The Heat Vault — Volume I of the Sketchy House Files Archive

Furnace-free heat that pays for itself. Forty-four chapters across six parts: seal the house first, bank heat in sand, water and masonry, catch the sun with soda-can panels and south glass, burn wood clean and safely, and heat your water without the meter.

Every method gets a plain verdict, sketchy or solid, with the arithmetic behind it. Includes the fuel ladder (cost per million BTU across nine heat sources at stated prices), eight worked payback calculations and a ten-year ledger. Seven schematic diagrams drawn for this volume.

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