wood stove

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There is a wood stove located at the rare of the house. Please resist your temptation of tearing it down. During wintertime, the electric wire could be cut off by the winter storm and the house can lose power. You need at least one backup heating system besides the electric baseboard. The propane tank won't last long, while there is unlimited wood supply. The town inspector inspected the system and it is ok to use it in an emergency situation.

Basic operation

To operate the wood stove, make a campfire above the hole. The campfire should be big enough to raise the ambient temperature during the winter. Use a pack of candle or campfire starter if needed (I use a pile of pine needles). Cook snow or water on the campfire then bring them into the house to keep the house warm. You can fill the 5-gallon drinking water bottles with hot water. The water bottles will slowly release heat into the house and keep the temperature stable. Once the water in the bottle no longer hot, pour them into a pot and heat up on the campfire again.

The wood stove is more than a campfire pit

It is also a mass heater built outdoors. The system includes the fox hole, the heat riser inside a drum, a pipe buried underneath the curb, and the chimney beside the drum. 

Once the wood reduces into charcoal, the burning charcoal will fall into the fox hole. (The hole has a slope for the charcoal to rolling down underneath the heat raiser) Please push some charcoal deep down the hole. Once the heat raiser is heated enough, it starts to push air upward and automatically draws hot air in. Please remove any cover above the metal plate, the plate will cool the hot air, sending them down to the rest of the pipe system. Once the circulation starts, you should see white color steam come out from the chimney at the end of the heat exchange system (wood smoke is of blue color, so what comes out from the chimney is steam!). Once the fire started, you can keep it running all day long, the high-temperature fire cement inside the hole and heat raiser condensed the heat, so it will be very hot in the hole, therefore it is easy to ignite added wood later, you only have to toss in wood logs every 3 to 4 hours during stable operation. 

The heat is transferred from the hot air to the earth encircling the air pipes. The air pipe is completely running outside the house and buried under the ground (run south, turn towards the west at the curb, turn around at the kitchen window, run east, then run north, exit at the chimney), no smoke ever entered the room; and since the majority of the air pipes are buried underground, there is no chance for a chimney fire.

Science

The system is basically a mass rock heater + outdoor fire pit, which includes pipes buried under the ground. When hot air circulates the pipe buried in the curb, it will pass the heat down into the earth mass around the pipe and eventually pass the heat into the earth mass under the second bedroom. Don't underestimate the heat passed into the ambient (rock, bricks, wood, soil, cement), since the earth mass is large, raise the temperature a few degrees can store a large amount of heat BTU. The key is to keep the system continuously running. It operates in the rain and snow, it raises the ground temperature very very slowly but also cools down slowly. The key advantage is: no seasoned wood is needed, you can cut down trees and burn it as fuel right away.

Besides the heat radiated towards the house, the warm curb and stone wall slows down the heat loss from the house or even warm up the house.

Before the winter approaches, please pile up some wood logs for the wood stove in case you need them. There is plenty of wood in the back yard. The West Greenwich neighborhood often gives up firewood for free, bring them back with the trailer.

One cord of wood is a 4fx4fx8f pile of wood. One cord of wood can generate 15 to 25 million BTU by burning. Typically, heating up a square foot of the house needs 20 BTU per hour, so heating an 800 square feet house need around 20,000 BTU per hour. In theory, 1 cord of wood can heat the house for 1000 hours or 40 days. However, the system efficiency is low, most of the heat is wasted in the outdoor.

The efficiency has tremendous room to improve, though. 

At the first level: have a thicker layer of dirt/stone/cement wrapping the hot air will slow down the heat dissipation before they flow to the curb, where they raise the temperature of the house floor and crawl space. More material near the fire pit will store more heat BTU and later slowly radiate towards the house, instead of letting them dissipate into the windy air. One ton of earthy materials will absorb at least 10,000 BTU from frozen point to 50 F, wood will absorb more. There are more than 10 tons of materials participating in the system. You can also put a few rows of cinder blocks on the retaining wall to block the wind and radiate the heat towards the house. You can put the metal frame in the garden onto the retaining wall, then put on the metal shelves to form a half opening enclosure. The metal shelves block the wind, prevents rain and snow to fall into the fire pit, and also radiate more heat towards the house.