Expert: James Ball - 1/30/2008

Question
I installed a wood burning stove in my basement and when we lit it all the smoke came out in the basement. There is nothing blocking the chimney. When you open the door the air blows out. It wont draw the smoke up the chimney. What could be the problem with that? Any help would be great. Thanks;

Answer
Hello Elwin, Smoking fireplaces/odors can happen for a number of reasons, dirty, blocked, improper construction, improper use…lets start with mechanical, this includes kitchen/bathroom exhaust fans, Radon systems, cloths dryers, even the boiler/furnace turning on all vent house air to the out side. The furnace return also pulls air out of the house and recirculation it in the home.
Now on to the hardest problem to figure out, “Negative Pressure” this is hot air rising, creating positive pressure on the upper floors and negative pressure on the lower floors and in most cases the hot air that is rising is getting out though attic doors, vents, and windows. In either case the house needs make up air, why? Chimneys work on a simple principle of hot air raising and pulling more air in behind it. Now lets look at the house as a chimney that’s right I said the house. If the house is air tight then the hot air will only rise so far and stop but if you have a pull down attic door, attic fans with louvers, or any other opening that will vent air out of the house, then your house is acting like a chimney, the air is going out through those gaps and spaces and when the air leaks out, the house needs make up air and it will come from the path of least resistance the fireplace (one fireplace can also feed another) other things that can cause this are lights in the ceilings the bulbs are hot and the top of the “can” they sit in is not sealed so the hot air goes up. Air rising up a staircase, the exhaust fans are drawing even when off.
Now you know why you are getting the air/smoke down the fireplace chimney when you are not using it and when you try to start a fire. Some times by just opening a door or window your relive the pressure of the house and allow the chimney to draw now when you light a fire the air is hot from the fire and it is hotter than the air in the house reversing the down draft. Then you can shut the window or door and burn your fire. The only draw back to using a fireplace this way is that as the air in the fireplace dies down and cools then the “House Stack Effect” will take over and may draw air, smoke and odor down the chimney again. If air is going up the chimney it needs to come from somewhere. The house needs make up air or find the outlet that is venting your hot air out of the house. Look at it this way if 10 gallons of air are going up the chimney or leaking out for the house per minute then you need to replace those 10 gallons with 10 gallons of air or your chimney will smoke/odor.
Try the open window and see if tht helps
James Ball