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Air Leakage Testing Garage to House Air Barrier

Scope

The air tightness of the garage-to-house air barrier can be tested with a blower door kit and two manometers
The air tightness of the garage-to-house air barrier can be tested with a blower door kit and two manometers

For homes with an attached garage, test the air barrier between the house and the garage to verify its integrity. The air barrier between the house and the garage should be tight enough to prevent any garage air from entering the home if and when the home becomes depressurized.

Pressure Mapping Test

  • Construct the house with a complete air barrier between the house and garage.
  • Test the air barrier between the house and the garage using a blower door kit and two manometers (one smart manometer and one standard two-channel manometer).
  • Use the smart manometer to set the blower door to keep the house at 50 Pascals (Pa) pressure difference with reference to outdoors.
  • Use the two-channel manometer with a T-fitted hose to simultaneously measure the house with reference to the garage and the garage with reference to outdoors.
  • The house pressure with reference to the garage should be greater than 45 Pa.

CFM 50 Test

  • As a separate test or as part of a regular blower door test, with only one manometer, record the CFM 50 when the house is at 50 Pa pressure difference with the garage door closed.
  • Turn off the blower door. Open the overhead garage door. Turn on the blower door and again get the house to 50 Pa pressure difference from the outside. Then, record the manometer CFM 50 reading again.
  • If the difference between the two readings is greater than 6%, the house-to-garage air barrier fails, even if it passed the first test. Inspect and perform additional air sealing then retest.

See the Compliance Tab for related codes and standards and criteria to meet the requirements of national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and EPA Indoor airPLUS.

Description

Air from an attached garage can enter the living space of the home if there are leaks in the air barrier between the two spaces and if the home is at a negative pressure with respect to the garage due to natural forces or due to the use of mechanical exhaust ventilation in the living space (Rudd 2014) or other depressurizing appliances like a range hood fan or a clothes dryer.

The surest way to keep garage fumes out of the house is to build a detached garage. Since most houses are designed with attached garages, plan ahead in house design and construction to make sure a continuous air barrier is installed between the house and the garage. Also consider installing supply or balanced ventilation rather than relying on exhaust fans alone for ventilation. DOE-sponsored research has shown that installing supply ventilation (a fresh air intake connected to the central air handler) or balanced ventilation such as an energy recovery ventilator (ERV) or heat recovery ventilator (HRV) can help keep the house pressure balanced or positively pressurized with reference to the garage which also minimizes the likelihood of garage air entry into the house (Rudd 2014).

Thorough air sealing of the house-to-garage air barrier and installation of an exhaust fan in the garage are two measures specified in the U.S. Environmental Protection Agency’s (EPA’s) Indoor airPLUS requirements that can help minimize the entry of garage emissions to the home if the home has exhaust-only ventilation. See the guides Air Sealing Attached Garage, Garage Rim/Band Joist Adjoining Conditioned Space, and Mechanical Ventilation for Attached Garage for more information.

Testing of the level of depressurization of the house with respect to the garage can also help indicate if air is moving from the garage into the home. Testing is required for EPA Indoor airPLUS certification if the home has an attached garage, if a garage fan is not installed, and if the home uses exhaust-only ventilation. This guide provides a simple test method that can be used to help determine whether the garage-to-house barrier is adequately air sealed, based on Building America-supported research and research by others (for example, Rudd 2014, FSEC, and Calcs-Plus).

Using a blower door test kit, plus two manometers, and several hoses with T fittings, while the house is pressurized or depressurized at 50 Pascals (Pa) with respect to the outdoors with all operable garage openings closed, a house-to-garage pressure measurement is taken. Ideally this pressure differential should be between 45 and 50 Pa. The closer the house-to-garage pressure differential is to 50 Pa, the tighter the house-to-garage air barrier is. If this test is being conducted to verify compliance with the EPA Indoor airPLUS requirement, the differential must be greater than 45 Pa.

The instructions below describe the test being conducted with a smart manometer and a two-channel manometer. During the test, the smart manometer is used to hold the house pressure with reference to (WRT) outside at -50 Pa (or +50 Pa if pressurizing the house) while the 2-channel manometer is used to measure the house WRT the garage and the garage WRT outside. The closer the house WRT the garage is to 50 Pa, the better the air barrier is that is separating the house from the garage. A perfectly tight air barrier would yield a reading of 50 Pa for the house WRT the garage and 0 Pa for the garage WRT outdoors. This would mean there would be no pressure difference between the garage and the outdoors; i.e., the garage would be completely connected to the outdoors with no openings or leaks to the house. This test is conducted with all windows and doors in the garage closed.

Some conditions, for example, if the house has a leaky house-to-garage interface and a very leaky garage-to-outside interface, can yield a false positive result; i.e., it might look like the house-to-garage air barrier is tight enough when in fact it isn’t. To confirm that the test isn’t yielding a false positive result, a second test is run with the same setup except that this time the overhead garage door is open. The CFM50 with the garage door open is compared to the CFM50 when the garage door was closed. If there is more than a 6% difference in the CFM50 readings, then the house fails and the house-to-garage air barrier should be inspected for air leaks (Rudd 2014). One way to do this is to depressurize the house and run a theatrical smoke machine in the garage. The smoke will be pulled in through any cracks in the wall showing you where the leaks are. 

How to Test Pressure Difference between the House and the Garage

1. Collect the equipment needed to test the pressure difference between the house and the garage while the house is being depressurized to 50 Pascals with reference to outdoors.

The equipment needed includes a blower door test kit, two manometers, and at least six pieces of plastic tubing along with two T-fittings for the tubing. In the drawings below, we are showing three pieces of red tubing and three pieces of green tubing to distinguish them (Figure 1). In this example one of the manometers is a  smart manometer (in this case, the DG1000 by The Energy Conservatory (TEC)), which has the ability to “cruise” control the blower door so that it will hold the home at 50 Pascals with reference to the outdoors. If you don’t have a smart manometer (SM), you can use a standard manometer; you’ll need a second person to control that manometer to keep the pressure at 50 Pa WRT outside. . The second manometer can be a standard two-channel manometer (2CM) (in this example, the DG700 by TEC, see Figure 2).

Equipment needed to pressure test the airtightness of walls separating the house from an attached garage
Figure 1. Equipment needed to pressure test the airtightness of walls separating the house from an attached garage. (Courtesy of Calcs-Plus.)

Two manometers are used when pressure testing the airtightness of the walls separating the house from an attached garage
Figure 2. Two manometers are used when pressure testing the airtightness of the walls separating the house from an attached garage. (Courtesy of Calcs-Plus.)

2. Set up the house for a building air tightness test per ANSI/RESNET/ICC 380-2016. Set up the home the same way you would when conducting a standard blower door test (all interior doors open, all exterior doors and windows closed, garage door to outside closed, HVAC system and all exhaust fans turned off, fireplace door closed or ashes removed or covered with wet newspaper).

3. Install the blower door in an exterior door of the house.

4. Set up the manometers as shown in Figures 3 and 4.

To test house-to-garage airtightness, first set up the blower door kit with the smart manometer in the blower door. Install a T-fitting in the (green) tubing that goes from the reference tap of channel “A” of the smart manometer. Run one tube outdoors. Connect the other tube to the reference tap on channel “A” of the two-channel manometer (2CM)
Figure 3. To test house-to-garage airtightness, first set up the blower door kit with the smart manometer in the blower door. Install a T-fitting in the (green) tubing that goes from the reference tap of channel “A” of the smart manometer. Run one tube outdoors. Connect the other tube to the reference tap on channel “A” of the two-channel manometer (2CM). (Courtesy of Calcs-Plus.)

To test house-to-garage airtightness, after connecting the green tubing as shown, connect the red tubing as follows: connect the input tap on channel “A” of the two-channel manometer (2CM) to the reference tap on channel “B” of the 2CM. Cut the tubing in half and reconnect the two pieces with a T-fitting. Connect the open end of the T-fitting to a longer piece of red tubing and run that tubing into the garage
Figure 4. To test house-to-garage airtightness, after connecting the green tubing as shown, connect the red tubing as follows: connect the input tap on channel “A” of the two-channel manometer (2CM) to the reference tap on channel “B” of the 2CM. Cut the tubing in half and reconnect the two pieces with a T-fitting. Connect the open end of the T-fitting to a longer piece of red tubing and run that tubing into the garage.  (Courtesy of Calcs-Plus.)

Set up the smart manometer to “cruise” the house at -50 Pa pressure difference with reference to outdoors. If you do not have a smart manometer, you can do this test with two standard 2-channel manometers, with a second technician operating the manometer controlling the blower door to manually keep the house at -50 Pa WRT outside. While the A channel on the smart manometer is connected (via the green T-fitting and tubes) to the outside and to the two-channel manometer, connect the garage (via the red T-fitting and tubes) to the input port of channel A on the two-channel manometer and to the reference port on channel B. So the 2CM A channel is comparing the garage with reference to the outdoors and the 2 CM B channel is comparing the house (the top open port on the B side) with reference to the garage (the red tube).

5. Power on the blower door and set the smart manometer to cruise the home at -50 Pascals with reference to outdoors.

6. Read the results. On the 2-channel monometer, on Channel A read garage pressure with reference to outdoors and on Channel B read house pressure with reference to the garage. Figure 5 shows us sample results for a test. These results show a pressure difference of -48 Pascals for the house with reference to the garage while the pressure difference of the garage with reference to outdoors is -2 Pascals. This shows that the garage is much more connected to the outdoors than to the house. (The closer you are to 0 the more connected you are.) It also tells us that, at -50 Pascals pressure difference, the air barrier between the garage and the house has a 4% leakage rate. So, at normal conditions with the garage doors closed, even if the bath fan were running and depressurizing the house, very little air is likely to come from the garage into the house.

In a test of house-to-garage airtightness, sample results show a pressure difference of -48 Pascals for the house with reference to the garage on Channel B of the two-channel manometer while the pressure difference of the garage with reference to outdoors is -2 Pa, as seen on Channel A; therefore, the garage is much more connected to the outdoors than to the house
Figure 5. In a test of house-to-garage airtightness, sample results show a pressure difference of -48 Pascals for the house with reference to the garage on Channel B of the two-channel manometer while the pressure difference of the garage with reference to outdoors is -2 Pa, as seen on Channel A; therefore, the garage is much more connected to the outdoors than to the house. (Courtesy of Calcs-Plus.)

7. Run a second test to eliminate false positives (Rudd 2014).

As shown in the example in Figures 6 and 7, set up the home for a building air tightness test as per ANSI/RESNET/ICC 380-2016. Using one manometer (a DG1000 by TEC is shown in Figures 6 and 7), bring the home to -50 Pa WRT outdoors (see the manometer manufacturer’s instructions). Record the CFM50 showing on channel “B.” In our example, the reading is 600 CFM50.

Turn the blower door off, open the largest overhead garage door to the outdoors. Leave the door between the garage and house closed. Bring the house to -50 Pa again. Record the CFM50 on channel “B,” in this case 635 CFM50.

During the first test, with the garage door closed, the amount of fan airflow required to maintain the house at -50 Pascals WRT outdoors was 600 CFM. In the second test, with the garage door open, the airflow required to get the house to -50 Pa was 635 CFM50. The difference between 635 and 600 is 35, which is 5.8% (35/600). This is less than a 6% difference so this house passes the test.

If the second test with the garage door open showed the CFM50 as greater than 6% (in this example, that would be 637 or higher), the house would fail even if it passed the first test. So, for example, if the results for the second test had shown a fan flow of 648 CFM to maintain the 50 PA pressure difference with the garage door open, then the house would have failed because 648 – 600 = 48. And 48/600 = 8%, which is greater than the 6% difference allowed. What could cause a false positive? While in the first test the house appeared to pass because there was a greater than 45-Pa pressure difference between the house and the garage, some of that pressure difference may have been due to the air tightness of the garage itself, not the house-to-garage wall air barrier because when the overhead garage door was opened, the house-garage wall appeared to be leakier.

8. If the house fails either test, inspect the house-to-garage air barrier and perform additional air sealing, then retest. Air leaks can be investigated by depressurizing the house and running a theatrical smoke machine in the garage. Any locations where smoke is entering the home from the garage are areas with leaks.

The air tightness of the house-garage air barrier can be tested using a CFM50 test that is first run with the garage door to outdoors closed
Figure 6. The air tightness of the house-garage air barrier can be tested using a CFM50 test that is first run with the garage door to outdoors closed. (Courtesy of Calcs-Plus.)

The air tightness of the house-garage air barrier can be tested using a CFM50 test that is run first with the garage door to outdoors closed and then with the overhead garage door to outdoors open. If the difference between the two readings is greater than 6%, the air barrier is too leaky and the house fails.
Figure 7. The air tightness of the house-garage air barrier can be tested using a CFM50 test that is run first with the garage door to outdoors closed and then with the overhead garage door to outdoors open. If the difference between the two readings is greater than 6%, the air barrier is too leaky and the house fails. (Courtesy of Calcs-Plus.)

 

Ensuring Success

Follow the procedures in the Description tab.

All homes with attached garages should have a hard-wired carbon monoxide (CO) alarm with a battery backup installed in the home. This is an EPA Indoor airPLUS requirement and a common sense precaution. Even homes with balanced ventilation can become depressurized, for example, if a high-powered range hood fan is operating with inadequate make-up air or if the clothes dryer and a few exhaust fans are operating simultaneously. Newer cars with remote keyless starters have been known to accidentally be started while located in a closed garage. Verifying the integrity of the house-to-garage air barrier in all homes is an important safety precaution that can save lives.

Climate

No climate-specific information applies.

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 to 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 are sealed and also an air barrier is 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 are 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.

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.

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.

ANSI/RESNET/ICC 380-2016

Procedures for testing the air tightness of the home’s building enclosure and duct system.

ASHRAE 62.2-2010, ASHRAE 62.2-2013, and ASHRAE 62.2-2016

Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings

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.

The procedure for testing garage to house air leakage is identical for new homes and existing homes. See the Scope and Description tabs.

See the U.S. Department of Energy’s Standard Work Specifications for more on the garage to house air barrier.

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): Building Science Corporation
    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): RESNET
    Organization(s): International Code Council
    Publication Date: February, 2016

    This Standard provides a consistent, uniform methodology for evaluating the airtightness of building envelopes and heating and cooling air ducts and the air flows of mechanical ventilation systems.

  4. 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.

  5. 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.

Last Updated: 06/04/2018