The main difference between plastic and tarp beside the cost is the tear resistance. The 12 mil tarps are much more tear resistant than the plastic. The other key differences are price and life expectancy.

Plastic is the less expensive option of the covers that we offer, and is 7.2 mil and available in white or clear. It generally runs between 15¢-20¢/sqft depending on the size piece you require. Life expectancy is 6-7 years for single layer plastic or 6-8 years for double plastic. 7.2 mil plastic is also available with an anti-condensate and infrared coating for even greater drip control and heat savings (see below for more info on these). Clear plastic comes with a 5 year warranty against deterioration by the sun, and white has a 4 year warranty against deterioration by the sun.

Plants need clear plastic to grow and flourish. Clear plastic is also used for swimming pool covers, as both applications require sunshine to come through. The white plastic is best when more shade is required and is ideal for livestock. It is slightly cooler inside the structure than the clear option. White plastic is also recommended for swimming pool applications where more privacy is required, as well as covering RVs or other equipment where fading would be an issue.

For greenhouses, swimming pools or livestock, we usually recommend a double cover, with roll up sides and an inflator fan. Double covers extend the life expectancy of the cover, reduce heat loss by 30%, which helps maintain the temperature in the structure, as well as reduce condensation. The small inflator fan that we offer and include in the double cover package prices, uses very little electricity and is left running all the time to keep air between the two layers so you can reap the benefits of the double cover.

Plastic can also come with an anti condensate coating which will reduce or eliminate dripping in your greenhouse. This is a detergent additive which will eventually work itself out of the plastic. This happens more quickly if you have very high humidity levels in your greenhouse. The cost is roughly 10% more then regular 7.2 mil plastic and is only available in full rolls (100′ or more).

One other variation on greenhouse plastic is that with an IR (infra-red) coating. The cell structure that this plastic is made from is significantly different from the regular plastic. This gives the plastic a much softer texture and feel and contributes to it not being as strong as regular plastic. This is why we suggest that it only be used as the inside layer of a double plastic installation. The slight restriction for people with shorter greenhouses is that the IR plastic only comes in 100′ and 150′ rolls. You would either have a friend who can buy/use the extra or be prepared to “waste” some. There are also not quite as many choices for available widths as with regular plastic.

The IR plastic can reduce your heat loss by up to 20% over a regular double poly installation. Even though this plastic has a hazy look to it, the light transmission properties are actually a couple percentage points better. This plastic comes standard with an anti-condensate coating which means there will be less dripping in the greenhouse. All of these features make IR plastic an attractive alternative for many people in spite of the fact that the cost is roughly 20% more then regular plastic. This plastic does not have an inside or outside.
Please call Norm to specifically inquire about more information regarding these special coatings.

Over the last year, our plastic supplier has been transitioning to a heavier and stronger plastic film as a structure covering. 
6mil mil UV stabilized plastic has been around for a long time. This has now been changed to 7.2 mil. This is a stronger material which is expected to last longer as well. 
With the extra weight (20% increase) there is an extra cost but with the extra projected life span, the cost per year should be about the same. 
This applies to both the clear and the white.
The IR plastic (infrared) has also been upgraded to 7.2 mil. This is a heat saving plastic with anti drip properties. Since it is also now stronger, it is okay to use as an outside layer.
There are a lot of references on our website and in our literature to 6mil plastic. We are going to do our best to get these all changed as quickly as we can.
We thank you for your patience and understanding and above all we thank you for your interest and business!
Norm

Tarp is more expensive than the plastic options, but is also more durable if equipment, car doors or hay might bump against the cover frequently. It is a 12 mil three ply woven material, available in white. It generally runs between 65¢-85¢/sqft depending on the size piece you require. Life expectancy is 8-10 years for the white tarp.  White tarp a 6 year warranty against deterioration by the sun.

Our white tarp consists of a white, clear and white layer. The white tarp is less noticeable in the summer (than other colours) especially once it is not new and clean, if camouflaging is a concern. The white tarp also lets light in, making it easier to work inside the structure because it’s not as dark inside. Tarps are fully waterproof.

Our white plastic is available in widths of 24′, 32′, 40′ and 48′. Our clear plastic is available in widths of 25′, 28′, 32′, 36′, 40′, and 48′. Our white tarp is available in widths of 25′, 32′, and 36′. A full roll of plastic is considered as 100 or more feet and is sold in multiples of 5′ for length.

One of the less often used roof coverings is the twin wall polycarbonate. It is generally considered to be a 15 year material and it has extremely high impact resistance. The double wall with honey comb shaped flutes also gives it very good heat retention properties for a light transmitting material. It is considered as a rigid material but it does have enough flex to be installed on our gothic shaped structures. This material sells for $2.50 – $3.00 per square foot and the structure also requires some modification. This material can also be used as an end and/or door covering when durability and appearance are extra considerations.

Whichever covering option you choose, it’s important you receive all the benefits you require for your application. We are able to assist you in weighing the options further, as well as providing you a sample of each for your review. We look forward to helping you find the cover solution that best fits your needs.