“greenhouse guts” lecture series greenhouse management & floriculture agriculture technology...
TRANSCRIPT
“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