i built this for bob. he hired me to repair the storm damaged end of his huge green house. things got a bit tangential and i ended up fixing the green house damage and we needed to provide heat without running the chimney through the melty plastic.
this is the end that was almost completely ruined by a huge tree. his green house is huge 30' by 100'.
i made it out of a combination of wood and steel. the wood was used only at a distance greater than 3 feet from the heater.