1321 15th St
1321 15th St is a 12-story building in Greater Downtown Denver with 76% of its floor area within daylight reach of a facade. This screen estimates 216 homes and scores it 72 out of 100 for office-to-residential conversion suitability.
CO-1 · Screened 2026-09-19 · Strong candidate
Also addressed as 1331 15th St, 1350 16th St, 1370 16th St, 1380 16th St, 1500 Market St, 1514 Market St, 1520 Market St, 1540 Market St, 1550 Market St and 1560 Market St: Denver’s address records place all 11 on this one footprint.
Where 1321 15th St is
Its block in Greater Downtown Denver, drawn from Denver's own building outlines and street centerlines.
- Already housing
- Not screened
- 1321 15th St
This building does not pencil at default assumptions, even with a modeled RESIDE Act grant.
Across its 11 residential floors this building carries 63,406 sq ft of windowless core — area that must be gutted, re-plumbed and sprinklered but can never be rented as an apartment.
Part of this building is already homes. Denver's property records list 36 apartments here, alongside 2 non-residential records. The figures here treat the whole building as convertible, so read them as an upper bound and check which floors are already housing.
Modeled conversion metrics for 1321 15th St, 2026-09-19.
| Suitability scoreStrong candidate | 72 / 100 |
|---|---|
| Storiesfrom 140 ft aerial-survey height ÷ 12 ft floor-to-floor | 12 |
| Height bandsfloor plate by floor range, from the city's roof outlines | Floors 1–2: 48,660 sq ft · Floor 3: 47,937 sq ft · Floor 4: 43,239 sq ft · Floor 5: 33,539 sq ft · Floor 6: 21,483 sq ft · Floor 7: 17,605 sq ft · Floors 8–11: 13,260 sq ft · Floor 12: 716 sq ft |
| Floor platetypical floor, from the city outlines | 13,260 sq ft |
| Daylight efficiencyshare within 35 ft of a facade | 76% |
| Deepest interior pointviability threshold is 80 ft | 51 ft |
| Windowless coretypical floor; the building-wide total is in the text above | 1,824 sq ft |
| Estimated homesat 750 sq ft average | 216 |
| Conversion cost$360/sq ft all-in on 266,220 sq ft | $95.8M |
| Gap before grantshortfall against completed value | $44.9M |
| Modeled RESIDE grantat the statutory per-award cap | $10.0M |
| BuiltDenver does not publish a construction year with this data | — |
| ZoningUnion Station | D-LD |
| Opportunity Zonenot in a 2018 designated tract | No |
The plan: window line, shape and floor rhythm
36 ft of exterior wall for each home the screen estimates — enough for two- and three-bedroom homes across the plan.
The typical floor has 484 ft of exterior wall, and across 11 residential floors the building carries 7,752 ft of it in total, divided among the 216 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 19.6 homes per floor. Its floors are not alike, though: the typical floor's deepest interior point is 51 ft from a facade, while its worst floor reaches 62 ft. The score follows the typical floor, so a podium that could not hold a bedroom does not by itself sink a slim tower above it — but it is there, and it is part of what would have to be drawn around.
Why 1321 15th St scores 72 out of 100
Daylight efficiency 72, Interior depth 72, Scale 100, Finance 39 — each out of 100, then weighted.
Score components for 1321 15th St. Points are the subscore times its weight.
| Component | Subscore | Weight | Points |
|---|---|---|---|
| Daylight efficiency76% of the floor area within 35 ft of a facade, scored from 40% up to 90% | 72 | 45% | 32.6 |
| Interior depthdeepest interior point 51 ft from a facade, scored from 80 ft down to 40 ft | 72 | 25% | 18.0 |
| Scale216 estimated homes, scored from 0 up to 150 | 100 | 15% | 15.0 |
| Financeremaining gap is 36% of conversion cost, scored from 60% down to 0% | 39 | 15% | 5.9 |
Most of what it earns comes from daylight efficiency, and what holds it back most is finance, at 39 out of 100: remaining gap is 36% of conversion cost, scored from 60% down to 0%.
What the conversion would cost
$360 per square foot all-in across 266,220 sq ft of converted floor, or $95.8M in total — about $444K for each of the 216 homes.
All-in cost per square foot for 1321 15th 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 63,406 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 $236K a home, which for 216 homes is $51.0M.
What would have to be true
A $44.9M gap before any grant, $34.9M after the modeled one. The smallest single change that would close it: average unit size 41% down.
The shortfall before any grant is $44.9M. Closing it from the value side means each of the 216 homes finishing at $444K rather than the $236K the model assumes — 88% more. Closing it from the cost side means getting all-in cost down from $360 to $191 per square foot.
A modeled RESIDE grant of $10.0M moves that threshold to $397K a home. That is still above the $236K assumed, leaving $34.9M uncovered, which is why the grant does not unlock this one.
Nor do all four levers have to move. For 1321 15th St, one alone would close the gap at:
Single-assumption flip points for 1321 15th St, each holding the other three at their defaults.
| Average unit sizethe binding constraint — the least this building would need | 41% downto 446 sq ft |
|---|---|
| Conversion cost per square foot | 50% downto $129/sq ft |
| Completed value per home | 68% upto $397K |
All four are sliders in the survey, where 1321 15th St re-scores against your own numbers.
How it compares in Greater Downtown Denver
1321 15th St ranks 109th of the 214 buildings screened here, against a median score of 72.
Its floor plate is better lit than 32% of them, and shallower than 63% of them at its deepest interior point. On size it is the 103rd largest by estimated homes. The full survey of all 214 buildings ranks and maps every one of them, and the list by address links each to its own page.
Within Union Station and the D-LD zone
23rd of 55 in Union Station, 10th of 29 zoned D-LD — the comparison that shares its rules, rents and streets.
Denver places 55 of the screened buildings in Union Station. 1321 15th St ranks 23rd of them against a median score of 69. 23 score 70 or more, their median deepest interior point is 61 ft from a facade against this building’s 51 ft, and together they would hold an estimated 13,167 homes. The group’s top scorer is 1600 17th St, at 95.
29 of the screened buildings are zoned D-LD. 1321 15th St ranks 10th of them against a median score of 68. 10 score 70 or more, their median deepest interior point is 61 ft from a facade against this building’s 51 ft, and together they would hold an estimated 5,069 homes. The group’s top scorer is 1600 17th St, at 95.
Its nearest match in size: 1900 17th St
The screened building closest to 1321 15th St in converted floor area is 1900 17th St: 262,309 sq ft over 13 stories, against 266,220 sq ft over 12 here.
1321 15th St scores 72 to its 91, and with the size held roughly equal most of that shortfall comes from daylight efficiency: 72 out of 100 here, 100 there (91% 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 falls short even with the modeled grant. The two stand about 2,100 ft apart.
Would it qualify for a RESIDE Act grant?
The model awards 1321 15th 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 1321 15th St
The 4 closest the screen also covers, from 140 ft away. They are the colored outlines on the plan at the top of this page.
- 1551 Larimer St26 stories · 90% daylit · already a condominium buildingabout 140 ft away
- 1431 15th St10 stories · 79% daylit · 311 estimated homes · scores 62/100 (Worth a feasibility study)about 310 ft away
- 1512 Larimer St13 stories · 87% daylit · already a condominium buildingabout 360 ft away
- 1575 Lawrence St6 stories · 97% daylit · already a condominium buildingabout 470 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.