Greenhouse Glazing Materials, Warranty vs Life Expectancy
I get asked a lot about how long certain greenhouse coverings will last. The thing is, the limit of the warranty does not equal the life expectancy of the material. I will address the following materials – 6 mil, 4 year polyfilm, reinforced polyfilm and polycarbonate sheets. I will be mentioning the UV protection. That is what keeps the materials from getting brittle, cracking, or turning yellow. The warranty will typically cover how long the manufacturer expects the UV protection to last, or it may refer to how much the UV protection may change in a certain period of time.
Greenhouse polyfilm is typically listed by the thickness and the length of the time that the UV protection is warranted for. 6 mil, 4 year polyfilm is 6 mil thick and has a UV protection that is warranted for 4 years. But, that does not necessarily mean that it will last the entire 4 years. The material will not get brittle, etc, but if it is damaged (due to a falling limb, hail, etc) there is a possibility that the cover will be lost. There is patching tape for the film coverings, but if you are not at the greenhouse when the damage occurs it may be too late to stop it. This will be the least expensive of the greenhouse glazing choices and is excellent for small hobby or commercial greenhouses. Although most of the commercial greenhouses will use a double layer of this film with a blower that blows air between the 2 layers. This will definitely increase the insulation factor for this material. I have had some growers report back to me that they feel the film is less likely to be damaged when using this double layer. They feel that the air between the layers “stretches” the film, making it tighter and less susceptible to damage from falling items.
The reinforced polyfilm is 2 layers of film laminated together with a rip stop feature in between the sheets. This has a one year warranty on the UV protection. But, we have had reports back from people who have gotten up to a 12 year lifetime from this material. The rip stop feature is what makes this possible. If the film does get a tear it cannot go any further than the cords of the rip stop. That will keep the area of the rip limited, and it is easily repairable once it is found.
Polycarbonate sheets are a rigid material. Many manufacturers offer a 10 year warranty that the light transmission will not vary more than 10%. The change in the light transmission is what causes the sheets to get brittle, yellow and crack. There are, however, some manufacturers out there now offering a comparable 20 year warranty. Please be sure to check with the company supplying you the sheets to see which warranty is offered. Polycarbonate is a tough material and typically has a 10 year warranty against hail damage. So, tearing or damage to the sheets is not near as big an issue as the polyfilm. In fact I have been dealing with polycarbonate sheets for over 20 years now and have never been involved in a warranty claim. I have had many people in the industry report back that they have seen polycarbonate sheets (with the 10 year warranty) last up to the 20 year mark. I personally have seen the 10 year warranty material remain usable at 15 years.
Hopefully this overview of the warranties and greenhouse glazing materials will give you the information you need to make the best decision for your greenhouse.
We couldn’t agree more!!!
Glass Greenhouses vs Polycarbonate Greenhouses
I get this question a lot. What is the difference between a glass greenhouse and a polycarbonate greenhouse. I am going to assume that the frames are basically the same, so the biggest difference will be in the glazing material.
Glass greenhouses will be more expensive than a polycarbonate greenhouse. Especially with a curved eave. The glass is all tempered (safety) glass, even the curve. The curved tempered glass is more expensive than doing a curved polycarbonate. The twinwall polycarbonate is flexible enough that it is bent right onsite as you are installing the kit. There are no special tools or processes needed to do this. You just simply bend it over into the curved frame and attach it.
Looks are another obvious difference. The glass greenhouse will have more of a timeless look to it. I suppose if you want to use the word “fancier” that could even be applied. Just in looks, not in function. A lot of people don’t like the polycarbonate glazed greenhouse as it will be translucent rather than transparent. It will not be like looking through a window like the glass greenhouse will. Twinwall polycarbonate is made up of 2 sheets, an interior and an exterior. These sheets are both clear and would look much like looking through a window if you peeled the walls apart. Multiwall polycarbonate is much like looking down the end of a cardboard box. You will have the exterior and the interior sheet with a rib in between them. The rib will run straight between the 2 sheets, not curvy like in a cardboard box. This rib is what distorts your view. You can see color in a polycarbonate greenhouse, just not a clear form.
The glass greenhouse will not be as well insulated as the polycarbonate greenhouse. A single glass greenhouse will have an R value of approximately 0.95. A 6mm twinwall polycarbonate greenhouse will have an R value of around 1.6. This means that if you have the same size single glass greenhouse and polycarbonate greenhouse in the same location, trying to heat it to the same temperature, the glass greenhouse will cost you more to heat. It seems from the difference in the R value that it would be about twice as much. That is not the case. There is a formula that uses the size of the greenhouse, the difference in the temperature inside and outside the greenhouse, and the glazing material. If this is a consideration in your instance, the best way to determine how many BTU’s you will need is to actually do the calculations.
Breakage is another issue. Tempered glass will break if it is hit in the right manner. There is just no way around it. But, it is tougher than regular float glass, and it will shatter into small pieces, so safety is not a concern. Polycarbonate has a 10 year warranty against hail damage. It is a very tough material. It will not break like the glass.
Lifetime of the glazing material is the last issue I will discuss. Glass will pretty much last forever unless it is broken. Polycarbonate generally has a warranty that the light transmission will not vary more than a specified number in 10 years. This is just a fancy way of saying that it will not turn yellow or get brittle. Some of the manufacturers have extended their warranties to 15 and even 20 years. I have personally seen sheets that were 15 years old and still in use. They looked just fine. I have had reports back of 20 year lifetime on the material.
Glass greenhouses vs polycarbonate greenhouses? What is the conclusion. They both have their benefits, it just depends on which fits best into your needs. The best decision is to make sure to get a greenhouse, no matter what type. It will give you hours of enjoyment, produce food for your family, protect your orchids, and be the envy of your friends and neighbors.
Are you building a homemade polyfim greenhouse, but are unsure about how to ventilate it? Here are a couple of solutions for you. You can see that this greenhouse has roll up sides, an option which is readily available, but can be costly. We have 2 options available that insert directly into your polyfilm covering without any additional framing. They use the channel base and wiggle wire to insert directly into the greenhouse covering. You simply cut the film and install these accessories directly into the film covering without any additional framing.
Intake Shutter with Solar Powered Opener
The first option is a solar powered greenhouse shutter. This has louvers and a wax cylinder powered opener. It will open when it is warm and close when it is cool automatically. They are available in 6 different sizes. If you would like to use this on another type of greenhouse such as polycarbonate, we can remove the base channel and you can insert this directly into a wood framed opening.
Solar Powered Roof Vent
The second way to do this is with a solar powered roof vent. This is a lightweight polycarbonate vent. It weighs less than 10 pounds, but you get all of the benefits of the durable polycarbonate covering. It also has the was cylinder powered opener that will automatically open and shut the vent as the temperature requires. To install this you simply cut the polyfilm and install it directly into the greenhouse covering.
A lot of people prefer to build their own greenhouses rather than purchase a kit. With these 2 ventilation options, there is no reason not to build your own polyfilm greenhouse.