125-135 Congress St

Where 125-135 Congress St is

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

The plan: window line, shape and floor rhythm

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

The typical floor has 329 ft of exterior wall, and across 7 residential floors the building carries 2,304 ft of it in total, divided among the 49 homes this screen estimates.

Its plate is compact at 0.78: close to a square or a circle, the most efficient envelope an office can have and the least generous one for apartments: little perimeter to divide among homes. How window line and plate shape are measured.

At the model’s 750 sq ft average, the plan works out at about 7.0 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 125-135 Congress St scores 90 out of 100

Daylight efficiency 100, Interior depth 100, Scale 33, Finance 100 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is scale, at 33 out of 100: 49 estimated homes, scored from 0 up to 150.

Built in 1910

Boston records this building as going up in 1910, which puts it in the pre-1920 stock.

As a rule, the era that converts most readily: load-bearing masonry, small floor plates laid out before deep-plan offices were possible, operable windows and generous floor-to-floor heights. The usual obstacles are not daylight but hazardous materials, lifts and bringing structure up to current code. 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 98% daylight figure above deserves.

What the conversion would cost

$360 per square foot all-in across 46,881 sq ft of converted floor, or $16.9M in total — about $344K for each of the 49 homes.

That cost is charged across every converted square foot, including the 889 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 49 homes is $21.6M.

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 $16.9M of work with $4.8M to spare. Value per home would have to fall to $344K — 22% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $461 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 125-135 Congress St:

All four are sliders in the survey, where 125-135 Congress St re-scores against your own numbers.

How it compares in Downtown Boston

125-135 Congress St ranks 36th of the 96 buildings screened here, against a median score of 89.

Its floor plate is better lit than 74% of them, and shallower than 71% of them at its deepest interior point. On size it is the 87th 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

18th of 52 zoned SKY — the comparison that shares its rules, rents and streets.

52 of the screened buildings are zoned SKY. 125-135 Congress St ranks 18th 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 39 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: 60-70 Temple Pl

The screened building closest to 125-135 Congress St in converted floor area is 60-70 Temple Pl: 50,005 sq ft over 7 stories, against 46,881 sq ft over 8 here.

The two land within a few points of each other — 90 here, 89 there — so at this size the screen reads them as much the same prospect. On the money they sit in the same place: each pencils without a subsidy. The two stand about 1,400 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 125-135 Congress St $2.9M, 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 125-135 Congress St

The 4 closest the screen also covers, from 80 ft away. They are the colored outlines on the plan at the top of this page.

• 42-60 Federal St
  10 stories · 92% daylit · 81 estimated homes · scores 89/100 (Strong candidate)
  about 80 ft away
• 14-24 Federal St
  11 stories · 98% daylit · 130 estimated homes · scores 98/100 (Strong candidate)
  about 120 ft away
• 70 Federal St
  9 stories · 100% daylit · 60 estimated homes · scores 91/100 (Strong candidate)
  about 160 ft away
• 1 Federal St
  43 stories · 68% daylit · 916 estimated homes · scores 62/100 (Worth a feasibility study)
  about 170 ft away