71-75 Kilby St

Where 71-75 Kilby 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

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

The typical floor has 1,301 ft of exterior wall, and across 12 residential floors the building carries 15,609 ft of it in total, divided among the 451 homes this screen estimates.

Its plate is elongated at 0.29: 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 37.6 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.

Why 71-75 Kilby St scores 84 out of 100

Daylight efficiency 99, Interior depth 39, Scale 100, Finance 100 — each out of 100, then weighted.

Most of what it earns comes from daylight efficiency, and what holds it back most is interior depth, at 39 out of 100: deepest interior point 64 ft from a facade, scored from 80 ft down to 40 ft.

Built in 1920

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

As a rule, steel or concrete frames with punched windows and plates still narrow enough for daylight to reach the middle, often with high ceilings. Among the most convertible stock there is, and the reason so many early conversions were of buildings this age. 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 89% daylight figure above deserves.

What the conversion would cost

$360 per square foot all-in across 473,005 sq ft of converted floor, or $170.3M in total — about $378K for each of the 451 homes.

That cost is charged across every converted square foot, including the 49,910 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 451 homes is $199.1M.

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 $170.3M of work with $28.8M to spare. Value per home would have to fall to $378K — 14% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $421 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 71-75 Kilby St:

All four are sliders in the survey, where 71-75 Kilby St re-scores against your own numbers.

How it compares in Downtown Boston

71-75 Kilby St ranks 60th of the 96 buildings screened here, against a median score of 89.

Its floor plate is better lit than 50% of them, and shallower than 24% of them at its deepest interior point. On size it is the 27th 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

32nd of 52 zoned SKY — the comparison that shares its rules, rents and streets.

52 of the screened buildings are zoned SKY. 71-75 Kilby St ranks 32nd 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 64 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: 93-101 Arch St

The screened building closest to 71-75 Kilby St in converted floor area is 93-101 Arch St: 495,092 sq ft over 22 stories, against 473,005 sq ft over 13 here.

71-75 Kilby St scores 84 to its 72, and with the size held roughly equal most of that lead comes from daylight efficiency: 99 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: 93-101 Arch St pencils only with the modeled RESIDE grant, while 71-75 Kilby St pencils without a subsidy. The two stand about 1,300 ft apart.

Would it qualify for a RESIDE Act grant?

The model awards 71-75 Kilby 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 71-75 Kilby St

The 4 closest the screen also covers, from 220 ft away. They are the colored outlines on the plan at the top of this page.

• 1 Liberty Sq
  13 stories · 84% daylit · 156 estimated homes · scores 87/100 (Strong candidate)
  about 220 ft away
• 147 Milk St
  10 stories · 100% daylit · 259 estimated homes · scores 100/100 (Strong candidate)
  about 380 ft away
• 14-24 Federal St
  11 stories · 98% daylit · 130 estimated homes · scores 98/100 (Strong candidate)
  about 400 ft away
• 43-65 State St
  45 stories · 67% daylit · 940 estimated homes · scores 61/100 (Worth a feasibility study)
  about 440 ft away