GREENHOUSE GLAZINGS

Glass

Film Plastic

Rigid-Panel

GLASSFloat-1/8” double strength common in US Light Transmission: Single Layer = 88%-94%Double Layer= 77%High air filtrationHigh thermal conductivity Lower relative humidity$2.00-$7.00 ft2

Low impact resistanceLife Span = 25+years

PLASTIC FILMS

Polyethylene

Vinyl

Polyvinyl Fluoride

Polyester

Tefzel

POLYETHYLENEMajor film used in the US6-mil exterior / 4-mil interior layers (double layer for insulation)UV inhibitors increase life span; 3 to 4 year lifeAntifog materials = less condensation problemsIR blockers = less heat loss

PLASTIC FILMS

POLYETHYLENECosts (per layer)6¢/ft2 for 3-year film (UV inhibitor added)7¢/ft2 for 3-year + antifog8¢/ft2 for 3-year + IR blocker9¢/ft2 for 3-year + antifog + IR blockerLabor to recover = 12¢/ft2 to 23¢/ft2 of

ground area covered by greenhouse (not of roof area)

PLASTIC FILMS

VINYLPolyvinyl Chloride

8 and 12 mil films (4 and 5 year life)

21.5¢/ft2 for 12 mil

Static charge is bad

Used in Japan

PLASTIC FILMS

POLYVINYL FLUORIDETedlar

95¢/ft2 for 4 mil / 2 mil tube

PLASTIC FILMS

POLYESTERMylar

Too expensive for glazing but is used for shade cloth material

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

PLASTIC FILMS

RIGID-PANEL

Polyvinyl Chloride

Fiberglass-Reinforced Plastic (FRP)

Acrylic and Polycarbonate

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

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

RIGID-PANEL

FIBERGLASS-REINFORCED PLASTIC (FRP)

more resistant to breakage than glasslight 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 abrasionglass lasts indefinitely, FRP may last half lifetime of grower

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

RIGID-PANEL

Corrugated Polycarb

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

RIGID-PANEL

Acrylic