Supplies Buyers Guide
Ventilation
Ventilation is a necessity for any greenhouse. Ventilation
serves two main functions a) provides fresh air, and b) greenhouse
cooling. Without good ventilation, a greenhouse is just a
solar furnace. Greenhouses are designed to store heat from
the sun during the day creating a warmer temperature in the
greenhouse versus outside of it. This makes cooling a greenhouse
on a hot day a difficult task that cannot be accomplished
without a good ventilation system. Cooling in the summer can
be accomplished easily with a combination of shade, proper
ventilation, and an evaporative cooling system like a misting
system, fogger, or evaporative cooler.
An exhaust fan ventilation system usually consists of a fan
setup to blow hot air out of the greenhouse and bring in fresh
cooler air inside the greenhouse via intake shutters mounted
on the opposite end of the structure. It should be able to
make a complete change of air in 1 to 3 minutes (about 1 minute
or less for small greenhouses, 2 to 3 minutes is acceptable
for large commercial size greenhouses) in summer to keep temperatures
in the greenhouse at a reasonable level.
Many people use roof and/or side vents to supply fresh air
to plants and cool their greenhouse. This is ideal for venting
during cold months because fresh air is supplied to plants
more gradually than an exhaust fan system reducing any "temperature
shock" to plants. Circulation fans are highly recommended
for use with side and/or roof mounted vent systems. These
fans move air throughout the greenhouse eliminating hot and
cold spots, which is useful when venting or heating your greenhouse.
The increased air movement helps to expel hot air out of the
window vents and provide fresh air for plants.
We recommend automating your ventilation system. Failing
to vent your greenhouse one hot day could destroy all of your
hard work. Thermostatic controls and solar powered auto vents
can also maintain a more consistent temperature in your greenhouse,
which promotes healthier plant growth.
Misting and Fogging
Misting and fog systems have a variety of uses in a greenhouse.
It is important to determine what you want to accomplish with
a misting system before purchasing one. Humidity: It is important
to maintain a healthy humidity level (50% to 70%) in a greenhouse.
This is healthy for the plants and higher humidity levels
also help reduce the watering frequency of plants in the greenhouse.
When the greenhouse is vented, essential moisture is lost,
and plants are more likely to dry out and wilt. Fog and Misting
systems with fine nozzles are very effective at this because
smaller water particles evaporate more quickly. Evaporative
Cooling: Misting systems help cool greenhouses with a fine
mist that lowers air temperatures when it evaporates. Smaller
nozzles work best for cooling also. Watering: Overhead misting
systems are used for watering many types of tropical and foliage
plants. Cuttings and seedlings are commonly watered with misting
systems or mist nozzles for hoses because watering with a
regular wand or watering can may disturb the surrounding soil
causing plants to take longer to root. Larger misting nozzles
are needed for cuttings and seedlings to make sure the soil
is properly saturated. View misting systems
Shading
Shade covers are the way professional growers keep their
greenhouses cool during those long hot summers. They block
a percentage of the sun's rays from entering the greenhouse,
which can reduce temperatures over 20% alone. Shade covers
are relatively inexpensive and also provide shade for plants
that don't grow well in full sun. The amount of shading necessary
varies depending on greenhouse design, your local climate,
and the light requirements of the plants in the greenhouse.
Most greenhouse shade cloths fall in the 45% to 65% shade
range. When buying a shade cover remember, more is not always
better. Excessive shading can slow plant growth and cause
plants to stretch. View shade covers
Heating
The heating requirements of a greenhouse depend on the
desired temperature for the plants grown, the location and
construction of the greenhouse, and the total outside exposed
area of the structure. Much of the daily heat requirement
may come from the sun, but if you want your greenhouse to
be more than a few degrees above the outside temperature at
night, you will need to provide it with a heat source. The
heating system must be adequate to maintain the desired day
or night temperature. Heating systems can be fueled by electricity,
gas, oil, or wood. The choice of a heating system and fuel
depends on what is locally available, the production requirements
of the plants, cost, and individual choice. Heating requirements
for your greenhouse can be determined with our Heater BTU
Calculator.
If you're using your greenhouse to start seedlings and root
cuttings in the spring, supplemental heating probably will
not be necessary. In mild climates, 12' x 12' and smaller
model hobby greenhouses can be adequately heated with electric
heaters (make sure electric heaters are not exposed to water
to avoid a dangerous shock). An electric heater is clean,
efficient, and easy to install and maintain. Small gas or
oil heaters will also work well in hobby greenhouses. With
larger size greenhouses and cold climates where temperatures
regularly fall below freezing, larger gas greenhouse heaters
are most commonly used because it is cheaper to heat with
gas than electric in most areas.
For safety purposes, and to prevent harmful gases from contacting
plants, all gas, oil, and wood burning systems must be properly
vented to the outside. Use fresh-air vents to supply oxygen
for burners for complete combustion. If you use a gas heater
in your greenhouse, it is recommended that natural "indicator"
plants like tomatoes, impatiens, and salvia be placed near
the heater. These plants are very sensitive to gases produced
from combustion in gas heaters and will have malformed leaves
and stems and/or prematurely lose flowers before other plants
if the gases are not being vented properly. Also, look for
safety features like automatic overheat controls when purchasing
a heater. Portable kerosene heaters used in homes are risky
because some plants are sensitive to gases formed when the
fuel is burned. View heaters
Flooring
The floor of your greenhouse is both functional and aesthetic.
It forms the surface you walk on and helps complete the image
of the greenhouse. The walkway and the area under the benches
are usually two different materials. The walkway should form
a firm nonskid surface for walking, be easy to clean, and
be durable enough to withstand constant moisture and dirt.
Common materials used for a walkway include concrete, brick,
stone, gravel, wood slats, and ground bark. A porous material
that can be dampened to help provide humidity and should allow
easy drainage of water usually covers the area under the benches.
For under bench areas, consider gravel, sawdust, ground bark,
or any other porous material. You will want to lay a sheet
of woven weed barrier (ground cover) under the floor covering
to prevent weed growth, because weeds harbor many pests and
diseases. For more information, take a look at our guide on
building a foundation and floor.
Benches
You will want benches in your greenhouse. They make a
world of difference in the ease of gardening and add a lot
of extra working space to your greenhouse. Benches also provide
the area under them with plenty of shade, which is an ideal
environment for many plants. Greenhouse bench tops should
have an open design, which allows water to drain, and fresh
air to flow through them. View benches
Lighting
If your growing area or the season does not provide your
plants with enough light, you may need to provide artificial
lighting. For detailed information about artificial lights
and options available, you can visit our Grow Light Guide.
View lighting systems
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