Double-sided unit notorious for problems
Bill and Kevin Burnett
Q: My husband and I have been frustrated by a problem since we moved into our circa-1965 house two years ago. The double-sided fireplace spews so much smoke that it's unusable.
Two chimney sweeps have told me it doesn't need to be cleaned and that these types of fireplaces just never work properly. Their only suggestion was to install a wood-burning stove inside the fireplace. There's no way we will do this.
The fireplace has two flues, which we've opened every time we've built a fire. Is there anything you can suggest to get this fireplace to draw?
A: A wood-burning stove inside a fireplace? That's nuts. There are a number of things you can try that may fix your problem.
To begin with, it's important that you understand a couple of basic laws of thermodynamics. First, hot air rises and cold air sinks. Second, fire requires combustion air. Simply put, to work properly a fireplace needs cooler air entering the firebox to replace the hot air, smoke and gases that leave via the chimney. The proper balance of cold and hot allows the fireplace to draw.
We can think of a number of reasons your fireplace smokes you out. You've dealt with the first couple by having a chimney sweep out and making sure the damper is open. Here are some other causes and possible cures:
- Wood should be dry and aged for at least one year. Hardwoods are best. They are denser and give off less smoke. Split the wood so that it burns efficiently. Avoid construction debris, as there's no telling what chemicals it might contain. Even if it's chemical free, Douglas fir and pine burn hot and fast and create creosote buildup in the chimney. If you burn pine or fir regularly, have a chimney sweep clean yearly.
- The rack where you place the wood should be placed directly under the damper. Raising the grate on bricks helps create more combustion air under the fire and gets the fire closer to the chimney opening.
- Two-sided fireplaces have inherent problems with draw. They're hit with drafts from both sides. Installing glass doors can solve this problem by cutting off air from one side of the fireplace to start and containing the hot air once the fire gets going.
- Have an experienced mason check the height of the chimney. Extending the height of the chimney should improve the draw.
- If it is either cold and/or raining, the air inside the flue will probably be cold and heavy, blocking the smoke from venting. Every time you build a fire, prime the chimney by rolling up a newspaper and lighting it, then holding the lit end close to the open damper inside the firebox to warm up the air in the flue. This has the effect of coaxing the warm air to go in the right direction -- outside, not into the house.
- Turn the heater off when you start a fire. Gas furnaces also need combustion air -- the same air the fireplace needs. If the heater is on, there is competition for the same air. If the furnace wins, you get smoked out.
- Houses are built or retrofitted much tighter than they used to be. Air pressure inside the house can be different from outside. This can slow air drawn through the flue and limit combustion air, resulting in a smoky fire. When you light a fire, crack open a window or door until it gets going.
- Finally, consider hiring a mason to install an air pipe from the outside into the firebox.
Our advice is to do the cost-free stuff first, try the glass doors second and if you don't get the desired result, consult with a good masonry contractor about general design and chimney height. We wish you many a cozy evening and, if you get a chance, let us know how things turn out.
Copyright 2011 Bill and Kevin Burnett