BTU –
British Thermal Unit. The amount of energy needed to heat your greenhouse to a desired temperature. 1 BTU is the amount of energy required to raise the temperature of 1 pound of water 1° F when the water is near 39.2° F.

Ballast –
A device used to provide the starting voltage or to stabilize the current in a circuit (as of a fluorescent lamp or HID lamp). This may be built into the reflector or may be a separate unit. Ballasts are specific to the type of bulb/lamp and cannot be interchanged.

Bar Cap –
Aluminum capping used externally to hold glazing to framework.

Base & Cap –
Two-piece plastic forms used to join TwinWall and other MultiWall polycarbonate panels while attaching them to the frame.

Beneficial Insects –
Insects that hunt, capture and consume your pest insects. They are harmless to people, plants and animals. Examples are ladybugs, nematodes, predatory mites and aphid predators.

CFM –
Cubic Feet per Minute. The measurement of the cubic feet of air moved by a fan within 1 minute.

CRI –
Color Rendering Index. The CRI refers to how close the spectral curve of the light approximates that of the sun in a percentage, with 100 being the closest. Any bulb with a CRI rating over 90 is considered a full spectrum bulb.

Caulk –
Filler for cracks and seams to make watertight.

Day Neutral –
Plants whose bloom cycle is not affected by the number of hours of light or dark they receive.

Door Drop –
The distance between the floor level and the top of the foundation.

Eave Height –
The measurement to where the top of the sidewall meets the lowest point of the roof.

End Cap –
“U” shaped plastic forms used to seal the top and bottom of TwinWall and other MultiWall Polycarbonate panels while attaching to the frame.

Exhaust Fan –
A fan that expels or exhausts air from the greenhouse. These fans are rated in CFM.

Extrusion –
Framing piece formed by pressing or squeezing aluminum or steel through a form. Also used to specify non-specific framing pieces in greenhouse.

Fluorescent –
A tubular electric lamp having a coating of fluorescent material on its inner surface and containing a vapor which when hit with electrons provides ultraviolet light, which causes the material to emit visible light. The coating determines the light spectrum emitted. For plants, a wide or full spectrum bulb is used. These bulbs come in the standard 4-ft. and 2-ft. tubes, which are effective up to 16″ from the soil. The new coil and other styles of bulbs may vary in height limits.

Foam Glazing Tape –
A closed-cell foam tape used to prevent water from entering between the glazing and the frame.

Foot-Candle –
A unit of measurement of light. 1 foot-candle falling on 1 square foot area.

Foundation –
The base upon which the greenhouse is set. This can be made of wood, concrete or concrete block.

GFI/GFCI –
Ground Fault Interrupt or Ground Fault Circuit Interrupt. A protected outlet that will shut off automatically when a short is sensed, turning off the current to the outlet and any outlet wired after the GFI outlet.

Glazing –
The skin of the greenhouse that transmits light.

Glazing Bar –
Aluminum framework to which glazing is attached.

Glazing Gasket –
A flexible seal used to prevent water from entering between the glazing and the frame.

“H” Channel –
A piece of aluminum or plastic shaped like a lower case “h” used for the bottom and/or top of TwinWall and other MultiWall polycarbonate panels, and glass.

HID –
High Intensity Discharge. Lights designed to simulate the spectrum and intensity of sunlight. MH and HPS are the most common type used in greenhouses.

HPS –
High Pressure Sodium. These lamps provide a light that is red/orange-orientated in the spectrum. It is the best type of light to be used as a secondary light source (in conjunction with natural, bluer light, or metal halides). This type of light promotes plant fruiting and flowering as it mimics the natural fall/winter spectral shifts that occur with the changes in the season. It is not recommended as a primary light source, as plants will become leggy without sufficient blue/green light.

Heat Mat –
An electrical mat used to raise soil temperature to increase propagation of seeds and cuttings.

Humidity –
A measure of the amount of water vapor in the air. The air’s capacity to hold vapor is limited but increases dramatically as the air warms. The relative humidity is the amount of vapor in the air divided by the air’s vapor-holding capacity at that temperature. This is the most common measure of humidity used in the greenhouse.

“J” Channel –
A piece of aluminum or plastic shaped like a “J” used for the bottom and/or top of TwinWall, and other MultiWall polycarbonate panels and glass.

Joiner Cap –
“H” shaped plastic used to join TwinWall and other MultiWall polycarbonate panels while attaching the TwinWall or other MultiWall to the frame.

Kelvin Ratings or Color Temperature –
Rating of colors in a temperature scale. This is the color where the spectral curve is “centered” or “balanced”. Think of color temperature as the color of a “black body” as it is heated to various high temperatures. A warm, reddish light is around 3500° Kelvin, and above 6000° Kelvin the light takes on a bluish tone. Sunlight is about 5000° Kelvin.

Light Period or Photoperiod –
This is the term applied to the length of time that light shines on a plant each day.

Long-Day Plants –
Plants that require longer than 12 hours of daylight to start flowers. They may also be called short-night plants (e.g., beans, cabbage, roses).

Lumen –
The amount of light generated by 1 candle.

MH –
Metal Halide. Provides a light that is blue-orientated in the spectrum. This color of light promotes plant growth and is excellent for green leafy growth and keeping plants compact. It is the best type of light to be used as a primary light source if no or little natural sunlight is available.

Mastic –
A gooey sealant / adhesive used to attach or waterproof a joint.

Organic –
Employing agricultural and horticultural practices that favor the use of naturally occurring fertilizers, pesticides and other growing aids. Can also refer to produce or plants that have not been exposed to synthetic chemicals.

Outside-to-Outside Foundation Dimensions –
The measurement from the outer most edge of the foundation to the outer most edge of the foundation on the opposite wall. The size the foundation should be made to fit the greenhouse.

Polycarbonate –
Shatter resistant plastic that is lightweight and flexible while maintaining high impact strength. Comes in many different styles.

Purlin –
An aluminum framing piece in the roof that runs the length of the greenhouse. The purlin provides support to the rafters or roof glazing bars.

“R” Value –
Resistance Value. The measurement of the capacity of a material to resist heat loss. The higher the number, the lower the heat loss.

Reflector –
A hood mounted directly over the bulb, which directs and reflects more light downward.

Ridge Beam –
The beam at the peak of the roof that the two sides of the roof attach to, or the beam that attaches the sloping roof to a support wall.

Roof Bar Length –
The measurement from the point of the eave to the ridge along the rafter.

Shade Cloth –
Material used to provide shade by blocking some percentage of sunlight. Density and life of material varies.

Short-Day Plants –
Plants that require less than 10-12 hours of light to start blossoms. They may also be called long-night plants (e.g., chrysanthemum, poinsettia, Christmas cactus, radish).

Shutter –
A cover for a vent that is fitted with hinged louvers.

Silicone Sealant –
Type of caulk for specific applications.

Sill –
The horizontal frame that forms the base of the greenhouse and attaches to the foundation.

Solar Vent Openers –
A term used to describe a non-electric, automatic vent opener. Charley’s uses vent openers that have a mineral wax cylinder that expands and contracts due to the temperature in the greenhouse.

Square –
To make the foundation such that all 4 corners are right angles.

TwinWall –
Double-walled polycarbonate that is UV protected. An insulated glazing. “R” value of 1.6.

TripleWall –
Three-walled polycarbonate that is UV protected. An insulated glazing. Comes in 8 mm with an “R” value of 2.1 and 16 mm with an “R” value of 2.5.

“U” Channel –
A piece of aluminum shaped like a squared-off “U” used for the bottom and/or top of TwinWall and other MutiWall polycarbonate panels.

UV Protected –
Material that has a coating or is impregnated with a substance that blocks UV (ultraviolet) light is considered “UV protected.”

Vent –
An opening in the greenhouse to provide ventilation.

Ventilation –
To circulate through and freshen air in a greenhouse or room.