Detroit averages 43 inches of snow annually and experiences sustained cold from late November through March. Your furnace runs almost continuously during this period, heating outdoor air that contains almost zero moisture when temperatures drop below 20 degrees. This creates indoor humidity levels between 10 and 20 percent, lower than the Sahara Desert. You cannot fix this with portable humidifiers. HVAC humidifiers integrate with your forced-air system to restore healthy humidity levels automatically. Detroit's housing stock, dominated by homes built between 1920 and 1960, suffers visible damage from chronic low humidity. The wood trim, plaster walls, and hardwood floors in these homes require 35 to 45 percent humidity to remain stable.