Chimneys Part 2: What Is Your House Doing To Your Wood Stove?

In understanding how your wood stove works it’s important you know some of the factors affecting it. The weather pays a big role, but not as big the house surrounding the stove.

A stove will tend to work better on an upper floor than in a basement, for example. Drying your clothes while loading your wood stove may cause smoke spillage into your house. Refinishing your basement may cause the stove and chimney to not work as well. Here’s why.

Air is constantly cycling through your house, slowly (hopefully) leaking out the top and being replaced from the bottom. This is called the “Stack Effect”.

Hot air rises to the top of your house and finds its way out. It may be through the bedroom window you leave open a crack, an attic hatch that doesn’t seal or even lights recessed into the ceiling. Air flowing out is called positive pressure.

The house replaces the air escaping from the top through the bottom.

Air is lazy and will come in the easiest way possible. Through cracks around basement doors & windows. Or… down your chimney – the big straw running up through your house! This intake of air to replace what’s leaving out the top is called negative pressure.

So as your stove is burning (especially if it’s in the basement), the smoke has to overcome the downward pressure in the chimney caused by the house. If it can’t overcome that negative pressure, you get smoke spilling into your house while loading the stove. Dang house! By the way, the taller the house the greater the stack effect and negative pressure.

Got negative pressure? Crack a window or a door – just a bit, 1/2” – 1”. Put your hand or a wet finger in front of the crack (try at the top and bottom). If you feel air coming in, that’s your house replacing air it’s losing upstairs somewhere. When you close that window or door the house will bring it in through the next easiest place, probably the chimney.

Some folks notice more smoke spillage after their basement is renovated. They have tightened the building envelope in the basement and now there are less cracks for replacement air to sneak in and more downward pressure on the chimney, the only inroad left.

Appliances can cause negative pressure too. Your clothes dryer, bathroom fan and range hood suck air out of your house. Replacement air has to come from somewhere…

Okay, so to minimize smoke spillage while loading your stove try these hints:

  • Seal your attic hatch tight & and other places near the top of the building envelope that could be leaking out air, including your bedroom window.
  • Make sure there are no appliances sucking air out when reloading the stove.
  • Crank the wood stove up before loading so that the embers & wood left burn as hot as possible for a bit. This will make the chimney warmer and draw better.
  • Open a window or door near the stove so the house has another way of getting air in while you’re loading the stove. It’ll take a few minutes for this to work.
  • Outside air connected directly to the stove can help too. This is not the magic solution some will claim, but it can help and is worth trying.

As with everything in wood stove world it’ll take some experimentation to see what works for you.

If you have specific questions about your stove & chimney call Gray Creek Store for answers. 250 227 9315.

By Dan Silakiewicz