A greenhouse is a structure with a glass or plastic roof and side walls that is used for the production of ornamentals and food crops and may be used seasonally or year round. The closed environment of a greenhouse has its own unique requirements, compared with outdoor production. Pests and diseases, and extremes of heat and humidity, have to be controlled, and irrigation is necessary to provide water. Significant inputs of heat and light may be required, particularly with winter production of warm-weather crops. (Douglas Cox, ,. 2010)
Consequently covering materials are ones used to cover greenhouse structures that must permit for full light transmission. They can be rigid or flexible, double-walled or single-walled, smooth or corrugated.
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4. POLYVINYL CHLORIDE (PVC):
This is flexible film that has light transmission qualities similar to glass. This material has been used extensively in Japan. While polyethylene sheets can be wide, PVC is narrow which a disadvantage in covering greenhouses is.
PVC has a number of properties that make it desirable as a covering.
PVC has excellent resistance to wear.
PVC film reduces the transmission of long wavelength infrared radiation, resulting in less heat loss at night using PVC as a covering than using polyethylene.
PVC film is more expensive than PE film, but you can expect it to last up to 5 years. PVC plastic is available with UV protection and you can find PVC that reduces condensation.
Oxidation has little effect on PVC, but heat and light break down PVC film in 2 to 3 years.
5. ETHYLENE-VINYL ACETATE
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EVA copolymers are transparent to visible light, and allow all those wavelengths essential for photosynthesis to pass through. In addition, they have good heat retaining characteristics to an extent which depends on the vinyl acetate content.EVA copolymers have good light transmission and thermal characteristics, but some have the defects of being liable to excessive stretching and tackiness. Because these properties are influenced by the vinyl acetate content, the final use for the film will determine the type of EVA copolymer required. Films for greenhouse covers should have good resistance to stretching at high temperatures. Otherwise, on warm, windy days the film will stretch and flap on its supports and this may result in damage to the structure. For greenhouse covers, therefore, the vinyl acetate content should be less than 15%. A long life is also required for films used to cover greenhouses. Special formulations are available with UV stabilizers which give films a life of at least 3
Snyder, R. (2009). Water In The Greenhouse. Growing Produce. Retrieved on March 20, 2014 from http://www.growingproduce.com/uncategorized/water-in-the-greenhouse/
Service life In terms of the effect of service life on the polymer, this additive has a long service life. Polyvinyl chloride is a substance that has this additive inside it. Due to this the additive makes the polymer stronger and makes the product last longer.
A screened enclosure can give your home, or business area, an increase in value when sell time comes.
Today, polyvinyl chloride (PVC) is used in many different products across the world. According to the APHA (2011), the material can be found in toys, medical supplies, floors, and even food wrapping. (p. 1) I believe that this material has made it possible for a lot of products to be made that have benefited the human population, but I believe there are many drawbacks to using this material.
It is a thermoplastic resin that is retrieved by the polymerization of ethylene. PE is a semi-crystalline polymer that has excellent chemical stability. Specifically, it is able to store high quantities of water insoluble components, such as most volatile molecules, due to its polyolefin nature. This occurrence is known as the aroma scalping, which causes a diminishment of content of aroma and/ or an imbalance. The stiffness, hardness and strength of the PE attain greater heights with an increase in the density of chain branches. Not only do containers made up of PE form stiff and strong holders, but they also lead to reduced moisture vapour transmission and clarity or transparency based on the density of polymer
Most existing homes and other structures are filled with fiberglass insulation that is very inexpensive, so it keeps the initial building costs down. It actually ends up costing the owner more money, because fiberglass rarely stops air leaks efficiently. Additionally, the material has a low R value and absorb moisture so it is prone to unhealthy mold and mildew. Spray foam insulation will stop the air leaks which will save you money on your utility bills. It also has a very high R value of eight for each inch. Fiberglass only has a R value of one for each inch.
won't deteriorate over time. The plastic that gets thrown out unto the coastline drifts into
National Center for Manufacturing Sciences. (2004, August 11). Environmental Roadmapping Initiative. Retrieved October 14, 2011, from Plastics Impacts, Risks and Regulations: http://ecm.ncms.org/ERI/new/IRRPlastics.htm
It is a kind of plastic that originates from consolidating ethylene (found in unrefined petroleum) and chlorine (found in salt). At the point when joined together these substances get to be Polyvinyl Chloride (PVC) gum, or as it is better known - Vinyl. It is then further handled to be made more adaptable, inflexible, semi-fluid, clear or bright, thick or thin.
PVC is classified as a thermoplastic, which can be re-shaped in the presence of heat. Situations where temperatures reach up to 160 degrees Celsius (melting point) would cause deformation to the PVC; this would be considered a
A greenhouse gas is any gaseous compound in the atmosphere that is capable of absorbing infrared radiation, thereby trapping and holding heat in the atmosphere. By increasing the heat in the atmosphere, greenhouse gases are responsible for the greenhouse effect, which ultimately leads to global warming. (EPA Environmental Protection Agency, 2014)
Other alterations such as dying the polymer are less cost efficient to recycle and can be more difficult as well. There are certain types of HDPE (high density polyethylene) that are blown into shapes such as bottles. Different chemicals are used in this process and therefore have to be separated into their own category when recycling. The reason people have moved away from landfill dumping and moved towards recycling is due to the fact that it is much more cost effective to recycle compared to paying engineers and environmentalist to designing landfills.4 The HDPE can also be mechanically recycled through curb side pick ups.
Plants are grown under controlled and sterile conditions which reduce the risk of being exposed to pests, pathogens and diseases.
Greenhouse gases play a vital role in the regulation of the Earth's energy balance. Greenhouse gases are a group of natural compounds such as carbon dioxide, water vapor, methane, nitrous oxide, and ozone that are able to trap heat in the atmosphere, keeping the earth's surface warmer than it would if the compounds were not there. The natural gases are the essential reason of the greenhouse effect. An increase in the amount of gases in the atmosphere enhances the greenhouse effect, creating a global warming and consequently climate change. Climate change is one of the most significant threats facing the world today. However the concern and awareness regarding Green House Gases was not vital until Global Warming and Climate Change occurred affecting every living being in the plant along with our planet itself. Author William Nordhaus of Yale University conducted a consensus on the likelihood of substantial warming over the coming century.
Bamboo is a building material that is mostly used in rural communities for houses, but even Architects and Engineers are beginning to use Bamboo for it strength as a structural component and a styling agent by means of bamboo window blinds and many more. Bamboo is also commonly used as a type of construction for schools, farms and bridges. Bamboo is also used as scaffolding, shutters, a reinforcing agent for concrete and water piping, the demand for bamboo has recently increased as a new development of variety of bamboo based panels (Dunkelberg, 1992) has been constructed and incorporated into many buildings. Small buildings both non-structural and structural in nature both can be made entirely out of bamboo with the obvious exception of chimneys and fireplaces due to bamboo being a fuelling agent for fires, but it is not used alone it...