This family was looking to replace their old inefficient windows with new, energy efficient windows, with a classic look.  The internal grids are placed between the glass panes to keep them from getting damaged.  The family chose to continue their high energy efficiency by going with casement windows as opposed to a double hung or slider.  The double casements mulled together lock when closed all of the way creating an airtight seal.  The round top window was included in a mulled unit with casements below it as well.