Alternative Ventilation Strategies to ERVs in Multifamily Buildings 

Alternative Ventilation Strategies to ERVs in Multifamily Buildings 

July 7, 2026

Energy Recovery Ventilators (ERVs) are considered a best-practice solution in multifamily building design. They optimize both ventilation and energy efficiency by transferring heat and moisture between incoming and outgoing air streams. 

However, in some projects, ERVs may not be included due to cost, space constraints, or design decisions. For projects without ERVs, it becomes especially important to use other strategies to maintain balanced airflow and indoor air quality across the building. 

Why Airflow Balance Matters in Multifamily Buildings 

Multifamily buildings rely on coordinated ventilation across many individual units stacked vertically and horizontally. When airflow is not properly balanced, it can lead to: 

• Uneven indoor air quality between units 

• Pressure differences between apartments and corridors 

• Increased energy use from HVAC systems working harder than necessary 

• Comfort issues such as drafts or stuffiness 

• Moisture and condensation issues in envelope components 

As buildings increase in height and number of floors, these challenges become more pronounced. Stack effect, the natural movement of air upward through a building, and pressure variations make it harder to maintain consistent performance from the bottom floor to the top.  This can be exacerbated by negative pressures accumulating from floor to floor and creating issues with opening and closing doors, especially in lower floors. 

Alternative Ventilation Strategies  

If a project is not using ERVs, one or more of the alternative ventilation strategies below can be used to properly balance airflow.  

1. Over Supply to the Corridors via DOAS 

One of the most common alternatives is the use of Dedicated Outside Air Units (DOAS).  In most cases these units are used effectively as a “common ERV”. Installed on the roof, DOAS collect exhaust air from apartment bathrooms throughout the building and supply conditioned outdoor air to the corridors. The corridors have an oversupply of outside air, which causes them to be positively pressurized, while the apartments are negatively pressured.  The intent is for air to transfer from the positively pressurized corridor into the negatively pressurized apartments through undercut doors and other transfer pathways. 

Pros	Cons
Retains energy recovery benefits	Doors often provide limited air transfer, so transfer grilles or jump ducts may be required to facilitate airflow between spaces
Requires less ductwork as supply ductwork only has to enter corridor
Less expensive than a dedicated ERV for each dwelling unit
Fewer ERVs to maintain long term

2. Exhaust Ventilation with Trickle Vents 

Another common method of balancing ventilation without the use of ERVs is to have a constant exhaust flow, such as from a bathroom or kitchen, and trickle vents.   

Trickle vents are openings in the exterior envelope that allow outdoor air to enter the building. The intent is for the incoming air from the trickle vents to offset the exhaust air being removed, helping to maintain ventilation balance. 

Pros	Cons
Inexpensive to install; no additional ductwork required	Areas near the trickle vents may be uncomfortably warm or cold since they allow unconditioned outside air to enter the space
	Additional humidity control may be required to avoid mold and mildew growth
	Does not provide any energy recovery benefit

3. Packaged Terminal Air Conditioner with Louver 

Another option for balancing pressures within a multifamily building is to use Packaged Terminal Air Conditioners (PTAC) with built-in outside air louvers.  This approach is similar to a trickle vent in that it allows outdoor air to enter the space and offset exhaust airflow. However, when the PTAC is operating, the incoming air is conditioned before entering the apartment. When the PTAC is not running, such as during periods of continuous exhaust ventilation, unconditioned outdoor air can still enter the space due to the negative pressure created by the exhaust system. 

Pros	Cons
Inexpensive to install	Unconditioned outdoor air can still enter the space during periods when the unit is off
Alleviates some of the unconditioned outside air entering the space	Does not address humidity in the incoming outdoor air, particularly when the PTAC is not operating
	Does not provide any energy recovery benefit

Balanced Ventilation Without ERVs – Key Points 

While ERVs remain a preferred solution for many multifamily projects, alternative strategies can still achieve effective ventilation when thoughtfully designed and coordinated early in the process.  The most successful multifamily projects are those where ventilation is not treated as a standalone system, but rather as an integrated part of the building’s overall energy and airflow strategy. 

When ERVs are not part of the design, successful ventilation strategies typically rely on a combination of systems, rather than a single solution. 

A well-balanced approach may include: 

• Over Supply to the Corridor via DOAS 

• Exhaust Ventilation with Trickle Vents 

• Package Terminal AC with Louver 

Each strategy plays a different role, but together they help maintain balanced airflow across the building. 

ReVireo helps project teams evaluate ventilation strategies through energy modeling, understand code implications, and develop practical solutions tailored to each multifamily project. Whether ERVs are included in the project plans or alternative approaches are needed, our team can help ensure systems are balanced, compliant, and aligned with long-term performance goals. Contact us to discuss your upcoming projects.