Explore the detail of the different types of greenhouses. This in-depth guide takes a deeper look into the varying designs and discusses the pros and cons of each type. We’ve also found some great plans and design details from local Universities, in case you want to build a DIY greenhouse in your backyard.
Greenhouses come in many shapes, sizes, and materials, we’re sure you’ll find the style that works best for your plants and property.
Greenhouse growing can allow you to enjoy fresh herbs and vegetables outside the normal growing season. There are many different types of greenhouses. What will work best for you? Consider your space, your budget, your DIY skills, your climate, and the types of plants you want to grow.
What Are The Different Types of Greenhouse Structures?
Greenhouses can be classified in several different ways—by building materials, size, attachment, etc. A good basic overview with plenty of illustrations can be found in the University of Georgia publication on hobby greenhouses.
The main advantage of building a greenhouse attached to your home is that it’s handy to sources of power, water, and heat. Also, using the wall of your home as one wall of the greenhouse can save on building materials.
My attached greenhouse opens off one of the rooms in my house. On cold dark days, my home heat keeps the greenhouse warm enough so the plants don’t freeze, and on cold sunny days, the greenhouse helps to keep my house warm.
There are also disadvantages. Positioning is limited; this only works if you have an open sunny area with reasonably level ground around, or at least on one side of, your house. And some locations require building permits for anything attached to your house, but not for freestanding agricultural buildings. (This varies depending on where you live. Check before you build.)
Here are a few types of attached greenhouses:
1. Window-mounted greenhouses are small lean-in structures that allow you to grow a few plants inexpensively. Several commercial models are available, or you can build your own. Mother Earth News offers a DIY window greenhouse plan with acrylic sheeting. This White Cottage Farm blog offers designs for a DIY window-mounted greenhouse made of windows:
2. Lean-to greenhouses are larger structures using the side of your house (or another building) as one of the long walls of the greenhouse. I grow my winter greens and spring seedlings in a lean-to greenhouse made from wood and recycled windows. This is sturdy and weather-tight. It also required a building permit and my brother’s excellent carpentry/construction skills.
You can also get prefabricated aluminum-framed lean-to greenhouse kits which can be assembled without much need for tools and experience. Build on a south- or southwest-facing wall that isn’t shaded by evergreen trees. (Some shading from broadleaf trees is OK since these will be leafless when your greenhouse most needs light and warmth).
When planning the size of a lean-to greenhouse, consider the following recommendations.
- The Clemson Extension office suggests a minimum efficient size of 6 feet by 10 feet for lean-to greenhouses.
- The Georgia Extension website says the width of the growing area shouldn’t be more than 7-12 feet, because with a solid back wall you won’t get adequate lighting further toward the back.
3. Attached even-span greenhouses are similar to freestanding greenhouses except that they are attached to your house at one end. This design gives you some more flexibility about location and orientation.
You could run one off the east or west side of your house so long as there is an unshaded area to the south of the long side of the greenhouse. Having a smaller shared wall area may make heating the greenhouse from your home a bit more challenging and costly. It will also require more construction materials.
Like attached greenhouses, these can be constructed from a wide range of materials—see next section.
4. Freestanding greenhouses are not attached to your building. You can set them up in any site that has good lighting and level ground, and that you can get to easily in winter.
5. Cold frames are small bottomless reach-in setups often used for season extension but not for growing right through the winter. I set out greens a month or so before the last frost in spring, and keep harvesting for a month or so after the first frost in fall, in cold frames made from plywood and salvaged storm windows. You can probably construct these with tools you have around the house. Instructions for building this type of greenhouse can be found at the NC Cooperative Extension website – Build a Cold Frame.
6. Hotbeds are similar to cold frames but have heating cables or hot-water pipes running underneath them. They allow you to extend the season further or grow more sensitive plants, but they require much more investment and effort. See an overview at the University of Georgia Extension office publication – Beds for Growing Small Plants.
7. High tunnels are walk-in greenhouses usually framed with metal or plastic and covered with polyethylene or polyvinyl chloride sheeting. These are lightweight and may be portable; you don’t have to dig foundations for them. Permanent heaters are not used in high tunnels, though space heaters may be brought in on cold nights.
While the Penn State University Extension office says that high tunnels, like cold frames, extend the growing season but aren’t suitable for year-round growing. The University of New Hampshire provides a solution. They say that even in New Hampshire’s chilly winters, cold-hardy greens can be grown in unheated high tunnels with frost blankets.
In high tunnels, as in cold frames, plants are generally grown directly in the ground.
8. Freestanding walk-in greenhouses suited for growing plants year-round come in a wide variety of sizes, shapes, and materials. These usually have plants grown on benches or in containers, not in the ground.
What Are The Different Greenhouse Materials?
Light can enter your greenhouse through glass windows, through fiberglass panels, or through various types of plastics. You can get a closer look at glazing material pros and cons here. (scroll to page 8)
Glass is the sturdiest, longest-lasting material for greenhouse windows. It doesn’t become opaque over time as plastic does. Double- or triple-paned glass retains heat. Tempered glass resists hail.
On the other hand, glass is heavy and requires a sturdy frame and footers dug into the ground. It can also be expensive, though reusing old windows in a greenhouse can save on expenses. A flexible plan for a recycled-window greenhouse can be found at Permaculturenews.org. (But, despite what they say about working around building permits, be sure to learn and follow your area’s building codes!) In any case, building a frame-and-glass greenhouse is a major time investment and requires solid construction skills.
All the Extension publications I’ve seen describe using clear, not tinted, glass for your greenhouse.
Structured rigid plastic panels with a double layer of plastic around an air pocket may be used in greenhouse kits. These are lighter-weight and require less framing than glass, and the air pocket means they retain some heat.
Like glass, they’re fairly expensive. The Tennessee Extension says they come in two materials, acrylics and polycarbonates. The polycarbonates resist hail damage better and are less flammable than the acrylics.
Fiberglass panels are lightweight and inexpensive. They also don’t hold heat very well, and they will degrade in sunlight unless specially treated to be UV resistant. Treated or not, they’re very flammable.
Polyethylene film or polyvinyl chloride film makes a flexible covering that can be rolled out over a lightweight frame. A double layer of polyfilm with air between will hold in heat. But polyethylene deteriorates in sunlight—in one year if you don’t use UV-resistant plastic, in five years if you do. PVC film is more expensive but transmits more heat and can last longer, especially if treated with UV inhibitors.
Most of the Cooperative Extension DIY greenhouse plans I’ve seen are for hoop houses covered with polyethylene film.
Here’s one detailed set of instructions for a 12×14 house with a PVC pipe frame: https://content.ces.ncsu.edu/a-small-backyard-greenhouse-for-the-home-gardener. At the time when this was published the materials cost was estimated at $100, but this varies widely according to time and place.
They say this design can be built in a few hours with some basic hand tools. This Louisiana Extension site offers diagrams of several different greenhouse designs with wooden frames and poly film coverings:
Other Greenhouse Choices
Heating and Ventilation
During some parts of the day and year, the sun will provide all the heat you need. You have several choices about supplemental heat.
Attached greenhouses can be heated by your house’s heating system. That’s all you’ll need for a window-mounted greenhouse, and it’s all I need for my attached lean-to greenhouse.
Passive solar greenhouses are freestanding structures unheated except for sunlight. This works best in warmer climates, or if you are planning to grow frost-hardy plants.
These passive solar greenhouses must be tightly sealed and should have double-glazing of some kind. The solid walls should be well insulated. A heat storage system can hold the day’s heat and radiate it back through the night. This can be as simple as a bank of full water jugs painted black. See details in this article: Growing Vegetables in a Hobby Greenhouse.
Active heating: You can also install a space heater, a stove, a bench heater, or heat lamps. For all but electric heaters, it’s very important to have a good ventilation system so carbon monoxide doesn’t build up. There’s an overview of heating options at Greenhouse Heating.
Whatever heat source you use, good ventilation is essential to prevent overheating. See that you have openable windows or doors on opposite ends of your greenhouse for a cross-breeze. (This isn’t necessary for tiny structures like window greenhouses, cold frames, or hotbeds.) You may also need a fan to keep air moving through on windless days. And if you have a heater in one spot you’ll want a fan to circulate the heated air throughout the greenhouse.
In-Ground Beds vs. Pots/Benches
You can grow your greenhouse herbs and vegetables either directly in the ground or in raised containers. (Hydroponic growing is also possible in greenhouses, but that’s another whole article…) The advantage of growing in-ground is that watering and feeding are easier and you don’t have to bring in large quantities of soil. On the other hand, container growing makes it easier to keep weeds out and to limit bending. A poured concrete floor in a greenhouse with container-grown plants can also act as a heat sink, absorbing the sun’s heat during the day and releasing it at night.
Cold frames are for in-ground growing, and window-mounted greenhouses for container growing. In many other types of greenhouses, you can choose what works best for you.
My attached greenhouse is a heavy-duty structure with a poured concrete floor, and I grow plants in a 12” deep 3×8 soil box and a variety of large pots. These are set on waist-high tables, both to save my back and to get them up off the cold ground.
You have many options for greenhouse growing. Choose something that looks useful and manageable in your situation, and then enjoy the fresh flavor, scent, and color of your herbs all year round.