Keeping Warm With Polycarbonate

Posted: November 20, 2013 in Outdoor, Polycarbonate
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One of the most common inquiries a plastic distributor will get is for the use of plastics in consumer, outdoor applications. And the majority of those will be for material to build a greenhouse or used in a cold frame. There are two important terms to know: “R-value” and “U-value” and as often happens with technical terms – they get confused! But we’re here to help with a brief crash course.

U-Value: this measures heat loss through a material. As you might expect, with a greenhouse you want that number to be as low as possible. Like your score in golf. There is a complicated formula but don’t worry about it, any reputable distributor would be able to get that value for you from the plastic manufacturer. For more info on U-values check out this writeup on here.

R-Value: Perhaps this could be seen as the mirror image of the U-value because the R-value measures heat trapped. IE. the values that we would typically ascribe to insulation. This is also the value most often used by contractors for household insulation (engineers prefer the U-value). In the case of R-value you want the highest number possible. Numbers that exceed 2.00 are very good, numbers that exceed 3.00 are excellent…In the case of household insulation.

For a greenhouse, twin-wall polycarbonate (6mm thick) usually has an R-value of around 1.5 and this is fine because the design of the polycarbonate, with its many cells, is what traps heat and increases the R-value. Polycarbonate with more than two walls, such as 16mm triple wall, is available and can have R-Values up to 2.5 – but it is more difficult to get ahold of and far more expensive.

With increased thickness comes a tradeoff in the amount of light that passes through the material. This is combined with the tradeoff for the increased price of triple wall (16mm). For most home greenhouses twin-wall will work just fine.

Please contact us if you have any questions or would like a quote on Redwood Plastics’ twin-wall polycarbonate.Polycarbonate-Greenhouse

CDN: 1 800 667 0999
USA: 1 866 733 2684


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