The City of Yes for Housing Opportunity expands the pool of office buildings that may be converted to housing. Conversion was previously allowed in central business districts for office buildings built before 1961 (or 1977, for certain districts). Now it is allowed for buildings built before 1991, anywhere residential uses are allowed. What had applied to some building midtown and lower Manhattan, and in the parts of Brooklyn and Queens now applies to far more buildings in nearly all parts of all five boroughs. This can address the city’s housing shortage by repurposing buildings rather than building entirely new ones.
But what does it take to transform an office building into livable apartments? Below are the key considerations architects and engineers must evaluate when adapting office buildings for residential use.
Air and Light: Designing for Livability
Residential buildings require significantly more natural light and access to air than office buildings. For example, a conference room in an office might be in the center of a building, without any natural light. That setup will not work for living spaces
To address this:
- Floor plans must be reconfigured so that living spaces (bedrooms, living rooms, dining rooms) can be positioned along or near building perimeter.
- Bathrooms, closets, and utility spaces can be placed inboard.
- In some cases, large floor plates may need to be partially demolished to allow for sufficient air and light.
Ventilation: Meeting Residential Codes
In an office building, ventilation systems are typically centralized—supplying outside air and exhausting restrooms via a pair of vertical duct risers that go up to fans on the roof. Residential units, however, require more, and more localized ventilation for:
- A greater number of bathrooms
- Kitchens with dedicated exhaust needs
- Compliance with Section 401.2 of the NYC Mechanical Code, which mandates mechanical ventilation in air-conditioned habitable rooms.
Solutions include:
- Additional risers for both exhaust and outside air
- Energy Recovery Ventilators (ERVs) to manage both intake and exhaust efficiently, with energy conservation benefits
- Ventilating each apartment through the façade, rather than up to the roof, bearing in mind aesthetic, air leakage (building tightness), and minimum distances between intakes and exhausts
Power: Upgrading Electrical Infrastructure
Many office buildings already have sufficient power for air conditioning, but apartment conversions introduce new demands:
- Electric appliances (ovens, dryers, etc.)
- Electric domestic hot water systems, in all-electric buildings
- Distributed HVAC systems for individual apartments
What’s often needed:
- A power service upgrade, which might require a new or enlarged main electrical room.
- New electrical switchgear and distribution systems, including metered or sub-metered panelboards at each apartment
- Coordination with local utilities for capacity and metering
Plumbing, Fire Protection: Reconfiguring for Distributed Loads
Office plumbing is centralized: clustered restrooms on each floor. In contrast, residential units have widely dispersed bathrooms and kitchens, leading to dramatically different demand patterns.
Key changes may include:
- Replacement of existing drainage, water, and vent risers, which likely don’t align with the new layout.
- New fire protection (sprinkler, standpipe) risers and sprinkler zones.
- Possibly and upsized water service.
- If the original restrooms had numerous fixtures, the existing sewer line may suffice—otherwise, expect upgrades here too.
Heating and Cooling: Individualized and Efficient
Legacy HVAC systems in office buildings are typically centralized and not easily adaptable for residential comfort or zoning.
Common strategies for conversion:
- Remove centralized cooling systems.
- Assess whether existing heating systems (e.g., steam or hot water radiators) can be reused in the short term.
Install decentralized systems such as:
- PTAC (Packaged Terminal Air Conditioner) or PTHP (Packaged Terminal Heat Pump) units
- Multi-zone Variable Refrigerant Flow (VRF) systems, with the caveat that newer A2L refrigerants require condensing units to be placed on the floors they serve.
- Should there be an existing cooling tower, it might be viable to provide each apartment with watersource heat pumps. This does require extensive piping, and a source of heat “injection” in winter, whether from an existing boiler (not great for emission, long term) or new, centralized air-source heat pumps (technology is improving, requires substantial power).
Sustainability and emissions laws matter:
- NYC’s Local Law 97 penalizes high-emissions heating systems, making all-electric solutions like heat pump systems increasingly favorable.
Domestic Hot Water: Planning for Higher Demand
Apartments require significantly more domestic hot water (DHW) than office buildings, mainly due to showers and kitchens in each unit.
Considerations include:
- Removal of undersized existing DHW systems
- Gas-fired boilers or water heaters (if gas service is available)—though emissions may lead to future penalties
- Heat pump water heating systems with storage tanks and condensing units, typically placed on the roof or in mechanical rooms. Design must account for where the system sources its heat: air-source units placed outdoors, or water-source units integrated with other HVAC systems.
Envelope
The envelope of the building might be leaky and old. A well-sealed, well insulated building, carefully ventilated, requires less heating and cooling. It’s more efficient. The following should be considered:
- Replacing the windows, with operable windows, as office buildings often have inoperable windows
- Whether to replace the entire façade, walls and windows, to better align with the new room layouts, and to refresh the building’s look
- Cladding the building or adding screening to mitigate solar heat gain and further improve energy efficiency
- Replacing the roof, possibly with a blue or green roof
467-m Property Tax Incentive Program
To help offset the costs of conversion, and increase the supply of affordable housing, the city worked with the state to pass 467-m, a new city property tax exemption if 25% of apartments are income restricted. See the NYC Comptroller’s recently published report on it here.
Final Thoughts
Converting office buildings to residential use in NYC offers an exciting path to increasing the city’s housing supply—but it requires thoughtful MEP design from day one. Every system must be re-evaluated for suitability, capacity, and compliance, and in many cases, entirely replaced.
With the right engineering strategies, adaptive reuse projects can be both functional and forward-thinking, offering comfortable homes while minimizing environmental impact.