greenhouse covers

Greenhouse Glass vs. Greenhouse Covers

So you’ve decided to build a greenhouse—now you just need to decide what materials you’ll use to cover it. Should you choose traditional greenhouse glass? Or opt for a woven greenhouse cover? In this article, we’ll detail the ins and outs of both types of greenhouse covers so you can make an informed decision.

The History of Glass Greenhouses

When you first think about building a greenhouse, it’s likely you imagine a traditional glass paneled covering. Glass has been used to grow plants in commercially controlled climates for hundreds, if not thousands of years. In fact, some of the earliest uses for glass-covered greenhouses included 17th-century orangeries—the French designed greenhouses meant to protect orange trees.

For centuries, glass has been used to warm fruits and vegetables by the sun, while keeping them safe from harsh winds and even harsher colds. Some more notable examples have included The Crystal Palace in London and the Glaspalast in Munich. But greenhouses saw a renaissance in the 1960’s when sheets of polyethylene were found to be more efficient and less expensive than their glass laden counterparts.

As polyethylene became more widely available, greenhouses grew in popularity, expanding beyond industrial agriculture and moving into the backyards of many small farms and home garden centers. The next several decades saw further advances in greenhouse materials. Durability was increased, UV protection was added, and lifespan was extended. Today polyethylene covers provide the most optimal greenhouse performance.

Is There Still a Place for Glass Greenhouses Today?

Today, glass greenhouses are used more for their traditional beauty than their agricultural functionality. Because of its high heat transfer rate—meaning cold can be easily transferred through the glass—it is the least efficient greenhouse material when it comes to retaining heat. It is also the least durable. Harsh conditions can cause the glass to break making it ineffectual not to mention expensive and time-consuming to replace.

Glass greenhouses can also be dangerous in the warm summer months. Because of their high clarity, too much light might be let into greenhouses causing plants to overheat or even burn. For all of the above reasons, glass greenhouses work best in cooler climates that require plenty of sunlight or when aesthetics are especially important.

Why Polyethylene Greenhouse Covers Are Better Than Glass

Today, most greenhouses rely on a modern form of polyethylene that is scientifically superior to its glass and even plastic predecessors. These clear, woven covers help retain humidity and warmth while protecting against pests, extreme weather, and frost. Known as BTL-12, BTL’s 12-mil greenhouse covering is the most popular.  It is thick, durable, and allows for 85% UV transfer, which allows more sunlight than other methods. Not to mention, it reflects infrared light back into the greenhouse making it the most efficient greenhouse material when it comes to retaining heat and saving money in heating costs.

BTL-12 is also extremely durable. Unlike glass, it won’t break or shatter, it is warrantied for five years, and it can be easily replaced if necessary. In the warm summer months when the sun might get a little too hot, light can be filtered through the fabric so that plants receive some or all of the light for shorter durations of time.

Growers who use light dep methods can even mimic nature’s growing season several times a year with blackout tarps that are fitted over greenhouses to control light cycles. Combined with supplemental heating and lighting, farmers can create a growing environment for year-round production. Not to mention, polyethylene greenhouse covers can be very aesthetically pleasing in gardens or small farms.

BTL’s greenhouse plastics can be fabricated in any size and finished for a broad range of applications. Our tarps are American-made from North American materials and come fully warrantied. Available for $0.25 a square foot, BTL 12 Clear Greenhouse Cover is the most efficient and affordable choice for greenhouse covering. The BTL-12 comes in a variety of thicknesses and offers an anti-condensate option. We will be offering a 20-mil clear and 10-mil clear in anti-condensate options soon. Contact us for more information.



11 responses to “Greenhouse Glass vs. Greenhouse Covers

  1. Any chance on getting a couple feet of sample BTL 12? I’m building patio/deck mini-greenhouses and plan to frame the poly as window, and not clamp to tubing or other traditional greenhouse method. Functional deck furniture. I need to work out my framing method for the “windows”. I just need to see how it bends and folds and holds.

    Thanks if you can.


  2. Thank you for your inquiry!! I would love to get some samples out to you! I have replied in a separate email!

    Julie Hughes

  3. Hi
    This BTL12 product sounds fantastic. We’re planning to build a back yard green house and would also love a sample of this product for proper planning.
    We are located in Manitoba and have harsh winters and would like your opinion as to what thickness of the product you recommend that can handle the winter elements but work well in the summers months to.

    Thank you

  4. Thank you for your online inquiry! I have replied by email for an address to send samples to!!


  5. Does this covering hold up with a PVC pipe frame? What is the projected time from order to delivery? I also would like samples.

    Thank you. Carolyn
    Bandon, OR

  6. Thank you for your inquiry Carolyn! I would be more than happy to get you samples of our greenhouse material! Please email me the address to ship them to @ Once the material is ordered and paid in full, we are 2 days out for fabrication right now and shipping to Bandon is 1-2 days for delivery.


  7. Hello!
    We have just moved to Ontario (near Cobourg) and we are making some cold frames to lengthen our growing season. They will fit on top of our raised beds. What thickness do you recommend…our winter this year has been long and cold with temperatures as low as -26 for days on end!!! I’d like to be able to have greens most of the winter, and start my tomatoes in April.
    Also- would we just staple the fabric to the wooden cold frame?

  8. Planning soon to build a 10’ x 12’ x 7’ high green house with aluminum framing. In the Atlanta, GA area.

    Need recommendation on which material to use and would like a small sample of the material. Also rough estimate on cost.

    Your product sounds perfect for us and am anxious to see it.


  9. Want to build a small greenhouse, but do not want to have to recover it every year. Also, how flexable is this oroduct? We do have some strong winds (thunderstorms). Would like small sample of BTL-12 and BTL -30 if possible.

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