A polytunnel (also known as a polyhouse, hoop greenhouse or hoophouse, grow tunnel or high tunnel) is a tunnel typically made from steel and covered in

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

, usually semi-circular, square or elongated in shape. The interior heats up because incoming

solar radiation Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible light perceptible to the human eye as well as invisible infrared (typically p ...

from the sun warms plants, soil, and other things inside the building faster than heat can escape the structure. Air warmed by the heat from hot interior surfaces is retained in the building by the roof and wall.

Temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...

and

ventilation Ventilation may refer to: * Ventilation (physiology), the movement of air between the environment and the lungs via inhalation and exhalation ** Mechanical ventilation, in medicine, using artificial methods to assist breathing *** Respirator, a ma ...

can be controlled by equipment fixed in the polytunnel or by manual opening and closing of vents. Polytunnels are mainly used in temperate regions in similar ways to glass

greenhouse A greenhouse is a structure that is designed to regulate the temperature and humidity of the environment inside. There are different types of greenhouses, but they all have large areas covered with transparent materials that let sunlight pass an ...

s and row covers. Besides the

passive solar In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...

heating that every polytunnel provides, every variation of auxiliary heating (from hothouse heating through minimal heating to unheated houses) is represented in current practice. The nesting of row covers and low tunnels inside high tunnels is also common. Superbay Polytunnel

Polytunnels can be used to provide a higher temperature and/or humidity than that which is available in the environment but can also protect crops from intense heat, bright sunlight,

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

stones, and

cold wave A cold wave (known in some regions as a cold snap, cold spell or Arctic Snap) is a weather phenomenon that is distinguished by a cooling of the air. Specifically, as used by the U.S. National Weather Service, a cold wave is a rapid fall in temp ...

s. This allows

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s and

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

s to be grown at times usually considered off season;

market garden A market garden is the relatively small-scale production of fruits, vegetables and flowers as cash crops, frequently sold directly to consumers and restaurants. The diversity of crops grown on a small area of land, typically from under to s ...

ers commonly use polytunnels for season extension. Beyond season extension, polytunnels are also used to allow cold-hardy crops to overwinter in regions where their hardiness is not quite strong enough for them to survive outdoors. Temperature increases of only above outdoor ambient, coupled with protection from the

drying Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semi-solid or liquid. This process is often used as a final production step before selling or packaging products. To be consider ...

effect of

, are enough to let selected plant varieties grow slowly but healthily instead of dying. The effect is to create a

microclimate A microclimate (or micro-climate) is a local set of atmosphere of Earth, atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as a few square m ...

that simulates the temperatures of a location several hardiness zones closer to the equator (and protects from wind as well). Bespoke Superbay Polytunnel

Every factor influencing a crop can be controlled in a polytunnel. Polytunnels are often used in

floriculture Floriculture (from ) is the study of the efficient production of the plants that produce showy, colorful flowers and foliage for human enjoyment in human environments. It is a commercially successful branch of horticulture and agriculture found ...

and

plant nurseries A nursery is a place where plants are propagated and grown to a desired size. Mostly the plants concerned are for gardening, forestry, or conservation biology, rather than agriculture. They include retail nurseries, which sell to the general ...

, as the

revenue In accounting, revenue is the total amount of income generated by the sale of product (business), goods and services related to the primary operations of a business. Commercial revenue may also be referred to as sales or as turnover. Some compan ...

value of the plants can justify the expense. In recent years the true adaptability of polytunnel structures has been realised by adapting them to suit livestock housing. It is now commonplace in the UK to see polytunnels used for housing

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

, alpacas,

goats The goat or domestic goat (''Capra hircus'') is a species of goat-antelope that is mostly kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of the famil ...

, calves and

poultry Poultry () are domesticated birds kept by humans for the purpose of harvesting animal products such as meat, Eggs as food, eggs or feathers. The practice of animal husbandry, raising poultry is known as poultry farming. These birds are most typ ...

Climatic differences

Temperate regions

Polytunnels are mainly used in temperate regions in similar ways to

s and cloches ( row covers). Modern designs allow sowing and harvesting machines to move inside the structures so as to automate production. Polytunnels have had a significant effect on the production of

strawberries The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit is appreciated f ...

in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

. Other soft fruits such as raspberries and

blackberries BlackBerry is a discontinued brand of handheld devices and related mobile services, originally developed and maintained by the Canadian company Research In Motion (RIM, later known as BlackBerry Limited) until 2016. The first BlackBerry device ...

are also cultivated in the same way. 5 bay Multi-span Polytunnel

Climate change and protected culture

In response to climate variability, many growers in colder regions are transitioning from open-field cultivation to protected agriculture using polytunnels and high tunnels. This shift allows for better control of temperature, less risk, and disease pressure—factors increasingly influenced by climate change. Large-scale projects now implement modern tunnel systems to extend growing seasons, reduce crop loss, and ensure more quality and higher yields. HARNOIS Greenhouses - Entreprises Pitre Project

HARNOIS Greenhouses - Entreprises Pitre Project

Other regions

In a tropical climate, temperatures are prone to soar above all normal levels. In such cases, foggers/misters are used to reduce the temperature. This does not increase the humidity levels in the poly house as the evaporated droplets are almost immediately ventilated to open air. High-tech poly houses even have space-heating systems as well as soil-heating systems to purify the soil of unwanted viruses, bacteria, and other organisms. The recent Indo-Israel collaboration at Gharunda, near

Karnal Karnal () is a city located in the state of Haryana, India and is the administrative headquarters of Karnal District. The city is well connected as it lies on National Highway 01, in the south of the city lies the cities of Panipat and Sonipa ...

is an excellent example of Polyhouse farming taking place in a developing country. FlockMaster Polytunnel

If developing countries were to develop a special incentive program solely for fruit-and-vegetable farmers, especially in demographically large nations like India, then the migration rate from rural to urban areas (as well as the loss of horticultural and fruit/vegetable farmers) to urban areas may be reduced. This brings a huge potential to improve the farming sector, which is key to long-term economic stability. The small polytunnels used by each farmer in each village promote the cultivation of vegetables both on-season and off-season, and would actually help to moderate the market rate for fruit and vegetables in long run, on a year-round basis, and would help to satisfy local market needs. For example, in India, the inability to grow tomatoes generates price spikes during the monsoon season. This is seen as an ideal time to grow tomatoes in polytunnels, since they provide the ideal climate for the crop. In India, the Abhinav Farmers Club grows flowers and organic vegetables in polytunnels.

Development

Hoophouses have existed at least since the 1940s, but they are much more commonly used with each passing decade, and their design continues to evolve. Because of the wide variety of constantly changing designs, in reality there is an entirely

continuous Continuity or continuous may refer to: Mathematics * Continuity (mathematics), the opposing concept to discreteness; common examples include ** Continuous probability distribution or random variable in probability and statistics ** Continuous ...

spectrum from high tunnels through low tunnels to the simplest row covers, although they are often thought about as discrete steps. Major themes of continuing development are (1) achieving the same results with lighter construction and less cost and (2) making hoophouses easily movable. The advantages of mobile hoophouses include greater

return on investment Return on investment (ROI) or return on costs (ROC) is the ratio between net income (over a period) and investment (costs resulting from an investment of some resources at a point in time). A high ROI means the investment's gains compare favorab ...

(with the same unit of investment getting greater use per year across different crops in different months) and more flexibility on

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the pro ...

without ever having to bother to dig the soil out of a stationary house (or use

soil steam sterilization Soil steam sterilization (soil steaming) is a farming technique that Sterilization (microbiology), sterilizes soil with steam in open fields or greenhouses. Pests of plant cultures such as weeds, bacteria, fungi and viruses are killed through ...

) to cure greenhouse soil sickness. A

US Department of Agriculture The United States Department of Agriculture (USDA) is an executive department of the United States federal government that aims to meet the needs of commercial farming and livestock food production, promotes agricultural trade and producti ...

program is helping farmers install polytunnels. The program was announced at the US

White House The White House is the official residence and workplace of the president of the United States. Located at 1600 Pennsylvania Avenue Northwest (Washington, D.C.), NW in Washington, D.C., it has served as the residence of every U.S. president ...

garden in December 2009. Farmers in

Iraq Iraq, officially the Republic of Iraq, is a country in West Asia. It is bordered by Saudi Arabia to Iraq–Saudi Arabia border, the south, Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq border, the east, the Persian Gulf and ...

are building these in increasing number and adding

drip irrigation Drip irrigation or trickle irrigation is a type of micro-irrigation system that has the potential to save water and nutrients by allowing water to drip slowly to the roots of plants, either from above the soil surface or buried below the surfac ...

to grow tomatoes.

References

External links

*. 11 December 2009 by {{YouTube, user= usda , title= USDA , link= no.
Polytunnels
on Hortweek 1 November 2016
Polytunnels: Second generation
on Hortweek 13 February 2015
Polytunnels – Fresh Produce
on Hortweek 6 November 2015
Polytunnels – FAQ & Buyers Guide
on First Tunnels 17 May 2023 Agricultural buildings Greenhouses Horticulture Portable buildings and shelters