Defaults reflect this space type. Same engine as the main calculator.
| Cooling load | — |
Standard sizing assumes walls that resist heat; a sunroom's envelope is designed to admit it. Solar gain through glazing can push effective loads to 40–60+ BTU per sq ft — double or triple a normal room — and the load swings violently between a sunny 2 p.m. and a cloudy morning. The estimate below stacks sunny exposure, poor insulation and roof gain to approximate this; treat it as a floor, not a ceiling.
Cellular blinds, exterior shades or low-E film can cut a sunroom's peak load 30–50% — far cheaper per BTU than compressor capacity. Then fit an inverter mini-split: its modulation range is the only equipment style that handles the sunny-peak-to-cloudy-trough swing without short-cycling half the day.
A typical sunroom (~200 sq ft) needs about 12,857 BTU/hr — a 1.5 ton unit in moderate US conditions; hot climates run 15–25% higher.
Plan on roughly 12,857 BTU/hr for a typical ~200 sq ft sunroom in a moderate climate, with the space-specific factors described on this page already included. Hot climates (Zone 1–2) add 15–25%.
Solar gain through the glass multiplies the load as the sun moves onto it — afternoon load can be 3× the morning's. Size for the sunny peak and rely on an inverter to modulate down, or cut the peak with shading.
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