Buying a greenhouse, important selection criteria

For those who are lucky to have a garden, perhaps you’re dreaming of one day being able to afford a garden greenhouse.

Of course, this is the dream of all plant-lovers in temperate climates.

If some greenhouses come out cheap at 200, 300 or 400 dollars, others can easily reach 5,000 dollars and more.

It makes sense to choose your greenhouse well before setting out to purchase it!

Land surface needed to have a greenhouse

Ensure that you have enough space for your greenhouse, because many people actually buy greenhouses that are too big for the space they have available.

  • Also ensure that you have enough space for assembling the greenhouse together.
  • You should be able to walk around your greenhouse freely.
  • Avoid setting the greenhouse in a walled-in corner or along a wall, because if a window breaks, replacing it means being able to access it from the outside.

Ideal exposure for a greenhouse

A thriving plant-filled greenhouse seen from the inside.The best exposure for a garden greenhouse is generally south, south-east and sheltered from strong winds.

In summer, if temperatures rise too much, it will always be possible to shade the inside with small curtains designed specifically for the purpose.

If possible, strive to avoid placing your greenhouse under trees because falling branches would fall and break the glass.

If a window pane breaks and a gust of wind blows into the greenhouse, the whole structure is at risk of flying apart and the superstructure might fold.

  • Exposing your greenhouse to strong winds might damage your greenhouse, especially in case of storms.
  • The wind surface area is so big that the greenhouse would collapse.

Preliminary work before setting up a greenhouse

These steps aren’t necessary, but they are highly recommended, as simple preparations are easier before the greenhouse is in place.

These preparations are related to connecting water and electricity for the greenhouse.

  • Bury electric cables and water pipes in accordance with local regulations, especially as regards electricity.
  • Special tubing is required to house the electric cables.
  • Inside the greenhouse, choose water-tight sockets and switches.

Some greenhouse manufacturers make it possible to anchor the greenhouse to the ground using concrete fixtures, this is highly recommended.

  • Choose high-strength concrete.
  • Don’t scrimp on the quantity of concrete used, because the better the anchorage, the more the greenhouse will stay put when the wind gets blowing.

A greenhouse in itself isn’t very heavy, because the structure is made from aluminum and glass is relatively thin, around ⅛th of an inch (3 to 4 mm).

  • This lack of mass is what must be compensated for with sufficient anchorage.

Invasive plants in greenhouses

If you grow plants that tend to take up space, your greenhouse may quickly turn out to be too small.

For example, a lime tree (Persian Tahiti lime tree) only 2 feet (60 cm) tall in 2007 was over 8 feet tall and 6 ½ feet wide just 4 years later.

  • To sum it up, if your budget allows for it and if you’ve got the space, go big.
  • What you want to do in a small greenhouse can be done in a larger one…

Greenhouse floor area, building permit and regulations

Some municipalities require building permits for greenhouses only when they exceed a given surface area, or are built as an extension of the house. In any case, it is rewarding to inquire at the local town hall or urban development office about this and put in the required paperwork.

  • Usually when surfaces are relatively small, a full-blown building permit isn’t called for and it is enough to fill in a preliminary declaration.

Also take care to follow regulated buffer zones where construction of certain extensions or greenhouses is not possible at a certain distance from your neighbors’ properties and public land.

  • Usually stipulated distances are of 12 feet or more between greenhouse and fence separating lots, but this is subject to local zoning ordinances which must be verified beforehand.

Doors and greenhouse ventilation

Ensure that the greenhouse has doors, preferably sliding doors, because a hinge door can slam with a gust of wind and break a pane of glass.

Choose a greenhouse type that allows for ventilation devices such as jalousies or dormer windows.

  • The number of ventilation openings may vary according to the length of the chosen greenhouse.
  • Some greenhouse designs can be fitted with extra dormers or jalousies.
  • Check with your manufacturer or sales representative.

Choosing the glass for a greenhouse

Some manufacturers offer different glass packages for the greenhouse windows, and this can heavily influence the price of your greenhouse.

Horticultural glass

Horticultural glass is the standard fitting and is nothing more than common glass in a thickness of an ⅛th of an inch (3 to 4 mm).

  • This type of glass is readily available in DIY stores and can even be cut to size there.
  • Very convenient to replace a broken window pane.

Toughened safety glass

This type of glass is also often available, and since it is toughened it is much more resistant than conventional horticultural glass.

It is said that this glass is 5 times stronger than standard horticultural glass.

  • It has a better resistance to thermal shock, weather, and scratching.
  • However, it is more expensive, and not always available everywhere.
  • This glass is stronger than conventional glass, and when it breaks, it breaks into tiny pieces just like a car windshield does.

Polycarbonate

Another type of pane can be used, and this is polycarbonate.

This is a sheet of plastic, with a thickness of around ⅝ths of an inch (1.5 cm), with a hollow core that makes it an excellent insulator.

  • Polycarbonate can bear heavier loads than glass can, which is an advantage in snow-prone areas.
  • It is also very light and might not be as sturdy for windswept locations.

Polythene

This replaces the notion of hard pieces of sheet glass or plastic with flexible polythene plastic film instead. The structure must be self-supporting and the film is attached to it with special fixtures. Sometimes simple plastic tubing shaped into hoops nicely does the trick.

  • This is the weakest and most fragile solution, since it’s essentially similar to thick plastic wrap and can be pierced or torn.
  • It’s the lightest and cheapest option.
  • Plastic films are often rated and tested for a specific guaranteed lifetime like 4, 5 or 8 years.
  • After that, they must be replaced due to tearing or coloring.
  • Not recommended for windy areas.
  • Very easy to set up.

Help on setting up your greenhouse

An iron and glass greenhouse in part shade in a garden.Assembling a greenhouse is often akin to assembling a puzzle, and to avoid mistakes during assembly it is recommended to follow this advice:

If you choose to assemble your greenhouse yourself, take particular care in getting things level, because if posts and frames aren’t level, it will be very difficult to fit the panes in.

  • Verify levels from the ground up, even the foundations should be level.
  • The base of the greenhouse guides the rest of the frame and panes, so leveling the base perfectly is critical from the very first step.

Choosing screws and fixtures

Some greenhouse kits are assembled with stainless steel nuts and bolts and this of course provides for a greater strength, because steel can be tightened well and it will not rust.

Other kits are delivered with aluminum screws, and since aluminum is a ductile metal, it cannot be tightened as much, otherwise the screws might break and the strength will be compromised.

  • Stainless steel fixtures mean a slight increase in purchase price, but in the end it is well worth it, particularly since this increases wind resistance.

Choosing raw materials for the greenhouse

Aluminium-framed greenhouse with brick foundations.Even though most greenhouses on the consumer market are designed with aluminum frames, recently more and more greenhouses are designed with wooden frames.

Wood is heavier, and greenhouses made from wood have an advantage when it comes to resisting strong winds, even if anchoring the structure with concrete is still needed.

The wood used is chosen specifically to be weatherproof and is often treated so that it won’t deteriorate as time goes by.

  • It’s also possible to paint or varnish it.
  • A wooden frame greenhouse is much more expensive than an aluminum frame greenhouse of the same size.

Philordi


Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Small greenhouse shared by EME under © CC0 1.0
Inside a greenhouse shared by Mariamichelle under © CC0 1.0
Iron & glass greenhouse shared by hsvall under © CC0 1.0
Brick foundations shared by artyangel under © CC0 1.0