The Snawfus Hearth

A masonry heater sounds like something you hire a specialist for. It isn't. It's brick, mortar, and a real design for how the heat routes through the mass before it escapes up the flue — and once you understand that one idea, the rest is stacking. Nobody hands you that framing up front, so we are: here's the exact spec, the exact tier ladder, and the tool list, so you can build the thing that heats your house instead of paying someone else to explain it to you.

A 20–30 minute hot batch fire, twice a day, radiates steady heat for 18–24 hours off the mass — the same principle as a true Russian stove, achieved through two stacked bells instead of a channel maze. The lower bell captures direct combustion heat; the upper bell cools the gas further and houses the bake oven and hot water coil, fed by a bypass damper that routes hot gas under the oven floor during the burn.

Tier Ladder

• Settler — Hearth Starter: small single-bell-pair unit, no oven, ~1,500–2,000 lb mass, sized for 400–700 sq ft.
• Homesteader — Hearth & Oven: adds a front-loading bake oven off the upper bell, ~3,000–3,500 lb mass.
• Foreman — Full Hearth (Greenbrier spec): adds a heated bench and a copper coil thermosiphoning to a hot water tank, ~4,500–5,500 lb mass.
• Monticello — Great Hearth: whole-home scale, 7,000–9,000+ lb, dual flue liner, optional radiant floor tie-in.
• Mythic — The Snawfus Hearth: 10,000+ lb, twin-firebox option, cast iron cook surface, cast bronze fittings — the heater is the house's core.

Technical Specifications (Foreman tier baseline)

• Firebox: refractory core, batch-burn, ~1.5–2 cu ft, secondary air injection
• Bell system: double bell (lower/upper), Chernov-style, no serpentine channels
• Hot water coil: copper, sited in the upper bell, thermosiphon (no pump) to insulated storage
• Footing: isolated geopolymer pillar footing, independent of the surrounding slab
• Efficiency target: 85–90%+

Construction Variant: Quick RMH Prototype (Pre-Settler)

A genuinely different build tradition, not a smaller version of the double-bell design above — a J-tube rocket mass heater (fuel magazine + burn tunnel feeding an insulated vertical heat riser, topped with an exposed steel barrel as a fast-radiant surface, ducted through a sand or cob thermal-mass bench) instead of the Chernov-style double bell. Confirmed real, buildable, and cheap: a materials list built around a 6" well-casing steel pipe heat riser, perlite insulation, and firebrick only where the burn tunnel and riser actually need it, ran a scrounged-materials build for roughly $150. Meant as a fast, low-stakes proof-of-concept for the "burn hot, store heat in mass" principle before committing budget to a Foreman-tier double-bell build — not a replacement for it, and not to be merged into the double-bell spec above.

• Sizing rule: no component's cross-sectional area should exceed the flue's; the burn tunnel is the smallest CSA in the system, riser height scales with system CSA.
• Firebrick required in the burn tunnel and riser (high-heat zones); standard brick is fine elsewhere (e.g. around the ash box).
• Clearance: the exposed barrel/riser cap is a genuine burn hazard — reaches several hundred °F on the surface. Needs a locked clearance or physical barrier spec before building around young kids, not just "use thick metal."
• Not currently recognized under standard mechanical/building code the way an EPA-certified wood stove is — needs a WV-specific permitting check before this goes in as a buildable plan.
• Do not cite "8x more efficient than a standard stove" — real efficiency gain, but that specific multiplier is an unverified anecdotal figure with no instrumented test behind it.

Specialist Sign-Offs Required Before Construction

• Masonry heater specialist — bell sizing, flue draft calculation, dual liner clearances at Monticello+ tiers
• Structural engineer — point load at footing, especially for elevated installations
• Local code/chimney sweep certification — solid fuel appliance inspection, clearance-to-combustibles verification (RMH prototype needs its own check — see variant above)

Open Items

• Bench length/orientation not yet fixed — waiting on final floor plan
• Twin-firebox zoning logic for Mythic tier (redundancy vs. simultaneous dual-zone heating) needs a build-sheet pass
• RMH prototype: kid-safe clearance/barrier spec and WV code check still open — see kb-build/drafts/mm-pin-vetting-kb.json (pin_003_rocket_mass_heater, pin_014_rmh_steel_sand_build)