Why fireplaces work, and how best to build them, has been a topic of hot debate literally for centuries. From the first stone rings stacked around the campfire to the modern factory-built fireplaces with carefully engineered dimensions, there has been a steady evolution of design parameters to make sure they draw well and cast as much heat as possible. Most of this evolution has been by trial and error, and some designs work much better than others.
Simply put, fireplaces work mainly because hot air rises. When you start a fire, the air inside the chimney becomes warmer and less dense than the air outside the chimney, and consequently, it starts to rise. As the warm air rises, cooler air from the room flows into the firebox, fanning the fire, and creating more heat in an ongoing cycle. There are also some pressure differentials produced as the wind moves across the top of your chimney.
There must be at least 100 reasons your fireplace doesn’t work or may not function properly. We will try to cover some of the basics here starting with the easy obvious solutions and working towards the more arcane. Please bear in mind this is a very simplified list of the more common reasons that fireplaces don’t work A true understanding of fireplaces requires extensive knowledge of airflow patterns, pressure differentials, and actual fireplace construction techniques. If the information provided here does not help you solve the problem with your fireplace, consider hiring an experienced, certified chimney sweep in your area. Often the problem is obvious to someone with enough experience once they can look over the entire situation.