Windows from the Past With windows having likely the most important architectural influence on the appearance of your house or company, historic windows are an ideal method to preserve the charm and beauty of these designs while boosting your property's energy efficiency. There are two main types of windows: frame-and-panel and flat. Frame-and-panel windows have thick wooden frames with glass inserted between each plank. The wood is usually oak or maple. Flat windows do not have any frames at all! They are made out of thin sheets of glass sandwiched together with air in between. Frame-and-panel windows were originally used as doorways because they did not allow light to pass through them. Later on, people began inserting glass panels into the openings of these doors and creating windows. These were the first window screens you might see today. They allowed sunlight in but kept out insects and weather. The first flat windows appeared around 1650 and were made out of glass plates that were held together with iron rods as thick as a man's leg. It is believed that they were designed by Christian Jensen, who was also responsible for the first electric lights. These windows could be opened from the inside using large handles which allowed fresh air in while keeping out pests and heat. In 1770, Samuel Polton invented one of the first factory methods for making glass.