Does this approach work for Mass Save or Specialized Stretch Code projects?

Yes. Massachusetts multifamily projects on the Specialized Stretch Code or a Passive House path already require balanced ventilation with ERVs or HRVs, which is exactly the condition that makes consolidation worth running. We've modeled the same approach on Massachusetts projects and the savings pattern holds, though the device count and dollar figures scale with unit count, bathroom count, and cooktop fuel.

How much does an upsized ERV cost compared to a ventilation-only unit?

The unit cost delta is typically a few hundred dollars per apartment, depending on target CFM and manufacturer. That delta is almost always smaller than the combined cost of the bath fans, range hood (on all-electric projects), circuits, penetrations, and caps you remove. The envelope-tightness and commissioning savings stacked on top are what make the payback immediate rather than gradual.

Do I need a separate kitchen range hood with an all-electric cooktop?

It depends on the code and program stack. Induction and electric resistance cooktops can often be served by a recirculating hood plus the ERV carrying the ventilation load, which is what makes the consolidation work. Gas cooktops almost always trigger a dedicated high-CFM hood with makeup air, which breaks the consolidation math and pushes you back to the default three-system design.

Why We Eliminated 240 Exhaust Fans on One Project

On an 80-unit Maryland LIHTC project, we collapsed three separate ventilation systems into a single upsized ERV per unit and pulled 240+ exhaust devices out of the mechanical scope. Every code and certification requirement still cleared.

April 22, 2026

Most multifamily ventilation designs stack three independent systems: ERVs for balanced ventilation, bath fans in every bathroom, and a kitchen range hood per unit. On a recent Maryland LIHTC project we collapsed all three jobs into a single ERV and pulled 240+ exhaust devices out of the mechanical scope. Every code and certification requirement on the stack still cleared.

The Real Project

The project was an 80-unit Maryland LIHTC build stacking four certification and regulatory programs. Every program on the stack required balanced ventilation, which meant ERVs were already sitting in the mechanical budget as a non-negotiable line item.

The default design carried small ERVs handling whole-unit ventilation only, with separate bath fans and kitchen range hoods running in parallel. Three systems, three sets of controls, multiple exterior penetrations per unit. Each bath fan and range hood also needed its own electrical circuit, its own wall or ceiling cap, and its own balancing at commissioning.

We resized the ERVs to handle all of it: bathroom exhaust, kitchen exhaust, and continuous whole-unit ventilation. One system, one set of ductwork, one commissioning pass per unit. All code and certification airflow targets met.

The Device Count

Each unit in the original design carried multiple bath fans plus a kitchen exhaust fan. Across 80 units with multiple bathrooms and kitchens each, that was 240+ individual exhaust devices in the mechanical scope.

Removing those devices removed the matching count of envelope penetrations, exterior wall caps, and dedicated electrical circuits. Fewer penetrations mean less blower-door leakage and fewer thermal bridges to detail around. Fewer circuits mean a shorter panel schedule and less electrical rough-in.

The hardware line item is only part of the saving. The larger compounded cost sits in the trades that would have touched each of those 240+ devices: sheet metal, electrical rough, exterior siding or masonry around the caps, insulation around penetrations, and commissioning.

The Ventilation Math

An ERV sized for whole-unit ventilation only is a small box. Sizing it to also handle peak bath and kitchen exhaust is a different calculation, but not a harder one. ASHRAE 62.2 ventilation targets and the code-required spot exhaust rates are known quantities, and most residential ERV manufacturers publish boost-mode performance curves that cover the spot exhaust range.

The key is that balanced ventilation already requires continuously running supply and exhaust fans in every unit. Adding boost-mode operation on a user call (bathroom switch, humidity sensor, kitchen occupancy) uses the same ductwork and the same fan that is already in the wall. The incremental cost is a slightly larger unit and better grilles, not a second mechanical system.

When Three Systems Still Wins

Consolidating exhaust into the ERV is not always the right call. There are projects where the default stack of separate bath fans, a range hood, and a small ERV is the cheaper or more practical answer.

Gas cooktops with high-CFM range hoods. If the kitchen appliance package is gas and the code or program requires a 300+ CFM range hood with makeup air, the ERV is not going to cover that duty. A dedicated range hood and makeup air path is the right design.

Projects without an ERV requirement. If the compliance path does not already require balanced ventilation, the capital cost of an ERV per unit can exceed what you save on the exhaust devices. The consolidation math only works when the ERV is already in the budget.

Unit layouts with long duct runs to remote bathrooms. If a bath is on the far side of the unit from the ERV and the duct route adds significant static pressure, a local bath fan can be cheaper and quieter than upsizing the ERV and running more trunk duct.

The Decision Framework

If your project already has ERVs in the budget because of code or a certification program, run the consolidation option before the mechanical scope is locked. The numbers swing with unit count, bathroom count per unit, and cooktop fuel, and the savings compound across envelope, electrical, and commissioning line items. If ERVs are optional on your stack, the analysis inverts and the default three-system design often wins.