Lawrence Berkeley, Oak Ridge Labs Urge Early Curtain Closure to Cut Summer Heat

Energy‑efficiency researchers at the United States' Lawrence Berkeley National Laboratory and Oak Ridge National Laboratory recommend that homeowners close curtains before direct sunlight reaches the windows. Their studies show that timing the shading to a house’s orientation—east‑facing rooms between 07:00‑10:00, south‑facing rooms between 10:00‑16:00, and west‑facing rooms between 14:00‑20:00—greatly limits solar heat gain, with shading capable of reducing indoor temperature rise by up to 77 %. Light‑colored or reflective curtains and blinds oriented at a 45‑degree angle further improve performance. After sunset, opening windows for ventilation helps exhaust accumulated heat. The researchers cite laboratory tests confirming that proper shading cuts cooling‑energy demand and lowers electricity bills.