Updated: July 14, 2019
Although greenhouses have been in use for centuries, it wasn’t until the 20th century that they started popping up frequently in backyards across America. It wasn’t an increased interest in gardening or growing tropical plants that did it, it was the invention of a material that revolutionized life for everyone. That magic material was plastic—and without it, the world would be a very different place today.
Gardeners love plastic greenhouses
There are lots of reasons to love and embrace a plastic greenhouse, but probably the best is the price. Plastic greenhouses, whether they’re constructed using polycarbonate panels or plastic sheeting, are affordable and appear at a number of price points, depending on just how elaborate of a structure you’re shopping for. From plastic high tunnels to portable greenhouses with roll up doors, the choices of shapes and sizes are overwhelming, and much less expensive than their glass counterparts.
Like glass greenhouses, plastic greenhouses can be very clear and allow a lot of light to penetrate, although you can also choose a more opaque plastic if you need to filter more light out for plants that can’t tolerate as much direct sunlight. Unlike glass, though, plastic greenhouses can be picked up and moved much more easily since both plastic panels and sheeting are significantly more shatter resistant and flexible.
Plastic is also easier to keep warm than glass and suffers less heat loss overall, especially when you’re using double-walled panels. If you need to add an exhaust fan or vent after construction is complete, it’s as simple as cutting a properly sized hole, where with glass you always risk shattering the panel you’re working on. You never know when you’ll need more air circulation, the easy adaptability of plastic greenhouses make them excellent for DIY projects.
Plastic isn’t good everywhere
Even though plastic is an excellent solution for many gardeners, there are some drawbacks to this space-aged material as a greenhouse skin. Plastic really shines in calm, moderate climates, but it has a number of problems in areas with more violent weather. Plastic, especially plastic films, suffer badly when exposed to extremes, such as:
Heavy snows – Plastic greenhouses aren’t typically designed with snow loads in mind, so when heavy snows build up on your building’s skin, it may bow, warp or collapse.
High winds – Boy, I could tell you stories about high winds and plastic greenhouses—if your building isn’t properly anchored (and sometimes even if it is), the relative light weight of these greenhouses means they can be picked up and tossed around by spring winds and summer storms. Plastic films may also tear loose, so keep a roll of duct tape handy.
Excessive heat – Plastic varies widely in its tolerance to heat, but plastic films tend to take heat very personal. Exposing your filmed or bagged plastic greenhouse to excessive heat and bright sunlight will accelerate the breakdown of the skin, shortening its useful life.
Polycarbonate greenhouses have few serious drawbacks, but their plastic-sheeted counterparts can be real trouble if you’re planning on using them over the long haul. Even under the best of conditions, these structures must be reskinned every few years—you can’t recycle plastic sheeting, so all that old, torn plastic will have to go into the landfill. This may be the biggest, most serious drawback to using a plastic sheet skinned greenhouse.
Deciding between glass and plastic? Read Glass Greenhouse vs. Plastic Greenhouse—Pros and Cons>>