Tips for Installing Your Greenhouse
Choosing the right location and creating a solid foundation for your greenhouse is very important. And not only that, ensuring it will have adequate sun exposure, be protected from the wind, sited on level ground and have proper access is also vital to extending your growing season.
1. Sun Exposure
Ideally, you should try to find a location on your property where your greenhouse will be getting at least 6 hours of direct sunlight per day during the winter. By orienting the greenhouse east to west, the largest side will get full southern sun exposure. If you don't have an area with enough sun, grow lights can also be added to compensate.
Uniform light distribution within your greenhouse will produce strong plants without hot spots disturbing their growth. Temperatures increase unevenly indoors if direct light strikes one greenhouse end while the opposite end remains in shadow. Responding particularly well to red and blue light found within the light spectrum, plants depend on diffused greenhouse light for optimum growth.
The southeast side of your property allows you to take advantage of as much sunlight as possible, especially in the morning. The reduced intensity of morning sunlight provides a comfortable photosynthesizing location for sensitive plants -- energy production starts as early as possible when the sun rises. In addition, the strategic southerly position provides plants with light even during the cooler winter months when the sun's position rests low on the horizon.
2. Air Flow
Excessive greenhouse temperatures result in poor plant growth, so ventilation is key. Greenhouses with roof and sidewall vents operate on the principle that heat is removed by a pressure difference created by wind and temperature gradients. Wind plays the major role in cooling your plants. In a well designed greenhouse, a wind speed of just 2-3 miles/hour provides 80% or more of the ventilation. Wind passing over the roof creates a vacuum and sucks the heated air out the vent. If sidewall vents are open, cool replacement air enters and drops to the floor level. If the sidewall vents are closed, cool air enters the bottom of the roof vent and the heated are escapes out the top of the vent.
Roof and side vents on conventional greenhouses need to be large enough to get good air movement. It's also beneficial to allow bees and other pollinators to have access to your plants. The best orientation for the greenhouse is to have the normal summer wind direction blow over the ridge so that it creates a vacuum on the leeward(downwind) ridge vent. For summer ventilation, the windward side vent opening should equal the leeward ridge vent opening. Grizzly provides both a louvre side vent option as well as roof venting in many greenhouses. We also provide solar triggered (by temperature) window opening arms to help with this.
To get adequate cooling on hot, sunny days, a shade kit system may be needed. It should be porous so that the heat generated below can escape up through the shade material. Evaporative cooling, either a fog system or portable evaporative coolers can also give added cooling. A large number of hanging baskets tends to reduce natural cooling.
3. Ease of Access
When positioning your greenhouse, it is important to know that you can access your water supply for hooking up hoses. Often a drip irrigation system on a timer which is plugged in via extension cord or outdoor protected outlet. It's also important to avoid large overhanging trees that may drop sap, or branches/leaves onto your greenhouse. Also, siting it in the shade of large trees can encourage algae/mildew to build up.
As you’ll be visiting your greenhouse very regularly, particularly during the summer, make sure it’s easy to get to and as near to the house as possible. Whether your visits are for damping down, daily watering, opening and shutting doors and vents, or just popping in to pick a few tomatoes for your lunch, you want it to be close at hand.
4. Level Foundation
Avoid putting your greenhouse on a slope. Although it is technically possible, it would make things complicated, as the staging inside needs to be horizontal. Definitely don’t site it at the base of a slope, as this is often a frost pocket where coldness lingers – which doesn’t make for successful winter growing.
If you’re planning on growing in the beds inside your structure, choose a spot with decent soil, if you can, as you’ll be asking a lot from it. Poor soil can be improved by digging in organic matter, and raised beds are a good option, particularly in a polytunnel. Try to avoid stony or rocky ground, as it can make the construction process problematic.
Ensure there is at least 1m of space all around your structure. Not only does this make putting it up easier, but it’s useful when panes or covers need replacing, and when cleaning or simply walking past. Leaving this space will also mean that fences and other structures aren’t close enough to cast shade or hinder ventilation.
Think ahead about anchoring down your greenhouse. You may wish to pour cement posts in each of the 4 corners, and then bolt the posts to boards to which you can anchor your greenhouse. Our greenhouses at Grizzly all provide clips and holes for anchoring the base to the ground. We even provide an anchor kit to help you secure it further.