Double glazing refers to the technique of combining window panes into two and creating a small gap in between them hence providing better insolation. It is a very common phenomenon in most modern homes. The energy saving characteristic combined with safety, security and the excellent looks makes it very popular. https://danielleelliott2blog.wordpress.com/2019/06/28/how-to-choose-the-right-company-for-your-double-glazing/