Install fresh air ventilation inlets away from contamination sources.
- Install air inlets at least 10 feet away from all contamination source terminations. Install air inlets in the wall at least 3 feet away from dryer exhausts and contamination sources that exit through the roof (as required by ENERGY STAR Single-Family New Homes).
- Install air inlets at least 2 feet above grade or above the roof deck (as required by ENERGY STAR Single-Family New Homes). Note: it is easier to install an air inlet at the gable end of the house than to try to lift it off the roof 2 to 4 feet.
- Ensure that ventilation air comes directly from outdoors and not from adjacent dwelling units, garages, crawlspaces, or attics.
- Install the air inlet duct in a location with the shortest, most direct path possible to the air handler unit, HRV, or ERV.
- Stretch the duct tight and support it adequately to minimize sagging and kinks.
- Air seal around the intake duct termination and seal the duct to the HRV/ERV or return side of the air handler with mechanical fasteners and metal tape or mastic.
- Install a ≤ 0.5-in.-mesh screen on all air inlets to keep out rodents, insects, and debris, except use a louvered damper rather than a mesh screen on clothes dryer vents.
See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Single-Family New Homes, and Indoor airPLUS.
When a home has a balanced ventilation system that uses a heat recovery ventilator (HRV), energy recovery ventilator (ERV), or central-fan-integrated supply ventilation, fresh air is brought into the home through a ventilation air inlet. To ensure good air quality, the inlet should be placed in a location away from possible sources of contamination, and where it has unobstructed access to clean air.
Possible contamination sources include bathroom exhaust fans, plumbing vent pipes, kitchen exhaust fans, dryer exhaust vents, furnace exhaust vents, water heater exhaust vents, fireplace flues, and whole-house fans. The locations for these outlets and inlets should be specified on plans. In addition, the HVAC contractor should coordinate with other subcontractors, including the framers, plumbers, and electricians, at the beginning of construction to determine the proper placement of both air inlets and contamination source terminations.
The air inlet should be located high enough above the ground, or roof surface, to prevent accumulated snow from piling up over it, rainwater from splashing into it, and plants from growing into it. It should be located outside, not in an attic, crawlspace, garage, or attached dwelling. The inlet should be covered with a mesh screen to prevent animal and insect entry. Ideally, it should be placed in a location where the home owner can check and clean it regularly.
Where to Install Ventilation Air Inlets
1. Verify locations of all contamination source terminations.
2. Install fresh air inlets so that they are
- at least 10 feet away from all contamination source terminations
- at least 3 feet away from dryer exhausts and contamination sources exiting through the roof
- at least 2 feet above grade or above the roof deck
* Note: it is easier to install an air inlet at the gable end of the house than to try to lift it off the roof 2-4 feet.
3. Install the air inlet duct in a location with the shortest, most direct path possible to the air handler unit, HRV, or ERV. Stretch the duct tight and support it adequately to minimize sagging and kinks. Air seal around the intake duct termination and seal the duct to the HRV/ERV or return side of the air handler with mechanical fasteners and metal tape or mastic.
4. Install a ≤ 0.5-in.-mesh screen on all air inlets to keep out rodents, insects, and debris, except clothes dryer vents which should have a louvered damper instead. See the guide Proper Clothes Dryer Venting for more information.
On the diagram of a house below, which has central-fan-integrated supply ventilation, the fresh air intake is located more than 4 feet above grade level and away from other contaminant sources such as other flue or exhaust pipe outlets on the house.
The metal frame for the fresh air intake duct grille has been installed in the ceiling of a covered porch of this home under construction.
The intake and duct have been installed for the fresh air inlet in the eave of the roof of this home under construction. The grille has not yet been installed.
Visually inspect the ventilation inlet to ensure that it is at least 10 feet from any known contamination sources, at least two feet above grade and above the roof deck. Make sure the inlet is not obstructed by any objects, that the ventilation air comes from outdoors—not from a garage, attic, crawlspace, or adjacent dwelling, and that the ventilation inlet is covered with a protective screen with ≤ 0.5–inch mesh. Dryer vents should have a louvered damper, not a mesh screen, covering the outside end.
No climate specific information applies.
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.
National Rater Field Checklist
7. Dwelling Unit Mechanical Ventilation Systems (“Vent System”) 45 & Inlets In Return Duct 46
7.7 Air inlet location (Complete if ventilation air inlet location was specified on design report; otherwise check “N/A”): 54, 55
7.7.1 Inlet pulls ventilation air directly from outdoors and not from attic, crawlspace, garage, or adjacent dwelling unit.
7.7.2 Inlet is ≥ 2 ft. above grade or roof deck; ≥ 10 ft. of stretched-string distance from known contamination sources not exiting the roof, and ≥ 3 ft. distance from dryer exhausts and sources exiting the roof. 56
7.7.3 Inlet is provided with rodent / insect screen with ≤ 0.5 inch mesh.
Footnote 45) As defined by ANSI / RESNET / ICC Std. 301-2019, a Dwelling Unit Mechanical Ventilation System is a ventilation system consisting of powered ventilation equipment such as motor-driven fans and blowers and related mechanical components such as ducts, inlets, dampers, filters and associated control devices that provides dwelling-unit ventilation at a known or measured airflow rate.
Footnote 46) Item 7.3 applies to any outdoor air inlet connected to a ducted return of the dwelling unit HVAC system, regardless of its intended purpose (e.g., for ventilation air, make-up air, combustion air). This Item does not apply to HVAC systems without a ducted return.
Footnote 54) Ventilation air inlets that are only visible via rooftop access are exempted from Item 7.7 and the Rater shall mark “N/A”. The outlet and inlet of balanced ventilation systems shall meet these spacing requirements unless manufacturer instructions indicate that a smaller distance may be used. However, if this occurs the manufacturer’s instructions shall be collected for documentation purposes.
Footnote 55) Without proper maintenance, ventilation air inlet screens often become filled with debris. Therefore, EPA recommends, but does not require, that these ventilation air inlets be located so as to facilitate access and regular service by the occupant.
Footnote 56) Known contamination sources include, but are not limited to, stacks, vents, exhausts, and vehicles.
Please see the ENERGY STAR Single-Family New Homes Implementation Timeline for the program version and revision currently applicable in your state.
Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
1995. Manual T Air Distribution Basics for Residential and Small Commercial Buildings. Manual T provides details on selecting, sizing, and locating supply air diffusers, grilles and registers, and return grilles.
ASHRAE Standard 62.2-2010 Ventilation for Acceptable Indoor Air Quality in Low-Rise Residential Buildings for purchase by following link above. The standard provides minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.
Guidance for the measures described in this guide is applicable to both new and existing homes.
For more information on assessing ventilation systems see the assessment guide on ventilation.
For more information on installing outdoor air inlets in existing homes see the U.S. Department of Energy’s Standard Work Specifications. Follow safe work practices as described in the Standard Work Specifications section on ventilation worker safety.
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.
The following authors and organizations contributed to the content in this Guide.
Fresh air balanced systems supply and filter outdoor air while exhausting an equal amount of indoor air. This type of system maintains a neutral balance in air pressure that minimizes moisture risks and optimizes mixing. These systems are often equipped with heat and moisture exchangers that optimize efficiency and comfort. This is achieved by exchanging heat and moisture between the incoming and outgoing air streams. This captures heat before it leaves the home in winter, heat before it enters the home in summer, moisture before it enters the home in summer, and moisture before it leaves the home in winter.