This section is from the book "The Gardener's Monthly And Horticulturist V24", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I notice in the Gardener's Monthly that the subject of steam heating for greenhouses is attracting a good deal of attention at present; and, if agreeable, I will relate our mode of heating with steam and water.
We use the ordinary four-inch cast iron pipe, put up the same as for hot water apparatus; but in place of hot water boiler, we have a cast-iron tank, five feet in length and two feet in diameter, placed in north end of house, underneath the floor, below the level of the pipes. In this tank there is a coil of one hundred and fifty feet of one and one-quarter-inch steam pipe. The steam is brought from a main pipe in one of the buildings nearest to the greenhouse in the same sized pipe, inch and a quarter, the entire distance from boiler, seven hundred feet, with twenty pounds of steam pressure. We have about five hundred feet of pipe in this house, and raising this one and a-quarter-inch valve the thirty-second part of an inch, will make the water boil. You can readily calculate how much water this steam will heat by opening the valve to its full extent.
In reading Mr. Murdoch's article in the Monthly, where he tells about taking out two thousand feet of four inch pipe, and putting in steam-pipe, I think he made a grand mistake, as he had the pipe on hand. And for all those contemplating putting in steam, I believe this mode of heating far superior, especially for those who have hot water in operation, because of it being more economical and safer ; for in case anything should get wrong with the steam, you have the pipes in the greenhouse full of hot water, which will retain the heat much longer than in steam pipes, and is more economical because of the saving of fuel to generate steam.