Example - for a 3-bedroom, 2,000-sq.ft. home, with an exhaust-only ventilation strategy, and a target ventilation rate of 50 CFM you would need to install a 50 CFM fan with an adjustable-speed DC motor for continuous operation.
Quick Answer. Trenches were built during World War I to protect stalemated troops on both sides from artillery and rifle fire. Although the war began with rapid movement of the German army, when the Allied forces stopped the Germans, both sides dug trenches to help avoid losing territory they had gained.
Other theories about the purpose of Stonehenge: some say it was designed as a celestial observatory to allow the prediction of eclipses, solstices, equinoxes, and other celestial events that were significant to the ancient people of that place.ther theories about the purpose of Stonehenge: some say it was designed as a celestial observatory to allow the prediction of eclipses, solstices, equinoxes, and other celestial events that were significant to the ancient people of that place.