Buyer’s Guide to Greenhouse Structures and Supplies

greenhouse

A greenhouse is a big purchase that requires a great deal of thought and research in order to get it right the first time. Do you know what questions to ask about the biggest investment you’ll make in your garden? Well, we do—let us walk you through buying your first or next greenhouse so that you get exactly what you had hoped for in an indoor growing space.

Should I Build or Buy My Greenhouse?


A simple greenhouse isn’t difficult to construct if you’ve got basic carpentry skills, but you can’t go about throwing up just any old greenhouse in any old spot.

Before you attempt to build your first greenhouse, look at the kits that are available for purchase. In many cases, you may find that when you compare the materials lists, pre-fabricated structures offer a significant savings. You’ll also have the benefit of knowing that your greenhouse has been field tested by other growers and the bugs are already documented and worked out.

If, however, you need a specialized structure, or a custom-sized lean-to style greenhouse, the added expense of customizing your own greenhouse may be worth it. Still, look at other models to ensure that your greenhouse has all the right vents and doors in the right spots. It’s easier to build ventilation, irrigation and climate control into a structure at the design phase than after you’ve already broken ground.

If you want to buy your greenhouse, check out our greenhouse guide.

How Will the Weather Affect What I’m Growing?


The best design, materials and equipment for your greenhouse will depend heavily on your local conditions. Windy or snowy areas need more structurally sound buildings with the ability to shed snow and allow winds to pass by without ripping the walls apart.

Warm climates call for better ventilation: roll-up walls, shade cloths and mounting areas for additional fans are the name of the game. In cold climes, extra insulation and heaters will help you maintain a stable environment.

Heating and cooling equipment needs depend heavily on what you intend to grow and how violently your weather changes. If nights stay above freezing and you only use your greenhouse to start seeds, you may be able to get away without heat, but trying to grow tropicals in the North will demand an efficient heating system.

Nearly everybody will need some type of cooling system because of the way greenhouses tend to amplify the rays of the sun, although many growers can get away with running fans and opening vents during the hottest parts of the day.

Shade cloths are handy if you’re growing plants with limited light tolerances or it gets more than a little warm in the greenhouse. Heat kills quickly, so this should be a serious consideration.

If your vents can’t move enough air to cool your structure, shade cloths can help prevent some heat from entering the structure in the first place. Trying your hand at an extremely cool greenhouse in a very hot, humid climate is a huge challenge, but swamp coolers and air conditioners can bring the temperatures into range.

Does Flooring Make a Difference?


Yes. And how—first of all, your greenhouse floor is most likely the largest heat sink in your structure, meaning that it will capture heat during the day and deal it out slowly as the ground cools at night. Depending on your needs and conditions, typical floors range from bare ground to gravel and even cement.

Cement floors are great for sanitation and keeping weeds from sprouting up unexpectedly in the greenhouse, but trap a lot of heat. If you struggle to keep your greenhouse cool, they’re not your best choice.

They’re great, though, in areas where supplemental heating is necessary or where perennial weeds are a problem, because they both capture the most heat of any typical flooring and create a permanent barrier between your growing area and any weed seeds below.

Gravel is a pretty typical flooring material, and neither captures a significant amount of heat nor returns much at night. If you prepare your greenhouse site carefully and layer the ground with heavy geotextiles before laying a thick layer of gravel, you may be able to keep weeds down for a long time, too. Gravel floors often fail when growers are trying to cut costs and refuse to line them or only lay a thin layer of gravel on top of landscaping fabrics.

Bare dirt will work for a greenhouse floor, but isn’t recommended for a number of reasons, notably for its willingness to let any weed or grass seeds near the surface to germinate. Greenhouses often have ideal conditions for rapid weed growth, your greenhouse may be taken over before you know it. Many weeds carry diseases and attract pests, further complicating your greenhouse efforts.

What Materials Should I Use for the Structure?


Greenhouses structures come in a wide range of materials, from wood and plastic to aluminum and powder-coated steel—greenhouse coverings are no less diverse with glass and polycarbonates being common.

Does it matter what you choose? If you plan to have your greenhouse around a while, it certainly does. Again, you should first limit yourself to materials that will handle your local conditions—don’t, for example, build a greenhouse out of PVC pipes if you know that your area regularly sees 12-inch snowfalls or high winds.

Most gardeners can’t go wrong with greenhouses made from powder-coated steel and covered in polycarbonate panels, but these structures can be costly and difficult to modify if you find you need more vents or want to add screens.

Cedar structures are also long-lasting and are easier to modify than steel or aluminum, though they may attract insects as they age or retain spores over time. Aluminum is rot-proof, but very lightweight, so any structure designed with this metal in mind will need to be weighed down. PVC pipe should only be used for temporary hoop houses due to the material’s light weight and short life span.

Glass or polycarbonate are excellent choices for skinning hobby greenhouses, but great care must be taken with glass if you plan to mow or weed eat nearby. Polycarbonate can get a little foggy or yellowish over time, but if you hit one of these panels with a little piece of gravel while mowing, it’s not likely to shatter into a million tiny shards.

Poly films and sheet plastics vary widely in their effectiveness over the long term—these thin plastics can become very brittle as they age and in windy areas, may tear frequently. When using film or sheet materials, thicker is always better.

What Accessories Does My Greenhouse Need?


The accessories your greenhouse needs will largely depend on outside factors, like your local conditions, the plants you intend to grow and how much time you have to devote to regular greenhouse chores.

Automation isn’t necessary, but it can be helpful if you’ve got too many garden chores and not enough hours in the day. These are the most important things to consider when looking at accessories:

Fans 

Description: Vital to any operation where breezes can’t be counted on to move excess hot air out of greenhouses quickly—fans are easy to control and get the job done. They can also be used to help keep air circulating around plants with mold issues and toughen up little seedlings that will eventually be exposed to windy areas.

Options: Greenhouses typically rely on circulation fans, exhaust fans, or some combination of both. Circulation fans include: HAF (Horizontal Air Flow) fans, (HVF) High Velocity Fans and VAF (Vertical Air Flow) fans. HAF fans, of course, move air horizontally. VAF fans push air down from the greenhouse ceiling. Exhaust fans pull air out of the greenhouse through its vents, much like the fan of a range hood does.

Pros: Exhaust fans are simple and effective at removing heat and humidity when paired with adequate vents to let in cooler air. Circulating fans imitate wind currents and can help strengthen young plants.

Cons: Depending on the size of your growing area, you’re likely to need a group of circulating fans to push air evenly across the entire space of the greenhouse. Even then, it can be difficult to measure.

Our Suggestion: There are a lot of fans on the market, but our suggestion is the iPower 12-inch Shutter Exhaust Fan.  This fan is durable, powerful, effective and affordable. It has a rotating speed of 1620 rpm and an air volume of 940 cfm, with a wind speed of 10.5 m/s. Its aluminum shutters and blades resist the elements, and its industrial-grade construction make it ideal for outbuildings.

It’s a convenient fan to install – it’s lightweight and comes pre-assembled. It’s also quiet to operate, with automatic shutters that open and close in tandem with the fan.

Heaters 

Description: Some areas need heaters more than others, but if you want to use your greenhouse all year, you’ll need one eventually. Various sizes are available, powered by gas, electricity, wood or solar—the size of heater you’ll need will depend on how much heat loss you anticipate on the coldest nights and the size of your greenhouse.

Options: Your options for heaters depend on depend on the size, portability and fuel type you want. Electric or ceramic space heaters are small, but versatile options. You can find electric, oil, gas, kerosene and hot water heaters. Wood stoves and pellet stoves are also used, as is solar heating.

Pros: Portable heaters give you the option to concentrate your heat on plants that need it most, while large, fuel-based heaters are fast and effective at heating larger spaces. Fuel-based heaters also won’t add to your electricity consumption.

Cons: Because of the emissions, fuel-based heaters aren’t suitable for small spaces. The temperature of a wood stove is difficult to regulate and needs monitoring for safety and consistency. Electric heaters are safer, but you may need more of them to achieve a consistent temperature. Pellet stoves can be expensive, as can solar systems.

Our Suggestion: We recommend the Bio Green PAL 2.0/USDT Palma Greenhouse Heater. This electric heater is perfect for smaller greenhouses up to 120 ft. ² We especially appreciated that the Bio Green heater is safe, effective and durable.

It has a 5118 BTU/1500 W heating output, can circulate 163 cubic meters per hour and is made to use in humid environments. It’s splash-proof rated to IP X4, with stainless steel housing and heating elements.

Compact and portable, this heater is designed as a floor-standing model. The Palma model features a remote digital adjustable thermostat for more precise temperature control.

Vent Openers

Description: You can open your vents manually if you know you’ll be near the greenhouse all day throughout your growing season. If you don’t think you can make that kind of commitment to your greenhouse, automatic vent openers are the next best thing. Set them up to open when the greenhouse starts to build up heat and close when temperatures cool again.

Options: Most vent openers are solar powered, which is a great feature. They’re meant for top and side-mounted vents, and will each have their own maximum load capacity.

Pros: Automatic vent openers provide consistency and peace of mind when you can’t be as consistent in your timing as you’d like. They save a bit of labour and give you greater control over the interior temperature of your growing area.

Cons: The only real con to this is that with every piece of equipment you add, you add one more piece of equipment to maintain. For many, though, replacing the occasional cylinder is well worth not having to make the trek out to the greenhouse twice a day.

Our Suggestion: Although it’s possible to find less expensive vent openers, we suggest the automatic greenhouse window opener from BIBISTORE. It’s more durable than many of its competitors, featuring dual spring construction. It’s made of aluminum and steel, with an oil-filled cylinder that expands with the sun’s heat to open the vent. Installation is quick and easy, and the unit can be clamped or screwed on.

This opener is rated up to 15 lbs/7 kg and opens to 18 inches/45 cm when fully opened.  The unit will be fully open at 35°C (93°F) and is not recommended for temperatures above 60°C ( 140°F ). The temperature at which it starts to open is adjustable, from 15°C to 23°C (59°F to 74°F).

Screens 

Description: They’re not always standard equipment for greenhouses, but they should be—after all, screens are your only hope for keeping bugs and various wind-borne seeds from finding their way in through your vents. The tighter the screen, the fewer things you’ll have inside, but you may need to expand ventilation openings to make up for the reduced air movement through the screen. Don’t forget to screen windows and doors while you’re at it. Read our page on screens for more>>

Options: There are a surprising range of screens available today, from simple screens designed to stop insects from entering the growing area, to motorized energy and shade screen systems that insulate the greenhouse and reduce heat transfer.

Pros: With an energy and shade screen system, you can see a significant reduction in heating and energy costs. With a basic screen, the big pro will be an immediate reduction in the insect population of your greenhouse. That means less effort, and for those who use pesticides, less pesticide use.

Cons: Energy and shade screen systems can be costly, and are often more feasible for larger greenhouse operations. With any screen, reduced air flow will need to be compensated for. The size of the mesh also needs to be carefully considered to minimize air flow disruption but maximize insect blockage.

Our Suggestion: It’s most cost-effective to order screening materials in bulk, or as a roll at your local hardware store. If you prefer a packaged option, try Agfabric’s Insect Barrier Netting. The mesh size is large, at 0.03 x 0.03 inches, but if you suffer from caterpillar infestations or have an issue with wasps, it’s a solid option.

The fabric can be hung over a hoop greenhouse or cut to fit vents and windows. It’s made of a UV resistant polyethylene, which lets light and moisture in while protecting plants. It’s lightweight, but sturdy enough for reuse.

Anchoring Systems

Description: You can’t keep a good greenhouse down—well, not without an anchoring system, at least. Some growers use sandbags or cement blocks and they’ll work reasonably well, but if you’re installing an expensive greenhouse in a permanent location, give it a finished look with a proper anchoring system and rest assured that you won’t lose your building to high winds.

Options: If your greenhouse is on the larger side, you can opt for a permanent anchoring system like concrete piers, or you can go in for something with the possibility to move or remove it, like stakes (such as auger-style anchors) and cables.

Pros: Concrete piers are highly secure, while a stake and cable anchoring system gives you the option of adjusting the placement of your greenhouse, should you need it. Stake and cable systems are less intrusive on your landscaping and easier to DIY.

Cons: Any permanent anchoring system is going to be labour-intensive. It will also require digging in your yard. Stake and cable systems are less robust. Any anchoring system also requires those working or playing around the perimeter to be careful about tripping over cables or stakes.

Our Suggestion: There are many options for DIY anchoring kits. We suggest Shelter Giant’s 30” auger anchors. They’re made of powder-coated steel to withstand the elements, and include a limited one-year warranty. The augers are easy to use and long enough to provide ample support for your small greenhouse. The cables are wire, with a clamp-on design for added stability.

The kit contains 6 augers and cables, which gives you a few different options for supporting your greenhouse. The augers are on the longer side, which makes them more difficult to put in the ground, but also more secure.

Climate Monitoring Equipment

Description: From the most basic hygrometer and thermometer to highly advanced equipment that can turn fans and heaters on and off, there’s a climate control system just right for your building and budget. Many systems offer wireless displays that you can keep in a handy place indoors so you always know what your greenhouse is doing, even when you’re working on something else.

Options: There are too many options to list here, but you’ll often be looking at equipment that will monitor some combination of temperature, humidity, light and shade, CO2, wind speed and direction and precipitation.

Pros: As with any new smart technology, climate monitoring equipment is both a blessing and a curse. First, the pros. It (ideally) gives you up-to-the-minute, accurate date about climate conditions in your growing space, even remotely. It saves time, labour and guesswork.

Cons: On the downside, this equipment can be expensive if you want something that checks more than temperature and humidity. It’s also constantly changing. As the technology advances, the purchases you make can quickly become out of date, requiring new purchases as equipment is phased out.

Our Suggestion: Although monitoring equipment gets much more involved than this, you could start with Govee’s wireless thermometer hygrometer. It monitors temperature and humidity, with a temperature gauge accurate to ±0.3°C and humidity to ±3%RH.

The big draw with this product is that you can monitor your greenhouse remotely with Alexa or with your phone. You can pre-set a temperature or humidity range, and the system will send an alert to your phone if the climate moves out of that range. Data storage lets you see trends over time, so you can track the effects of any changes you make to your greenhouse set up.

Irrigation Systems

Description: Irrigation systems can be as simple as a watering can or a hose, or highly complicated drip or mist systems on timers. A very small hobby greenhouse doesn’t need a lot, but larger greenhouses can be difficult to keep watered in the heat of the summer. Consider an individual system for each type of plant you’re growing so each plant gets watered exactly right. Some systems allow you to push nutrients through to plants as well.

Options: If you’ve decided a watering can is not sufficient for your needs, you’ll have lots of choices. Overhead sprinklers, misting and drip irrigation systems are common, as are subsurface systems. For subsurface systems, you can set up drip tubes on capillary mats, or install a trough or ebb and flow benches.

Pros: Drip irrigation systems are highly precise so they waste much less water than conventional sprinklers. Subsurface irrigation systems also tend to be less wasteful than overhead sprinklers or misters. Sprinklers, however, can cover a much larger area and are less work to set up.

Cons: In addition to wasting water, overhead sprinkler or misting systems increase the chances of disease in plants by keeping leaves moister. Drip systems and subsurface systems can require more in the way of installation and ongoing maintenance. Subsurface systems are typically used in concert with a holding tank, which isn’t ideal in smaller greenhouses.

Our Suggestion: The Flantor Garden Irrigation System is an easy-to use automatic drip irrigation kit that includes everything you need to start irrigating. The system includes ¼ inch tubing and covers 20-25 m². It’s a flexible system, in that you decide where the nozzles need to go and assemble then yourself. Each nozzle has adjustable pressure, which lets you water each plant according to its individual needs. Some users recommend hose splitters, as the pressure will start to decrease as the nozzles get further away from the water source.

Benches 

Description: Benches don’t seem like a big deal, but if you’ve ever been in a greenhouse that had poorly designed benches or none at all, you know they’re as important as the walls themselves. Select easy to clean benches made of aluminum or coated steel for best results, though wooden benches will work in a pinch if they’re thoroughly cleaned often and repainted or resealed yearly.

Options: Benches can be simple or decorative, fixed or portable, single or multi-level, solid or mesh-topped. They come in a range of materials, all designed to withstand higher levels of moisture and a lot of wear and tear.

Pros: Wood is inexpensive and readily available, plus, species like cedar resist decay. Galvanized steel is highly durable. Expanded metal won’t sag. Plastic benches are lightweight and need little to no maintenance.

Cons: Wood needs more maintenance and can also warp. Metal that’s not properly treated is prone to rust. Expanded metal tends to be more expensive. Plastic that’s exposed to extreme temperatures can crack. Plastic benches also can’t support as much weight as other options.

Our Suggestion: RMP Aluminum Greenhouse Potting Bench is a heavier duty, highly functional bench that will last. Made of repurposed aluminum, it measures 42 x 24 inches and stands 32 inches high. Its versatile surface features rows of round holes separated by solid strips, so you can easily water your plants on it and still have a bit of solid space to work on if you need it.

At 18 pounds the bench is lightweight and portable, but it holds up to 50 pounds. Assembly is simple – it just needs to be screwed together. It’s not the least expensive table on the market, but it’s well worth the price for how sturdy, low-maintenance, well-made and well-designed it is. It’s also not fancy, but the real star of the show is your beautiful plants.

Image credit: nosha via Compfight cc

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