That dot was the soul of the room.

Her grandfather’s voice echoed in her memory: “The chart doesn’t lie, Ellie. It just shows you what the air is too shy to say.”

She spread it across the folding table in the attic of the abandoned textile mill, the afternoon heat pressing against the single round window like a held breath. The chart’s title read, in careful serif letters: Psychrometric Chart – Barometric Pressure 29.92 inHg .

Elara sat back, the pencil behind her ear. Through the round window, the sun had shifted, casting long rectangles of light across the dusty floor. The chart rustled slightly in a breath of cooler air.

To Elara, it was a map of the invisible.

And there it was. The computer model had called for a 20-ton unit. But the psychrometric chart, with its patient, hand-drawn logic, showed that the latent load—the moisture from hundreds of future showers, coffee breaths, and coastal summer nights—was 40% higher than the sensible load. The 20-ton unit would cool the air fast, but it wouldn’t run long enough to dehumidify. The result? Lofts that felt like a damp cave: 72°F and clammy, with condensation streaming down the windows and mold blooming behind drywall.