Thanks to improvements in plastic technology, manufacturers of plastic products can now modify plastics that would conventionally quickly deteriorate in outdoor settings with coatings, coextrusion and/or additives to increase their outdoor lifespan. These enhanced plastic products exhibit superior performance features and wear down less quickly when exposed to the elements. Therefore, they usually provide more years of service in outdoor environments.

If you intend to use plastic film as covering for your greenhouse, you should be aware of the factors that may affect the lifespan of the sheeting. This way, you can know how you can design and build your greenhouse covering to last longer.

Below is an overview of some top factors that can determine how long your plastic covered greenhouse will last in the outdoor life.

Exposure to the sun's UV light

The sun's UV light usually causes regular plastic film to degrade and fade much faster. The rate of degradation and discolouration varies based upon the UV stability of the plastics and the addition of UV stabilisers, coextrusions and top layers to protect the material.

To minimise the material's exposure to the UV light, you should consider the orientation of your greenhouse in relation to the sun. Building the structure at a location that does not get too much sunlight can help slow the rate at which your plastic coverings wear down.

Variations in relative humidity 

Relative humidity is the ratio of the amount of moisture present in the air to the amount of moisture needed for saturation to occur at that same temperature. Extremely high or low humidity reduces the life of plastics. 

High relative humidity provides excess moisture, which promotes damaging chemical reactions in plastic films. Low relative humidity typical of the winter weather result in desiccation of the plastics, thus leading to premature deterioration. Greenhouses with plastic film covering should have humidity control equipment, such as indoor horizontal air flow fans to help blow excess moisture out of the greenhouse when needed.

Temperature fluctuations

High temperatures within and/or outside the greenhouse can shorten the lifespan of the plastic films you use as greenhouse covering. Incorporating additives that can filter out radiative heat at the greenhouse cover or shading the roof of the greenhouse cover is an effective way to considerably reduce the heating load, thus preventing premature degradation of the covering by heat. Reducing the heating load also helps avoid overheating of the air within the greenhouse.