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.
Rating Newest Oldest. Best Answer: Trench warfare was an extremely effective strategy because trenches were a form of defensive warfare. The Germans marched on Paris in 1914, but when they were halted they dug in. From then on both sides fought in trenches and neither side could break through.