Top-floor unit in a NYC luxury high-rise with PTAC units. Floor-to-ceiling windows on two walls, flat roof above. The building installed new PTACs in May 2026. Temperatures didn't improve. The building's own HVAC technician confirmed the cause is structural — the roof and windows absorb and radiate heat far faster than the equipment can remove it.
The problem isn't broken equipment. The equipment works. The problem is the building's thermal envelope — and no amount of PTAC maintenance changes that. Humidity isn't the culprit either: indoor moisture held near a comfortable 46%, so the failure is purely thermal — it's the heat, not the air quality.
Deployed Govee temperature and humidity sensors throughout the living room. Pulled 15-minute readings from through — days of continuous monitoring. Layered in Open-Meteo outdoor temperature and humidity at the same 15-minute cadence, aligned to the same timezone, so every indoor/outdoor comparison is apples-to-apples.
As the study evolved, sensor placement changed. Before May 16, two sensors covered the living room and kitchen. On May 16 all four sensors were concentrated in the living room to map the cooling gradient from the PTAC side to the far end. Those changes are marked on the timeline.
Used the data in conversations with the building and HVAC professionals to explore options beyond the current PTACs — including rewiring for a higher-capacity unit. The data made the case clearly: the existing setup can't keep pace with outdoor temperatures on warm days, regardless of which units are installed.
The floor unit added June 3 finally cooled the space. But it draws significant electricity and is loud enough that it runs part-time, not continuously. Managing the heat load means keeping shades down, running the unit strategically, and accepting elevated temperatures during parts of the day.
Livability in this apartment means trading off temperature, power cost, noise, and effort. That's not a complaint — it's the finding. The fact that it takes all of that to stay comfortable is precisely what the data shows about the building's envelope performance.
The hardest part isn't the peak temperature — it's that I'm not home when it happens. I leave in the morning and can't lower the shades when the afternoon sun comes in, can't adjust the units, can't react. On July 8 the outdoor high never even reached 90°F, yet with the shades up and no one home, the living room climbed to 89°F and stayed above 85°F for more than two hours. My dog is home during those hours. That's not a comfort issue — it's a safety one.
This is where the problem becomes one of automation. A structural fix — better glazing, roof insulation — is the root solution. Short of that, what's missing is control I can't exercise remotely: shades that close automatically on solar gain, a thermostat that pre-cools before the peak, temperature alerts when a room crosses a safe threshold. The data doesn't just show the building runs hot. It shows the failure happens exactly when no one can step in.
Room ~13'8" × 19'3". Right and bottom walls are full windows. The transect (Jude → Eddie → Heath) runs diagonally from the PTAC across the room to the floor unit — tracking the cooling gradient. Chris sits off the transect on the interior wall as a baseline.
Predicted coolest on the transect before June 3 (in the direct airstream). After June 3, possibly warmer relative to Heath as the floor unit's influence takes over from the opposite end. Watch for the airflow caveat: a sharp drop may reflect blown air, not room temperature.
The window wall position may make Eddie the stubborn warm spot after June 3 — too far from the floor unit to benefit much, on maximum solar exposure. If one sensor stays hot after June 3, expect it to be Eddie.
Predicted hottest before June 3 (farthest from the PTAC, on the window wall). Should flip to coolest after June 3 as the floor unit comes online at the opposite corner. A dramatic post-June-3 drop in Heath is the clearest signal the floor unit is working — if it shows up.
Chris (interior control, off the transect) should be the most stable line across June 3 — least solar gain, equidistant from both units. Divergence from the transect sensors is the gradient; convergence would suggest full room mixing.
Four Govee temperature/humidity sensors, nicknamed after actors. Readings at 15-minute intervals. Exported as CSV from the Govee app.
Open-Meteo Historical Forecast API — 15-minute cadence, outdoor temperature and humidity, in Fahrenheit and aligned to the America/New_York timezone to match the indoor sensor cadence directly. Coordinates are supplied as a build-time input only and never stored in any output.
A Python script (build_hvac.py) handles all data processing:
payload.json with a built-in anonymization check — scans for identifying strings before writingSingle self-contained HTML file. No frameworks, no CDN, no external dependencies. Chart rendered with the browser's Canvas 2D API.