Ventilation Guide
Dedicated Outdoor Air Systems (DOAS) in New York City
A DOAS gives ventilation its own system, kept apart from heating and cooling, so a NYC building gets steady fresh-air delivery, real humidity control, and lower energy bills. Here’s how they work, where they fit, and why they matter so much for Local Law 97 electrification.
All GuidesThe Concept
What “Decoupling Ventilation” Means
In a normal HVAC system, one unit tries to do everything at once. It recirculates indoor air, mixes in a little outdoor air for ventilation, and heats or cools the whole blend. It works, but it forces trade-offs. How much fresh air you get is tied to the heating and cooling demand, and dehumidification suffers because the system can’t condition the ventilation air on its own.
A dedicated outdoor air system splits those jobs apart. The DOAS is on the hook for one thing: pulling in 100% outdoor air, conditioning it, and pushing measured fresh air out to the building. Separate terminal equipment (heat pumps, fan coils, VRF, or an air handler) carries the space heating and cooling load. Each system does one job, and each gets sized and controlled for that job.
That split is where all the value is. Ventilation stays steady and code-compliant no matter what the thermostat is asking for, humidity control gets a lot better, and the building runs leaner. All of that counts for more in NYC than it does in a milder climate.
Why NYC
Why NYC Buildings Are Installing DOAS
- Ventilation & indoor air quality. A DOAS delivers a measured volume of fresh air no matter what the heating and cooling side is doing. That answers code ventilation requirements and the higher bar tenants set on air quality these days.
- Humidity control. Because it conditions outdoor air separately, a DOAS can dehumidify effectively without overcooling the space — a real problem in NYC’s humid summers that mixed-air systems handle poorly.
- Efficiency & Local Law 97. Ventilating a building in NYC’s climate carries a real energy cost. Pairing a DOAS with energy recovery and heat pump conditioning slashes that cost and cuts reportable emissions. See our commercial heat pump guide for how DOAS fits an electrification plan.
Electrification
DOAS Heat Pumps and Energy Recovery
Two features turn a basic DOAS into a Local Law 97 asset: heat pump conditioning and energy recovery.
A DOAS heat pump tempers the incoming outdoor air electrically — heating it in winter, cooling and dehumidifying it in summer — instead of relying on gas heat or a steam/chilled-water coil. For a building electrifying under Local Law 97, that removes one more combustion load and moves it to electric, right alongside apartment- or zone-level heat pumps.
Energy recovery ventilation (ERV) captures heat and moisture from the air the building exhausts and uses it to pre-condition the incoming fresh air — warm exhaust pre-heating cold winter intake, and the reverse in summer. Because a DOAS moves 100% outdoor air, energy recovery is especially valuable: it dramatically reduces the energy needed to temper ventilation air in NYC’s cold winters and humid summers. We include energy recovery in most NYC DOAS designs for exactly this reason.
System Integration
How a DOAS Fits With the Rest of the System
A DOAS never works alone — it handles ventilation, and something else handles the space load. Common pairings in NYC buildings:
- DOAS + through-wall heat pumps. The DOAS delivers fresh air while apartment-level through-wall condensers handle heating and cooling — a clean fit for multifamily electrification.
- DOAS + fan coil units. The DOAS tempers ventilation air; fan coils in each zone trim the space temperature. Common in hydronic buildings. A slim hydronic unit like the Jaga Briza fan coil fits this role on a heat-pump loop.
- DOAS + air handler retrofit. When a building is already modernizing an air handler, adding a DOAS decouples ventilation cleanly — see our AHU retrofit guide.
Logistics
Installation, Cost, and NYC Realities
DOAS projects are quoted per building, and in NYC the equipment is rarely the hard part — the routing is. Where the unit lands (rooftop or mechanical room), how supply and exhaust ductwork run through the building, and how intake and exhaust penetrate the facade all drive cost and schedule. Rigging access, riser space, and DOB filing for ductwork and mechanical changes are the usual constraints.
We handle DOAS design and installation across Manhattan, Brooklyn, and Queens, and we scope every project against two things: the building’s ventilation requirements and its Local Law 97 targets. That way the system is sized for the fresh-air load it actually needs and configured to help, not hurt, the building’s emissions math.
Common Questions
NYC DOAS FAQ
What is a dedicated outdoor air system (DOAS)?
A dedicated outdoor air system (DOAS) is a unit that does one job: bring in fresh outdoor air, condition it, and distribute it. It doesn’t heat or cool the space. A normal system takes one unit, mixes recirculated indoor air with a little outdoor air, and does everything at once. A DOAS splits those jobs apart. It handles 100% outdoor air ventilation on its own, and heat pumps, fan coils, or other terminal units handle the actual heating and cooling. You get tighter ventilation control, real humidity control, and better efficiency.
Why would a NYC building install a DOAS?
Three reasons come up again and again in NYC. First, ventilation and indoor air quality. A DOAS delivers a measured amount of fresh air no matter what the thermostat is doing, and that matters for code and for what tenants expect after 2020. Second, humidity. Because the DOAS conditions outdoor air on its own, it can pull moisture out without freezing the space to do it. Third, efficiency and Local Law 97. Ventilating a building in this climate costs real energy, and pairing a DOAS with energy recovery and heat pump conditioning cuts that cost and lowers the emissions you have to report.
What is a DOAS heat pump?
A DOAS heat pump conditions the incoming outdoor air with a heat pump instead of gas heat or a chilled-water or steam coil. It warms the ventilation air in winter and cools and dehumidifies it in summer, all on electric. For a building electrifying under Local Law 97, that takes the combustion out of tempering ventilation air. It’s one more gas load moved over to electric, and it sits nicely next to apartment or zone-level heat pumps.
What is energy recovery and why does it matter for DOAS?
Energy recovery ventilation (ERV) grabs heat and moisture off the air a building throws out and uses it to pre-condition the fresh air coming in. In winter, the warm exhaust pre-heats the cold intake. In summer it runs the other way. Since a DOAS moves 100% outdoor air, energy recovery earns its keep. It cuts a big chunk of the energy needed to temper ventilation air through cold NYC winters and sticky summers. That’s why we put energy recovery on most of the NYC DOAS systems we design.
How does a DOAS fit with the rest of the HVAC system?
A DOAS only does ventilation, so it pairs with whatever conditions the space, whether that’s through-wall heat pumps, fan coil units, VRF, or an air handler. The DOAS feeds tempered fresh air to the zones, and the terminal equipment carries the heating and cooling load. Splitting the work that way lets you size and control each piece for one job, and you end up with better comfort, better humidity control, and better efficiency than one unit trying to do both.
What does DOAS installation cost in NYC?
We quote DOAS projects per building because the number rides on the ventilation load, on whether you want energy recovery and heat pump conditioning, and, this is the big one in NYC, on how the ductwork and unit get routed and rigged into the building. Rooftop or mechanical-room placement, riser routing, and facade penetrations all move the price. We scope every job against the building’s ventilation requirements and its Local Law 97 targets, and we quote the whole installed system, not just the box.
Considering a DOAS?
Tell us your building type, ventilation needs, and what conditions the space today, and we’ll scope a dedicated outdoor air system that fits — energy recovery, heat pump conditioning, and all. Reach out or fill out a sizing request form to get started.