https://www.reimersinc.com/boiler-blowoff

Electric boilers are quiet and require no penetrations of the roof or floor to exhaust gases or deliver fuel. The quietness is that there are no fans or mechanical leverages to control fuel and air flow. Reimers has an SCR option that allows infinite turndown ratio and makes no sound to regulate power to the vessel. Shipment of the boiler in the US no concern. Exporting is no problem but does require "heat treated or chemical treated" crating in some areas. Reimers has wood that can be stamped with the appropriate symbols showing compliance with treatment rules. https://www.reimersinc.com/boiler-blowoff