25 New Chardon St
25 New Chardon St is a 7-story building in Downtown Boston with 78% of its floor area within daylight reach of a facade. This screen estimates 87 homes and scores it 67 out of 100 for office-to-residential conversion suitability.
MA-7 & MA-8 · Screened 2026-10-04 · Worth a feasibility study
Where 25 New Chardon St is
Its block in Downtown Boston, drawn from Boston's own building outlines and street centerlines.
- Already housing, or excluded for residential records on a shared parcel
- Not screened
- 25 New Chardon St
This building's conversion pencils at default assumptions without any subsidy.
Every floor carries 3,957 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment. Across 6 residential floors that is 23,741 sq ft of cost carrying no revenue.
Modeled conversion metrics for 25 New Chardon St, 2026-10-04.
| Suitability scoreWorth a feasibility study | 67 / 100 |
|---|---|
| Storiesfrom 83 ft aerial-survey height ÷ 12 ft floor-to-floor | 7 |
| Floor plateper floor, from the city footprint | 17,652 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 78% |
| Deepest interior pointviability threshold is 80 ft | 65 ft |
| Windowless coreper floor — renovated but never rentable | 3,957 sq ft |
| Estimated homesat 750 sq ft average | 87 |
| Conversion cost$360/sq ft all-in on 105,913 sq ft | $38.1M |
| Gap before grantpencils unsubsidized | -$283K |
| Modeled RESIDE grantbelow the statutory cap | $5.2M |
| BuiltBoston's own record of the construction year | 1968 |
| ZoningDowntown Boston | SUDBURY STREET RESTRICTED GROWTH AREA |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
38 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 546 ft of exterior wall, and across 6 residential floors the building carries 3,273 ft of it in total, divided among the 87 homes this screen estimates.
Its plate is compact at 0.75: 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 14.5 homes per floor, repeated on every residential floor, since this building's outline does not change as it rises.
Why 25 New Chardon St scores 67 out of 100
Daylight efficiency 75, Interior depth 37, Scale 58, Finance 100 — each out of 100, then weighted.
Score components for 25 New Chardon St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency78% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 75 | 45% | 33.8 |
| Interior depthdeepest interior point 65 ft from a facade, scored from 80 ft down to 40 ft | 37 | 25% | 9.3 |
| Scale87 estimated homes, scored from 0 up to 150 | 58 | 15% | 8.7 |
| Financecompleted value covers conversion cost with 14% 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 37 out of 100: deepest interior point 65 ft from a facade, scored from 80 ft down to 40 ft.
Built in 1968
Boston records this building as going up in 1968, which puts it in the post-war stock.
As a rule, the period when plates got deep and facades became curtain wall: sealed glazing, lower floor-to-floor heights, and mechanical systems designed around a sealed box. Conversions here usually turn on whether the windows can be made to open and whether ceilings survive new plumbing. 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 78% daylight figure above deserves.
What the conversion would cost
$360 per square foot all-in across 105,913 sq ft of converted floor, or $38.1M in total — about $438K for each of the 87 homes.
All-in cost per square foot for 25 New Chardon 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 23,741 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 87 homes is $38.4M.
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 $38.1M of work with $283K to spare. Value per home would have to fall to $438K — 1% below the assumption — before the conversion stopped penciling, or all-in cost would have to rise from $360 to $363 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 25 New Chardon St:
Single-assumption flip points for 25 New Chardon St, each holding the other three at their defaults.
| Circulation efficiencythe binding constraint — the least this building would need | 12% downto 70% |
|---|---|
| Average unit size | 14% upto 854 sq ft |
| Completed value per home | 14% downto $378K |
| Conversion cost per square foot | 20% upto $312/sq ft |
All four are sliders in the survey, where 25 New Chardon St re-scores against your own numbers.
How it compares in Downtown Boston
25 New Chardon St ranks 80th of the 96 buildings screened here, against a median score of 89.
Its floor plate is better lit than 28% of them, and shallower than 21% of them at its deepest interior point. On size it is the 67th 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.
Its nearest match in size: 390-400R Atlantic Ave
The screened building closest to 25 New Chardon St in converted floor area is 390-400R Atlantic Ave: 100,939 sq ft over 7 stories, against 105,913 sq ft over 7 here.
25 New Chardon St scores 67 to its 71, and with the size held roughly equal most of that shortfall comes from interior depth: 37 out of 100 here, 49 there (deepest interior point 60 ft from a facade, scored from 80 ft down to 40 ft). On the money they sit in the same place: each pencils without a subsidy. The two stand about 3,900 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 25 New Chardon St $5.2M, 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 25 New Chardon St
The 4 closest the screen also covers, from 160 ft away. They are the colored outlines on the plan at the top of this page.
- 15 New Chardon St12 stories · 82% daylit · 154 estimated homes · scores 79/100 (Strong candidate)about 160 ft away
- 14 Bowdoin St25 stories · 75% daylit · 633 estimated homes · scores 74/100 (Strong candidate)about 560 ft away
- 100-110 Sudbury St46 stories · 90% daylit · excluded: residential records on a shared parcelabout 570 ft away
- 2 Congress St10 stories · 48% daylit · excluded: residential records on a shared parcelabout 740 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.