Office Building Conversion Tool

Overview

The Office Building Conversion tool assesses the feasibility of converting an office building into residential housing that meets New York City building code compliance. This tool is designed to assist developers in quickly identifying office buildings whose designs lend themselves to residential conversions with limited demolition.

Background

New York City is experiencing a housing crisis; over 560,000 residential units will need to be added by 2030 to meet demand. New construction in an increasingly land scarce city is expensive and infeasible to meet demand. The covid epidemic has unlocked a new entry point to increasing the housing share, and that’s through office building conversions whose vacancy rates are increasing amongst a shift to work-from-home and co-working models. As of February 2024, office building vacancy in the city grew to 22%, where pre-covid levels hovered around 11%.

Methodology

Process plan

Design space model

CAD of city building data is passed into the model, which processes these inputs in batch in order to create a score for each building being analyzed. The model output is area data that can be exported as .csv in order to compare the rentable area of each building, its projected construction costs and profit.

Input parameters

The tool is designed to calculate and compare floor areas across multiple office buildings. Our decision of where to source our data was premised on three constraints:

1. We needed spatial data to calculate areas. To calculate usable area, it was essential to access floor plans that clearly identified the location of the circulation core.
2. Rooftop areas mattered more than ground floor area. Due to New York City’s setback regulation, the upper floors are often smaller in area than the lower floors, and thus have a greater percentage of floor area with the necessary light intrusion needed to host residential units.
3. The data had to be publicly available. This keeps the operational costs of our tool down.

The city’s repository of 3D building models, parsed by community district, met these conditions, and thus the Manhattan Community District 1 (CD01), containing the Financial District and its extensive office building sector, was passed into our model.

Data is cleaned so only rooftop plans remain. In pink, the highlighted rooftop areas to be used in our analysis

Input sanitization

The input data is scrubbed of any information beyond the Rooftop Layer. This layer contains simple, planar surfaces of building rooftops and the corresponding lift overruns and cooling towers that sit above the roof plane. Surfaces from the same building are grouped, and the rooftop plane is identified based on it having the largest area within the group.

Using the Zoning and Land Use Map, we then identified office buildings in CD01 that represent a variety of core configurations, and they are singled out for analysis.

Floor plate analysis

The exterior curve and interior curve(s) are extracted from the surface and stored as the building perimeter and the building core(s), respectively. The interior curve is offset by 8ft to represent a simple corridor needed to navigate from the elevator to a residential unit. The exterior is offset by 30ft to represent the maximum allowable depth for a residential unit that meets New York City light intrusion requirements.

Once these two offsets are created, three area zones are calculated:

1. “Dead Zone,” the circulation core extended to the width of its wraparound corridor
2. “Usable Zone,” including any area that lies within the 30ft offset, excluding any intersection with the Core Area. This zone can be dedicated to residential units.
3. “Wasted Space,” which consists of any remaining area that lies outside of both the Dead Zone and Usable Zone. This area is not essential to circulation and would require a non-residential program to turn a profit.

Relationship between usable zone, dead zone, and wasted area

These area calculations apply to the baseline metric, where the core is centrally located inside a building. We created a logic tree that modifies the method of identifying the dead zone to satisfy irregular conditions — such as cores that are located near a building’s edge, or a building that contains more than one core.

Examples of how different considerations for light intrusion (shown in green, ranging from 8ft to 30ft offset from the building’s perimeter) reduce the size of the wasted area (shown in pink)

Output

The resulting outputs is a visualization depicting the relationship between the usable area, wasted area, and existing circulation. Their relative area sizes are listed out, in order to determine if the wasted area is larger than the usable area of a given building, which would conclude that a conversion into residential units will likely be unprofitable.

In this case, the wasted space exceeds 20,000 sqft.

Next Steps

• Exporting the data as a .csv file to a pro forma that can analyze the profitability of a building conversion based on whether the price per square foot of usable area exceeds the construction costs necessary to renovate both the usable zone and the wasted zone.
• Automating the input process so that the program can run across a variety of community districts without manual selection.
• Incorporating GIS data into the input, so that non-office buildings are excluded automatically from analysis.
• Developing a web interface where office buildings can be visualized on a map and color-coded according to the profitability of their conversion.