Polycarbonate Greenhouse

  Best of the Best Great Value Cheapest compare 4 compare 5
  Palram Glory 8 x 8 Palram Mythos 6 x 8 Palram Harmony 6 x 4 Palram Hybrid 6 x 8 Palram Lean To 4 x 8
palram polycarbonate greenhouse 8 x 8ShedStore
palram mythos silver polycarbonate greenhouse 6 x 8ShedStore
palram harmony polycarbonate greenhouse 6 x 4ShedStore
palram hybrid 6 x 8 silverAmazon
palram 4 x 8 lean to polycarbonate greenhouseSheds.co.uk
  Roof type
Roof type Apex Apex Apex Apex Pent
  Roof thickness
Roof thickness 10mm 4mm 1mm 4mm 4mm
Framing Aluminium Aluminum – Silver Aluminum – Green Aluminum – Silver Aluminium
Door Single, hinged, locakable Single, hinged, locakable Single, hinged, locakable Single, hinged, locakable Single, hinged, locakable
  Doorway width
Doorway width 80.5cm 56.5cm 56.5cm 56.5cm 56cm
  Glazing material
Glazing material 10mm Polycarbonate twinwall Twin wall polycarbonate Clear Polycarbonate 4mm polycarbonate roof, 1mm polycarbonate walls 4mm polycarbonate roof, 1mm polycarbonate walls
  Window type
Window type Light diffusing Light diffusing Clear Diffusing roof & clear sides Diffusing roof & clear sides
  Light transmission
Light transmission 82% 82% 90% 82% 82%
Vents One auto-vent opens at 12-15C, one side louvre One roof vent One roof vent One roof vent One roof vent
Dimensions 240cm x 240cm / 7’10 x 7’10 185cm x 247cm / 6’1″ x 8’1″ 185cm x 126cm / 6’1″ x 4’2″ 185cm x 247cm / 6’1″ x 8’1″ 125cm x 244cm / 4’1
  Max height
Max height 268cm 208cm 208cm 208cm 225cm
  Other sizes
Other sizes 6′ x 8′ upto 8′ x 20′ 6′ x 4′ upto 6′ x 14′ 6′ x 4′ upto 6′ x 14′ 6′ x 4′ upto 6′ x 14′ 4′ x 2′, 4′ x 8′
Treatment Galvanized steel base Galvanized steel base Galvanized steel base Galvanized steel base Galvanized steel base
Guarantee 10 year 5 year 5 year 5 year 5 year
Summary Extra thick polycarbonate for a robust finish. Wide door with small lip for problem free entry. Auto vent and side louvre allow easy temperature control. Highly acclaimed in the gardening community. 100% protection from harmful UV. Wind resistant to 90km/hr. Built in gutters for re-using rainfall. Window vent prone to blowing open so consider upgrading this part. Thin panels flex in wind causing noise. Frame too flimsy to withstand harsh northern weather, only consider if in a sheltered position. Intelligent mix of materials to ensure diffuse light from above whilst allowing you to see in from other angles. Great option for a south facing wall. Includes wall mounting kit. Hybrid design with twin-wall roof and clear single panel sides.

Buying Guide

If you’re keen to produce more of your own food, a polycarbonate greenhouse is a great way to expand the range of fruit and veg you can grow and lengthen the growing season.

You can become more sustainable and ensure that your food is organic and free from chemicals. Over the longer term you should be able to save money on your weekly shop and benefit from tastier more nutritious food. You may even find yourself giving food away if you have a bumper crop.

Below we discuss some of the key things you should consider when buying a polycarbonate greenhouse, this covers some of the more common questions and gives some advice. If you’re ready to buy, the comparison table above should help you quickly review the key features of some of the best greenhouses available in the UK at the moment.

Design Features To Think About

  • Size is always a prime consideration and the accepted wisdom is to buy a little bigger than you think you will need.
  • Guttering and down pipes can be really useful to feed rainwater into water butts. This will allow you to use freshwater which will be free of fluoride and chlorine.
  • Air vents are a must, these will help control temperature and air flow. Some greenhouses have automatic vents which open as the temperature increases to help you control conditions without having to visit the greenhouse multiple times a day. These operate without electricity.
  • Louvres or side vents are another handy feature which can help control airflow and temperature.
  • Door width is worth checking if you think you’ll be wheeling things in and out with a wheelbarrow.
  • Whether you want clear or diffused panels will also need a little thought. This is discussed in a little more depth below.

Types of Polycarbonate Panels


These allow you a higher percentage of light to reach the plants; 90% compared to about 82% for diffused panels. They also have the benefit of allowing you to see inside the greenhouse from elsewhere in your garden, and to see out if you’re working inside.


Light diffusing panels ensure a more even distribution of light throughout the greenhouse and prevent plant burn whilst also minimising shaded areas. A twin-wall polycarbonate also retains heat more efficiently.

If your panels are rattling, add some silicon sealant to keep them secure, this can also prevent water ingress into twin walls.

Frequently Asked Questions

What is a polycarbonate greenhouse?

The key difference between a traditional greenhouse and a polycarbonate greenhouse is that plastic “polycabonate” glazing is used instead of glass. When compared to glass, polycarbonate is cheaper, lighter and able to withstand strong impacts without breaking. The material is used for safety goggles, riot shields and plane cockpits amongst other things. It doesn’t warp or discolor and it’s also one of the most easily recycled plastics.

Glass or polycarbonate greenhouse?

A polycarbonate greenhouse is typically cheaper than it’s glass counterpart due to the lower cost of the glazing. Aside from the cost it’s worth considering for the durability and safety aspect; any impacts won’t result in shattered glass which is re-assuring if you have children running around.

How thick should polycarbonate be for a greenhouse?

Typical thicknesses are 1mm sheets, 4mm twinwall and 10mm twinwall. The 1mm size is prone to flexing so is not ideal in windy areas since it. The twinwall is the preferred choice since it’s sturdier, but you need to prevent water ingress which can otherwise lead to algae type growths on the inside.

How long does a polycarbonate greenhouse last?

Most come with a 5 or 10 year guarantee, the plastic glazing shouldn’t degrade but will need occasional cleaning. If you’ve chosen a cheaper model the the frame or door hinges are more likely points of failure.

Consider adding additional latches to window vents to secure them during high winds.

Should you Buy a Cheap Polycarbonate Greenhouse?

It’s always tempting to buy the cheapest option available but it’s worth considering a few other factors. All things being equal, the smaller the greenhouse, the cheaper it is, so if you can make do with a smaller one you’ll be able to keep your costs lower.

If it’s your first greenhouse it could make sense to go for a cheaper option. As you learn new gardening techniques and how to care for plants in a greenhouse you might realise that you can live without certain features, whilst others are a must have. Your experience will inform your choices if and when you decide to upgrade to something a little bigger or a greenhouse with more vents or windows.

Strong winds?

If you live in a part of the UK with strong winds, be aware that a cheap frame may not have the inherent strength needed to withstand a constant battering. I’ve read several reviews of flimsy greenhouses being destroyed by storm systems, so if you live on an exposed coastline take a close look at how sturdy the frame looks.

Once complete, always bolt your greenhouse down firmly; a light frame can be susceptible to high winds if a door or window is blown open by a strong gust.

Lean to Polycarbonate Greenhouse

A “lean-to” has a few benefits over a free standing structure. The stability is greatly enhanced due to the attachment to a solid wall and makes the “lean to” less susceptible to strong winds; It’s not unheard of for greenhouses to be blown over, so having a solid wall serving as an anchor is a big plus.

Concrete and brick also retain heat quite well, so if placed against a south facing wall the temperature within the greenhouse will be kept higher for longer.

You may also be short of space; a lean to is narrower than most greenhouses so can be placed in smaller gardens without occupying too much space. The Palram lean to is only 4 foot wide so can be a great way to grow vegetables in a smaller garden.

Twinwall Polycarbonate

Twin wall is a lightweight yet strong panel. It’s about 200 stronger than glass at half the weight. The double wall gives a more rigid structure than single wall. This results in less flexing and a less flimsy feel than a single sheet.

The twin wall also greatly increases the thermal capacity meaning that your greenhouse will be kept warmer for longer. Durability is another benefit and guarantees of upto 15 years are commonplace.

If you do need to replace the panels for any reason, panels are cheap, widely available and can be cut to size without much fuss.

Other Polycarbonate Greenhouses we considered