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"Building Your Own Greenhouse" by Max Clarke

Page 64 of 123

accordance to the weather conditions in your area. Strict

adherence to these codes helps to prevent freezing or cracking

of the foundation of your greenhouse.

Mark chalk lines across the ground area for your greenhouse

and dig trenches according to your local building codes along

the marked chalk lines. Set level concrete footings eight

inches wide into the trench. Your steel rod footings should be

tied horizontally or vertically inside foundation forms before

the pouring of concrete.

Flooring of Your Greenhouse

Ensure the ground area across your flooring to be as level as

possible. Dump in gravel and smooth it.

Next, pour in crushed stone and tar paper. You could use

builder's heavy plastic too. Then, set the mesh and pour in the


In hot weather, cover concrete with plastic and sprinkle water

intermittently to help the flooring become strong and sturdy.

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Leave two-inch drainage holes four feet apart in the

foundation. After the footings settle well into the foundation,

remove your forms and fill the foundation with gravel or dirt.

Installing gravel or tile drainage channels with drainage holes

can allow easy drainage within your greenhouse.

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Selecting the Right Lights

Greenhouse cultivation does not depend on natural weather

conditions. It all depends on the artificial environment you

create within your greenhouse. Therefore, your artificial

arrangements should be in accordance with the natural

requirements of plants for healthy growth.

Light Requirements

Sunlight forms the essence for the growth of any plant. All

greenhouses allow easy penetration of sunlight. However,

available sunlight may not be sufficient during the winter

months and on cloudy days. Therefore, you need to arrange

artificial lights.

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Selection of artificial lights depends on:

Your plants’ requirements

The area of your greenhouse

Availability and intensity of sunlight

Many different types of lights are available; fluorescent lamps,

incandescent lamps, mercury vapor lamps, neon lamps,

sodium vapor lamps and others.

Different color combinations of lights exist. Color choices

depend on the requirements of your plants.

Lights could increase the temperature within your greenhouse

if they are in addition to reasonable sunlight. Choosing lights

that emit more light and less heat energy can help to maintain

greenhouse temperatures at appropriate levels.

Types of Lights

Fluorescent lamps: These lamps are most popular for use in

greenhouses. These lamps are available in various colors. The

highest preference is for white fluorescent lamps. These lamps

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provide more light with less heat. High intensity fluorescent

tubes of 1500 ma can deliver a high wattage of around 2000-

foot candles.

Soft lights of this type contain the entire spectrum of sunlight.

Having such lights over seedlings with poor growth can boost

their growth. Restricting use of these lights over smaller areas

can be a good option.

Incandescent lamps: Incandescent lamps are available in

different wattages, ranging from sixty to five hundred watts.

These lights can make the plants think days are longer in your

greenhouse. You can vary foot-candle levels by adjusting the

spacing and mounting height of the lamps over your plants.

High-intensity discharge (HID) lamps: As the name

suggests, these lamps provide high emission of light. These

lights last for a long time; for over five thousand hours.

Efficiency of these lights increases with the addition of sodium

and metal-halides.

Metal Halide Grow Lights: These lights emit the blue and

violet colors of the spectrum. Such light is normally available

during spring. These lights best suit growing plants and

support their early developmental stages to promote stronger

roots, increased resistance to diseases and a more compact

green growth.

High-Pressure Sodium Lights: These lights produce orange and red colors of spectrum that encourages plant growth like

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you see in autumn and early fall. Therefore, this light suits

plants in a mature stage.

You can use a convertible grow light system to alternate

between metal halide lights and high-pressure sodium lights.

You can use metal halide lights for starting seedlings and then

shift to high-pressure sodium lights as they grow into mature


This can save you money compared to purchasing separate

lighting systems.

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Part-IV: Environmental Systems

Cooling, Ventilation and Your Greenhouse

Greenhouses essentially lock in sunlight to provide a more

suitable environment for plants to grow. But, trapped sunlight

should not exceed required levels. Otherwise, your plants may

wither. Use adequate cooling strategies within your

greenhouse to maintain optimum temperature and humidity


Cooling and Ventilation of Greenhouses by Plants

Plants have an inbuilt mechanism to cool themselves. They

regulate their temperatures by evaporating water through the

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process of transpiration. Plants can keep themselves cool in

greenhouses if there are many leaf surfaces.

If your greenhouse houses plants with many large leaves, the

atmosphere in the greenhouse can be cooled to a considerable


To help plants transpire easily and effectively, you should

supply them with lots of water. Irrigate your plants in the

greenhouses extensively and frequently. This neutralizes salt

levels in plant roots so that high salt levels do not interfere

with their intake of water.

Next, provide sufficient ventilation within the greenhouse so

that moist air transpired through leaf surfaces goes out and

cool dry air enters greenhouse. Employing proper air

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circulation techniques can help provide this environment for

your plants.

Cooling and Ventilation by Blocking Sunlight

You can maintain cool temperatures in the greenhouse by

blocking sunlight. Fix retractable or fixed sunshades to restrict

the amount of sunlight entering your greenhouse. Maintain an

adequate supply of sunlight for plants to photosynthesize their


Light requirements of plants depend on the specific species

and the intensity of available light too. If your greenhouse has

many crops with dense foliage, use little restrictive shades so

that these plants and their foliage do not suffer from lack of

adequate sunlight.

Use semi-permanent shade materials like screens and

coatings. These are very flexible in adjusting light


Ventilation Equipment

Roof vents help remove hot air from within the greenhouse

and replaces it with cool outside air. Hand-operated roof vents

require regular temperature checks. You have to open and

close vents according to the changes in outside weather. This

is necessary to prevent excessive cooling or heating of air

within the greenhouse.

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Install sidewall or gable exhaust fans underneath curtains to

remove trapped, heated air.

Curtains pulled in an east-west direction prove useful in

regulation of penetrating sunlight. Use curtains of open-weave

materials so that hot air rises through the roof.

Ventilation systems function in relation to the area of your

greenhouse. The height of your greenhouse does not play any

role in effective ventilation. An effective ventilation system

should be able to exhaust eight to ten cubic feet of air per

minute from every square foot of your greenhouse.

Further, ventilation should be uniform all over your

greenhouse. If outside temperatures are very high and dry,

use ventilation systems in combination with the natural

transpiration systems of your plants to maintain necessary

coolness within the greenhouse.

This requires frequent regulation of the air in the greenhouse.

Another way of cooling your greenhouses is through use of

mechanical cooling; refrigeration or air-conditioning. This

technique could prove very costly.

Other cooling techniques include mists, fogs, pads and fan

systems and sprinklers. All these work fine if moisture content

in the air is not perfect.

Mists, fogs, and sprinkler systems can function independently

or synchronize with other mechanical ventilation systems. But,

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you should regulate air and humidity temperatures for these

systems to function smoothly. You can switch them on and off


These systems have their own problems too. Impurities in the

water could lead to clogging and foliage could suffer from

continuous wetting too. You can regulate the even dispersion

of water by regulating the size of particles and avoid chances

of over-wetting.

However, effective cooling depends more on the amount of


Shading equipment includes roll-up screens of aluminum,

wood, vinyl, paint-on materials or plastic shades. These

shadings function with the help of nylon ropes or pulleys. You

can adjust the shade according to outside weather conditions.

You can use shading compounds too. Apply them on the

exterior of the greenhouse glass.

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Plants in a greenhouse

Automated Cooling and Ventilation Techniques

Automated cooling and ventilation systems can offer

systematic and controlled regulation of temperatures within

greenhouses. These automated techniques do not require you

to maintain personal controls. Systems have an in-built

mechanism that manages irrigation levels, operate suitable

shading systems and provide necessary ventilation by

operating relevant cooling.

This occurs by coordinating various pieces of automated

equipment in relation to the varying requirements of your


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Automated vents have a special thermostat and electric motor

systems that remain open to allow the necessary amount of

cool air. They also allow warm air to flow out similarly.

Maintenance of such moderate temperatures within a

greenhouse promotes healthy growth of plants.

Automated systems function independently and you do not

have to keep changing them according to different seasons.

You can use a single thermostat, or a controller with a

temperature sensor. Sensors should always be in the shade

and located at around plant height. White sensor boxes can

reflect solar heat and give accurate temperature readings.

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Understanding Heating Methods,

Systems, Sources, and Distribution

Heating systems are essential for greenhouses to function

normally. Solar energy is the main source of heat energy

necessary for greenhouses. Nevertheless, you should have

adequate alternative heating systems to maintain systematic

heating all year through.

These heating systems can regulate temperatures within

greenhouses and maintain a conducive environment for plants

to grow and flourish.

Heating Systems and Methods

There are different heating systems for regulating

temperatures within greenhouses. You can use that which best

suits your greenhouse requirements.

Pipe Heating: This has many metallic or plastic pipes

carrying steam or hot water spread across the greenhouse.

These pipes heat the greenhouse through convection and later

radiate heat directly to the leaves. Overhead pipes should be

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closer to plant surface for effective heating without loss

through radiation. Similarly, hot pipes passing near the ground

in the greenhouse can stimulate better circulation of hot air.

Pipes passing through the middle of greenhouse can provide

excellent radiation of heat. Take care to avoid scorching of

plants through heat from the pipes.

Warm Floor Heating: This heating system involves placing

hot water pipes below the concrete of the greenhouse. This

system helps in uniform heating of the entire ground surface

of the greenhouse and uniform distribution and circulation of

heat throughout the plant canopy.

Heating the root system promotes plant growth. But, this

system may be too expensive for many.

Bench Heating: This heating system involves placing hot

pipes on, or under, the benches. This can assure uniform

spreading of the heat across plant roots and improve air

movement extensively. Although this system can reduce the

incidence of root pathogens by warming soil, it can cause

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excessive stress on the plants closest to heaters. Similarly,

plants farthest from heaters may not receive equal benefit.

Air Heating: Overhead heated air directed through fans and

perforated polyethylene tubes can heat greenhouses quickly.

You have to maintain perfect on-and-off timings to regulate

temperature within your greenhouse. This system could prove


Central Heating Systems: These heating systems generate

heat from a centralized location, normally a huge boiler. This

heating system proves efficient for huge commercial

greenhouses, although installation and maintenance costs are

expensive. Hot water produced in a boiler, pumps into your

greenhouse at 180° F. This system also requires extensive

plumbing and circulating systems to maintain the necessary

supply of heat. You can use steam centralized heating systems

as they provide heat at 215° F.

Radiant heaters: These heaters have aluminum tubes with

reflectors. Combustion of fuel within the tubes cause

temperatures to rise to around 900° F. Reflectors direct the

infrared radiation downwards to plant surfaces and benches.

These surfaces absorb radiation and heat. These heaters

require low-flow or poly-tube fans to maintain necessary air


The number of heating units should be such that there are no

cold spots. Initial costs are high.

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Fuel Sources for Heating Systems

There are different fuel sources for heating systems of

greenhouses. You can choose fuel according to cost,

availability, pollution regulations, storage possibilities, boiler requirements and maintenance requirements.

Popular Fuels:

Natural Gas: This fuel source may be currently one of the

most inexpensive and has low maintenance costs. It offers

clear burning and there is no need for storage tanks.

Propane and Butane: Although similar to natural gas, they

are more expensive and require storage tanks.

Oil: You need storage tanks to keep this fuel source. It

requires regular boiler maintenance as it does not burn


Wood chips or Logs: These fuel sources require huge

storage area and extensive handling with regular boiler

maintenance and cleaning.

Coal: This low-cost fuel requires extensive storage space and generates immense pollution too. You require regular boiler


While using coal, oil, or gas heaters, there should be a

constant supply of fresh air to avoid any build-up of carbon

monoxide. Fans can help to maintain the necessary air

circulation within greenhouses.

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Heat Distribution inside Greenhouse

Even distribution of heat inside a greenhouse is as essential as

generation of heat. Uneven distribution can cause many


Some of the most important are:

• Irregular growth of plants

• Improper maturation

• Excessive dry regions, and

• Stunted growth of plants

Different heating systems generate and distribute heat in

different ways. Centralized heating systems can be through

hot water or steam. Heat distribution takes place through a

network of aluminum, cast iron, or copper pipes. Steam offers

less resistance and therefore you can use pipes with a smaller

diameter. Steam additionally delivers higher heat than hot

water. Efficient distribution of heat requires proper placement

of pipes. This can increase heating and reduce heat loss.

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Potted plants in a greenhouse

Placing pipes in layers can reduce heating efficiency. Instead,

place pipes singly.

Unit heaters are not very efficient in distributing heat.

Temperature differences occur along the length of a

greenhouse. Temperatures close to the heater are high. Use of

multiple unit heaters across each other can solve this problem.

It helps to maintain uniform heat across the entire length and

breadth of the greenhouse.

Additionally, you can use horizontal airflow fans to promote

movement of air within greenhouses.

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Unit heaters mounted onto greenhouse gables and connected

to polyethylene jet tubes can distribute heat evenly. In cooler

seasons, you can switch off the fuel source and firebox and

use a fan of unit heaters with polyethylene tubes with outside


Heating systems placed low in the greenhouse can help to

maintain warmer temperatures. Leaf surface temperature

above dew point can prevent condensation. It helps prevent

various greenhouse diseases.

Other heating systems should be as close to the canopy as

possible. This saves lots of energy too.

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Calculating Energy Requirements

for Heating Systems

Energy requirements for heating greenhouses are not the

same everywhere. It depends on various factors, including:

Size of the greenhouse

Difference in outside temperature and temperature within

greenhouse, and

Single or double layered covering of glasshouse in plastic or


Normally, greenhouse sellers educate you about heating

requirements of your specific greenhouse so that you can

make use of these systems too. You can calculate heat energy

requirements through simple processes.

You must seal all cracks and holes in your greenhouse as soon

as they are located.

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Energy Requirements for Your Heating System

The most important factor is to calculate the temperature

difference between the lowest outside temperature and the

temperature you want to maintain in your greenhouse. If the

coldest temperature outside is around -10 degrees while you

want to maintain sixty degrees within your greenhouse, the

temperature difference is around seventy degrees.

Find the total surface area of the inside of your greenhouse

including roof ends and the sides in square feet. The area

should essentially be of exposed plastic or glass of your


Find the product of the greenhouse area and the temperature

difference. If the total exposed area of your greenhouse is

3,400 sq. ft. the product would be 238,000.

Your greenhouse could have two layers of glass or plastic or

have a single layer. If it is a single layer, multiply 238,000 by

1.2. If it is a double layer, multiply 238,000 by 0.8. This

product is the required BTU capacity of your heater per hour.

For a double-layered greenhouse, it would amount to maybe

190,400 BTU per hour while it could be around 285,600 BTU

per hour for a single-layered greenhouse.

You can calculate heat energy requirements of your

greenhouse by calculating the total heat loss.

First, determine the total exposed surface area of your

greenhouse covering, be it glass, poly, fiberglass, or other

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material. Also, determine the exposed surface area of other

materials like brick, poured cement, concrete block etc.

Next, determine the maximum difference between the outside

lowest temperature and the optimum temperature necessary

within your greenhouse.

Calculate the conduction heat loss factor for materials used in

your greenhouse.

Using relevant tables, calculate the air filtration heat loss.

According to the volume of greenhouse, calculate the total

heat loss of your greenhouse. You need similar energy to heat

your greenhouse and maintain optimum temperature for the

best possible growth of plants within the greenhouse.

Normally, the heat requirements are less in double-glazed

greenhouses like those of polycarbonate or glass. Similarly,

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the types of crop you want to grow within the greenhouse

affect the heat energy requirements.

Summer crops normally require more heat than winter crops.

While calculating outside temperatures, always keep an extra

margin for seasonal variations from the recorded averages. At

times, it could turn out to be much colder than the average

minimum temperatures you use in your calculations. Procuring

heating equipment with a larger load is advisable to adjust to

odd weather changes.

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Watering Systems and Insulation Techniques

Greenhouse Watering Systems

Water is an essential ingredient for growing plants anywhere,

equally so in your greenhouse. Having a water source close to

your greenhouse can prove beneficial.

Different types of watering systems include:

Capillary Matting: Capillary mats through bottom of trays or pots can supply the water requirements of seedlings across

the floor of your greenhouse. You can use an automated

system for capillary matting or a hand-filled reservoir.

Drip irrigating systems: These provide a continuous water

supply to plants within the greenhouse by flowing down in

drips. This helps conservation of water and supplies the

necessary amount of water to each plant directly.

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Self-Watering Tray Kits: These kits are available in different sizes. They consist of a black plastic water reservoir fitted with an aluminum tray. This creates a raised flat surface for

capillary matting. This system can help water your plants for

around two weeks, depending on the number of plants within

the greenhouse and the type of plants too.

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Watering Cans and Garden Sprayers: You can use plastic watering cans available in different sizes. You can also use

these for spraying fertilizers and chemicals.

Tropf Blumat Drip Irrigation System: This watering system

helps plants to control the amount of water. This can prevent

excessive watering.

Greenhouse Misting Systems: These systems provide a

mist of water over your plants in the greenhouse. Water mists

can help plants absorb water according to their requirements.

Insulation Techniques in Greenhouses

Effective insulation systems are essential to maintain

necessary warmth within greenhouses. They also are excellent

energy savers. They can help you save around thirty percent

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on your heating costs. You can extend greenhouse

productivity periods by around six weeks.

This allows greater flexibility in choosing sowing times and the

type of plants for growing in your greenhouse.

The best way to insulate your greenhouse is to use bubble

wrap. Bubble wrap retains maximum heat for a considerable

period too. Wrapping your greenhouse in bubble wrap could

reduce light levels within the greenhouse. However, such

reduction is minimal and does not cause any worry.

Use UV-stabilized and tri-laminated bubble insulation. UV

treatments prevent your bubble wrap from becoming hard and

brittle. Therefore, you can use it year after year during the

cold winter months. Additionally, tri-laminated bubble wrap

retains more heat of the day and provides better insulation.

Fixing bubble wrap around your greenhouse is not a big job.

Aluminum framed greenhouses have glazing bars with a

channel down the center. This has many cropped bolts in

addition to spacers, alliplugs and corner adapters.

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These accessories help secure bubble wrap to your

greenhouse easily. Spacers create a gap of 25mm between

glass and material. This helps keep warmth in during cold


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Part-V: Upholding Your Greenhouse

Basic Greenhouse Care

Essential Accessories and Equipments for Maintenance

Regular daily maintenance of your greenhouse can help you

have a clean and attractive greenhouse. It does not take much

time if you fit it in within your daily routine.

Simple accessories that will help in your maintenance work on

a small greenhouse might include:

• Mist sprayer

• Watering can

• Canes

• Shade nets

• Trowel or hand fork

• Pesticides

• Washing-up Gloves

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• Garden Disinfectant

• Scrubbing Brush

• Old toothbrush for scrubbing corners

• Clean Bucket and Water

You should keep your greenhouse neat and tidy. This ensures

the greenhouse to be free of pests and associated diseases. It

also ensures a good and healthy environment for your plants

to grow and flourish.

Diseases often develop in greenhouses due to the hot and

humid conditions within.

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Follow these essential maintenance tips to ensure a clean and

healthy greenhouse:

• Water all plants regularly

• Do not allow compost to dry and harden

• Take off weeds around plants and plant beds. Weeds

grow very fast. Therefore, weeding is essential every

few days.

• Place canes for plants that require support to grow well.

You can tie emerging shoots together loosely. This

prevents shoots from mingling with plants in other pots

and creating a jumble.

• Pruning is essential in summer to remove dried twigs

and flowers. Prick out and take off drying plants when


• Fix shade nets to safeguard plants from scorching

sunlight. Alternatively, you can spray shading washes on

outside of greenhouses during summer and wash them

off in autumn.

• Never water plants in mid-afternoon when the sun is

hottest as it scorches plant leaves.

• Some plants require humid conditions. Splash the floor

with water through a handheld mist sprayer during the

summer to create humid conditions.

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• Pests like mealy bugs, red spider mites and aphids and

diseases like mildew and botrytis thrive in humid

conditions. Refrain from making your greenhouse too

humid to protect your plants from such diseases.

• Sterilize flats and pots with disinfectants before re-using


• Annual thorough cleaning of your greenhouse is

essential. Take out all your plants from the greenhouse

and clean the shelves, benches, and walkways of your

greenhouse thoroughly. Use a spray hose to take away

dirt and debris and wash down surfaces. Next, apply a

disinfectant. Allow the disinfectant to soak in. Rearrange

the greenhouse the next day.

• Remove stubborn algae spots from greenhouse glass

with disinfectant or a household bleach.

• Use lubricants on metal frames, vents and door hinges.

This prevents rusting and jamming of doors and vents.

• Take away insulation in the summer and preserve them

well for use during winter.

• Keep all greenhouse tools in their proper places.

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Greenhouse Maintenance Checklist

Maintenance is of key importance in any greenhouse.

Without adequate and proper maintenance, it is not possible

to have the necessary environment for optimum growth and

development of plants. Maintenance of your greenhouse

requires you to write out a detailed plan and adhere to it

religiously. Efficient maintenance includes regularly inspecting

all components of your greenhouse. You can hire maintenance

specialists if you lack any necessary specialized equipment

and expertise.

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Maintenance Checklist for Your Greenhouse

Fiberglass Covering: Repair all cracks and holes, change

damaged and darkened panels, clean all sides of dirt and

algae and make glass clear for proper light penetration. You

can fix a polyethylene inner layer when required too.

Glass Covering: Fix new panes in place of damaged ones and

adjust panes if they are out of place. Scrape and paint all bars

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and seal panes where necessary. Clean glass pane sides of all

dirt and algae and make all panes free of shading compound

when no longer required, to allow maximum light penetration.

You can use a double layer inflated film inside the glass if the

expected light intensity does not seem likely to cause any


Double Poly Covering: Clean all inflation fans and put in new poly to replace old, discolored and damaged poly. Repair all

holes by fixing the poly tape. Use dry inflation air to remove

condensation between poly layers.

Vent System: Check vents for free movement and operation.

Adjust vents to reduce all cracks on matting surface. Repair

loose vents.

Plastic Seals: Remove all dirt and algae from plastic sealing and replace dirty and worn-out plastic films. Seal all joints to

prevent wind penetration.

Doors: Check all door closures and springs. Seal door moldings and frames, and weather-strip them.

Thermal Blankets: Check that the opening system operates through a complete cycle. Check that all seals, wires and

pulleys are tight. Repair all holes, lubricate them and tighten

all loose drive-shaft couplings. Remove all dirt and algae and

check lubrication of motor and gears.

Standby Generator: Clean all parts of your battery and

check it’s working. Drain generator fuel tanks and refill them

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too. Check for any leaks in fuel tanks. Ensure all lubricants are

at the correct levels. Check all wires (for any looseness) and

switches and ensure the alarm system is functioning properly.

Service the cooling system of your generator.

Heater: Use the correct fuel and maintain an adequate supply of fuel throughout the heating season. Check fuel pressure

and burner nozzles. Clean burner nozzles. Adjust and clean all

pilot lights and make sure outside air is available to burners.

Check all fuel lines for any leaks, cracks, carbon and dirt build-

up. Ensure good quality water is available for the heaters.

Clean fan motors and lubricate them. Check the condition of

the wiring and heat exchangers for any build-up of dirt, carbon

and fix cracks.

Boilers: Check for any mechanical damage in the boiler and

pipes. Adjust air-fuel ratio and check if all relief valves are

working properly without any signs of leakage. Clean blower

fan blades and repair all cracks, patches. Clean the fireside

and waterside tubes thoroughly. Lubricate all bearings and

maintain accurate water treatment records. Replace all

inoperative and leaking valves. Check all back-up boilers

which should function just like the main boiler. Ensure good

quality water is available for the boiler so that it has a long


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Getting the Most from Your

Cooling and Ventilation Systems

Cooling and ventilation systems are essential to maintain

optimum temperature and humidity levels within greenhouses.

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The following tips can help you get the best from your systems

and ensure their sustained performance:

Excessive Ventilation: Refrain from over-ventilating your

greenhouse, especially in summer months. Hot air from

outside could prove too much for your plants. They may die if

you do not employ suitable humidifying techniques. Over-use

of the ventilation systems may harm them.

Retractable Shade Curtains: These curtains function

according to specific light levels. During cloudy days, curtains

could have excessive movement due to unexpected changes of

light and shade. This can cause a breakdown of these

systems. Fix a specific time-delay so that there is no excessive

pressure on your curtains. If your plants are extremely

sensitive to sunshine, use external shading compounds or

fixed curtains.

Pad and Fan Temperature Gradients: Air temperature at

the pads is always cooler than near exhaust outlets,

irrespective of the length or size of your greenhouse. Place fog

or mist lines at right angles at two thirds and one-thirds of

your greenhouse to get the maximum benefit.

Ventilation with Shade Systems: Place shade curtains in

such a way that they allow extensive air exchange. Keeping

little gaps between shade curtains is a good idea.

Mineral Residues: Cooling water may contain minerals like

iron and bicarbonates. Similarly, roof sprinklers and mist

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systems could also leave deposits that could pose problems

with pad and fan systems and the functioning of the electronic

humidity sensors. Regularly clean off residues.

Maintain Proper Air Balance: Do not operate evaporative

systems continuously. This could cause lack of sufficient dry

air. Stop evaporative cooling early in the day. This can ease

problems of excess humidity and wet foliage.

Roof Sprinklers: These may be best in greenhouses with low

evaporative cooling requirements and natural ventilation

systems. Limit roof vent opening angles so that they do not

drip on to your plants within your greenhouses. Mineral

deposits through such sprinklers could stain greenhouse


Humidity and Temperature Sensors: Place the sensors

midway between inlet pads and the fan exhaust. Do not place

them in the direct path of fog or mist nozzles. This helps in

efficient circulation of air within your greenhouse and

maintains proper humidity and temperature levels.

Dust Cleaning: Dust accumulation on fan blades and shutters reduces their efficiency by more than thirty to fifty percent.

This restricts free movement of the blades too. This could

cause irregular and insufficient ventilation within the

greenhouse, leading to accumulation of stagnant air in specific

pockets. This, in turn, also increases heating costs.

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Lubrication: Lubricate all fan bearings, shutters, motors and all free-moving parts of your greenhouse equipment.

Inspection of Ventilation Systems: Check all electrical

cords in your greenhouse. Replace any splits and cracks in

electrical wiring immediately with approved insulated wires.

Check rotation of fan wheels. Improper installation could

cause reverse movement of fans. This restricts fan movements

and results in inefficient circulation of air within the


Humidistat and Thermostats: Check functioning of these

systems in accordance with environmental conditions. Remove

any dust accumulation from sensing elements of the controls

of these systems before re-calibrating them. These should

always be at plant height to provide the best environmental


Pads and Frames: Check these to ensure their perfect

condition. Seal all cracks around the pads to prevent entrance

of air from places other than cooling pads.

Restricting Growth of Algae: Use fungicides in the water

supply to reduce growth of algae and possible accumulation of

it on cooling pads. Algae can destroy cooling pads and

increase airflow.

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Maintaining the Heating Systems

Heating systems in greenhouses are most often hot water

heaters, unit space heaters or steam heaters.

Unit space heaters normally use oil or gas as fuel. Hot

water and steam heaters use boilers to produce heat. Fans help to distribute heat uniformly throughout the greenhouse.

Tips for Maintenance of Heating Systems

Ensure good air circulation through installation of auxiliary

fans, if needed.

Your vent stack of fossil-fueled unit heaters should extend to

more than four feet above any nearby house ridge or


Restrict exposure of the thermostat to any heat source

through a protective shield. Use the fan to aid thorough air

movement and maintain proper air temperatures at bed


Ideally, place thermostats near plant level.

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Check and clean fan blades, burner nozzles and oil fan motors

according to the manufacturer's instructions.

Check all pipes of hot water or steam heating systems for any

possible leaks.

Check the capacity of your boiler or furnace before extending

bench hot water lines or increasing the number of hot water

units. The boiler needs to have sufficient capacity to handle

the additional load.

Keep all hot water pipes clean, without any accumulation of

dust. Dust accumulation definitely retards efficiency.

Check the movement and efficiency of fan blades in the unit's

hot water system. Lubricate them regularly and check

orientation of each of them to assure systematic and thorough

heat and air distribution within the greenhouse. In some

cases, fans could be belt or pulley driven. Check these

systems to ensure smooth functioning.

It is best not to use fossil fuel heaters without vents. If it is

necessary to use such heaters, provide extensive mechanical

or natural ventilation. This helps to remove all by-products of

combustion and assures a healthy environment for plants to


In poly tube heat distribution systems, check the length of the

tubes, spacing, and location of tube openings in accordance

with your plants’ heating system. Perfect configuration of the

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heating system is essential for efficient heating of the


Ensure all boiler components are in perfect condition before

the start of the heating season. Also, contact your fuel dealer

before the season starts to check costs and assure continuous

supply of fuel.

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Control Greenhouse Pests and Diseases

Humid conditions in greenhouses can be a breeding ground

for various pests and diseases that will prove harmful to your

growing plants and seedlings. Maintain a clean, regularly

disinfected greenhouse to curtail such problems. Clean your

greenhouse in either late winter or early spring.

Cleaning Materials and Tools for a Small Greenhouse

• Washing up Gloves

• Brush or Mop

• Wire Wool

• Scrubbing Brush

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• Domestic Cleaner

• Disinfectant

• Fungicides and Insecticide with necessary biological


• Non-Drying Glue

Cleaning and Disinfecting Your Greenhouse

First, empty greenhouses of all pots, plants and other


Then, clean greenhouses of any weeds, dead plants and

rotting leaves.

Wash all accessible glass with warm soapy water.

Clean all pots with disinfectant.

Use fresh compost in pots for sowing seeds and seedlings. Use

a covered watering can with copper-based fungicide in the

water to water your seedlings.

Hang yellow sticky traps near plant tops in your greenhouse.

These prevent build-up of different flying pests like the white


Vine weevils often attack the roots of plants in pots. Check for

these pests while re-potting your plants. Applying non-drying

glue as a band across pots can stop any influx of adult

weevils. You can also use soil drenches, composts and other

biological controls as protection against adult weevils.

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Allow as much air circulation as possible within your

greenhouse. Keep open roof vents and windows to prevent air

stagnation. Powdery Mildew and Grey Mold are common

diseases in greenhouses with stagnant air. Fan heaters

blowing in cool air can act as a good remedy.

Spider mite populations thrive in a hot and dry climate. In the

summer, greenhouses present this sort of atmosphere that

allows spider mites to multiply rapidly. These appear as yellow

and brown specks with fine webs on the leaves of your plants.

Move out as many plants as possible from the greenhouse

during such weather. Use handheld mist sprayers to increase

humidity levels within the greenhouse. You might use

systemic insecticide spray too.

Grow different crops and plants every year in your greenhouse

to prevent growth and spread of soil pests and diseases.

Cover potted plants with sand or grit to prevent an influx of

sciarid fly or fungus fly. This greenhouse pest eats off the

plant stems just above ground. Grease a yellow card and hang

it near the plants.

Botrytis is the most common greenhouse disease causing

brown spots and patches of gray mold over the plants. The

best way to control this pest is to increase air circulation and

avoid planting seedlings in pots kept in damp and shady parts

of the greenhouse.

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Mildews affect young shoots, like those of rose, fruits,

poppies, begonias etc., in your greenhouse. Remove and burn

affected leaves. Increase air circulation within the greenhouse

and, if the problem is very severe, spray dispersible sulfur or

copper fungicide.

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Part-VI: Greenhouse Accessories

Greenhouse Accessories Guide

Numerous greenhouse accessories may be helpful to maintain

an efficient, productive greenhouse.

These accessories play an equally important role in growing

plants in greenhouses.

Wireless Thermometer: This is a digital thermometer that

helps you find the temperature within your greenhouse

without you actually moving out of your house.

Budding/Grafting Knife: These knives have special hand-

made blades that help you cut and graft your plants with


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Cleaner: Cleaners with no toxic properties are the best for cleaning your greenhouse. They prevent spreading of any

poisonous fumes within the greenhouse.

Greenhouse Shade Netting: This provides temporary or

permanent protection to your plants and crops within the

greenhouse. The netting has strong tying points with eyelets

woven into their seams.

Traditional Wooden Riddle: This common greenhouse tool can help you clean gravel for paths, remove stones from soil,

provide fine layered soil for sowing seeds and do similar work

in your greenhouses.

Warming Pads: These pads help in quick germination of

seeds within the greenhouse. Space crunch is common in

greenhouses. These pads speed up the germination process

and offer more free space.

Garden Track: This accessory consists of heavy-duty plastic tiles linked with clips. Join these to form wide outdoor

walkways. Making many pathways within greenhouse does not

take much time.

Magic Seeder: This accessory helps you dispense seeds in

plug trays and pots easily. All you need is little bit of thumb

pressure for accurate planting.

Aluminum Staging Foot Plates: Use these plates in

greenhouses with soft floors. These prevent seed tray rack

legs from sinking into the ground.

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Small Fixing Support: These small supports help you tie

growing vines and similar creepers. These supports have

cropped bolts to help easy fixing.

Glazing Spring Clips: These steel wire clips are W-shaped.

They help to hold glass in aluminum greenhouse frames.

'S' Hooks: These hooks provide necessary support for

hanging baskets within greenhouses.

Aluminum Lap Strips: You can bend these strips in any

shape you want. They are very useful within greenhouses.

Greenhouse Door Wheels: These wheels are best for use in

a greenhouse with sliding doors. You can change the wheels to

suit your preferences.

Greenhouse Fix Clips: These clips prove useful in many

ways in your greenhouse. You only need to insert the clip in

the bolt slot within the glazing bar and twist it to make it

secure. These are easy to use and can help fix insulation and

shading in aluminum greenhouses. You can use spacers with

the fix clips to create small gaps of about an inch between

lining material and greenhouse glass.

Greenhouse Seed Tray Racks: These racks help you grow

numerous seedlings within a minimum space. They can prove

very useful in crowded greenhouses. Normally, these trays

hold four full-size seed trays on each tier.

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Cropped Head Bolts & Nuts: These bolts are rectangular in shape and fit into slots of the aluminum glazing bars. They help you fix things without having to dismantle anything first.

Greenhouse Shelving: These aluminum shelves create extra

space within the greenhouse. These are available with suitable

brackets and bolts. They can hold numerous extra structures

within your greenhouse to add options and save space.

Greenhouse Propagators: These offer the necessary

amount of heat for every part of the plants within

greenhouses, especially to ensure healthy growth of plant

roots. Use propagators that best suit your requirements.

Garden Netting: There are different types of garden netting available for use in greenhouses. These include insect mesh,

butterfly netting, anti-bird netting, windbreak netting,

greenhouse shading and others. They offer protection for your

plants within your greenhouse.

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Know Your Equipment and Supplies

Greenhouse gardening is becoming very popular. You can

have a greenhouse on a commercial level or have it as your

hobby. Certain essential equipment and supplies are

necessary in any greenhouse to help the plants in the

greenhouse to grow healthily. Greenhouses are like chambers.

You regulate light and temperature within your greenhouse to

promote optimum growth of the plants.

Essential Greenhouse Supplies

Fog System and Watering System: Water is essential for

all plants in the greenhouse. According to the type of plants,

they may require daily watering or watering on alternate days.

You should have a proper watering system - a can for a small

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greenhouse, ranging up through a capillary system, dripping

system, etc., to provide the necessary water to your plants.

Fog systems help maintain essential humidity levels in


Heating System: Although the glass panes on greenhouses

bring in essential heat, it may not be sufficient during the cold

winter months and at night. You need a heater to regulate

temperatures within your greenhouse. You can use a fuel

heater or electric heater according to your choice, depending

on costs and other factors.

Ventilation: This is very essential to aid proper air circulation within the greenhouse. Heaters release fumes and you need to

push out this air.

Greenhouse thermometers: Help to detect the prevalent

temperature within your greenhouse. You can then act

according to temperature readings on your thermometers.

Lighting Arrangements: Light is essential for proper growth of plants within your greenhouse. Normal sunlight may suffice

for your plants’ requirements. You can have additional lighting

arrangements with fluorescent bulbs and other lamps for

cloudy days and the winter months.

Shading Equipment: However, excessive light can prove

harmful too. Therefore, you require special shading materials

like shading compounds, blinds or plastic curtains to filter any

unwanted light from entering your greenhouse.

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"Building Your Own Greenhouse" by Max Clarke

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Flooring and Benches: Use a functional, non-skid flooring

for your greenhouse with gravel. Non-skidding surfaces can

prevent accidents during watering. Additionally, place benches

within the greenhouse for you to rest and take in the beauty

of your greenhouse while caring for it.

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Cold Frames and Hotbeds

Cold Frames

Cold frames are boxes without bottoms, but they have

removable tops. These prove helpful in protecting plants from

the extremities of weather; cold temperatures and harsh

winds. Cold frames use sunlight to heat soil within the box

during daytime. This heat radiates back to the plants at night

and keeps them warm.

You do not usually need any artificial manure or fertilizers

within cold frames.

Cold frames help you start your growing season early. You can

grow seasonal vegetables and flowers within these cold

frames. Such protected growth lets you transplant your plants

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"Building Your Own Greenhouse" by Max Clarke

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early too. These cold frames provide the ideal environment by

allowing you to save your seedlings from the winter frost. The

setting is similar to that within a portable greenhouse.

Anthurium and other plants in a greenhouse

There are different types of cold frames available, like Juliana

Cold Frames, Halls Cold Frame Kits and others.

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These kits are available in two models. The single cold frame

has two sliding and hinged vents with polypropylene glazing.

The double cold frame has polypropylene glazing with four

hinged and sliding vents.


A bed of soil within a plastic or glass frame constitutes a

hotbed. Steam, electricity, manure or hot water pipes heat the

bed of soil. Hotbeds prove useful for growing seedlings and

small plants early and easily too. You can sow seeds of flowers

and vegetables long before you could sow them in the outside


Hotbeds prove to be a good initial sowing ground for

propagating growth of your seedlings. The hotbed should

normally be on well-drained soil. In some places, you need a

three-inch gravel base underneath the prepared soil mixture

of hotbeds.

If you use electricity for heating hotbeds, lay cables at the

bottom of the bed or on a bed of sand and cover it with

gravel. There should be a covering of two inches of sand over

the cable. If you intend sowing seeds directly into the hotbed

and not in pots, use wire screening mesh covering of inch-

wide overheating tape to prevent any damage from cutting


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Facts about Famous Greenhouses

1) Greenhouses have different names across different

countries. The British prefer calling greenhouses

“conservatories” as they conserve plants. The French

call their greenhouses “orangeries” as they prevent

oranges from freezing.

2) Leamington in Ontario houses the largest greenhouse

complex in the world. More than two hundred acres of

land is under glass for commercial cultivation of


3) The concept of the modern greenhouse started in Italy

in the sixteenth century. It then spread to Netherlands

and England. Samuel Cocking built the first greenhouse

in Japan in 1880. David Chelf from the University of

California in Berkeley designed the first air-supported

and wind-assisted greenhouse.

4) The Palace of Versailles houses a huge greenhouse with

a length of five hundred feet that is forty-two feet in

width and has a height of forty-five feet.

5) The New York Crystal Palace, London's Crystal Palace,

Kew Gardens in England, and Munich’s Glaspalast are

among the different greenhouses that have been used

for horticultural and non-horticultural exhibitions.

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