Gardener Scott
12 minutes
Water Barrels Store Daytime Heat to Buffer Cold Frame and Tunnel Nights
Water stores heat as \( Q = m\,c\,\Delta T \): a 200 L dark barrel cooling 10 °C releases \( 200 \times 4.18 \times 10 \approx 8{,}400 \) kJ overnight. The effect is modest, so mass works best in small, well-sealed spaces.