Choosing a Greenhouse

The greenhouse featured in this project is a 12- by 12-foot structure that is set up against a garage for easy access. The greenhouse is located in Zone 4, which has an annual average low of –30 to –20 degrees F. The region's inclement weather requires special considerations for preparing a greenhouse.

Although the greenhouse in this project is fairly large for a hobby greenhouse, it's only one of a variety of greenhouses available. When deciding on a style for your home, the sky's the limit. There are small solariums, medium size greenhouses and larger structures like conservatories.

You'll find most greenhouses are made from aluminum, which is lightweight and weatherproof. Galvanized steel is also lightweight and very sturdy. You can also use wood, but be sure to choose pressure treated lumber, cedar or redwood for weather resistance.

No matter which type of greenhouse you decide on, there are several considerations when choosing a building site:

Light

• Sun-loving plants need six hours of sunlight. Sites with less need supplemental light.
  
• A sheltered area is good, but too much shade results in poor growth. Look for trees, shrubs and structures that may cast shade.
  
• Southern exposure is best, east or west is okay, but northern exposure is probably too shady.
  
• The greenhouse in this project attaches to a garage, which will cast a shadow on the far end of the greenhouse. This will be important to consider when placing plants.

Exposure

• If the site is too exposed, it will be costly to heat in winter and keep cool in summer. Insulation can help in this situation.
  
• Protection from wind will keep the greenhouse sturdy longer.
  
• Too much shelter can mean not enough light.

Foundation

• In this project, the greenhouse foundation was dug in and anchored with pressure-treated lumber. For this type of foundation, be especially careful to choose a level area where water doesn't collect.
  
• Many foundations are dug in and then filled with concrete.
  
• Plan ahead when possible; the less frozen, wet or snow-covered your yard is the easier it is to lay foundation. Contractors can thaw frozen ground and move snow, but it costs more.

Proximity to your home

• Putting a greenhouse against a house makes connecting water, gas and electricity easier.
  
• The area in front of the greenhouse should be clear of obstacles.
  
• The path leading to the greenhouse should be level and wide enough for a wheelbarrow. Be sure the ground is hard enough to withstand wheelbarrow traffic.

• The greenhouse in this project is made from galvanized steel, which is lightweight, sturdy and won't rust. It can withstand weight up to 100 pounds. It's also good for windy areas because it can withstand winds up to 70 miles per hour, making it a good choice for Zone 4 inclement weather.
  
• The greenhouse walls can be constructed from glass, which is heavy and can be expensive; film plastic, which is economical but not insulating enough for this region; or a rigid plastic, which is shatterproof and retains heat.
  
• This greenhouse design also features a storm door that is 36 inches across.