builders can take to help keep garage fumes out of the house. Many of these steps are required or recommended by EPA’s Indoor airPLUS or ENERGY STAR Certified Home, both of which are requirements for certification to DOE’s Zero Energy Ready Home Program.

  • Air-seal the common walls and ceilings between attached garages and living spaces before installing insulation (TES Sections 3 and 5).
  • Use weather stripping or an equivalent gasket to ensure all doors between living spaces and attached garages are substantially air-tight.
  • Install an automatic door closer on all connecting doors between living spaces and attached garages.

See the following Building America guides for more information:

How to Install a Garage Exhaust Fan

1. Ensure that any walls and ceilings separating the garage from living space are thoroughly air sealed and have a continuous air barrier. Seal drywall to top and bottom plates and at seams; use airtight electrical boxes; seal around all wiring and piping; install self-closing doors and weather strip the door framing. See Figure 2 and the guides listed above for more details.

Install a self-closing weather-stripped door and thoroughly airseal the shared house-garage walls to help keep auto exhaust and other pollutants out of the home
Figure 2 - Install a self-closing weather-stripped door and thoroughly airseal the shared house-garage walls to help keep auto exhaust and other pollutants out of the home. (Source: EPA Indoor airPLUS 2014).

2. Select a fan location that is not near any windows, doors, or air intakes. (See the guide Ventilation Air Inlet Locations for more information.)

3. Select an ENERGY STAR-rated exhaust fan that has a minimum installed capacity of 70 cfm and is wired for continuous operation or is equipped with a motion detector that will activate the fan when the garage is occupied and for at least 1 hour after the garage has been vacated. A list of ENERGY STAR-qualified fans can be found by visiting the ENERGY STAR website.

4. Remove siding if necessary and cut a hole for the fan in the wall or ceiling and roof; install flashing that is integrated with the exterior wall or roof drainage plane.

5. Install the fan per manufacturer’s instructions, re-install siding if needed, and flash around the fan. Integrate the flashing with exterior cladding.

6. Install an automatically closing louvered cover over the fan if desired and verify that it opens and closes.

7. Provide the homeowner with information regarding indoor air quality, the dangers of operating any combustion engines in the garage when the doors are closed, and the need for ventilation when working in the garage for extended periods of time.

Ensuring Success

The continuity of the air barrier between the house and the garage can be tested by using a blower door to verify that the garage-to-house air barrier can maintain a pressure difference of greater than 45 Pascals while the home maintains a 50-Pascal pressure difference with respect to the outdoors. All operable garage openings should be closed during this test. See the guide Air Leakage Testing of Garage-to-House Air Barrier for more information on this test.

Climate

This information is applicable to all climate zones.

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Garage Exhaust Fans
    Publication Date: June, 2018
    Author(s): Dillon
    Organization(s): IBS Advisors

    Video by Brett Dillon, of RESNET, explaining simple wiring for installing a garage exhaust fan and reasons for garage fans.

CAD Images

None Available

Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

DOE Zero Energy Ready Home

DOE Zero Energy Ready Home (Rev. 06) Exhibit 1, requires certified homes comply with the ENERGY STAR Certified Homes Version 3/3.1 Rev. 08 and the EPA Indoor airPLUS checklist.

ENERGY STAR Certified Homes (Version 3, Rev. 08)

Rater Field Checklist,

2. Fully Aligned Air Barriers: a complete air barrier is provided…at 2.4 Walls adjoining porch roof or garages, 2.6 Floors above garages….

4 Air Sealing 4.7 Walls that separate attached garages from occupiable space sealed and also an air barrier installed and sealed at floor cavities aligned with these walls.

4.9 Doors adjacent to unconditioned space (e.g., attics, garages, basements) or ambient conditions made substantially air tight with weather stripping or equivalent gasket.

7. Whole-House Mechanical Ventilation System

7.7.1 Air inlet location pulls air directly from outdoors and not from attic, crawlspace, garage, or adjacent dwelling unit.

EPA Indoor airPLUS Version 1 (Rev. 04)

5.4 Attached garages: In homes with exhaust-only whole-house ventilation EITHER

  • 70 cfm exhaust fan installed in garage OR
  • Pressure test conducted to verify the effectiveness of the garage-to-house air barrier.

5.4 Attached Garages

NOTE: Completion of the ENERGY STAR requirements satisfies the following Indoor airPLUS requirement:

Isolate attached garages from conditioned spaces as follows:

  • Air-seal common walls and ceilings between attached garages and living spaces before installing insulation (Rater-F 2.4, 2.6, and 4.7).
  • Use weather stripping or equivalent gasket to ensure all doors between living spaces and attached garages are substantially airtight (Rater F 4.9).

Additional Indoor airPLUS Requirements:

  • Install an automatic door closer on all connecting doors between living spaces and attached garages, AND
  • In homes with exhaust-only whole house ventilation meet one of the following two requirements:
    • Equip the attached garage with an exhaust fan with a minimum installed capacity of 70 cfm that is vented directly outdoors. The fan shall be wired for continuous operation or with automatic fan controls (e.g., a motion detector) that activate the fan whenever the garage is occupied and operate for at least 1 hour after the garage has been vacated. If a ducted fan (not through-the-wall) is used, test and verify minimum capacity of 70 cfm, OR
    • Verify that the garage-to-house air barrier can maintain a pressure difference of greater than 45 Pa while the home maintains a 50 Pascal pressure difference with respect to the outdoors. All operable garage openings shall be closed during this test.

Advisories:

  1. EPA recommends installing a garage exhaust fan if the homebuyer is expected to occupy the garage for work or recreational activities over extended periods of time.
  2. ENERGY STAR certified fans are highly recommended.
  3. Provide occupants with information in the Buyer Information Kit on the importance of, and methods for, ensuring adequate ventilation in the garage while occupied for extended periods of time.

Other Considerations from EPA Indoor airPLUS:

4.3. No air-handling equipment or ductwork installed in garage.

4.3 Location of Air-Handling Equipment and Ductwork.

Indoor airPLUS Requirement:

  • Do not locate air-handling equipment or ductwork in garages.

Note: Ducts and equipment may be located in framing spaces or building cavities adjacent to garage walls or ceilings if they are separated from the garage space with a continuous air barrier.

5.2 Carbon Monoxide Alarms

Indoor airPLUS Requirement:

  • All homes equipped with combustion appliance(s) or an attached garage shall have a carbon monoxide (CO) alarm installed in a central location in the immediate vicinity of each separate sleeping zone (e.g., in a hallway adjacent to bedrooms.) The alarm(s) shall be hard-wired with a battery back-up function and placed according to NFPA 720.

7.3 Owner and Resident Information Kit

Advisory: Provide the homebuyer with information that addresses the importance of ensuring that manually controlled ventilation options (e.g., bathroom, garage (if applicable), kitchen exhaust fans; operable windows, and doors, etc.) are used when strong pollutant sources are present, such as when using common household products (e.g., cleaning products, pesticides) and when using the garage for hobbies or other pollutant generating activities.

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

Scope

Installation instructions for installing a garage exhaust fan in an existing home are the same as those for a new home.  

See the U.S. Department of Energy’s Standard Work Specifications for more on installing a garage exhaust fan and other guidance for air sealing garages

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

Case Studies

  1. Author(s): BSC
    Organization(s): BSC
    Publication Date: April, 2017

    This case study describes work with a production home builder K Hovnanian to evaluate air transfer between the garage and living space in a single-family home with an attached garage.

References and Resources*

  1. Author(s): Health Canada, Environment Canada, Canada Mortgage and Housing Corporation
    Organization(s): Health Canada
    Publication Date: June, 2001

    Document reporting results from a study done to evaluate effects of automotive emissions from attached garages on the indoor environment.

  2. Author(s): Rudd
    Organization(s): BSC
    Publication Date: September, 2014

    This report describes research conducted to evaluate air transfer between the garage and living space in a single-family detached home constructed to the 2009 IECC by a production home builder in Maryland.

  3. Author(s): Health Canada, Environment Canada, Canada Mortgage and Housing Corporation
    Organization(s): Health Canada
    Publication Date: June, 2004

    Results from a research program testing airtightness, implications of air leakage and contaminant reduction over the garage-to-house interface.

  4. Author(s): Aspen Publishers
    Organization(s): Aspen Publishers
    Publication Date: January, 2000
    Report with information for builders and retrofitters to help eliminate hazards and coincidental energy losses that come from attached garages.

Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Pacific Northwest National Laboratory

U.S. Environmental Protection Agency Indoor airPLUS Program.

Last Updated: 06/12/2018