The Burn

Rocket mass heater as the primary combustion-based heat source. Extreme wood efficiency (often 90%+ less wood than a conventional stove), 24-hour radiant heat from the thermal mass, and ability to cascade waste heat into water heating or cooking.

Footprint Living room or central spaceFirebox + insulated horizontal flue + large thermal mass (cob, brick, or stone bench, floor, or wall) that radiates for 12–24+ hours. Yield Whole-house or primary living space heatOne fire per day can keep a well-insulated space comfortable in most climates. 90%+ less wood than typical wood stove. Cycle 1 fire per day (or every other day in mild weather)Load and light in evening; mass radiates through night and next day.

Cost tier substantialDifficulty seasonLand noneFirst benefit ~7 days

② The Manifest

The parts list. Cores are what you actually need; “if you prefer” opens cheaper, local, or heritage swaps — never budget fallbacks, just other good ways.

Firebox + rocket flue

J-tube or similar firebox with tight air control + insulated horizontal flue (6–8" pipe or brick, perlite/clay insulated)~$200–800 in materials (varies with DIY vs pro)

The rocket effect creates strong draft that burns wood very hot and clean. Horizontal flue must be well insulated and run inside the mass. Small-diameter wood (2–4") is ideal.

if you prefer… (1)

Commercial rocket mass heater kit or core$1,000–3,000+Faster and more predictable; still requires mass construction.

Thermal mass

Cob, brick, stone, or combination — bench, floor, or wall that surrounds the flue~$300–1,500+ in materials + significant labor (cob is cheap materials, high labor)

The mass is the battery. Dense material in good contact with the flue stores the heat and releases it slowly over 12–24+ hours. A bench is the classic comfortable form.

if you prefer… (1)

Pre-cast or modular mass systemshigher material, lower laborLess custom but faster install.

Heat exchanger / cascades (optional)

Coil or exchanger in the mass or early flue for domestic hot water or space heating loop~$100–500

Free bonus heat. Simple loop can preheat or fully heat DHW or feed thermal loop to other rooms.

Chimney / exhaust

Properly sized, insulated chimney that exits above roof line with good draftincluded in design or $500–1,500

System must draft correctly for clean burn and safety. Follow code for clearances.

Tools and accessories

Ash rake or hoe, poker, moisture meter for wood, CO detector, fire extinguisher~$50–150

Safety first. Know your wood moisture (under 20% ideal). Keep area clear.

③ The Sequence

01Design for your climate and housePlanning 1–3 days Size to heat loss of space and local climate. In super-insulated house it can be small. In drafty building pair with serious Efficiency Audit first. Decide if it will also heat water or provide cook surface. Sketch flue path — must be horizontal and well-insulated for rocket effect.
02Build the firebox and flue (the rocket)3–10 days (depending on scale and cob vs brick) Firebox typically J-tube with tight air intake. Horizontal flue (6–8" pipe or brick) must be insulated (perlite/clay) and run inside the mass. Rocket effect creates strong draft that burns wood very completely and cleanly.
03Build the thermal mass5–15 days (cob is labor-intensive but low-cost and beautiful) Mass (cob, brick, stone) surrounds the flue and stores the heat. Bench is classic — you sit or sleep on it and it radiates upward. Floor or wall mass also works. Must be dense and in good thermal contact with flue. Finish with plaster or tile.
04Add heat cascades if desired (water, cooking)1–4 days (integrated during mass construction) Coil or exchanger in mass or early flue for DHW or space heating loop. Flat surface over firebox or early flue can be cooking/griddle area. Bonuses that increase value with small added complexity.
05Test, tune, and document the burn protocol1–2 weeks of daily use + seasonal tuning First fires for curing and tuning draft. Learn right size and type of wood (small diameter, dry, split), how to load, when to damper, and how mass feels next day. One fire per day is the goal. Keep simple log first season. Should be smokeless or nearly so when running correctly.
06Integrate with Forge wood supply and Efficiency disciplineOngoing seasonal wood processing + house maintenance Burn is only as good as wood supply (Forge/Mill) and house's ability to hold heat (Efficiency Audit + insulation). Well-built Burn in tight house can heat with astonishingly little wood. In leaky house it will still burn through fuel. Rewards good upstream work.

⑤ The Echo

One Fire, All Day Heat12 min

Why rocket mass heaters are fundamentally different from wood stoves. The rocket draft burns wood so completely that creosote and smoke are minimal. The mass stores the heat and releases it slowly over 12–24 hours. You tend one fire in the evening and the house stays warm.

Small Wood, Big Comfort10 min

The beauty of burning small-diameter, split wood (the kind that is easy to process with hand tools or small mill). No need for big logs or lots of chainsaw work. The system loves the stuff that would otherwise be waste or kindling. Paired with Forge and Mill, the Burn closes a beautiful loop: trees → lumber/heat → more trees or more heat.

⑥ Feeds

How this rig connects to the rest of the Ark.

→ energy The Walipini Rocket mass heater → heats greenhouse via piped air or water loop
← energy The Gut Biogas → cooking fuel
← energy The Mill Wood → fuel for rocket mass heater
→ material The Smokehouse Waste hardwood and charcoal from The Burn supply the firebox and smoke generator, closing the wood loop — scrap oak/apple/hickory becomes smoke.

Power · The Burn · power/the-burn Offline? Same path on any Ark Mirror.