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6mm VS 4mm Polycarbonate in Greenhouse


The polycarbonate panels play a crucial role in the agricultural market place. Their ability to allow abundant light into the interior spaces, lightweight and easy to install properties have been the key advantage for their popularity, especially in greenhouses. 

A hard and durable greenhouse can offer a long-term cost saving, and they are not only used to protect the plants, but it is also used as a state-of-the-art garden feature.

There quite a number of polycarbonate profiles available in the market, however, when it comes to the insulation value of polycarbonates, a twin-wall polycarbonate sheet greenhouse is preferred.

 As a nation, we have a long history of gardening enthusiasm. In recent years, we have seen numerous new traders starting importing greenhouses into New Zealand. However, the majority of the new traders are bringing the 4mm thick polycarbonate greenhouses, due to their cheaper retail price. 

After seeing plenty of disappointed owners of 4mm greenhouse - a lot of these doesn't last for one season, we decide to write this information to help you make the right choice when you choose a greenhouse. 


1. Insulation

"R-value" is a commonly used term to measure a material’s energy conserving (or insulating) properties. It is a measure of resistance that a material has to the flow of heat. The below R-values reflect real-world outdoor situations.The more energy conserving a material is, the higher it’s R-value.

Glass, single layer 0.9

Polycarbonate 4mm 1.3

Glass double layer 1.5-2.0

Polycarbonate 6mm 1.6

The 50% greater air gap between the walls, creates 20% effectiveness in heat protection. 


2. Strength

2mm doesn't seem a lot, but 6mm sheet is 50% thicker than a 4mm sheet. Also, the aluminum profile is made thicker and wider to accommodate the extra thickness. 


3.Light Diffusion

6mm polycarbonate sheets have 5-10% less light transmission than 4mm ones. This might sound like a reduction in light transmission, but it is diffused by the polycarbonate, which means light gets more evenly distributed to what would be darker areas in your greenhouse.


4. Lifespan

4mm is the entry level greenhouse, most of these are made aiming for the lowest cost. Thus the majority of these we have seen from NZ greenhouse market, are made from recycled material. Some of the 4mm polycarbonate sheets are not even UV treated, which won’t last few months under NZ weather.