Why does moisture form on the inside of my windows in winter, and how can I minimize the amount of moisture?

Condensation will occur whenever warm air hits a cold surface because warm air can hold more water vapor than cold air. If you have single-paned windows, adding storm windows will keep the inner pane of glass warmer and reduce the amount of condensation. Monitoring your indoor humidity and keeping it in the range of 40 – 50% (even less in very cold weather) will also help.  You can reduce the humidity level in your home by installing a heat recovery ventilator.  A dehumidifier may also help. If you purchase a dehumidifier, be sure to purchase an ENERGY STAR^® model as it will use 15% less energy – you can save $10 on energy efficient dehumidifiers during Instant Rebate campaigns.