Greenhouse/Dome Set Up

Gardening Dome Set Up-1

Exterior Structure:

The first decision in setting up your gardening dome, or other greenhouse, is to decide on your exterior structure.  There are many venues to choose from: Heated greenhouse, Hoop House, Dome, attached to a structure or freestanding.  There are many companies that have pre-fabricated gardening greenhouse structures, or you can design and build your own.  Your local topography, weather, and personal preference will dictate your final gardening greenhouse design. Your local gardening club or university extension service is a good place to start for information.  You will also need to decide if you wish to actively heat your gardening greenhouse or if you with to use passive solar only.  Heat retention is discussed in Gardening Dome Set Up-2.  Which method works for you and your gardening ideas?  Two possibilities are shown below.

Figure 1 shows a hoop house using a protective covering that can be raised and lowered to ventilate during hot summer days.  Its main purpose is to extend the growing season.  The protective environment allows you to plant earlier in spring and harvest later in fall while protecting crops from frost, wind, and hail.

Figure 2 shows a dome greenhouse structure set up for three to four season growth based on passive solar and reflective insulated panels.  The temperature regulated vents open during extreme heat and a solar vent system can help with air circulation.  A small solar fan can be added to circulate heated air through the soil in flexible pipes to extend the gardening season through the winter if desired.

Gardening Dome Set Up-2

Heat Retention:

Heating and heat retention is a critical element of your gardening greenhouse structure.  During your cooler seasons, especially in cooler gardening climates, you will want to assure your heat retention for optimal growth of your garden greenhouse plants.

Heat Retention:

Heat Sink:

There are many possible heat sinks you can use to ensure heat retention in your garden greenhouse.  The following are just a few ideas to consider.

Soil – The soil has a significant mass that can help with your heat retention.  Raised beds heat faster and retain heat well.  If temperatures at night outside your greenhouse are expected to be significantly below freezing, watering the soil early in the day will help retain heat even more through the increased heat retention of the water in the soil.

Brick – Raised beds built with brick, as in the figure 1 below, add a significant heat sink that can radiate heat well into the evening and help keep the soil warm.

Rock/Cement – Some greenhouse users have rock towers, or are built on an adjoining cement wall, to act as their heat sink.  A rule of thumb is to use 80 pounds of rock, brick, or cement for every square foot of greenhouse for adequate heat retention in a passive solar garden greenhouse.

Water – A water reservoir can also be a significant heat sink.  The water reservoir can take the form of an open pool, which can double as a fishpond or fountain.  Many companies sell bladders that can either be framed on one wall, or lay on the ground, possibly under your seedbeds, for heat retention.  Water walls built of stacked jugs have also been used successfully for heat retention.  A 500 square foot greenhouse needs about a 1000 – 1200 gallon heat sink (about 2 gallons of water for every square foot of space) for adequate heat retention in a passive solar greenhouse. Figure 2 below shows a water bladder in a dome structure.

Reflective Panels:

Another possibility to aid heat retention in your garden greenhouse is to use reflective panels or reflective insulation on the northern most wall (southern most wall for those who live in the southern hemisphere).  A commonly used material is a foil covered bubble insulation, which can be cut to fit your insulating needs.  See Figure 2 – reflective insulation is above the bladder.

Active Heating:

Active heating can be attained through a gas or electric powered heater or blower.  This type of heating is necessary for the more avid greenhouse gardener who needs more consistent heating during the winter season.  It can even be combined with a cooling and humidity control system for year round climate control.

Gardening Dome Set Up-3

Venting and Cooling:

Venting your garden dome or greenhouse is as critical as heating.  Especially in warmer, sunnier climates ventilation will become critical. There are different venting systems that can be used to prevent your garden dome or greenhouse from overheating, or becoming uncomfortable during the heat of summer.

Vents: Vents can be manual or automatic, solar powered or electric.  Venting can be as simple as raising a sidewall plastic curtain or opening a greenhouse shutter installed in the side of your greenhouse.  An automatic solar vent is shown in Figure 1 below.

Fans: There are many fans to choose from – exhaust fans, circulation fans, and portable fans that can be placed at strategic spots for best circulation.  These may be wired into an existing electrical system, or use an electric solar panel to power them.

Evaporative Cooler:

There are portable, wall mount, and wall pad evaporative cooling systems that are commonly used in garden greenhouses.  Many are thermostatically controlled to allow you to keep your garden greenhouse within a certain temperature range.  True “Air Conditioners” are rarely used in a greenhouse setting, as the added humidity of an evaporative cooler is a plus, especially in dry western climates.

Shade Cloth:

There are many types or grades of shade cloth available for your garden greenhouse or dome.  The grade of shade cloth you use will depend on the amount of sun you wish to block.  The plants in your garden dome or greenhouse may need more protection from the sun than is naturally filtered by the greenhouse siding you are using.  Shade cloth can block from 30 to 95% of the sun’s rays.  This can help keep your greenhouse cooler in the daytime, and many gardeners also feel that if the shade cloth is hung inside the greenhouse it can also help retain heat at night.  Shade cloth can be hung inside or draped outside of your dome or greenhouse structure.

Gardening Dome Set Up-4

Interior Structure:

After establishing your exterior garden structure, you will need to choose your plant growing method.  Again, the choices are limited only by your imagination, but there are three basic gardening methods: In-Ground gardening, Raised Bed gardening, and Container Gardening.  In many cases you may wish to combine these methods to meet your gardening needs.

In figure 1, you can see that in-ground gardening is being used.  This works well for the hoop structure, with both ends opening enough to allow a tiller or small tractor to enter and work the soil for planting.

Figure 2 shows raised bed gardening in a gardening dome.  Raised bed gardening allows the soil to warm faster, retain its heat with the brick edging, and allow for easier planting and weeding.  It would also allow for bringing in soil to the gardening site, if the local soil was not amenable to gardening specific varieties of plants.  This gardening dome structure also allows for hanging containers from the crossbars.