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How to Choose a Greenhouse or Polytunnel

Updated: Jul 28, 2020

You know you want to take your gardening to the next level but the choices are endless! Greenhouse or polytunnel? And then which combination? One rule applies - always buy the biggest you can afford, as long as it’s strong given Ireland‘s stormy weather!

Greenhouse versus Polytunnel

  • Polytunnels are cheaper so you’ll get more growing space for your money

  • Polytunnels are better suited for growing directly in the ground

  • Greenhouses typically retain heat better than polytunnels and are useful for seed starting early in the season and for tropical plants

  • Greenhouses tend to last longer than polytunnels which must be recovered every 5-10 years

Choosing a Greenhouse

  • Aluminium or Wood? Most greenhouses on the market are made of anodised aluminium. It‘s a cheaper lighter material so is easier to ship and handle when installing. However if you live in an extremely windy area, a wooden greenhouse is heavier and more resistant to wind. Red cedar is the traditional wooden choice as it has natural preservatives and doesn’t require ongoing treatment.

  • Polycarbonate or Horticultural glass or safety glass? Polycarbonate retains heat better and if included is best placed for the roof, as it lets less light through than glass. For glass always choose safety glass as if horticultural glass breaks it can be dangerous while safety glass will not disintegrate into shards. Ideally a minimum of 10mm thick polycarbonate and 4mm thick glass.

  • Other important points to watch out for: make sure the greenhouse has bar capping to hold the glass in place. If it only has clips they are likely to pop out during a storm. look for extra reinforcement bars in the greenhouse. Staging (shelves) along the full length of the greenhouse also help to strengthen it. An integrated base makes it easier to install and again strengthens the greenhouse. Look for models that have as many vents and windows are possible to prevent overheating in summer.

Choosing a Polytunnel

  • I love a bargain as much as anyone but please stay away from cheap polytunnels if you want it to last more than the summer, unless you are in an extremely sheltered location. Expect to pay a minimum of €500 for a Polytunnel. Cheaper polytunnels are made from plastic hoops or weak metal hoops which will twist in the first strong storm. They will also tend to be very light and have a tendency to fly off once it’s windy.

  • Polycarbonate or Polythene? Polycarbonate looks a lot neater and will retain heat in your greenhouse better. However it may have a tendency to pop out during storms, placing the whole polytunnel at risk. It also makes a lot of noise when there is wind! Polythene needs to be very tightly installed and wont look as neat, but stands up better in expose areas to storms, it will need to be replaced every 5-8 years.

  • Other important points to watch out for: even in Ireland polytunnels can reach 40-50C in summer! So ideally find a Polytunnel with roll up sides to let the heat out in summer!

hopefully that makes your decision a bit easier!

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