Greenhouse vs. Polytunnel – Which one is better?

Both, a greenhouse and a polytunnel, are used for growing crops and flowers. People usually hesitate which one to choose as both structures serve the same purpose. To make the right choice, buyers should know the difference between a greenhouse and a polytunnel.

One of the most common questions people ask is how to prepare the ground for a polytunnel or a greenhouse. Yet, there are several factors, such as ventilation, heat retention, etc. to pay attention to, as well. They play a major role when deciding which structure suits your requirements better.

What to keep in mind

Site Preparation and Construction:

Polytunnels can be constructed on a slightly uneven surface in a day. Greenhouses take longer to install. They should be also erected on a perfectly flat and levelled surface. There are several ways to prepare the ground for your greenhouse:

  • Paving slabs base – They allow you to plant crops and flowers only into pots.
  • Compacted soil base – You can plant your crops directly into the ground.
  • Compacted soil and paving slabs base – It allows you to plant both in the soil and in containers.

People consider paving slabs to be the best base for a greenhouse. It helps prevent damp build-up and fungal problems, as well as diseases that uncovered soil can develop. Both types of structures should face North-South to avoid direct sunlight.


Most of the plants may dry out if a change in temperature occurs. Polytunnels offer a much better control over its air circulation. Large doors at both ends provide sufficient air flow through the tunnel. Greenhouses provide ventilation through an opening on the roof, the door and side vents. Keep all doors and vents open during sunny days to achieve effective ventilation.


When it comes to longevity, there isn’t much of a difference between greenhouses and polytunnels. Both types can last for many years. Polytunnels can last between 15-20 years but the covers need to be replaced every few years. A common question asked is “How long does a polytunnel cover last?”. Well, this will depend on where you’ve positioned the polytunnel structure. The plastic covers need a little care, too so you can ensure that they stay in good condition for a few years. Place your polytunnel on a spot, protected from strong winds. Clean the covers regularly from fallen leaves and trim nearby foliage. This will keep your polytunnels in good condition for longer.

Most greenhouses may even last for a lifetime if they are well taken care of. We have several tips on how to maintain a greenhouse:

  • Scrub the windows to let more sunlight in.
  • Frequently check and maintain the heating system components.
  • Clean the floors and tables regularly.
  • Let ladybugs and spiders in to control pests.

Which one is better looking:

Greenhouses can be the highlight of any garden, especially if they have a fancy design. They come in various shapes and models that you can choose from. Orangeries, Dwarf Wall or Victorian Style greenhouses are the most popular designs on the market.

Polytunnels, however, are a far more practical option but not so appealing. They can also come in various shapes, forms and sizes – each of them – with their own benefits. For instance, semi-circular arc-shaped polytunnels allow the rain to run easily off the surface. High-tent polytunnels, on the other hand, allow taller plants, such as tomatoes, to grow as high as they need.

Heat Retention and Shading:

These constructions protect crops from bad weather conditions. They create a pleasant environment by retaining heat and moisture. The plastic sheeting that polytunnels use also affects heat retention. Note that green polytunnel covers do not let enough light permeate through the tunnel. This makes transparent covers a much better option. Condensation issues in polytunnels can be resolved by installing Thermal Anti-Fog covers, which effectively reduce moisture levels. This type of sheeting can also improve heat retention.

Greenhouses offer maximum heat retention and better light transmission. But they are vulnerable to overheating, which is why plants need more shading. There are several ways to achieve that. Some people paint some of the glass panels to reduce the quantity of light coming through the structure. Fitting partially your greenhouse with external blinds will also have a similar cooling effect. The fixtures effectively prevent the sun’s rays from passing through the glass. Internal blinds, on the other hand, stimulate heat generation as the sun passes through the glass.

Internal Microclimate:

Specialised equipment controls the temperature, humidity, air flow and irrigation systems. Polytunnels are prone to drought and so are greenhouses. You might need to add an extra layer of bubble insulation to protect your plants better in cold weather.

The benefits of rainwater collection

Water collection is an important factor to keep in mind. Rainwater harvesting has many benefits. It is an eco-friendly process, a money saver and a nutrients supplier. Greenhouses are easier to adapt than polytunnels, with regards to fitting them with an effective rainwater harvest system. Well, a good solution to the water collection problem in polytunnels is using a gutter system. You can install a rainwater gutter to one of the sides of your polytunnel, leading straight into a water tank. This way, you’ll have sufficient quantity of irrigation water that you can use whenever you need to.