Recessed Lighting FAQ

Q: What is recessed lighting?

A: Recessed lighting refers to fixtures that are set into ceilings or walls. Commonly called cans because of their shape, they include the housing (the internal part in the ceiling that you don't see) and the trim, which is visible. With little or no profile, recessed lighting provides effective ambient and accent illumination for both residential and commercial use.

Q: Which type of housing should I use: Remodel or New Construction?

A: There are two types of housings, New Construction and Remodel. Determining which type to use will depend on your application. If you have access to your ceiling from above, you will want to use a New Construction housing. If you do not have access, you will want to use a Remodel housing.

Q: What is the difference between IC vs. Non-IC rated housings?

A: IC rated housings allow insulation (either laid in or blown in) to be installed on or around the housing. Non-IC housings require that insulation be kept at least 3" away from the housing at all times.

Q: How many lights am I going to need?

A: This question has no easy answer, as opinions on this subject vary greatly. However, a good rule of thumb is to take the height of the ceiling and divide it in half. This is the distance that each light should be from one another. For example, a room with an 8' ceiling, should have lights approximately 4' from one another (8' ceiling / 2 = 4' apart). The total number of lights will also be affected by the type and wattage of bulb being used. Spot lights with narrow beams will produce pockets or pools of light, while flood type bulbs will produce broader amounts of light.

Q: Can I use a dimmer?

A: Yes, a dimmer can be used on most recessed lighting. Line Voltage recessed lighting can be dimmed with a standard incandescent dimmer. While Low Voltage recessed lighting will be dimmed with either a Low Voltage Electronic or Magnetic dimmer. The type of transformer (Electronic or Magnetic) used in the housing will determine which type of dimmer you need.

Q: What is meant by Air-Tight down light and why would I want to use one?

A: Any air-tight rated down light has demonstrated in an independent testing laboratory environment that it will prevent air flow through the fixture. This is important because it saves money in heating and cooling costs. Just as important, some state regulations are now requiring that new home construction use this type of down light.

Q: Can I use a CFL or LED bulb in a Line Voltage Housing and Trim?

A: Yes, CFL and LED bulbs can be used in Line Voltage Housings and Trims. These types of bulbs are readily available in Par, R and A shaped bulbs. It's important to note, that the shape of the bulb should be as close to the bulb specified by the manufacture as possible. For example, if the housing and trim are recommending a Par/R shaped bulb, the CFL or LED bulb should be in a Par/R shape. Spiral CFL bulbs can be used as they have the same socket base as a Par/R bulb, however due to the length and width of some bulbs, the light pattern given off by the bulb and the overall look, may not be what was originally intended.

Q: Can recessed lights be installed in a bathroom?

A: Yes, recessed lighting trims and housings are suitable for damp locations (porch or bathroom) using any trim. Wet locations, above a shower or outdoors, require the use of specific wet location trims.

Q: Why Consider Die Cast Trims over Stamped Trims?

A: Aluminum die cast trims provide stronger construction, more precise shapes and superior heat dissipation properties than corresponding stamped metal options. Die cast trims are stronger due to their single piece construction versus a stamped trim that is made up of multiple pieces of metal that are fastened or welded together. The die cast process produces trims with tighter tolerances than stamping, thus resulting in greater precision of shapes with smoother edges. Stamped trims are similar in appearance to die-cast trims as they utilise the same powder coat finish. In summary, die cast trims look similar in appearance the corresponding stamped trim, but die cast trims are superior quality.

** Above useful information is from YLighitng.com. Thanks for it!

Hydroponics is basically growing plants without soil. It is a more efficient way to provide food and water to your plants. Plants don’t use soil – they use the food and water that are in the soil. Soil’s function is to supply plants nutrients and to anchor the plants’ roots. In a hydroponic garden, you provide your plants with a complete nutrient formula and an inert growing medium to anchor your plants’ roots so they have easier access to the food and water.

Because the food is dissolved in water, it goes directly to the roots. Plants grow faster and are ready for harvest sooner. You can grow more plants in the same space as you can with a soil garden, and since there’s no soil, there’s no worry about soil-borne diseases or pests – and no weeding.

Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, biochar, mineral wool,expanded clay pebbles or coconut husk.

Researchers discovered in the 18th century that plants absorb essential mineral nutrients as inorganic ions in water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics. Hydroponics is also a standard technique in biology research and teaching.

Origin

Soilless culture

Gericke originally defined hydroponics as crop growth in mineral nutrient solutions. Hydroponics is a subset of soilless culture. Many types of soilless culture do not use the mineral nutrient solutions required for hydroponics.

Plants that are not traditionally grown in a climate would be possible to grow using a controlled environment system like hydroponics. NASA has also looked to utilize hydroponics in the space program. Ray Wheeler, plant physiologist at Kennedy Space Center’s Space Life Science Lab, believes that hydroponics will create advances within space travel. He terms this as a bioregenerative life support system.

Advantages

Some of the reasons why hydroponics is being adapted around the world for food production are the following:

• No soil is needed for hydroponics.
• The water stays in the system and can be reused - thus, a lower water requirement.
• It is possible to control the nutrition levels in their entirety - thus, lower nutrition requirements.
• No nutrition pollution is released into the environment because of the controlled system.
• Stable and high yields.
• Pests and diseases are easier to get rid of than in soil because of the container's mobility.
• Ease of harvesting.
• No pesticide damage.

Today, hydroponics is an established branch of horticulture. Progress has been rapid, and results obtained in various countries have proved it to be thoroughly practical and to have very definite advantages over conventional methods of horticulture.

There are two chief merits of the soil-less cultivation of plants. First, hydroponics may potentially produce much higher crop yields. Also, hydroponics can be used in places where in-ground agriculture or gardening are not possible.

Disadvantages

Without soil as a buffer, any failure to the hydroponic system leads to rapid plant death. Other disadvantages include pathogen attacks such as damp-off due to Verticillium wilt caused by the high moisture levels associated with hydroponics and over watering of soil based plants. Also, many hydroponic plants require different fertilizers and containment systems.^[10]

Techniques

The two main types of hydroponics are solution culture and medium culture. Solution culture does not use a solid medium for the roots, just the nutrient solution. The three main types of solution cultures are static solution culture, continuous-flow solution culture and aeroponics. The medium culture method has a solid medium for the roots and is named for the type of medium, e.g., sand culture, gravel culture, or rockwool culture.

There are two main variations for each medium, sub-irrigation and top irrigation^[specify]. For all techniques, most hydroponic reservoirs are now built of plastic, but other materials have been used including concrete, glass, metal, vegetable solids, and wood. The containers should exclude light to prevent algae growth in the nutrient solution.

Static solution culture

In static solution culture, plants are grown in containers of nutrient solution, such as glass Mason jars (typically, in-home applications), plastic buckets, tubs, or tanks. The solution is usually gently aerated but may be un-aerated. If un-aerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen. A hole is cut in the lid of the reservoir for each plant. There can be one to many plants per reservoir. Reservoir size can be increased as plant size increases. A home made system can be constructed from plastic food containers or glass canning jars with aeration provided by an aquarium pump, aquarium airline tubing and aquarium valves. Clear containers are covered with aluminium foil, butcher paper, black plastic, or other material to exclude light, thus helping to eliminate the formation of algae. The nutrient solution is changed either on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter. Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added, A Mariotte's bottle, or a float valve, can be used to automatically maintain the solution level. In raft solution culture, plants are placed in a sheet of buoyant plastic that is floated on the surface of the nutrient solution. That way, the solution level never drops below the roots.

Continuous-flow solution culture

In continuous-flow solution culture, the nutrient solution constantly flows past the roots. It is much easier to automate than the static solution culture because sampling and adjustments to the temperature and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants. A popular variation is the nutrient film technique or NFT, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is recirculated past the bare roots of plants in a watertight thick root mat, which develops in the bottom of the channel and has an upper surface that, although moist, is in the air. Subsequent to this, an abundant supply of oxygen is provided to the roots of the plants. A properly designed NFT system is based on using the right channel slope, the right flow rate, and the right channel length. The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen, and nutrients. In all other forms of production, there is a conflict between the supply of these requirements, since excessive or deficient amounts of one results in an imbalance of one or both of the others. NFT, because of its design, provides a system where all three requirements for healthy plant growth can be met at the same time, provided that the simple concept of NFT is always remembered and practised. The result of these advantages is that higher yields of high-quality produce are obtained over an extended period of cropping. A downside of NFT is that it has very little buffering against interruptions in the flow, e.g., power outages. But, overall, it is probably one of the more productive techniques.

The same design characteristics apply to all conventional NFT systems. While slopes along channels of 1:100 have been recommended, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas. As a consequence, it is recommended that slopes of 1:30 to 1:40 are used. This allows for minor irregularities in the surface, but, even with these slopes, ponding and water logging may occur. The slope may be provided by the floor, or benches or racks may hold the channels and provide the required slope. Both methods are used and depend on local requirements, often determined by the site and crop requirements.

As a general guide, flow rates for each gully should be 1 liter per minute. At planting, rates may be half this and the upper limit of 2 L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems. Depressed growth rates of many crops have been observed when channels exceed 12 metres in length. On rapidly growing crops, tests have indicated that, while oxygen levels remain adequate, nitrogen may be depleted over the length of the gully. As a consequence, channel length should not exceed 10–15 metres. In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed halfway along the gully and reducing flow rates to 1 L/min through each outlet.

Aeroponics

Aeroponics is a system wherein roots are continuously or discontinuously kept in an environment saturated with fine drops (a mist or aerosol) of nutrient solution. The method requires no substrate and entails growing plants with their roots suspended in a deep air or growth chamber with the roots periodically wetted with a fine mist of atomized nutrients. Excellent aeration is the main advantage of aeroponics.

Aeroponic techniques have proven to be commercially successful for propagation, seed germination, seed potato production, tomato production, leaf crops, and micro-greens.^[11] Since inventor Richard Stoner commercialized aeroponic technology in 1983, aeroponics has been implemented as an alternative to water intensive hydroponic systems worldwide.^[12] The limitation of hydroponics is the fact that 1 kg of water can only hold 8 mg of air, no matter whether aerators are utilized or not.

Another distinct advantage of aeroponics over hydroponics is that any species of plants can be grown in a true aeroponic system because the micro environment of an aeroponic can be finely controlled. The limitation of hydroponics is that only certain species of plants can survive for so long in water before they become waterlogged. The advantage of aeroponics is that suspended aeroponic plants receive 100% of the available oxygen and carbon dioxide to the roots zone, stems, and leaves,^[13] thus accelerating biomass growth and reducing rooting times. NASA research has shown that aeroponically grown plants have an 80% increase in dry weight biomass (essential minerals) compared to hydroponically grown plants. Aeroponics used 65% less water than hydroponics. NASA also concluded that aeroponically grown plants requires ¼ the nutrient input compared to hydroponics. Unlike hydroponically grown plants, aeroponically grown plants will not suffer transplant shock when transplanted to soil, and offers growers the ability to reduce the spread of disease and pathogens. Aeroponics is also widely used in laboratory studies of plant physiology and plant pathology. Aeroponic techniques have been given special attention from NASA since a mist is easier to handle than a liquid in a zero gravity environment.

Passive sub-irrigation

Passive sub-irrigation, also known as passive hydroponics or semi-hydroponics, is a method wherein plants are grown in an inert porous medium that transports water and fertilizer to the roots by capillary action from a separate reservoir as necessary, reducing labour and providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water or on a capillary mat saturated with nutrient solution. The various hydroponic media available, such as expanded clay and coconut husk, contain more air space than more traditional potting mixes, delivering increased oxygen to the roots, which is important in epiphytic plants such as orchids and bromeliads, whose roots are exposed to the air in nature. Additional advantages of passive hydroponics are the reduction of root rot and the additional ambient humidity provided through evaporations.

Ebb and flow or flood and drain sub-irrigation

In its simplest form, there is a tray above a reservoir of nutrient solution. Either the tray is filled with growing medium (clay granules being the most common) and planted directly or pots of medium stand in the tray. At regular intervals, a simple timer causes a pump to fill the upper tray with nutrient solution, after which the solution drains back down into the reservoir. This keeps the medium regularly flushed with nutrients and air. Once the upper tray fills past the drain stop, it begins recirculating the water until the timer turns the pump off, and the water in the upper tray drains back into the reservoirs.^[14]

Run to waste

In a run to waste system, nutrient and water solution is periodically applied to the medium surface. This may be done in its simplest form, by manually applying a nutrient-and-water solution one or more times per day in a container of inert growing media, such as rockwool, perlite, vermiculite, coco fibre, or sand. In a slightly more complex system, it is automated with a delivery pump, a timer and irrigation tubing to deliver nutrient solution with a delivery frequency that is governed by the key parameters of plant size, plant growing stage, climate, substrate, and substrate conductivity, pH, and water content.

In a commercial setting, watering frequency is multi factorial and governed by computers or PLCs.

Commercial hydroponics production of large plants like tomatoes, cucumber, and peppers use one form or another of run to waste hydroponics.

In environmentally responsible uses, the nutrient rich waste is collected and processed through an on site filtration system to be used many times, making the system very productive.^[15]

Deep water culture

The hydroponic method of plant production by means of suspending the plant roots in a solution of nutrient-rich, oxygenated water. Traditional methods favor the use of plastic buckets and large containers with the plant contained in a net pot suspended from the centre of the lid and the roots suspended in the nutrient solution. The solution is oxygen saturated from an air pump combined with porous stones. With this method, the plants grow much faster because of the high amount of oxygen that the roots receive.^[16]

Bubbleponics

"Bubbleponics" is the art of delivering highly oxygenated nutrient solution direct to the root zone of plants. While Deep Water Culture involves the plant roots hanging down into a reservoir of water below, the term Bubbleponics describes a top-fed Deep Water Culture (DWC) hydroponic system. In this method, the water is pumped from the reservoir up to the roots (top feeding). The water is released over the plant's roots and then runs back into the reservoir below in a constantly recirculating system. As with Deep Water Culture, there is an airstone in the reservoir that pumps air into the water via a hose from outside the reservoir. The airstone helps add oxygen to the water. Both the airstone and the water pump run 24 hours a day.

The biggest advantages with Bubbleponics over Deep Water Culture involve increased growth during the first few weeks. With Deep Water Culture, there is a time where the roots have not reached the water yet. With Bubbleponics, the roots get easy access to water from the beginning and will grow to the reservoir below much more quickly than with a Deep Water Culture system. Once the roots have reached the reservoir below, there is not a huge advantage with Bubbleponics over Deep Water Culture. However, due to the quicker growth in the beginning, a few weeks of grow time can be shaved off.^[17]

Fogponics

Fogponics Fogponics is an advanced form of aeroponics which uses water in a vaporised form to transfer nutrients and oxygen to enclosed suspended plant roots. Using the same general idea behind aeroponics except fogponics uses a 5-10 micron mist within the rooting chamber and as use for a foliar feeding mechanism.

Rotary

A rotary hydroponic garden is a style of commercial hydroponics created within a circular frame which rotates continuously during the entire growth cycle of whatever plant is being grown.

While system specifics vary, systems typically rotate once per hour, giving a plant 24 full turns within the circle each 24 hour period. Within the center of each rotary hydroponic garden is a high intensity grow light, designed to simulate sunlight, often with the assistance of a mechanized timer.

Each day, as the plants rotate, they are periodically watered with a hydroponic growth solution to provide all nutrient necessary for robust growth. Due to the plants continuous fight against gravity plants typically mature much more quickly than when grown in soil or other traditional hydroponic growing systems. Due to the small foot print a rotary hydroponic system has, it allows for more plant material to be grown per sq foot of floor space than other traditional hydroponic systems.

Substrates

One of the most obvious decisions hydroponic farmers have to make is which medium they should use. Different media are appropriate for different growing techniques.

Expanded clay aggregate

Expanded clay pebbles.

Baked clay pellets, are suitable for hydroponic systems in which all nutrients are carefully controlled in water solution. The clay pellets are inert, pHneutral and do not contain any nutrient value.

The clay is formed into round pellets and fired in rotary kilns at 1,200 °C (2,190 °F). This causes the clay to expand, like popcorn, and become porous. It is light in weight, and does not compact over time. The shape of an individual pellet can be irregular or uniform depending on brand and manufacturing process. The manufacturers consider expanded clay to be an ecologically sustainable and re-usable growing medium because of its ability to be cleaned and sterilized, typically by washing in solutions of white vinegar, chlorine bleach, or hydrogen peroxide (H
2O
2), and rinsing completely.

Another view is that clay pebbles are best not re-used even when they are cleaned, due to root growth that may enter the medium. Breaking open a clay pebble after a crop has been grown will reveal this growth.

Growstones

Growstones, made from glass waste, have both more air and water retention space than perlite and peat. This aggregate holds more water than parboiled rice hulls.^[18]

Coir

Coco Peat, also known as coir or coco, is the leftover material after the fibres have been removed from the outermost shell (bolster) of the coconut. Coir is a 100% natural grow and flowering medium. Coconut Coir is colonized with trichoderma Fungi, which protects roots and stimulates root growth. It is extremely difficult to over water coir due to its perfect air-to-water ratio, plant roots thrive in this environment, coir has a high cation exchange, meaning it can store unused minerals to be released to the plant as and when it requires it. Coir is available in many forms, most common is coco peat, which has the appearance and texture of soil but contains no mineral content.

Rice Hulls

Parboiled rice hulls (PBH) decay over time. Rice hulls allow drainage,^[19] and even retain less water than growstones.^[18] A study showed that rice hulls didn't affect the effects of plant growth regulators.^[19] Rice hulls are an agricultural byproduct that would otherwise have little use.

Perlite

Perlite is a volcanic rock that has been superheated into very lightweight expanded glass pebbles. It is used loose or in plastic sleeves immersed in the water. It is also used in potting soil mixes to decrease soil density. Perlite has similar properties and uses to vermiculite but, in general, holds more air and less water. If not contained, it can float if flood and drain feeding is used. It is a fusion of granite, obsidian, pumice and basalt. This volcanic rock is naturally fused at high temperatures undergoing what is called "Fusionic Metamorphosis".

Pumice

Like perlite, pumice is a lightweight, mined volcanic rock that finds application in hydroponics.

Vermiculite

Like perlite, vermiculite is a mineral that has been superheated until it has expanded into light pebbles. Vermiculite holds more water than perlite and has a natural "wicking" property that can draw water and nutrients in a passive hydroponic system. If too much water and not enough air surrounds the plants roots, it is possible to gradually lower the medium's water-retention capability by mixing in increasing quantities of perlite.

Sand

Sand is cheap and easily available. However, it is heavy, does not hold water very well, and it must be sterilized between use.

Gravel

The same type that is used in aquariums, though any small gravel can be used, provided it is washed first. Indeed, plants growing in a typical traditional gravel filter bed, with water circulated using electric powerhead pumps, are in effect being grown using gravel hydroponics. Gravel is inexpensive, easy to keep clean, drains well and will not become waterlogged. However, it is also heavy, and, if the system does not provide continuous water, the plant roots may dry out.

Wood fibre

Wood fibre, produced from steam friction of wood, is a very efficient organic substrate for hydroponics. It has the advantage that it keeps its structure for a very long time. Wood fibre has been shown to reduce the effects of "plant growth regulators."^[19]

Sheep wool

Wool from shearing sheep is a little-used yet promising renewable growing medium. In a study comparing wool with peat slabs, coconut fibre slabs, perlite and rockwool slabs to grow cucumber plants, sheep wool had a greater air capacity of 70%, which decreased with use to a comparable 43%, and water capacity that increased from 23% to 44% with use. Using sheep wool resulted in the greatest yield out of the tested substrates, while application of a biostimulator consisting of humic acid, lactic acid and Bacillus subtilis improved yields in all substrates.^[20]

Rock wool

Rock wool (mineral wool) is the most widely used medium in hydroponics. Rock wool is an inert substrate suitable for both run to waste and recirculating systems. Rock wool is made from molten rock, basalt or 'slag' that is spun into bundles of single filament fibres, and bonded into a medium capable of capillary action, and is, in effect, protected from most common microbiological degradation. Rock wool has many advantages and some disadvantages. The latter being the possible skin irritancy (mechanical) whilst handling (1:1000). Flushing with cold water usually brings relief. Advantages include its proven efficiency and effectiveness as a commercial hydroponic substrate. Most of the rock wool sold to date is a non-hazardous, non-carcinogenic material, falling under Note Q of the European Union Classification Packaging and Labeling Regulation (CLP).^{[citation needed]}

Brick shards

Brick shards have similar properties to gravel. They have the added disadvantages of possibly altering the pH and requiring extra cleaning before reuse.

Polystyrene packing peanuts

Polystyrene packing peanuts are inexpensive, readily available, and have excellent drainage. However, they can be too lightweight for some uses. They are used mainly in closed-tube systems. Note that polystyrene peanuts must be used; biodegradable packing peanuts will decompose into a sludge. Plants may absorb styrene and pass it to their consumers; this is a possible health risk.^{[citation needed]}

Nutrient solutions

Plant nutrients used in hydroponics are dissolved in the water and are mostly in inorganic and ionic form. Primary among the dissolved cations (positively charged ions) are Ca²⁺ (calcium),Mg2+
 (magnesium), and K+
 (potassium); the major nutrient anions in nutrient solutions are NO−
3 (nitrate), SO2−
4 (sulfate), and H
2PO−
4 (dihydrogen phosphate).

Numerous 'recipes' for hydroponic solutions are available. Many use different combinations of chemicals to reach similar total final compositions. Commonly used chemicals for the macronutrients include potassium nitrate, calcium nitrate, potassium phosphate, and magnesium sulfate. Various micronutrients are typically added to hydroponic solutions to supply essential elements; among them are Fe (iron), Mn (manganese), Cu (copper), Zn (zinc), B (boron), Cl (chlorine), and Ni (nickel). Chelating agents are sometimes used to keep Fe soluble, and humic acids can be added to increase nutrient uptake.^[21] Many variations of the nutrient solutions used by Arnon and Hoagland (see above) have been styled 'modified Hoagland solutions' and are widely used. Variation of different mixes throughout the plant life-cycle, further optimizes its nutritional value.^[22] Plants will change the composition of the nutrient solutions upon contact by depleting specific nutrients more rapidly than others, removing water from the solution, and altering the pH by excretion of either acidity or alkalinity.^[23] Care is required not to allow salt concentrations to become too high, nutrients to become too depleted, or pH to wander far from the desired value.

Although pre-mixed concentrated nutrient solutions are generally purchased from commercial nutrient manufacturers by hydroponic hobbyists and small commercial growers, several tools exists to help anyone prepare their own solutions without extensive knowledge about chemistry. The free and open source tools HydroBuddy^[24] and HydroCal^[25] have been created by professional chemists to help any hydroponics grower prepare their own nutrient solutions. The first program is available for Windows, Mac and Linux while the second one can be used through a simple Java interface. Both programs allow for basic nutrient solution preparation although HydroBuddy provides added functionality to use and save custom substances, save formulations and predict electrical conductivity values.

The well-oxygenated and enlightened environment promotes the development of algae. It is therefore necessary to wrap the tank with black film obscuring all light.

Organic hydroponics uses the solution containing microorganisms. In organic hydroponics, organic fertilizer can be added in the hydroponic solution because microorganisms degrade organic fertilizer into inorganic nutrients. In contrast, conventional hydroponics cannot use organic fertilizer because organic compounds in the hydroponic solution show phytotoxic effects.

Commercial

Some commercial installations use no pesticides or herbicides, preferring integrated pest management techniques. There is often a price premium willingly paid by consumers for produce that is labelled "organic". Some states in the USA require soil as an essential to obtain organic certification. There are also overlapping and somewhat contradictory rules established by the US Federal Government, so some food grown with hydroponics can be certified organic. Most hydroponically grown produce cannot be sold as organic due to the fact that they do not use soil as a growing medium.

Hydroponics also saves water; it uses as little as ¹⁄₂₀ the amount as a regular farm to produce the same amount of food. The water table can be impacted by the water use and run-off of chemicals from farms, but hydroponics may minimize impact as well as having the advantage that water use and water returns are easier to measure. This can save the farmer money by allowing reduced water use and the ability to measure consequences to the land around a farm.

To increase plant growth, lighting systems such as metal-halide lamp for growing stage only or high-pressure sodium for growing/flowering/blooming stage are used to lengthen the day or to supplement natural sunshine if it is scarce. Metal halide emits more light in the blue spectrum, making it ideal for plant growth but is harmful to unprotected skin and can cause skin cancer. High-pressure sodium emits more light in the red spectrum, meaning that it is best suited for supplementing natural sunshine and can be used throughout the growing cycle. However, these lighting systems require large amounts of electricity to operate, making efficiency and safety very critical.

The environment in a hydroponics greenhouse is tightly controlled for maximum efficiency, and this new mindset is called soil-less/controlled-environment agriculture (CEA). With this growers can make ultra-premium foods anywhere in the world, regardless of temperature and growing seasons. Growers monitor the temperature, humidity, and pH level constantly.

Hydroponics have been used to enhance vegetables to provide more nutritional value. A hydroponic farmer in Virginia has developed a calcium and potassium enriched head of lettuce, scheduled to be widely available in April 2007. Grocers in test markets have said that the lettuce sells "very well", and the farmers claim that their hydroponic lettuce uses 90% less water than traditional soil farming.^[26]

Advancements

With pest problems reduced, and nutrients constantly fed to the roots, productivity in hydroponics is high, although plant growth can be limited by the low levels of carbon dioxide in the atmosphere, or limited light exposure. To increase yield further, some sealed greenhouses inject carbon dioxide into their environment to help growth (CO
2 enrichment), add lights to lengthen the day, or control vegetative growth, etc.

Choosing The Right Hydroponic System

Choosing a system is the first step in a successful hydroponic gardening experience. Consider your available space, lighting, budget, and time constraints before purchasing any equipment or settling on a unit to build yourself. Also think about what you want to grow, whether you may want to expand, and recurring costs.

The simplest way to start is with a passive system. These use a wicking material to draw nutrients up to the roots, or the root tips are suspended in a stationary solution with the main portion of the rootball hanging in the air. Passive systems are affordable and easy to build yourself. They are best suited for smaller plants. Active systems are best for larger plants and gardens. An active system uses a pump and timer to flow nutrients around the plant’s roots and to provide aeration. It costs more, but is more efficient and requires less attention, since the pump and timer handle everything automatically. Once you’ve looked at passive vs. active systems, you’ll need to choose between media-based and water culture systems.

Media-based systems such as ebb-and flow (flood-and-drain), top-feed (drip), or bottom-feed systems rely on a growing medium to support the plants and hold nutrient solution around their roots. Most operate on timers, alternately wetting the medium to wash out salts and replenish nutrients and then draining so the plants can draw in atmospheric oxygen. Setup is more complex, costs are higher, and media needs to be replaced occasionally. These systems need to be protected from power outages, which can leave vulnerable roots high and dry if the pump stops functioning. On the other hand, these systems are super efficient, since nutrients are recycled back into the reservoir, and use of timers means they need less attention from you.

Water culture systems usually operate without media. Plants are anchored in a plank that floats on the reservoir, suspending the roots in the nutrient solution. This kind of system is simple and inexpensive to set up and is great for water-loving plants, though special care must be taken if you want to use it with large plants. You can use rockwool cubes or small amounts of gravel to anchor plants like tomatoes and cucumbers that get top heavy when they start to bear fruit. You can also use plastic flaps, foam rings, fiber cups, or plastic collars for plant support, or tie plants to a trellis.

Commercial growers have been using efficient hydroponic methods for years. There's no worry about soil-born diseases or pests, and there's no weeding. For professional growers, quicker harvests and higher yields are good reasons to use hydroponics.

Most commercial Hydropoinc Equipment Manufacturers have adapted these proven techniques to convenient home gardening systems. They have incorporated high performance technology with quality professional-grade materials, and designed a full range of systems for your personal use.

Grow Lights Basics

Most commercial Hydropoinc Equipment Manufacturers have taken highly effective but cumbersome commercial greenhouse technology and created a broad selection of high intensity lighting systems for both the novice indoor gardener and the seasoned indoor grower. Our high intensity grow lights are easy for home gardeners to use. They come pre-wired and are rated at 120 volts (your normal home current), so they’re compatible with any standard home outlet. Just hang them from a simple ceiling hook, plug them in, and start growing.

With those sun-like high intensity lighting, you can turn any room of your home into a virtual greenhouse. Grow any plant, anywhere, anytime you choose! Imagine harvesting fresh tomatoes, picking peppers or growing a rare orchid in your basement – these lights make it possible. A single system can easily provide all the light needed to cover anywhere from a 1' x 2' area up to a 12' x 12' area, depending on what size wattage system meets your growing needs.

Now the full spectrum fluorescents and lighting systems make it easy to grow the garden you want – whether you’re starting seedlings for your outdoor spring garden or growing your favorite plants indoors. Use our lower wattage fluorescents for seedlings, cuttings and low light plants like African violets. Higher wattage fluorescent grow lights provide an excellent starter light for year-round gardening indoors.

High Intensity Lights are Easy to Use

The most important innovations has been to take the effective but cumbersome commercial greenhouse lights and make them easy for home gardeners to use. The High Intensity Grow Light can be hung from a simple ceiling hook and plugged in as easily as a home table lamp.

The systems are completely pre-wired, UL, cUL or ETL listed (with lens), and ready to plug in. Everything is rated at 120 volts (your normal home current) and plugs into any standard home outlet.

Not all light is the same.

Plants respond differently to different colors of light.

Light on either end of the spectrum, blue light or red light, have the greatest impact on photosynthesis.

Kinds of Light

Blue light, referred to as cool light, encourages compact bushy growth.

Red light, on the opposite end of the spectrum, triggers a hormone response which creates blooms.

Grow lights producing the orange and reddish light typically produce substantial heat, however, some lights are able to produce full spectrum light without the heat.

Grow lights come in all shapes, sizes and price ranges.

As a general rule, inexpensive lights to purchase tend to be the most expensive to operate and the least effective. While price is not necessarily an indicator of performance, many of the efficient grow lights require ballasts as well as specialized fixtures.

Image of vegetable being grown indoors under artificial light is via fortikur.com.

Basic Types of Grow Lights

These lights run the gamut of performance and price range.

Incandescent Lights.

The least expensive lights to purchase cost around $30. These incandescent lights work well for specific plants where the light is placed a minimum of 24” from the plant. These lights get extremely hot so they must be used with care. Spot grow bulbs, color corrected incandescent lights, install easily and are good for use with a specific plant or a small grouping of plants. Most spot incandescent bulbs last less than 1,000 hours. Some light fixtures come with a clip handle so you can put them exactly where they’re needed. 

Fluorescent Grow Lights.

They are a common choice for homeowners. Fluorescent lights are reasonably energy efficient and relatively easy to install. A typical fluorescent bulb will last approximately 20,000 hours. Fluorescent light is typically on the blue end of the spectrum. Blue light encourages bushy compact growth which makes them perfect for seed starting. Blue light is also cool to the touch making it possible to place lights within just a few inches of the seedlings.

New Full-Spectrum Fluorescent Lights.

Provide the red spectrum as well to encourage blooming.

Combining the lights in a fixture makes for even, all around growth.

The next generation in fluorescent lighting includes the new T-5 lights.

These new lights have extremely high output but are energy efficient and long lasting.

The T-5 lights triple the light output of normal fluorescent lights without increasing the wattage. Plants absorb a high percentage of T-5 lighting because the fixtures function well very close to plants. High output bulbs require a high output fixture to operate, so the bulbs and normal fluorescent fixtures will not work together.

LED Lights

The newest type of grow lights use LED technology.

One major advantage to the LED lights is the small size.

LED lights are only a few inches in diameter and are easy to mount.

In some greenhouses, LED lights may be the only practical light option.

Hanging most grow lights requires a strong greenhouse structure and a place to hang the lights.

LED lights weigh a fraction of other lights and are easy to configure where needed. According to LED manufacturers, LED grow lights maximize blue and red light to provide and excellent balance for plants.

They do not have much green-yellow light. Since humans see green-yellow light best LED grow lights appear dim to our eyes. This is an exciting new technology that will be interesting to watch as it develops.

The Best Grow Light Option

Now that I’ve given you a good rundown on greenhouse lighting options, it’s also important to mention darkness.

Almost all plants benefit from a period of six hours or more of darkness.

It’s a good idea to know how much light your plants need, but unlike commercial growers, hobbyists often have a wide variety of plants so they need to take a broad approach to lighting.

Fluorescent lights offer excellent overall lighting options.

Other Considerations

If you chose to use any type of fluorescent lighting, you will need to account for plant growth.

Fluorescent lights perform best when positioned very close to plants.

As plants grow into the light, it is important to raise the fixture.

Generally only the plants touching the lights will burn, but be prepared because they grow quickly.

Adjustable hangers are a good solution. These hangers move easily allowing you to make quick adjustments.

* Above documents are via or from urbanorganicgardener.com

The color temperature of a light source is the temperature of an ideal black body radiator that radiates light of comparable hue to that of the light source. Color temperature is a characteristic of visible light that has important applications in lighting, photography,videography, publishing, manufacturing, astrophysics, horticulture, and other fields. In practice, color temperature is only meaningful for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e. those on a line from reddish/orange via yellow and more or less white to blueish white; it does not make sense to speak of the color temperature of e.g. a green or a purple light. Color temperature is conventionally stated in the unit of absolute temperature, the kelvin, having the unit symbol K.

Color temperatures over 5,000K are called cool colors (bluish white), while lower color temperatures (2,700–3,000 K) are called warm colors (yellowish white through red).^[1] This relation, however, is a psychological one in contrast to the physical relation implied by Wien's displacement law, according to which the spectral peak is shifted towards shorter wavelengths (resulting in a more blueish white) for higher temperatures.

Categorizing different lighting

The color temperature of the electromagnetic radiation emitted from an ideal black body is defined as its surface temperature in kelvin, or alternatively in mired (micro-reciprocal kelvin).^[4] This permits the definition of a standard by which light sources are compared.

To the extent that a hot surface emits thermal radiation but is not an ideal black body radiator, the color temperature of the light is not the actual temperature of the surface. An incandescent lamp's light is thermal radiation and the bulb approximates an ideal black body radiator, so its color temperature is essentially the temperature of the filament.

Many other light sources, such as fluorescent lamps, or LED's (light emitting diodes) emit light primarily by processes other than thermal radiation. This means the emitted radiation does not follow the form of a black body spectrum. These sources are assigned what is known as a correlated color temperature (CCT). CCT is the color temperature of a black body radiator which to human color perception most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, derived from the comparison to a black body radiator.

The Sun[edit]

The Sun closely approximates a black body radiator. The effective temperature, defined by the total radiative power per square unit, is about 5,780 K.^[5] The color temperature of sunlight above the atmosphere is about 5,900 K.^[6]

As the Sun crosses the sky, it may appear to be red, orange, yellow or white depending on its position. The changing color of the sun over the course of the day is mainly a result of scattering of light, and is not due to changes in black body radiation. The blue color of the sky is caused by Rayleigh scattering of the sunlight from the atmosphere, which tends to scatter blue light more than red light.

Daylight has a spectrum similar to that of a black body with a correlated color temperature of 6,500 K (D65 viewing standard) or 5,500 K (daylight-balanced photographic film standard).

For colors based on black body theory, blue occurs at higher temperatures, while red occurs at lower, cooler, temperatures. This is the opposite of the cultural associations attributed to colors, in which "red" is "hot", and "blue" is "cold".

*** Contents are from wikipedia.org

Color temperature applications

Lighting

Color temperature comparison of common electric lamps

For lighting building interiors, it is often important to take into account the color temperature of illumination. For example, a warmer (i.e., lower color temperature) light is often used in public areas to promote relaxation, while a cooler (higher color temperature) light is used to enhance concentration in offices.^[8]

CCT dimming for LED technology is regarded as a difficult task, since binning, age and temperature drift effects of LEDs change the actual color value output. Here feedback loop systems are used for example with color sensors, to actively monitor and control the color output of multiple color mixing LEDs.^[9]

Aquaculture[edit]

In fishkeeping, color temperature has different functions and foci, for different branches.

• In freshwater aquaria, color temperature is generally of concern only for producing a more attractive display.^{[citation needed]} Lights tend to be designed to produce an attractive spectrum, sometimes with secondary attention to keeping plants alive.

• In a saltwater/reef aquarium, color temperature is an essential part of tank health. Within about 400 to 3000 nanometers, light of shorter wavelength can penetrate deeper into water than longer wavelengths (see Electromagnetic absorption by water),^[10][11][12] providing essential energy sources to the algae hosted in (and sustaining) coral. This is equivalent to an increase of color temperature with water depth in this spectral range. Because coral, typically living in shallow water, receives intense, direct tropical sunlight, the focus was once on simulating this with 6,500 K lights. Higher temperature light sources have become more popular, first with 10,000 K and more recently 16,000 K and 20,000 K.^{[citation needed]} Meanwhile, actinic lighting is used to make the somewhat fluorescent colors of many corals and fish "pop", creating brighter "display" tanks.

Digital photography[edit]

In digital photography, color temperature is sometimes used interchangeably with white balance, which allow a remapping of color values to simulate variations in ambient color temperature. Most digital cameras and RAW image software provide presets simulating specific ambient values (e.g., sunny, cloudy, tungsten, etc.) while others allow explicit entry of white balance values in kelvins. These settings vary color values along the blue–yellow axis, while some software includes additional controls (sometimes labeled tint) adding the magenta–green axis, and are to some extent arbitrary and subject to artistic interpretation.^[13]

Photographic film[edit]

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Photographic emulsion film sometimes appears to exaggerate the color of the light, as it does not adapt to lighting color as human visual perception does. An object that appears to the eye to be white may turn out to look very blue or orange in a photograph. The color balance may need to be corrected while shooting or while printing to achieve a neutral color print.

Photographic film is made for specific light sources (most commonly daylight film and tungsten film), and used properly, will create a neutral color print. Matching the sensitivity of the film to the color temperature of the light source is one way to balance color. If tungsten film is used indoors with incandescent lamps, the yellowish-orange light of the tungsten incandescent lamps will appear as white (3,200 K) in the photograph.

Filters on a camera lens, or color gels over the light source(s) may also be used to correct color balance. When shooting with a bluish light (high color temperature) source such as on an overcast day, in the shade, in window light or if using tungsten film with white or blue light, a yellowish-orange filter will correct this. For shooting with daylight film (calibrated to 5,600 K) under warmer (low color temperature) light sources such as sunsets, candlelight or tungsten lighting, a bluish (e.g., #80A) filter may be used.

If there is more than one light source with varied color temperatures, one way to balance the color is to use daylight film and place color-correcting gel filters over each light source.

Photographers sometimes use color temperature meters. Color temperature meters are usually designed to read only two regions along the visible spectrum (red and blue); more expensive ones read three regions (red, green, and blue). However, they are ineffective with sources such as fluorescent or discharge lamps, whose light varies in color and may be harder to correct for. Because it is often greenish, a magenta filter may correct it. More sophisticated colorimetry tools can be used where such meters are lacking.

Desktop publishing[edit]

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In the desktop publishing industry, it is important to know a monitor’s color temperature. Color matching software, such as Apple's ColorSync for Mac OS, will measure a monitor's color temperature and then adjust its settings accordingly. This enables on-screen color to more closely match printed color. Common monitor color temperatures, along with matching standard illuminants in parentheses, are as follows:

• 5,000 K (D50)
• 5,500 K (D55)
• 6,500 K (D65)
• 7,500 K (D75)
• 9,300 K.

D50 is scientific shorthand for a standard illuminant: the daylight spectrum at a correlated color temperature of 5,000 K. Similar definitions exist for D55, D65 and D75. Designations such asD50 are used to help classify color temperatures of light tables and viewing booths. When viewing a color slide at a light table, it is important that the light be balanced properly so that the colors are not shifted towards the red or blue.

Digital cameras, web graphics, DVDs, etc., are normally designed for a 6,500 K color temperature. The sRGB standard commonly used for images on the Internet stipulates (among other things) a 6,500 K display whitepoint.

TV, video, and digital still cameras[edit]

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The NTSC and PAL TV norms call for a compliant TV screen to display an electrically black and white signal (minimal color saturation) at a color temperature of 6,500 K. On many consumer-grade televisions, there is a very noticeable deviation from this requirement. However, higher-end consumer-grade televisions can have their color temperatures adjusted to 6,500 K by using a preprogrammed setting or a custom calibration. Current versions of ATSC explicitly call for the color temperature data to be included in the data stream, but old versions of ATSC allowed this data to be omitted. In this case, current versions of ATSC cite default colorimetry standards depending on the format. Both of the cited standards specify a 6,500 K color temperature.

Most video and digital still cameras can adjust for color temperature by zooming into a white or neutral colored object and setting the manual "white balance" (telling the camera that "this object is white"); the camera then shows true white as white and adjusts all the other colors accordingly. White-balancing is necessary especially when indoors under fluorescent lighting and when moving the camera from one lighting situation to another. Most cameras also have an automatic white balance function that attempts to determine the color of the light and correct accordingly. While these settings were once unreliable, they are much improved in today's digital cameras, and will produce an accurate white balance in a wide variety of lighting situations.

Artistic application via control of color temperature[edit]

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The house above appears a light cream during the midday, but seems a bluish white here in the dim light before full sunrise. Note the different color temperature of the sunrise in the background.

Video camera operators can white-balance objects which aren't white, downplaying the color of the object used for white-balancing. For instance, they can bring more warmth into a picture by white-balancing off something light blue, such as faded blue denim; in this way white-balancing can serve in place of a filter or lighting gel when those are not available.

Cinematographers do not "white balance" in the same way as video camera operators; they can use techniques such as filters, choice of film stock, pre-flashing, and after shooting, color grading (both by exposure at the labs and also digitally). Cinematographers also work closely with set designers and lighting crews to achieve the desired effects.

For artists, most pigments and papers have a cool or warm cast, as the human eye can detect even a minute amount of saturation. Gray mixed with yellow, orange or red is a "warm gray". Green, blue, or purple, create "cool grays". Note that this sense of temperature is the reverse of that of real temperature; bluer is described as "cooler" even though it corresponds to a higher-temperature black body.

"Warm" gray	"Cool" gray
Mixed with 6% yellow.	Mixed with 6% blue.

Lighting designers sometimes select filters by color temperature, commonly to match light that is theoretically white. Since fixtures using discharge type lamps produce a light of considerably higher color temperature thantungsten lamps, using the two in conjunction could potentially produce a stark contrast, so sometimes fixtures with HID lamps, commonly producing light of 6,000–7,000 K, are fitted with 3,200 K filters to emulate tungsten light. Fixtures with color mixing features or with multiple colors, (if including 3,200 K) are also capable of producing tungsten like light. Color temperature may also be a factor when selecting lamps, since each is likely to have a different color temperature.^[14]

* Above good text are from wikipedia.org

The "color" of light sources is derived from a complicated relationship derived from a number of different measurements, including correlated color temperature (CCT), color rendering index (CRI), and spectral distribution. In general, color is most accurately described by a combination of CCT and CRI.

Correlated Color Temperature (CCT)
The first factor in choosing a lamp color is the correlated color temperature. For example, if a retailer wants lighting to blend in with warm halogen accent lamps, the retailer may choose a Venture® MP 100W/C/U/3K, which has a correlated color temperature of 3200K. CCT is defined as the absolute temperature (expressed in degrees Kelvin) of a theoretical black body whose chromaticity most nearly resembles that of the light source. The CCT rating is an indication of how "warm" or "cool" the light source appears. The higher the number, the cooler the lamp color will appear. The lower the number, the warmer the lamp color will appear.

Spectral Energy Distribution
When we look at a light source, the eye "perceives" a single color. In reality, we are seeing literally thousands of colors and hues made up of a combination of different wavelengths of light. These different combinations and the relative intensity of various wavelengths of light are used to determine the CRI of a light source.

Color Rendering Index (CRI or Ra)

In general, CRI is a numeric indication of a lamp’s ability to render individual colors accurately relative to a standard. The CRI value is derived from a comparison of the lamp’s spectral distribution to the standard (e.g. a black body or the daytime sky) at the same color temperature. 

Color Shift and Variation
Different colors are produced in metal halide lamps by using various arc tube shapes and metal halide salts. In new lamps these halides need to "burn-in" for approximately 100 hours before they reach their optimum color. This is why new lamps can sometimes be unstable or vary in color.

As metal halide lamps age, chemical changes occur causing shifts in color. Generally, traditional probe start lamps shift approximately twice as much in CCT over life compared to Uni-Form® pulse start lamps. 

Special Colors:
Designer Color® lamps that produce blue, green, aqua and pink light are available for special applications where color is needed without light loss due to filters.

Different Colors
Venture Lighting offers lamps in many colors to suit virtually any lighting application. Outlined below are the various color temperatures (CCT) currently available:

27K 2700K - Used as a replacement for very warm incandescent lamps (coated only).

3K 3000K-3200K - Used as a general warm, white light source, available in clear or

coated finish for retail or interior applications; blends with halogen lamps.

4K 3700K-4000K - Used as a neutral white light source, available in clear or coated finish for general lighting, factories, parking lots, warehouses.

5K 5000K - A moderately high CCT daylight source used in general and retail lighting applications

6K 6500K - A high CCT daylight source used to simulate average outdoor light conditions

10K 10,000K - A very high CCT, daylight light source, used in horticulture and aquarium applications.

Open or Enclosed
All ratings based on the use of a 9000 lumen rated 100 watt metal halide, vertically oriented lampin a commercially available 8" aperature, black baffled downlight.

Light Output 
The lumen output values at specific hours of lamp life can be measured and plotted. This lumen maintenance (or lumen depreciation) curve contains important data for lighting designers. Though initial lumen ratings at 100 hours are frequently the basis for comparing light sources, mean lumens, determined at 40% of rated lamp life, are the most important. Mean lumen ratings are based on the lamps operating at 10 hours per start (except where noted). Lamp lumens are measured on a reference ballast in the designed operating position at the rated lamp wattage.

Lumen maintenance curves represent the lamp manufacturer’s estimate of the best lamp lumen output plotted over time. Typically, each group of lamps tested will display a range or scatter of lumen maintenance values at each interval measured. Therefore, individual lamps may vary from published mean lumen ratings.

Many factors affect the performance of metal halide lamps over time. Most of these factors (see table) are controllable in the design of the lighting system. Incorporating as many of the optimized conditions as possible will deliver the best performance from any given metal halide lighting system. More light reducing conditions present in the design of the lighting system create a gap between published "optimized" ratings and actual lighting system performance.

For example, Venture’s Uni-Form® pulse start lamp operated on an a low current crest factorSingle Voltage Hybrid or HX magnetic ballast, and other optimized conditions, can be expected to deliver mean lumens approaching 80%. In contrast, astandard metal halide system operating under light-reducing conditions may deliver only 50% lumen maintenance. Venture Lighting publishes "optimized mean lumens."

Even within the Uni-Form pulse start system, you can expect a range of lumen maintenance from 70% to 80%. (see chart below) Performance will vary depending on the number of light-reducing conditions present. By selecting a Uni-Form pulse start lamp, a low current crest factor Single Voltage Hybrid or HX magneticballast, and optimizing the system conditions, significant improvements in lighting system performance can be achieved

.