How Does a Greenhouse Work?

greenhouse set in a garden

If you are an avid gardener and wish to add income to your small farm, you should consider a greenhouse. How does a greenhouse work and how can it benefit you?

What is a Greenhouse?

A greenhouse is a man-made structure that creates the optimal environment for plants to grow. They come in all sizes, shapes, and materials and that versatility allows you to choose the one which works best for you.

A greenhouse supplies three things that are necessary for plant growth – water, air, and sunlight.

Benefits of Greenhouses

girl planting seedlings

Greenhouses offer a controlled environment that is perfect for plant growth. By controlling the amount of sunlight, water, and air circulation, greenhouse growers can produce bigger, healthier plants. They can also extend the growing season by starting plants earlier in the spring and keeping them going later into the fall. With some effort, you can have an indoor growing season, even in winter.

If you love growing plants and are looking to create income from your small farm, a greenhouse can give you a significant income. The initial investment might be as much as $5,000-$10,000 depending upon the size and complexity of your greenhouse. Since the pandemic, there has been renewed interest in growing vegetables and flowers. In many areas of the US, you can expect to have a profit of $50,000-$100,000 per year after a few years in business. Those figures also depend upon a good business plan, marketing, and good management.

How Does a Greenhouse Work?

The most important part of a greenhouse is the transparent roof and walls. Greenhouses work by trapping heat from the sun inside the structure. The sun’s rays (light energy) pass through the covering and are absorbed by the ground, which then heats up the air (heat energy) inside the greenhouse. This heat energy makes the temperature inside the greenhouse rise, which is perfect for growing plants that might not survive in colder climates.

Many greenhouses have heating and cooling systems, as well as fans and vents to help control the temperature and humidity levels. All must be adjusted to the needs of the greenhouse plants. You will also need some basic tools and machinery, both to build it and to maintain it.

Cold Climate Solution

In extreme northern climes, gardeners have experimented with many ways to keep their greenhouses warm. Some use composted manure, while others use light bulbs. One interesting method is to coat the outside with bubble wrap, but it seems to me that would be hard to remove in the spring.

I have also heard of greenhouse owners putting another tent or smaller greenhouse, usually made of plastic sheeting, within their original greenhouse. If the climate is really cold, they will keep adding these tents, one within the other, until they reach the optimum temperature for what they are growing. Each layer will raise the temperature inside the smallest structure by 10 degrees.

Structural Makeup of a Greenhouse

Since it is important that direct sunlight enters the building, the ceiling and walls are made of translucent materials. Glass walls and roof are the best, but also cost the most. Many greenhouses today use translucent plastic sheeting or panels, costing much less. The sunlight is critical to plant growth, so converting light energy to heat energy is only doable with the translucent walls and roof.

The structure itself can have an aluminum, plastic, or wooden frame.

Types of Greenhouses

Ranging from personal to commercial size, greenhouses come in every configuration and price range. Before you buy, have a clear idea as to what you want to do with a greenhouse, then research the possibilities.

Cold Frame

home-made cold frame
Cold frame for plants

The design of a cold frame is ancient and it is the very simplest of greenhouses. It tends to be small and used for personal gardens. A cold frame is basically a glass or plastic box set on or in the ground.

Great for starting seeds in early spring, the design of a cold frame gives your seeds real sunlight, yet protects them from cold weather. You can purchase a cold frame or build it yourself. It’s not really designed for commercial use.


lean to greenhouse

The lean-to is a structure that is built onto or leans into another permanent structure, such as your home or barn. Again, how you site it is important if you want optimum sunlight. The small lean-to is best for the home gardener, for there is not enough space for a commercial operation.

Detached Structure

detached greenhouse

The detached structure can be either a hooped or ridged roof. It can be small, for home use, or easily extended to be large for commercial use. These detached structures are freestanding greenhouses.

In areas where you have high winds, plastic sheeting will be too fragile and will rip. This closed environment will need glass or plastic panels to resist wind damage.

gutter-connected greenhouses

Gutter Connected

Gutter-connected greenhouses are multiple greenhouses connected at the gutter height. You see this type of greenhouse in large, commercial operations. They can have glass walls or roofs, but frequently you will see walls and roofs made of light plastics which are replaced every season.

Needs of a Greenhouse

The needs of a greenhouse depend upon the size and use of the structure. The basic needs for any structure are light energy, heat energy, and a water supply.

For personal use, if you live where the weather goes below freezing during the winter and you wish to use your greenhouse during that time, you will have to install a heater to keep warm air around your plants. If you have only a few days of sunlight, you will also have to install grow lights to create the ideal environment.

commercial greenhouse ventilation system

For commercial use year-round, the building needs specialized greenhouse heating and a proper ventilation system, both of which will be controlling temperatures. The air inside will always be different from the outdoor temperature; in summer, the air should be cooler and in winter, the building should have warm air. The heating system in colder climes is critical for keeping your plants warm and growing.

When you have one of the large, commercial greenhouses, you might find a drone handy to survey what is happening at distance. A drone can also spray fertilizers or insecticides from above, just with the click of a switch.

In addition, in commercial operations, you will need a reliable source of water. There are special irrigation systems for greenhouses that can be set on timers for watering.

Regardless of whether your operation is commercial or personal, you need to work toward establishing a perfect growing environment for your plants.

My Personal Greenhouse Experience

Gaudry greenhouse

We purchased a simple greenhouse kit about 10 years ago to supplement our extensive personal gardens. It is made of plastic panels set within a hard plastic framing and is 6 feet wide by 8 feet long. With 2 of us working, it took us about 4 hours to assemble the kit (no special tools), and to this day, it has served us well.

My husband made simple shelving of planks and cement blocks, and I added a potting bench at one end. We store unused pots on the ground, bags of dirt on the bench shelf.

How We Utilize Our Greenhouse

We only actively use it for about 6 months of the year, and the rest of the time, we store unused garden equipment in there.

cement block and board to make greenhouse shelving
potting bench

In early March, I buy tomato seedlings and put them in the greenhouse. Every few weeks, I repot them, so by the time we can plant them in the garden (after the middle of May), they usually have tomatoes on them.

We also have a lamp and table in the garage to start seeds, and once these tender plants are started, they all go into the greenhouse to grow until the danger of frost is past.

Daily, I must water everything in the greenhouse, and I am always watching the temperature (we keep a thermometer in the greenhouse) and will start up a heater if the weather gets too cold. All of these plants require a warm environment for optimum plant growth.

Greenhouse Considerations

Do your research if you are considering a greenhouse. There is some maintenance involved and definitely initial and ongoing costs. Personal greenhouses are easy to take care of, but I suggest that you start small and make sure you know how to grow and sell plants before you commit to a big operation.

Once you start a commercial operation, you will have to do everything all other entrepreneurs do: marketing, labor, planning, purchasing, etc. If you plan well, you can reap great rewards.

Here’s more information:

Cold Frame Greenhouses

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