Everything You Need to Know About Polytunnels vs Greenhouses

Each year, those who cultivate plants are faced with the question, “Is a polytunnel better than a greenhouse?” Selecting between these two plant-protective constructions can be daunting without thorough knowledge.

Polytunnels and greenhouses work to grow plants in a controlled environment, but that’s where the similarities end. Differences in versatility, cost, aesthetics, durability, labor, and maintenance are pros and cons of polytunnels and greenhouses every grower should know about.

Continue reading for a deep dive into the pros and cons of polytunnels and greenhouses. Is a polytunnel better than a greenhouse? You’ll find out as you better understand which structure suits your needs.

Polytunnels and Greenhouses: How Are They Different?

Polytunnels

Polytunnels are usually round, steel structures covered in plastic to protect crops from harsh weather and prolong the growing season.

The steel used in polytunnels is often created to withstand harsh conditions. Polytunnels come in many sizes to accommodate the necessary working space for growers. 

Northern Polytunnels and Horticultural Supplies describe polytunnels as “generally made up of galvanized steel hoops, crop bars, base rails, and a polyethylene cover.”

Polytunnels are sometimes confused with greenhouses as polytunnels are also standing structures, originally built so that farmers could easily work under them.

I love the Northern Polytunnel range, and they have some great ways of adding ventilation, making these tunnels very good.

So much so that I recently bought a 36ft x 16ft tunnel and made a video of the full construction. You can see the video below.

You usually grow plants or crops in polytunnels on the ground, whereas plants or crops are grown in planters and pots in greenhouses.

Intervale Community Farm says polytunnels adapt to four or three seasons, while greenhouses always function for four seasons.

Polytunnels have been around since the 1940s when polyethylene was first synthesized for World War II, says First Tunnels. It is hard to pinpoint where their use originated, but the use of polytunnels for commercial and recreational purposes has since spread across the globe.

Greenhouses

Greenhouses are heated, climate-controlled structures covered in polycarbonate plastic, polyethylene, fiberglass, or glass.

Greenhouses do not have the level of versatility that a polytunnel has, but they offer you some options; attached or freestanding.

If you choose to have an attached greenhouse, you can use a load-bearing wall on your property as one of the walls of your new greenhouse and take some load off the other three walls of your new greenhouse.

Building a freestanding greenhouse will allow you to place your greenhouse anywhere on your property, offer you an aesthetically pleasing escape from your house, and allow you to plant earlier in the year.

As more people grow their crops or expansive gardens at home, polytunnels and greenhouses each offer a unique advantage.

Is a polytunnel better than a greenhouse? The pros and cons here should help you decide if this question is lingering.

Pros: Polytunnels

Flexibility and Versatility

Polytunnels are much more versatile and can dynamically fit the grower’s needs due to their lightness, mobility, and easy installation process.

According to Rimol Greenhouse Systems, they can be moved at the discretion of the grower, adjusted in size, and expanded as needed and are not permanent structures, unlike greenhouses.

This feature allows plants housed in polytunnels to live longer and for a longer growing season once it gets cold. Polytunnels were not designed with controls like electricity, climate control, and the amount of ventilation a greenhouse receives. These additions are possible, adding to the possibility of what a polytunnel can do.

Cost-Effectiveness

If cost is one of the main factors affecting your decision, polytunnels are far less expensive to install than greenhouses.

HomeAdvisor says the average cost to build a greenhouse in 2021 is USD 15,746. A polytunnel can cost USD 50-4,000, depending on the size and materials you choose for construction.

A more in-depth analysis of building a polytunnel is included here by the University of Arkansas. Polytunnels are the best bang for your buck, costing ⅓ of what a greenhouse would cost on average, including any repairs or replacements that You may need for the future.

Cons: Polytunnels

Aesthetic

There is no denying the charm that a glass-paned, house-like greenhouse can add to a small garden. While both a polytunnel and a greenhouse can be warm, verdant sanctuaries during the colder months, greenhouses can provide a view of what lies beyond your growing structure.

Polytunnels are functional and efficient but do not lend to the peaceful oasis aesthetic that some more expensive greenhouses often have going for them.

Consider if aesthetics matter to you. You will likely spend a lot of time in your polytunnel or greenhouse-will you still be happy if your daily view is of steel frames and plastic covering?

Weather-Prone

Polytunnels are slightly more weather prone than greenhouses, with only one layer of plastic covering, strong but not immovable anchors, higher ground posts, and little reinforcement. Polytunnels will withstand a certain amount of bad weather.

Still, when it comes to extreme weather such as high winds, tornados, hurricanes, flash floods, or heavy snow that could cause tunnel collapse, a polytunnel may not be able to protect what’s growing inside of it.

If your region is prone to extreme or unpredictable weather, you should consider if the risk is worth it.

Shading

While it is fairly easy and commonplace to shade a greenhouse with shade paint, it is not as easy to shade polytunnels where you only have one covering of polyethylene to work with. You’ll have to get creative.

Polytunnel Gardening recommends increasing ventilation by having doors at both ends of your polytunnel and shading your current plants by planting more plants near them to absorb sunlight.

Shading using new plants is fairly commonplace to shade in a polytunnel. Still, you should consider it not as straightforward as adding a layer of paint to the glass or polyethylene in a greenhouse.

You will put extra time and money into your polytunnel in the summer if you live where it is likely to get hot.

Pros: Greenhouses

Light Absorption, Heat Retention, and Climate Control

Greenhouses absorb the most light and retain the most heat, allowing plant protection if cold weather comes early or stays late.

Greenhouses can also be more easily climate-controlled with HVAC systems or, naturally, prevent overheating while not having to worry about your plants getting enough sunlight.

You can prevent excessive light absorption by treating a greenhouse covering with a shade to reflect some sunlight. This treatment is cost-effective and eco-friendly, and another measure is taken to protect the plants growing in your greenhouse.

Ventilation

Greenhouses allow very little room for heat retained from light absorption to get out. Mechanical and natural ventilation are viable options to keep your greenhouse from overheating.

Ventilation assists in pollination, exchanging gases between plants and the atmosphere needed for growth, better air movement, and regulating temperature and humidity.

Ventilation of a polytunnel is possible, but there are not as many options available, and it is not as easy to install ventilation systems in polytunnels.

Cons: Greenhouses

Labor and Building Considerations

Greenhouses will take two days minimum to build, while polytunnels can be constructed in 1 day. You also must take into consideration what land you are working with. Constructing greenhouses on flat surfaces is very important, while you can build polytunnels on sloping surfaces.

Evaluate if you are willing to put extra time and money into landscaping to create a flat surface for your new greenhouse or if you would rather work with any uneven land you have. Greenhouses are not intrinsically hard to build but take more time and human resources to set up.

If you hire someone to put a greenhouse together, Fixr reports a contractor will charge anywhere from $50.00-100.00 USD per hour of labor.

Maintenance

The greenhouse maintenance expense will vary based on whether your greenhouse is commercial or for your pleasure.

You must consider fixed costs such as ventilation, potential electricity costs, automated watering systems if you choose to have one, and other business-associated costs for those operating commercial greenhouses.

You can also consider how much you buy in plants and how much revenue you take in if you sell those plants. Greenhouses are much more upkeep than polytunnels because they are climate-controlled, ventilated, and often have electricity and automated watering systems. Decide if this responsibility is an investment you are ready to make.

Glazing

Greenhouses require glazing, the sheath around the bare bones of the structure. Consider if you want to put in the work of glazing when deciding whether or not to build a greenhouse. Glazing is a vital part of every greenhouse and one more step between your dream of a plant paradise becoming a reality.

Glazing lets the sun and warmth in -a greenhouse absorb and holds sunlight best- while holding the climate at bay. Common glazing methods are glass, plastic sheeting, and polycarbonate.

You can also expect to use a shading material on your glazings, such as shade netting or shade paint, to reflect some sunlight into the atmosphere.

According to Greenhouse Planter, the material you glaze with depends on what you seek in your greenhouse. Prioritizing looks, location, durability, or affordability will affect which material you decide to glaze with.

You can achieve a quaint aesthetic at a steep cost and potential damage if you want to glaze with glass.

On the other hand, you can save a lot of money and potentially products wasted if you glaze with polycarbonate. However, it may not look like the greenhouse of your dreams.

Polytunnels are more affordable and versatile, while greenhouses are longer-lasting and easier to climate control and ventilate. However, polytunnels are more prone to weather-related accidents, require more effort to shade your plants from heat, and don’t give you the same aesthetic a residential greenhouse might.

Greenhouses typically consume more time, money, and resources to buy, build, and keep the greenhouse. Now that you know more about the benefits and downsides of polytunnels and greenhouses, decide which structure best suits your needs, and start growing a year-round paradise in your backyard today.

Conclusion On Polytunnel Vs. Greenhouses

Although greenhouses are more aesthetically pleasing and can withstand harsher weather and grow all season round, Polytunnels make great advances towards this. By adding more ventilation and heating systems, Polytunnels give you much more room for your budget.

That said, glass holds out frost and retains heat much better than plastic. One major issue is that glass overhead could be a major safety issue in greenhouses not put together well or an aging greenhouse.

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