Recently I visited Bob Walker at Katchkie Farm in Kinderhook, NY. He gave me a tour that included lots of inspiring innovations, probably the most elaborate of which is his greenhouse setup.

Last year Bob installed a new heating system for his three greenhouses: in one, to heat the soil directly for in-ground crops; and in the others, to heat the benchtops where trays of seedlings sit. There are lots of efficiencies in the system, which in ideal circumstances heats some of the greenhouses year-round and uses waste vegetable oil as a practically free fuel source.

The heart of the system is the waste oil furnace located in the farm’s equipment workshop, just across the driveway from the greenhouses. The furnace is tuned to burn waste veggie oil with optimal efficiency, heating water to ~180 degrees F. The water can then be sent through a manifold to heat any of the three greenhouses, or to heat the workshop through a radient system of tubing in the concrete slab. From the furnace, the water flows through separate lines of pex tubing through an insulated pipe underground, one out to each of the greenhouses.

Each of the greenhouses has an independent loop of hot water lines that is constantly circulating water, thanks to an electric pump in each house. The loops each have a thermostat that, when triggered, will call to the controller in the workshop to cycle on the pumps at the main manifold, by the furnace, to pump more hot water into the loop, until it is brought back up to the desired temperature. This system of injecting very hot water into the loop only when needed eliminates the need for the heating water to be constantly flowing back to the furnace as it circulates.

In the production houses, the ground is heated by pex lines that run under the soil surface; Bob installed the pex by jury-rigging a way to pull the lines through the ground, attached to a chisel plow point; no excavation needed.

In the seedling houses, the heating water runs through main lines and then out into small rubber tubing that snakes across the bench tops, sandwiched between the seedling flats and a layer of insulation below. There are manifolds and valves allowing individual sets of tables to be heated, or excluded from the loop.

Before Bob installed the main furnace for all three greenhouses, the water for this loop was heated with an on-demand hot water heater in the greenhouse. It was retrofitted once the new furnace was installed, but because the small rubber tubing lines heating the benchtops can allow oxygen into the heating water– which could make for a rusty furnace– there is a heat exchanger so that the water in the greenhouse loop never actually mixes with the water from the furnace. In the seedling houses there is also a forced air heater that cycles on if the air temperature falls below freezing, which is rare. My visit was during mid-March, when nighttime lows were still in the mid-teens, but there were nearly ready-to-plant tomato seedlings, soon to be moved into the in-ground greenhouse.

Another great feature of the seedling house is the design of the seedling benches. The frames are farm-built of galvanized square tubing, and the table tops rest on top of round lengths of galvanized pipe. This allows the tables to roll back and forth on the frames, which means that tables can be parted to create an aisle for access, and then pushed back together to close the space, allowing an aisle at the next table down the line. This means that there only needs to be room for one aisle in the entire block of tables, conserving as much greenhouse space as possible for seedlings.