Greenhouse vs Polytunnel: The Pros and Cons

Choosing a greenhouse vs polytunnel can make a significant difference in how your crops and flowers grow and thrive so it’s important to consider when it comes to creating the ideal environment for your garden. Both options offer unique benefits and challenges, and understanding these can help you make the best choice for your growing space. Here’s a comprehensive look at the polytunnel vs greenhouse debate to aid in your decision-making process.

Key Similarities Between Polytunnels and Greenhouses

Both provide shelter and protection for plants from too much rain and wind, and extend the growing season possibilities.

Shelter and Protection for Plants

When it comes to greenhouse vs polytunnel, both act as protective sanctuaries for plants, shielding them from extreme weather and pests. However, they do so in slightly different ways:

  • Greenhouses: With their rigid frames and glass panels, greenhouses are particularly effective at insulating against cold weather, making them ideal for tender plants and seedlings. The clear glass not only keeps plants warm but also enhances the aesthetic appeal of your garden. Making them a perfect space for mastering chilli seedling care.
  • Polytunnels: Known for their flexibility and cost-effectiveness, polytunnels use metal hoops covered with polythene to create a warm, protected environment. The polytunnel gardening setup is less permanent than a greenhouse, making it easier to move or adjust as needed.
Drone overhead photo greenhouses and polytunnel in october 20231K

Extension of the Growing Season

Both greenhouses and polytunnels allow you to start your planting season earlier and extend it later into the season, which is a boon for producing a more abundant harvest. Here’s how they compare:

  • Greenhouses: Glass or polycarbonate greenhouses are excellent at retaining heat, which can be a major advantage for heat-loving plants.
  • Polytunnels: While they heat up quickly, polytunnels also lose heat faster than greenhouses. However, they can be quickly adjusted to accommodate sudden weather changes, providing a more adaptable environment for a variety of plants.

Importance of Ventilation

I learned the hard way that good airflow is crucial no matter which you choose, to keep plants healthy. My first year growing chillies, I underestimated how fast a greenhouse can overheat on a sunny day.

The air got so hot and stuffy, my cherished plants wilted before my eyes. That painful lesson taught me that proper airflow is critical in both greenhouses and polytunnels to prevent diseases and manage internal temperatures:

  • Greenhouses: Equipped with vents and sometimes automatic opening mechanisms, greenhouses offer sophisticated solutions to manage airflow, helping to keep the internal climate ideal for plant growth.
  • Polytunnels: These structures typically include manual options for ventilation, such as rolling up the sides. Although this method is less refined than greenhouse systems, it is effective and straightforward to use.

One thing I learned last year – polytunnels get hot very quickly. Whilst some of my super hot chillies thrived, other chillies did not do so well with the heat.

Keep an eye on heat and moisture and be prepared to make changes.

Fundamental Differences – Greenhouse vs Polytunnel

The options differ in their structural materials, design, and flexibility. Polytunnels are usually made of polythene and are used for growing a variety of plants, while greenhouses often feature toughened glass panels and are designed to create the best possible growing conditions for specific plants.

Initial and ongoing costs also vary greatly between the two structures.

Barney in polytunnel walking around the hydroponics plants

Structural Materials and Design

Choosing the right structure involves understanding the materials and construction of each option:

  • Greenhouses: Offer durability and a classic look with materials like aluminum and glass. These materials are more resistant to weathering and can significantly enhance the visual appeal of your garden. But they take more time to install – why not watch the timelapse of my largest greenhouse being built?
  • Polytunnels: Use simpler, more affordable materials like polythene stretched over metal hoops. This design allows for easier and cheaper modifications and expansions.

Initial and Ongoing Costs

Budget and value for money is a major consideration when choosing between a greenhouse and a polytunnel:

  • Greenhouses: Demand a higher initial investment but generally have lower long-term maintenance costs, especially if constructed with durable materials like toughened glass.
  • Polytunnels: Buying a polytunnel is cheaper upfront, they require the polythene covering to be replaced every few years, which can add to long-term costs.
view from outside greenhouse with chilli plantrs bursting at the seams

Greenhouse vs Polytunnel: The Pros and Cons

DurabilityPro: Greenhouses constructed with toughened glass are incredibly durable and can last a lifetime without the need for structural replacement.Con: The polythene cover of a polytunnel needs regular replacement every few years, which can add to the long-term costs and effort.
Temperature RegulationPro: Thanks to the thermal properties of glass, greenhouses maintain internal temperatures more effectively, which is crucial for extending growing seasons in colder climates.Con: Polytunnels heat up and cool down quickly, which can be less effective for heat retention and maintaining optimal growing conditions.
Environmental ImpactPro: Glass, a renewable material, offers an eco-friendlier option compared to the plastics used in polytunnels, contributing less to long-term environmental damage.Con: Frequent replacement of the polythene contributes to environmental waste, as it is not as easily recyclable as glass.
Light QualityPro: The clarity of glass allows for excellent light transmission directly to the plants without the need for diffusion, promoting healthier plant growth.Con: While diffusing light can benefit some plants, polytunnels generally have lower light transmission compared to glass, which may affect plant growth.
VentilationPro: Greenhouses are often equipped with advanced ventilation systems, including auto-venting windows that respond to temperature changes, ensuring optimal growing conditions.Pro: Polytunnels typically have manual options for ventilation, such as rolling up the sides. It is effective and straightforward to use.
Aesthetic and Structural IntegrityPro: A greenhouse typically provides a more permanent structure that enhances the aesthetic appeal of any garden.
CostCon: The initial cost of a greenhouse is significantly higher—often five to six times more than a similarly sized polytunnel.Pro: Polytunnels are a far cheaper option upfront, making them accessible for gardeners on a budget.
Construction Requirements/TimeCon: If you’re looking to build a greenhouse you need a perfectly level and square base, which can complicate setup and limit placement options. However, a base can be made from paving slabs, concrete or a wooden frame.Pro: Typically, a polytunnel can be set up much quicker than a greenhouse and if you have a slightly uneven surface, it’s not the end of the world.
Expansion/Flexibility in SetupCon: Once set up, expanding a greenhouse is more complex and costly compared to extending a polytunnel.Pro: Extending a polytunnel is as simple as adding more hoops and covering material. The construction of polytunnels is forgiving of ground irregularities, and they are easier to erect than greenhouses.
AdaptabilityPro: Mistakes during the construction of a polytunnel can be easily adjusted without affecting its functionality.
Keeping it Clean/DisinfectionPro: While greenhouses might require more meticulous cleaning due to issues like algae and complex structural components (like shelving and glass panes), they are generally easier to clean due to the durability and resistance of materials like glass and metal.Con: Polytunnels, though perhaps quicker to air out and initially wipe down, can face difficulties with the polythene covers becoming stained or degraded.
Collecting RainwaterPro: Most greenhouses come with gutters and allow you to collect rainwater. As you know, I prefer using rainwater to water my chillies and other vegetables.Con: Polytunnels do not easily allow for the collection of rainwater.

Decision-Making Guide

When it comes time to deciding – greenhouse vs polytunnel, consider these factors:

  1. Budget: Assess both the initial cost and potential long-term expenses.
  2. Space: Whether you have a garden or an allotment, determine how much room you have and what structure best fits that space.
  3. Climate: Match the structure to your local weather conditions—greenhouses for colder climates and polytunnels for areas with milder weather.
  4. Plant Needs: Choose based on what you plan to grow. Delicate plants might thrive better in the controlled environment of a greenhouse, while hardier plants can benefit from the versatility of a polytunnel.

Greenhouse vs Polytunnel – Conclusion

In wrapping up, we’ve debated the pros and cons of greenhouse vs polytunnel and I’ve shared my thoughts and experiences, which I hope you found useful. We’ve covered practical factors like materials, cost, and purpose to guide you in making an informed decision.

Understanding these structures will lead to more efficient plant growth and better yields

Remember, deciding which structure is best is key to creating the perfect growing conditions for your plants in any climate.

Still not sure? Watch the video for a quick recap:


1. What’s the main difference between greenhouse vs polytunnel?

The main difference lies in their structure and material. Greenhouses are often made of clear glass or plastic panels, offering more durability but at a higher cost. Polytunnels, on the other hand, use a metal frame covered with plastic sheeting—more affordable and easier to set up but may need replacing every few years.

2. Can both greenhouses and polytunnels extend my growing season?

Absolutely! Both constructions serve the same purpose—to protect your plants from bad weather conditions and create ideal growing conditions that can extend your growing season. Depending on where you are in the world and your setup it could provide you with year-round growing space.

3. Are there any cooling tips for greenhouses to prevent overheating?

Yes, indeed! To avoid vulnerable plants from overheating during hot days, you can shade or paint some of the glass to reduce the quantity of light coming in or keep all doors and vents open to achieve effective ventilation.

4. How often do I need to replace polytunnel covers?

Polytunnel covers typically need to be replaced every few years due to wear and tear from weather exposure—unlike greenhouses which types can last for many years without needing such frequent maintenance.

5. Which is better for taller plants, a greenhouse or polytunnel?

Greenhouses usually allow taller plants thanks to their solid structure with an opening on the roof or side vents that can also help manage temperature by providing similar cooling effects as found in commercial polytunnels.

6. How do shading needs differ between these structures?

Plants inside greenhouses might need more shading compared to those in polytunnels since clear glass can intensify sunlight exposure—polytunnels retain heat well but diffuse light more evenly across your plants.

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