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So, you’ve got this dream in your head. You want a greenhouse, square in the middle of your backyard, so you can grow the biggest, fattest, juiciest tomatoes on the block and start your seedlings earlier for a higher yield. Every gardener knows the feeling, and many gardeners have looked at their materials, found that they’re a little low on plexiglass, and asked, can I build a greenhouse without a clear roof?
So, does a greenhouse need a clear roof? A greenhouse needs a transparent roof because sunlight must shine in for the greenhouse to work its magic. A nonclear roof will hinder or block the sun’s rays and therefore won’t heat the greenhouse as desired.
This article will talk about what makes a greenhouse a greenhouse and discuss why it needs a clear roof. We’ll also look at a couple of different materials that you can use for a greenhouse roof and talk about which one is most cost-effective.
Why Does a Greenhouse Need a Clear Roof?
Without further ado, let’s jump right into the main question.
A greenhouse is a fickle thing. Too much shade covering the greenhouse, and you won’t be getting enough heat for your plants. Too little, and some of your plants may be getting too much sunshine. But no sunshine at all- now that’s a problem.
You see, a greenhouse lives and breathes on sunshine. Here’s how it works- a clear roof, made from glass or plastic, will let sunlight in while blocking out the circulation of the surrounding air. That means that as the sunshine strikes objects in your greenhouse, the air heats up gradually until you reach that sweet spot only a greenhouse can allow.
Without a clear roof, sunlight can’t get into your greenhouse. This means that you won’t be getting any of the warmth from the sun, and ultimately, you won’t be giving your plants any distinct advantage.
Now, let’s make this clear- having a semitransparent roof won’t kill your plants, so long as they’re receiving sunshine. But a greenhouse with an opaque roof is just as good as a house with a window- so why go to the trouble of building a whole new structure when you could just grow plants in your window?
The real advantage of a greenhouse lies in a combination of sunlight, constant temperatures, and decent hydration. If you ever had a high school biology class, you’ll likely remember an experiment where your teacher had you put bags doused in water over plants and then measure plant growth.
What students do in this experiment is create a makeshift greenhouse. Heat is trapped in the bag, allowing the plant to thrive at a constant temperature, while evaporated water circulates evenly amongst the leaves.
Now imagine you spray-painted the bag. Do you think you would get the same outcome? Most likely, the plants you would grow in these conditions would be stunted and small, nothing like what you would have gotten if you had allowed for a clear or translucent surface.
So, all in all, if you want to get the most out of your greenhouse plants, you’re going to want a clear roof. Clear rooves allow sunlight to pass into your greenhouse, which allows heat to spread evenly throughout it. This creates the tropical environment some of your plants love.
What Materials to Use for a Greenhouse Roof?
If you’re reviewing your options for a clear greenhouse roof, you might be blown away by how expensive a greenhouse can get. While we recognize that a higher price will usually deliver better results, we also acknowledge that there are always corner-cutting options for stingy gardeners.
Read on for a comprehensive list of materials you might use on your greenhouse project.
Alright, here’s an option that might break the bank if you’re working with limited funds.
Polycarbonate is such a great material because it’s light, portable, and exceedingly easy to build with. Making rooves and other structures out of sheet glass takes hours of research and, without practice, you’re likely to cause hairline cracks and other complications that will really derail your project.
Polycarbonate is different because, while it’s almost as clear as a good sheet of glass, it’s as easy to build with as corrugated tin. If you’ve got a drill, hammer, or nail gun, you can create impressive, useful greenhouses with very little polycarbonate.
All this maneuverability doesn’t come without a price, though. A sheet of corrugated polycarbonate, the kind most frequently used for greenhouse projects, will most likely run you up somewhere above 30 bucks a sheet.
Considering the fact that you might need just around 15-30 sheets, depending on the size of your build, this can get a little expensive.
But, if you’ve got the money on-hand, corrugated polycarbonate can make for an excellent building material that will allow sunshine into your greenhouse while keeping your plants insulated from fluctuating temperatures.
Corrugated polycarbonate is good, but polycarbonate twinwall is better. So- so much better.
The problem with corrugated polycarbonate is that it’s hard to insulate. Those curved surfaces mean that gardeners have to come up with unique solutions to keep the edges impregnable while maintaining a decent amount of circulation for their plants. After all, too much humidity and heat is a bad thing too.
Polycarbonate twinwall solves this problem by creating a transparent surface that’s flat on both sides. With two flat faces to work with, amateur builders will have a much easier time insulating their greenhouses.
Polycarbonate twinwall isn’t without its drawbacks, however. On average, polycarbonate twinwall costs around double what you’d pay for corrugated polycarbonate. This means that whatever price you’re estimating for your greenhouse will be doubled when using polycarbonate twinwall.
All that being said, polycarbonate twinwall is a unique surface with distinct advantages. Its dual-layered design means that it insulates a greenhouse like no other material and keeps temperatures constant even on the chilliest of spring nights. If you want a really dependable greenhouse, polycarbonate twinwall (Amazon link) may just be the way to go.
We promised more cost-effective solutions to your greenhouse issues, and we’re going to provide them. Plastic sheeting is a cost-effective solution that will insulate your greenhouse while letting in the sunlight your plants need to survive and thrive.
If you’re looking for a more cost-effective solution to the greenhouse lining problem, you’re looking for a good roll of plastic sheeting (Amazon link). a 100 ft. X 20m ft. roll of plastic sheeting likely won’t cost you any more than $120, and unless you’re building an especially gigantic greenhouse, this will likely be enough to insulate and cover the whole thing.
We see plastic sheeting being used in all sorts of exciting ways. For example, some people create mini makeshift greenhouses with little PVC hoops and a single roll of sheeting. These small greenhouses rise to the level of a gardener’s knee but can keep cold-tolerant plants growing all winter.
If plastic sheeting can do this, imagine what it can do for your heat-loving plants in the summer. While it’s more translucent than transparent, plastic sheeting allows an ideal amount of light to pass through your greenhouse roof and provide your plants with the sunshine they need to survive and thrive.
Do Greenhouses Always Need Direct Sunlight?
To take advantage of your greenhouse’s clear roof, you’re going to want as much sunlight as you can get. To do this, direct sunlight is best. If you want your greenhouse to remain a warm, nurturing environment for your precious plants, you’ll want direct sunlight.
When we’re talking about greenhouses, we’re essentially talking about two different things: shady greenhouses and sunny greenhouses.
Sunny greenhouses will work best for most kinds of plants because what type of plant doesn’t like a fair bit of warmth and an adequate amount of sunlight?
On the other hand, Shady greenhouses are most common in city or town environments, where backyards are often penned up behind walls and houses- not the best conditions for direct sunlight.
A greenhouse can work to protect your plants from animals and harmful insects in a shady environment, but only if your plants are geared to grow in the shade.
That being said, you’ll still want that clear roof. While shade-loving plants can grow in low-light environments, they still need some sunlight to grow. You’ll be hard-pressed to find a plant that can grow in complete darkness, and an opaque greenhouse roof is likely to provide something near these conditions.
If you want to build a shady greenhouse with less exposure to sunlight, make sure to tailor your growing repertoire to your greenhouse’s conditions. Shady greenhouses require shady plants, and there are plenty of decent options for low-sunlight growing.
All in All
All in all, a greenhouse with an opaque roof is just as good as growing plants in an indoor window. It offers protection from insects and animals, and that’s about it. Without the clear roof, your greenhouse just won’t let sunlight in, and it won’t incubate your plants.