Designing a Backyard Greenhouse
Determine where your greenhouse will be located and how large you want it by doing some measuring. Next to your house, garage or another building in an area that receives full sun is a good location. Keep it simple by designing a structure that will fit compatibly in the area you have chosen. Unless you plan to use your greenhouse for a fairly large commercial operation, you can keep it small---6 by 10 feet is a good size for a backyard hobby greenhouse.
Sketch out your planned greenhouse either on your computer or by using a pencil and graph paper. This will help you to determine how much lumber and other materials to purchase. Each wall of a rectangular greenhouse needs only four two by fours for the sides, top and bottom, and one for center support. If you're planning a 6 by 10 foot greenhouse that is 8 feet tall with a hinged roof, this will equal 204 total feet of lumber.
Plan for shelves or planter boxes. If you build several shelves the length of your greenhouse, you will have plenty of room for placing pots and flats of your favorite plants and seeds. One or more planter boxes can give you a small garden bed where you can grow lettuce or other plants without having to worry about them being harmed by frost and cold temperatures.
Plan for a heat source if you want to keep your greenhouse warm on winter nights. You can do this by using an electric space heater, kerosene heater, or passive solar energy. To use passive solar energy, you can use rocks, barrels or buckets full of water or concrete walls, which will retain daytime warmth and keep your greenhouse warm at night. If you want, you can invest in a small solar panel and the materials needed to make it function. Your goals for your greenhouse will determine your needs.
Plan for a source of light. Even if your greenhouse will receive plenty of natural light through its roof and sides, many plants need supplemental light in order to grow properly. Fluorescent shop lights are the most economical choice, but you can get fancy with metal halide and other special lights for growing plants.
Make sure you have a source of water handy, even if it's simply a nearby garden hose. Many plants, such as orchids, need the humidity that a misting system provides. To make things easy, you could set up a drip irrigation system in your greenhouse that is run on a timer. Special misters are available where drip irrigation supplies are sold. (See Resources.)
Set up one or more fans to keep the air circulating. Fans can help to prevent plant fungal diseases that a closed environment can generate.