101 Federal St
101 Federal St is a 31-story building in Downtown Boston with 91% of its floor area within daylight reach of a facade. This screen estimates 569 homes and scores it 93 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate
Where 101 Federal St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing
- Not screened
- 101 Federal St
This building's conversion pencils at default assumptions without any subsidy.
Across its 30 residential floors this building carries 51,641 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment.
Modeled conversion metrics for 101 Federal St, 2026-10-04.
| Suitability scoreStrong candidate | 93 / 100 |
|---|---|
| Storiesfrom 376 ft aerial-survey height ÷ 12 ft floor-to-floor | 31 |
| Height bandsfloor plate by floor range, from the city's roof outlines | Floors 1–30: 20,105 sq ft · Floor 31: 2,103 sq ft |
| Floor platetypical floor, from the city outlines | 20,105 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 91% |
| Deepest interior pointviability threshold is 80 ft | 50 ft |
| Windowless coretypical floor; the building-wide total is in the text above | 1,781 sq ft |
| Estimated homesat 750 sq ft average | 569 |
| Conversion cost$360/sq ft all-in on 585,149 sq ft | $210.7M |
| Gap before grantpencils unsubsidized | -$40.6M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltBoston's own record of the construction year | 1987 |
| ZoningDowntown Boston | SKY |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
40 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 774 ft of exterior wall, and across 30 residential floors the building carries 22,630 ft of it in total, divided among the 569 homes this screen estimates.
Its plate is elongated at 0.42: a slab or an L, which is why so much of the floor lies within reach of a window: the outline buys daylight that a square plan of the same area would not. How window line and plate shape are measured.
At the model’s 750 sq ft average, the plan works out at about 19.0 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 101 Federal St scores 93 out of 100
Daylight efficiency 100, Interior depth 74, Scale 100, Finance 100 — each out of 100, then weighted.
Score components for 101 Federal St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency91% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 100 | 45% | 45.0 |
| Interior depthdeepest interior point 50 ft from a facade, scored from 80 ft down to 40 ft | 74 | 25% | 18.4 |
| Scale569 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financecompleted value covers conversion cost with 24% to spare, which tops out the component | 100 | 15% | 15.0 |
Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 74 out of 100: deepest interior point 50 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1987
Boston records this building as going up in 1987, which puts it in the late-modern stock.
As a rule, typically the hardest to convert: the deepest plates of any era, large central cores, and floor-to-floor heights tight enough that running residential drainage under a ceiling can be the thing that ends a project. That is the era’s general tendency rather than a finding about this building — the model reads an outline and a height, and can see nothing inside — but it is the first thing an architect would want to know, and it colours how much confidence the 91% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 585,149 sq ft of converted floor, or $210.7M in total — about $370K for each of the 569 homes.
All-in cost per square foot for 101 Federal St: base cost plus the code work a change of use triggers.
| Base conversion cost | $260/sq ft |
|---|---|
| Plumbing risers to every unit | $40/sq ft |
| Operable windows and glazing | $30/sq ft |
| Additional egress stair | $18/sq ft |
| Fire sprinklers (NFPA 13R) | $12/sq ft |
| All-in | $360/sq ft |
That cost is charged across every converted square foot, including the 51,641 sq ft of windowless core, which has to be gutted, re-plumbed and sprinklered like the rest of the building and then earns nothing. Against it the model sets a completed value of $442K a home, which for 569 homes is $251.2M.
What would have to be true
This one already clears the bar. The question is how much room it has before it stops.
At $442K a home, completed value covers the $210.7M of work with $40.6M to spare. Value per home would have to fall to $370K — 16% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $429 per square foot. Neither is a wide margin in a market that moves, but this building does not need a grant to work.
Each of these, moved on its own, would be enough to undo that for 101 Federal St:
Single-assumption flip points for 101 Federal St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 20% downto 64% |
|---|---|
| Completed value per home | 20% downto $353K |
| Average unit size | 25% upto 938 sq ft |
| Conversion cost per square foot | 33% upto $346/sq ft |
All four are sliders in the survey, where 101 Federal St re-scores against your own numbers.
How it compares in Downtown Boston
101 Federal St ranks 18th of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 55% of them, and shallower than 46% of them at its deepest interior point. On size it is the 23rd largest by estimated homes. The full survey of all 96 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within the SKY zone
9th of 52 zoned SKY — the comparison that shares its rules, rents and streets.
52 of the screened buildings are zoned SKY. 101 Federal St ranks 9th of them against a median score of 88. 40 score 70 or more, their median deepest interior point is 51 ft from a facade against this building’s 50 ft, and together they would hold an estimated 19,019 homes. The group’s top scorer is 147 Milk St, at 100.
Its nearest match in size: 207-211 Congress St
The screened building closest to 101 Federal St in converted floor area is 207-211 Congress St: 627,961 sq ft over 32 stories, against 585,149 sq ft over 31 here.
101 Federal St scores 93 to its 84, and with the size held roughly equal most of that lead comes from daylight efficiency: 100 out of 100 here, 84 there (82% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they sit in the same place: each pencils without a subsidy. The two stand about 400 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 101 Federal St $10.0M, on the assumption it qualifies. Whether it does, no published dataset can say.
That figure assumes the building meets the Act’s vacant-and-abandoned test, which turns on code-enforcement and receivership records no city publishes.
It does not sit in a 2018 designated Opportunity Zone, so it would not draw that Section 201 priority.
Other buildings screened near 101 Federal St
The 4 closest the screen also covers, from 110 ft away. They are the colored outlines on the plan at the top of this page.
- 75-101 Federal St21 stories · 89% daylit · 257 estimated homes · scores 96/100 (Strong candidate)about 110 ft away
- 100 Federal St50 stories · 62% daylit · 1,164 estimated homes · scores 35/100 (Marginal)about 240 ft away
- 20 Winthrop Sq6 stories · 100% daylit · 36 estimated homes · scores 89/100 (Strong candidate)about 240 ft away
- 133 Federal St13 stories · 91% daylit · 117 estimated homes · scores 90/100 (Strong candidate)about 270 ft away
A screen, not a feasibility study, from outlines and heights rather than plans: the method and how to correct a figure. If you know this building’s interior, you know what this model cannot see.