Polytunnel Vs. Greenhouse, which is right for your plants?

Many of today’s gardeners are looking for ways to improve their yield, and to extend the gardening season as much as possible. The classic solution to this issue has been to build a greenhouse in order to keep the plants warmer in cooler times and to have a functional space for germination and harvesting. However, the costs of glass or polycarbonate greenhouses are typically extremely high. Now, with the mainstreaming of the polytunnel, there is another option for creating outdoor rooms for plant growth. This article looks at the Polytunnel vs. Greenhouse, and examines the advantages and disadvantages of each.

Growing Plants Indoors

For the last 10,000 years, humans have cultivated crops. It was the Romans who first thought of growing plants under cover. They built their version of a greenhouse, calling it a Specularium, though this means “Conservatory.” Designing transparent sheets of the mineral mica for the roof, they also lit fires against the outside walls for heat.

In 1800, the French botanist, Charles Bonaparte, came up with the revolutionary idea of building a glass house. It’s worth mentioning that he was the nephew of the famous Napoleon, as a point of interest. We have come a long way since the first Romans tackled growing indoors in c30AD. In modern times, we now have choices in the various types of housing we wish to grow our plants indoors.

From conservatories as an extension of our home to a greenhouse in our backyard.

If you have the room on your land, you could also consider a poly-tunnel.

These are all modern ways of cultivating under cover.

An avid gardener loves fresh vegetables, herbs and colorful flowers on their table. With today’s ever-changing weather patterns, indoor growing almost guarantees a bountiful crop, with little risk.

It is fast becoming popular for people to prefer growing their own food. What then, is the best type of housing for your indoor cultivation?

Polytunnel vs. Greenhouse

If you are serious about harvesting your own crops, then you will soon outgrow a conservatory. These are fine for one or two decorative plants, but we also tend to put furniture in there too. That means you will need to weigh up the pros and cons of other methods, such as a greenhouse or a poly-tunnel.

See this article hor more information on the best polytunnel greenhouses.

Let us look at the various factors that go into making a purchase decision, in order to identify the major issues to consider.

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Initial Cost for Frame

Without a doubt, a poly-tunnel is the least expensive option for a garden building. Greenhouses are typically made from glass (the most expensive option), though cheaper options like polycarbonate and plastic are also available.

Greenhouses are generally much more substantial buildings than polytunnels are, so it makes sense that they are more expensive. Of course, one must keep in mind that there’s also the additional cost of assembling the greenhouse, which is a much larger endeavor than assembling a polytunnel.

For the sake of comparing prices, we will compare a typical walk-in growing structure. There is a great deal of variability between brands, models, and sizes, but with a quick glance, you can get a pretty good sense of the general order of costs.

Greenhouse Structure

Glass

A fairly large sized walk-in glass greenhouse can have an area of around 80 sq feet. This would have measurements of approximately: W7’9″ x L10’2″ x H8’6″.

Built with strong aluminum frames, these buildings are made to withstand some bad weather.

The windows are around 4mm depth of tempered glass, with rubber seals.

Often, they will double doors plus window in the roof.

Glass greenhouses are generally considered the top end choice among greenhouses and carry the highest price tags. premium model.

When spending over $5,000 for materials alone, customers would be right to expect aesthetic quality and great functionality.

Tempered glass is around 20% more expensive than normal glass, but it is much safer. Should it break, it shatters into tiny smooth squares, without any jagged sharp edges.

This Exacto Victorian Greenhouse can give you the general idea of the cost and beauty of a glass greenhouse. Don’t forget to factor in several thousand more for assembly, unless you plan to do it yourself!

Last update on 2024-12-18 / Affiliate links / Images from Amazon Product Advertising API

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Polycarbonate Greenhouses

There are also the polycarbonate models available, many of which we looked at in our Polycarbonate Greenhouse article.

These greenhouses tend to be a bit smaller than glass greenhouses, typically in the range of 50-60 sq feet of growing space.

Keeping in line with glass houses, Polycarbonate greenhouses typically have aluminum frames to withstand some bad weather.

Again, the polycarbonate window panels have around 4mm-6mm depth. Polycarbonate material is almost unbreakable, though it can crack. This FarmTek Elite greenhouse is a good example of a typical polycarbonate model. We look at several FarmTek options here.

Like the glass greenhouses, figure significant cost for assembly, unless you plan to do it yourself.

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Polyethylene Greenhouses

If you don’t have much room and don’t want to spend much money, you could consider a portable polyethylene greenhouse. These units consist of a (usually) steel frame, surrounded by a polyethylene tarp material, similar to what is used on a polytunnel. They are not tunnel-shaped, and are usually, well, house-shaped.

These units can be set up and taken down pretty easily, and there’s no need to pay for assembly. Of course, they are much less robust than glass or polycarbonate greenhouses. This Homewell greenhouse is a nice example of a polyethylene greenhouse. If you want, you can go even smaller and get a mini greenhouse.

Last update on 2024-12-13 / Affiliate links / Images from Amazon Product Advertising API

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Polytunnel Structures

Poly-tunnels provide more growing space for less cash outlay. They are usually steel framed, but the structures go up and are taken down quite easily, with no outside help or costs needed.

The covers are made of a durable and tough polythene and have zippered doorways for entry. A poly-tunnel may need guy ropes for full support.

One bonus is that they can be mobile as they need no foundations, which we will discuss later. These, of course, come in varying size profiles, but a general scale for a tunnel is L12ft x W7ft x H7ft, as shown in the BenefitsUSA tunnel below. Compared to a typical greenhouse, buyers are getting larger spaces, usually laid-out quite effectively, in a polytunnel.

This sized model can have a cost of around $100, but they do come cheaper depending on the brand.

Most are made of similar material, though of course there are varying qualities to the plastic cover.

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Customers can pay more for larger sizes, such as this Idealchoice Polytunnel that is 20′ long. If you compare square footage, then the poly-tunnel is the cheaper option.

Last update on 2024-12-18 / Affiliate links / Images from Amazon Product Advertising API

Though most poly-tunnels look pretty much the same, no matter the size, you can buy different types of plastic covers depending on the brand and format.

Polyethylene Covers

• Standard Polythene is the cheapest option.
• Thermal Anti-Fog deals with possible condensation problems.
• White Polythene gives more shade and is perfect for plants that don’t need much light.

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Building Aesthetics

All walk-in poly-tunnels are formatted more or less in the same way. With a curved roof, they look like a tunnel, hence the name. The only difference will be size and scale. Some have zipper doors at both ends, others only have one doorway.

Guy ropes help to strengthen the structure in bad weather, as otherwise, it may collapse or blow away on a windy day.

Air vents are found in the form of gauzed or netting material, which help keep out the bugs but allow a reasonable airflow through the interior.

The winner in looks should be the traditional greenhouse. They can look quite classy, like the original Victorian glass houses.

A greenhouse can also be designed to lean against a brick or wooden wall, looking equally as good.

The basic greenhouse with a polythene plastic cover is a similar principle to the poly-tunnel. The difference is that it still has the angled, straight lines of a greenhouse.

This must be down to personal choices:

• Do want to use your growing house as an attractive piece of garden structure?
• Or, do you want it to serve the functional purpose as a practical place to grow plants?

Now that we are discussing shape, let’s look at the uses of the inside of both greenhouse and poly-tunnel.

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Functionality of the Building Shape

Greenhouse

The greenhouse lends lots of room for shelf space, much the same as a garden shed allows. While the walls will not take much weight, standalone shelving space will be at a premium.

You’ll have plenty of great places to stand those tubs of seedlings to rest upon. You can also grow a few hanging plants, by using the frames of your shelves.

There is little to no growing space in the ground, as a greenhouse needs good foundations.

Without a solid floor, the frame will buckle and become out of shape. Then, you will you lose your advantage of an aesthetically pleasing growing house.

A warped frame will leak and the solid covering will weaken and crack.

Poly-Tunnel

Not so easy to put shelves up, but there are other advantages to its shape.

There is more ground space in a polytunnel. This means you can use tables or potting benches to place your growing pots upon.

Once you figure you have your plants on tables, you can then also use the ground to grow vegetables, such as tubers, carrots, and potatoes.

This gives you the best of both growing methods, over and underground.

This design gives an advantage that the larger the poly-tunnel, the more growing space you have!

This leads us on to the next consideration, that of actually erecting your grow house.

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Construction and Build Quality

Greenhouse

In terms of the complexities of construction, without a doubt, a greenhouse is more difficult than a polytunnel. It can be so complicated that, according to firsttunnels.co.uk, around 60% of customers tend to bring in the experts when it comes to the greenhouse together.

This is especially important if you are not fully able to move around easily. Constructing a greenhouse from scratch is quite physical.

Glass and Polycarbonate greenhouse frames must have a solid base of either concrete or wood. The frame for the polyethylene plastic covered one does not need to be solid, as the sides are not solid.

A greenhouse needs a straight, level foundation to be installed before construction. Once you have your foundation, then you need to start the construction process. This, in itself, can be difficult as it involves different parts of the frame fitting together in the correct order.

Installing the glass panels is the last stage, and if all has gone well, then they should slot into place.

If not, you may have to take it all apart and start all over again. There’s not a ton of tolerance for error when it comes to large glass or polycarbonate panels.

Poly-tunnel

This is easy to explain in a few sentences, as it is much the same process as putting up a tent.

• Make up the frame.
• Roll out the polythene cover over the frame.
• Peg out in place to provide a secure covering.

According to firsttunnels.co.uk, Only around 5% of customers do not erect their poly-tunnel themselves, that proves how easy it is.

There you have it!

Final Thoughts on Assembly

Your poly-tunnel could take an hour or so. Whereas the greenhouse could potentially take days, especially if you have to wait for a concrete foundation to set.

Another couple of major advantages in the construction of the poly-tunnel, are:

• It is easy to move, making it mobile.
• It can be put up on a slope. Whilst the plastic covered greenhouse can also be moved around fairly easily, none of the greenhouse structures can be placed on slopes.

This leads on to the question of how long you can expect the lifespan of each one to last.

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Lifespan

Greenhouse

This will depend on which model you have chosen. A polythene-covered greenhouse is not going to last as long as a glass one. Glass is going to last until an accident breaks it. The glass is fairly tough as it is treated, but we all know that glass can break if something hits it. This should be a rare occurrence, so hopefully, it will last a lifetime.

If your greenhouse has polycarbonate panels, these are actually tougher than glass, but will not last a lifetime. At the moment, they tend to have a 10-year lifespan.

It’s not that they will all break after 10 years, but they will lose their guaranteed UV layer of protection, though manufacturers are working on improving this.

Finally, there is also the option of UV-resistant acrylic panels. These are much cheaper than polycarbonate and glass, but their lifespan is only around 4 years.

Poly-tunnel

There are different qualities to the plastic covers of a poly-tunnel, but they mostly look the same:

• For thermal benefit, buy a thicker one of around 200 microns.
• To reduce light and the heat from the sun, buy a white one.
• For plants that prefer shady areas, choose a green one.
• These are but a few, but they are all UV protected with around 5-7-year guarantees. Many customers are reporting that they can last up to double this time if you buy a good quality cover.

Much will depend on the climate:

• Sun will wear out its UV coating.
• Rain and hail will reduce its toughness.
• It can become damaged much easier than greenhouse glass or polycarbonate can. Though you can patch up the material of a poly-tunnel.

Ensure Replacement Fabric is Available

One very important consideration is to ensure that your polytunnel manufacturer sells replacement polytunnel fabric in the configuration of your tunnel. You can get cut-your-own stuff, but it’s much easier to just order another fabric from the company if yours tears or otherwise fails.

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Growing Quality

Growing plants undercover is fast becoming popular as more people wish to grow their own food. The advantage of indoor growing is that you can also grow out of season foods all year around. Do crops grow any better in a greenhouse than they do in a poly-tunnel?

Humidity and Temperature

The greenhouse WINS on ventilation of humidity and temperatures. This is because they usually have windows that open.

Heat Retention

The poly-tunnel WINS on retaining heat better. For heat in a greenhouse in the evening, you may need extra equipment like a greenhouse heater to keep temperatures at the right level.

Make sure that you still have plenty of air movement in the poly-tunnel, such as net vents and an open doorway. If the heat is too humid, then bacteria will grow.

One way to bring down the heat inside the poly-tunnel is to add a second cover on the south side, which will be the hottest. Having doors at either end is ideal, rather than a single door, then a fresh breeze can blow through.

Sun Exposure

The poly-tunnel requires less sun than a greenhouse because it retains the heat better.

When using a greenhouse, if possible position it East to West. That way the largest wall receives the most sun. Or you could use grow lights if you have positioned the growing house in the shade.

Keep in mind that too much sun is not good either, and this can be a problem with a greenhouse.

Winter Usage

In the winter, both will benefit with extra layers, made up of horticultural bubble wrap. It will block out drafts and retain any heat you have gained.

If you want to grow many types of fruit trees or exotic plants in cold climates, a polytunnel or greenhouse will be a huge help.

Additional Equipment

For both, you can purchase equipment to help with ventilation and humidity. Outdoor fans are quite useful in helping to move air around, and outdoor misting fans can help supply water and humidity.

Machinery, though will need electricity, so that needs to be considered.

This also means added costs not only to the purchase of your growing house but also to the running and maintaining of heaters and coolers.

However, once you’ve got the full setup, you can be growing crops all year round!

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Conclusion: Polytunnel or Greenhouse?

In summary, we have learned:

Pros for Greenhouse

• Will not need replacing as often.
• Looks aesthetically pleasing.
• Can come quite small, so can still have one in a small yard.

Cons for Greenhouse

• More expensive to buy.
• More difficult to put up.
• Requires a square, level foundation.
• Has less growing space.
• Can get too much sun if not positioned correctly.
• Sometimes built with better ventilation.

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Pros for Poly-tunnel

• Retains heat better.
• Cheap to buy.
• Easy to erect.
• Much more growing space, including the ground itself.
• Needs no foundation.
• Less prone to suffering from direct sunlight.
• Can be positioned on a slant.

Cons for Poly-tunnel

• Cover needs replacing every 5-10 years.
• Does not look as quant as a greenhouse, though some believe it looks more natural.
• Ventilation can be an issue but can be overcome quite easily.
• Need quite a lot of space in your yard to erect one.

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The Bottom Line

At first glance, there appears to be more Pro’s for the poly-tunnel and more Cons for the greenhouse. However, it really does depend on your personal preferences, and on what you are growing.

Many hobby gardeners are including hydroponic growing into their lives. The poly-tunnel serves better for this purpose, as it is more spacious. Of course, to use hydroponics, you would then need a power supply.

A greenhouse is great for pottering around in. Not that you cannot potter around in a poly-tunnel, because you can. But, you cannot see through the windows whilst admiring your horticultural efforts.

For the more serious gardener, the poly-tunnel offers more diversity than a greenhouse. Planting directly into the ground, and no worries about direct sunlight are two such advantages.

This, really, is the crux of the discussion.

Buy a greenhouse if you love to garden, work with pots and plants, and love to putter around. Buy a poly-tunnel if you want a larger harvest and want to maximize your plant growth.

Happy gardening!

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