Seed Start House

Our Seed Start House is 12’ wide by 48’ long, and it is the warmest and smallest of our growing structures. It was specifically designed for starting all the seedlings we use at the ranch. The greenhouse technology is a mix of old and new ideas. The house, like the other growing structures, has a south facing orientation. The triple-walled polycarbonate window strikes a balance between light emission and insulation. The polycarbonate wall is angled at 46 degrees to meet the angle of the sun in late February when we begin the bulk of our tomatoes and first seedlings. Other than the slanted south wall, all other walls are fully enclosed and insulated, trapping in as much heat as possible during colder months and limiting solar gain during the hottest summer months.

To heat our greenhouse, our seed start house is equipped with a Ground to Air Heat Transfer system (GAHT). A GAHT system is a passive method of heating and cooling a building by exchanging heat with the ground. In this system, a network of pipes is buried underground, typically a few feet deep. These pipes are connected to a heat exchanger and fans above ground. During the day, when the building needs cooling, a fan pushes warm air from the building into the underground pipes, where it releases heat to the cooler ground. At night, when heating is required, the fans pull the stored warm air from the ground, providing heat to the building. This process helps regulate the temperature indoors by utilizing the ground as a natural heat sink or source.

We also employ thermal mass storage strategies to help heat our greenhouse passively. Our GAHT system was buried with 113 tons of gravel, allowing for the gravel to heat up during the day, and slowly release at night.

We lined the north wall of our greenhouse with Phase Change Material (PCM). PCM is a substance that releases/absorbs sufficient energy at phase transition to provide useful heat/cooling. The bio-based PCM that we use changes state at 72ºF. By melting and solidifying at the phase change temperature (PCT), a PCM is capable of storing and releasing large amounts of energy compared to sensible heat storage. At only about ½ inch depth, this material takes up a fraction of the space of water, is more efficient at releasing/absorbing energy, and the cost is tolerable for most systems.

The south side of the Seed Start House is lined with mice-proof metal-legged seeding tables, while the north side is lined with tables. The northwest corner of our seed start households the seeding area and germination chamber. More details on the seeding area and germination chamber can be found in the sections related to seeding.

We have a packing shed outside on the north side of the Seed Start House. This open-air packing shed has a concrete floor, cabinets, wash sinks and tables, and a walk-in cooler. We use this space for vegetable washing and packing and the storage of harvest materials, irrigation supplies, and packaging.