“Greenhouse Guts”Lecture Series

Greenhouse Management & FloricultureAgriculture Technology Department

Plymouth High School

Feb 17

TARGETS• LECTURE: Glazings• ACTIVITY:

• Understand how the systems are used in the Plymouth HS Greenhouse• Understand how the computer controls the GH climate.• Discover the purposes of the head house

Covering (Glazing)Glass

AcrylicPolycorbonates

Vinyl (polyvinyl cholride)Polyethylene (#1 used)

G l a z I n g sFactors to Consider

when choosing a Glazing• Capital available• Desired energy savings• Crop(s) grown• Period of time the GH is in

operation• Natural environmental

conditions• Above 80% light transmission is

good

• u-value– ability of heat to move through

the product– Lower value (more heat

trapped)– High value (more heat is lost)– #/ft2/hour

• Strength of Glazing– Dead loads

• Snow• Live loads

• Google: National GH Manufacturing Association– NGMA: building codes

Glass• Thickness:

- Single Strength: (SSB): 1/16”- Double Strength (DSB): 1/8”

• Light transmission: 90%• u-value = 1.13• Life Expectancy ???(no rocks through windows)

• Cost: $3.50-7.00 per ft2 (what does this all include?)

Fiberglass Reinforced Polyester

• Dimensions: -51 ½” wide, up to 24’ long

• Cost ($.85-$1.75/ft)• 10-15 years life expectancy, UV light breaks

down fibers, turning material yellow• u= 1.2• 35% savings over glass• 88% light transmission (diffuses light)• Surface deteriorates

Acrylics• Trade names: • Exolite, Acrylite, Plexiglass, Lucite, Deglas

• Holds 10-60 lbs/ft2

• Dimensions:- 5/8” thick, ¼” flexible

• Light transmission: 83%• Build houses E-W• Heat:

– u=.56-.6– 40-50% savings over

glass

• Longevity: 10yr• Guaranty 30yr

• Growers still getting same light penetration, do not yellow

• Snow load• Flammability: can burn• $2-$4/ft2

B. Acrylics

http://www.greenhousemegastore.com/Deglas-Acrylic-Panel-16mm-Clear/productinfo/CPC-DG16/

Impact Modified Acrylic• Used a lot in the hail belts in the US• Multi-wall• 85% light transmission• 10x impact strength of acrylic (hail zones)• Like acrylic

• Tradenames: • Exolite, Lexsaon, Tuffak,

Polygal, Primex, cryoflex, qualex, Twin Wall

• ¼” thick to 5/8” thick• Width=48” Length= up to 32’

long sheets• U=.58 -.69

• (40-50% heat savings)• Good for 10yrs, light

intensity, looses 1%/yr

Polycarbonates• Fire: self-extinguishing• Light: about 80% + 1%

loss/yr• Snow: 25lbs/ft2

• Cost: $1.35, $3, $4 per ft2• Coatings available

– Anti-condensation– Acrylic for UV protection

http://site.green-house-kit.net/GrnHouseGlazingMaterials.jpg&imgrefurl

http://www.greenhousemegastore.com/Polycarbonate-Panels/departments/1034/?gclid=CKiiidvLvaQCFcPsKgod5hzwzw

Examples of glazing

Other coverings• Plastic Films

– 2-8mils (.002” - .008”)• Vinyl (polyvinyl chloride)

– 8-12 mil– $$$– 4-5yrs– Static electricity

• ETFE (ethylene Tetraflouoroethylene)– $$$

• Polyester– $$$– Durable for 7 yrs

www.farmwholesaleag.com

http://www.stuppy.com/commercial.aspx

Polyethylene• # 1 Glazing Film used– Life Expectancy 3-4 yrs– Tradenames: Visqueen

1504, Arco Tufflite• Single layer or Double layer• Light Transmission– 67% double and 87% for

single– Diffused light

• u=1.1

6ml

4ml

• Heat Savings: dbl= 40%• Dbl: stability against wind

• Cost $.06 to .09/ft2 (about $5/ft2 for entire house)

¾” to 8” spacing of too big =air currents (2” is optimum).2 to .3 static pressure

END OF TODAY

• Wednesday– Early Release