BTU/Burn efficiency question

[Dunadan]

So far this year, while burning, I've been very focused on maintaining good stove temps so as to maintain (as much as possible) good secondary burn. It's easy to tell by peaking out at the the chimney. No smoke = good efficient burn, smoke = poor inefficient burn.

I'm getting better at maintaining a good efficient burn. I've started letting my fires burn down to the point, where it doesn't look like there are any coals left in the stove, especially when the temp in the house is comfortable (mid 70s). Last year I didn't stretch the fires out in this way, and instead just added more wood so that I constantly had a fire going. I'm now finding with a good bed of ash in the stove, even after 6-7 hours of no visible fire, the coals can be quickly revived using a bit of kindling and small splits.

I find when I'm not burning efficiently, it's always when I'm trying to turn the fire down, not because too much heat is being put out, but more because I want to get a nice long burn.

My question is this....

From the standpoint of heating the house over a period or time, does it matter how long it takes to burn to go through a complete burn cycle? If so, to what degree?

By this I mean, if a given load of wood is slated to put out X number of BTUs, does it matter whether I spread those BTUs over an 8 hour period, versus putting them out in a 4 hour period? I'm thinking, obviously, the house gets warmer by cranking out more BTUs in a shorter period, but once they're out, it then will take longer for the house to cool to any given temperature.

This question assumes that when running shorter, intenser fires, you are not overheating the room with the insert to a point that it's not comfortable anymore.

Curious what people's thoughts are on this.

 

[Todd]

I think it all depends on your houses floor plan, insulation, and outside weather. If your house is good and tight, you can stretch those btu's out longer.

 

[Corey]

To me, there definitely seems to be a 'sweet spot'. You can burn hot, clean fires but if the air is flushing through the stove too fast, it is hard to transfer any heat to the metal. You can damper down some so that the heat stays in the stove long enough to give up a lot of it's heat. But if you damper down too much, you get into smoky inefficient combustion and most of your energy leaves in the smoke.

If I had to give a general rule, the most efficient burn to me seems to be get the fire going hot, then damper down to a point just before it starts to smoke.