I have a functioning greenhouse! Last Sunday, three days ago, I planted seeds of seven vegetables including arugula which germinates in three to seven days. Tonight I saw the first small emerging plants.
The work isn't quite finished. I have to install venting into our bedroom to capture extra heat, benches on top of water barrels to maximize areas to hold containers, door trim, a sink and a folding potting shelf. I can complete the work while watching plants grow.
The design of the greenhouse was dictated in part by the area bounded by the south wall of a bedroom and the east wall of the utility room. I had an area twelve feet by twelve feet that I enclosed with an insulated east wall and a south wall of polycarbonate. I want a larger greenhouse and plan on building a second one but I wanted to use this area for multiple reasons. First, I have a small greenhouse with minimal expenditure of money and labor. Second, the greenhouse encloses an exterior closet that houses a water heater. The addition keeps the water heater and pipes warmer which translates into hot water in the house more quickly, less propane to maintain the temperature in the tank and elimination of a need for heat tapes in winter to keep pipes from freezing. Third, the bedroom which is the coolest room in our house is warmer due to the addition and will be warmer still after the installation of vents.
I installed 15 barrels, almost 900 gallons of water mass, for heat storage. On a sunny day the water in the tops of the barrels is over eighty degrees. Over the last few nights the temperature inside the greenhouse has been mid-forties to mid-fifties in spite of strong winds, snow and mostly cloudy days. Originally I intended to use fewer barrels but decided to increase the mass. I bought a trailer load of barrels a few years ago for fourteen dollars each and had the barrels on hand. The angle of the sun in mid-winter would have resulted in the barrels on the north row being partially shaded by barrels on the south so I decided to stack the two rows. Then I chose to install two additional barrels that will result in partial shading but I think this is more than offset by the extra mass.
Greenhouse southeast corner. Trim is missing from the door and the cat door to the right of the door needs final trim.The gray containers sitting on the barrels have been seeded and covered with glass to retain moisture and deter cats.
Since we will be using the walk way in the greenhouse on a daily basis I wanted a solid, durable surface easy to keep clean, one that wouldn't track dust and small pebbles into the utility room. About a year ago I bought several hundred new brick for fifteen cents each. I had no use for them at the time but thought the price to be a good investment. Julie suggested we use the brick for the walk. I put down a bed of crushed glass beneath the brick and they settled in level and solid. The rest of the floor is a mixture of crushed glass and miscellaneous colors of gravel left from other jobs. I bought a yard of chocolate one inch gravel for the top layer to give a uniform surface that wouldn't shift and get caught in the tread of my boots. I thought a dark color like chocolate would increase the heat when the sun was shining.
Greenhouse northeast corner. None of the containers have been filled with potting mix.
I installed 12 square feet of low vent and 12 square feet of high vent to create a passive air flow in an effort avoid using electric fans. In the near future I'll install a vent into the house to capture excess heat on cold winter days. If I close the vents on a sunny day the temperature in the greenhouse will pass one hundred degrees. Last Saturday it peaked at 108. Sunday was partially sunny and the high temperature was 98.
Greenhouse northwest corner. A sink and hinged potting shelf will be installed which will require redesigning the cat steps leading to their door that enters the utility room.
I don't have enough decent soil and compost so I've found two sources to buy enough to fill a large tub and several containers. Next weekend I'll plant more seed. Over the next few weeks I hope to plant several items as trials.
The next two years will be a period of experimenting to learn how to manage shading and venting, to learn which varieties do best and how to keep a continuous supply of vegetables throughout the winter.
Greenhouse after dark. Julie installed the lights to give it a festive atmosphere.
I have two pieces of scrap polycarbonate that measure six feet by by five feet. My next task is to use these pieces to construct cold frames.