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GREENHOUSE GLAZINGS

GREENHOUSE GLAZINGS. Glass Film Plastic Rigid-Panel. GLASS. Float-1/8” double strength common in US Light Transmission: Single Layer = 88%-94% Double Layer= 77% High air filtration High thermal conductivity Lower relative humidity $2.00-$7.00 ft 2 Low impact resistance

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GREENHOUSE GLAZINGS

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  1. GREENHOUSE GLAZINGS • Glass • Film Plastic • Rigid-Panel

  2. GLASS • Float-1/8” double strength common in US • Light Transmission: Single Layer = 88%-94% Double Layer= 77% • High air filtration • High thermal conductivity • Lower relative humidity • $2.00-$7.00 ft2 • Low impact resistance • Life Span = 25+years

  3. PLASTIC FILMS • Polyethylene • Vinyl • Polyvinyl Fluoride • Polyester • Tefzel

  4. PLASTIC FILMS POLYETHYLENE • Major film used in the US • 6-mil exterior / 4-mil interior layers (double layer for insulation) • UV inhibitors increase life span; 3 to 4 year life • Antifog materials = less condensation problems • IR blockers = less heat loss

  5. PLASTIC FILMS POLYETHYLENE • Costs (per layer) • 6¢/ft2 for 3-year film (UV inhibitor added) • 7¢/ft2 for 3-year + antifog • 8¢/ft2 for 3-year + IR blocker • 9¢/ft2 for 3-year + antifog + IR blocker • Labor to recover = 12¢/ft2 to 23¢/ft2 of ground area covered by greenhouse (not of roof area)

  6. PLASTIC FILMS VINYL • Polyvinyl Chloride • 8 and 12 mil films (4 and 5 year life) • 21.5¢/ft2 for 12 mil • Static charge is bad • Used in Japan

  7. PLASTIC FILMS POLYVINYL FLUORIDE • Tedlar • 95¢/ft2 for 4 mil / 2 mil tube

  8. PLASTIC FILMS POLYESTER • Mylar • Too expensive for glazing but is used for shade cloth material

  9. PLASTIC FILMS TEFZEL T2 • Ethylene tetrafluoroethylene • Should last 20 years • 95% light transmission for single layer • 91% light transmission for double layer • More IR loss than polyethylene • $1.20/ft2 (but lasts 20 years) • Use limited by 50-inch width limit right now

  10. RIGID-PANEL • Polyvinyl Chloride • Fiberglass-Reinforced Plastic (FRP) • Acrylic and Polycarbonate

  11. RIGID-PANEL POLYVINYL CHLORIDE (PVC) • Has been phased out for the most part • 2+ year life span • 4x the cost of polyethylene film • Light exposure = dark and brittle

  12. RIGID-PANEL FIBERGLASS-REINFORCED PLASTIC (FRP) • more popular in past • 5-20 yr. life expectancy, depending on grade • panels flexible enough to conform to the shape of quonset frames • transmits 88-90% PAR • -$1.00 ft2

  13. RIGID-PANEL FIBERGLASS-REINFORCED PLASTIC (FRP) • more resistant to breakage than glass • light distribution more uniform than glass because  • less expensive to cool (20% less than glass) • fewer structural members than glass • FRP surface subject to etching by dust abrasion • glass lasts indefinitely, FRP may last half lifetime of grower

  14. RIGID-PANEL ACRYLIC AND POLYCARBONATE • Double or triple-layer • 10 yr. Life • Often coated to prevent condensation drip; acrylic coating on polycarbonate slows UV degradation Corrugated Polycarb

  15. RIGID-PANEL ACRYLIC AND POLYCARBONATE • Used for glazing side and end-walls • 8mm-16mm thick, thinner can be bent, thicker cannot • Acrylic-83% PAR; • Polycarbonate-79% PAR • Acrylic-$2.10 ft2 • Polycarbonate-$1.60 ft2 Acrylic

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