Classroom Heat: Passive Cooling Priced per Learning-Ready Hour

A reference hot-climate classroom — 40 pupils and one teacher in 60 m², concrete-block walls, a corrugated metal roof over an uninsulated ceiling board, and 12 m² of single glazing — was modelled with a single-node thermal simulation over three representative hot-season day types totalling 130 school days a year. A learning-ready hour is defined as a school hour (08:00–15:00) in which the operative temperature, adjusted for air movement where ceiling fans are fitted, is at or below 30.0 °C. The unmodified classroom provides only 50 of 1,040 school hours per year at or below that threshold. Priced singly, night-flush ventilation is the cheapest source of learning-ready hours at $0.96 per hour gained, fans cost $1.50, external shading $3.06, a reflective insulated roof lowers temperatures by up to about 2 °C but buys no learning-ready hours on its own, and added thermal mass on its own is counterproductive (−50 hours per year). The full bundle of all five measures provides 710 learning-ready hours per year at an annualised cost of $694, or $1.05 per learning-ready hour gained. The bundle nevertheless fails on peak-season days from 10:00 onward: 180 peak-season school hours per year remain above threshold under every passive configuration tested. Passive design should therefore be specified and priced as done here, but it should not be represented as a complete answer to peak-season afternoon heat.