The woodstove chimney is divided up into three sections, a tall vertical portion which stays very hot, a horizontal section that loses most of the heat before exiting the cottage and then the short vertical section that goes upward again above the roof. Most of the chimney is inside the house. This helps the chimney stay warmer so it doesn’t cool the smoke too fast and it lets the heat go into the house rather than being wasted to the outdoors. This convoluted path provides turbulance which enhances the burn. There is also a high turbulance area right after the fire box in the vertical chimney section that also enhances flue gas burning.
Based on measuring the starting and ending temperature our woodstove and chimney are about 88% efficient. That is to say that about 88% of the heat has been removed from the flue gases before they exit the house. Once they exit the house they hit the outer metal chimney and air which is much colder which provides lift. On a cold day that may be 20°F or more below zero, sometimes as low as -45°F. This causes the water vapor in the smoke to precipitate catching some of the soot particles making this glorious black ice. I just need to figure out a use for it.
So what’s with the weird shape of the ice??? Wind! The wind comes from the north, the back of the house, over Sugar Mountain. We’re pretty protected by the ridge line, the north field tree line, the home field tree line and then an embankment. The turbulence right there near the peak of the house must be interesting because it has roiled the icicle as it froze creating the weird alien tentacle thing shape to it.
Outdoors: 49°F/26°F Partially Sunny
Farm House: 31°F/30°F
Tiny Cottage: 65°F/55°F