155 Federal St

155 Federal St is a 18-story building in Downtown Boston with 92% of its floor area within daylight reach of a facade. This screen estimates 191 homes and scores it 95 out of 100 for office-to-residential conversion suitability.

MA-7 & MA-8 · Screened 2026-10-04 · Strong candidate

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Where 155 Federal St is

Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.

Suitability score

0–29

30–49

50–69

70–100

Already housing
Not screened
155 Federal St

155 Federal St and the 1,000 ft of Downtown Boston around it. The streets are drawn at the width of the right-of-way they run down, sidewalks included, and named, and every building on these blocks is drawn. What is left open and stippled is neither: a surface lot, a plaza or a vacant parcel. The screened buildings are colored by the ramp above, the same one the district map uses, carry their score, and each is a link to its own page. Each casts a shadow as long as its measured height lets it, so towers stand out from the low buildings around them; the unscreened buildings have no measured height and cast none. 155 Federal St is outlined in its own score color at the outline it covers at ground level. Dashed inside it is the typical floor, the one the floor-plate figure below draws, because this building steps back as it rises. Its windowless core is hatched. The inset places it among every building the screen covers.

Typical floor plan: 92% of the building’s floor area sits within daylight reach of a facade; the drawing shows its typical floor, where the share is 91%. The shading is daylight, darkest at the windows and gone 35 ft in. The hatched area is windowless core: 1,041 sq ft per typical floor that must be renovated but can never be rented as an apartment. The dimension marks the deepest interior point, 49 ft from the nearest window. A–A is where the section beside it is cut.

Section A–A: cut across the depth of the plate, through the middle of the core. Daylight reaches 35 ft in from every facade, fading as it goes, and the hatched stripe left between the lit edges is floor that gets converted and can never be rented: 1,041 sq ft on the floor the screen scores, and 16,027 sq ft over 17 residential floors. The steps are where the building sets back as it rises. The shaded ground floor is converted like the rest and counted as no homes.

This building's conversion pencils at default assumptions without any subsidy.

Across its 17 residential floors this building carries 16,027 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 155 Federal St, 2026-10-04.

Suitability scoreStrong candidate	95 / 100
Storiesfrom 212 ft aerial-survey height ÷ 12 ft floor-to-floor	18
Height bandsfloor plate by floor range, from the city's roof outlines	Floors 1–16: 11,758 sq ft · Floor 17: 10,012 sq ft · Floor 18: 8,744 sq ft
Floor platetypical floor, from the city outlines	11,758 sq ft
Daylight efficiencyshare within 35 ft of a facade	92%
Deepest interior pointviability threshold is 80 ft	49 ft
Windowless coretypical floor; the building-wide total is in the text above	1,041 sq ft
Estimated homesat 750 sq ft average	191
Conversion cost$360/sq ft all-in on 195,126 sq ft	$70.2M
Gap before grantpencils unsubsidized	-$14.1M
Modeled RESIDE grantat the statutory per-award cap	$10.0M
BuiltBoston's own record of the construction year	1983
ZoningDowntown Boston	SKY
Opportunity Zonenot in a 2018 designated tract	No

The plan: window line, shape and floor rhythm

41 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.

The typical floor has 455 ft of exterior wall, and across 17 residential floors the building carries 7,857 ft of it in total, divided among the 191 homes this screen estimates.

Its plate is moderately compact at 0.71: a squarish plan, with enough perimeter for a conventional double-loaded corridor. How window line and plate shape are measured.

At the model’s 750 sq ft average, the plan works out at about 11.2 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 155 Federal St scores 95 out of 100

Daylight efficiency 100, Interior depth 78, Scale 100, Finance 100 — each out of 100, then weighted.

Score components for 155 Federal St. Points are the subscore times its weight.

Component	Subscore	Weight	Points
Daylight efficiency92% of the floor area within 35 ft of a facade, scored from 40% up to 90%	100	45%	45.0
Interior depthdeepest interior point 49 ft from a facade, scored from 80 ft down to 40 ft	78	25%	19.5
Scale191 estimated homes, scored from 0 up to 150	100	15%	15.0
Financecompleted value covers conversion cost with 34% 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 78 out of 100: deepest interior point 49 ft from a facade, scored from 80 ft down to 40 ft.

Built in 1983

Boston records this building as going up in 1983, 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 92% daylight figure above deserves.

What the conversion would cost

$360 per square foot all-in across 195,126 sq ft of converted floor, or $70.2M in total — about $368K for each of the 191 homes.

All-in cost per square foot for 155 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 16,027 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 191 homes is $84.3M.

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 $70.2M of work with $14.1M to spare. Value per home would have to fall to $368K — 17% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $432 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 155 Federal St:

Single-assumption flip points for 155 Federal St, each holding the other three at their defaults.

Circulation efficiencythe binding constraint — the least this building would need	26% downto 59%
Completed value per home	29% downto $315K
Average unit size	35% upto 1,016 sq ft
Conversion cost per square foot	47% upto $383/sq ft

All four are sliders in the survey, where 155 Federal St re-scores against your own numbers.

How it compares in Downtown Boston

155 Federal St ranks 15th of the 96 buildings screened here, against a median score of 89.

Its floor plate is better lit than 57% of them, and shallower than 52% of them at its deepest interior point. On size it is the 46th 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

8th of 52 zoned SKY — the comparison that shares its rules, rents and streets.

52 of the screened buildings are zoned SKY. 155 Federal St ranks 8th 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 49 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: 255 State St

The screened building closest to 155 Federal St in converted floor area is 255 State St: 206,638 sq ft over 11 stories, against 195,126 sq ft over 18 here.

155 Federal St scores 95 to its 68, and with the size held roughly equal most of that lead comes from daylight efficiency: 100 out of 100 here, 68 there (74% of the floor area within 35 ft of a facade, scored from 40% up to 90%). On the money they part ways: 255 State St pencils only with the modeled RESIDE grant, while 155 Federal St pencils without a subsidy. The two stand about 2,500 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 155 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 155 Federal St

The 4 closest the screen also covers, from 180 ft away. They are the colored outlines on the plan at the top of this page.

175 Federal St
20 stories · 83% daylit · 232 estimated homes · scores 87/100 (Strong candidate)
about 180 ft away
133 Federal St
13 stories · 91% daylit · 117 estimated homes · scores 90/100 (Strong candidate)
about 190 ft away
172-180 Federal St
7 stories · 91% daylit · 63 estimated homes · scores 88/100 (Strong candidate)
about 200 ft away
100 Summer St
35 stories · 74% daylit · 856 estimated homes · scores 67/100 (Worth a feasibility study)
about 230 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.