How to Build and Pimp out a Greenhouse

Greenhouses come in many shapes and sizes, with various designs suited for different applications. However, in general, the primary purpose of a greenhouse is to extend the growing season, allowing growers to plant earlier and harvest later. Greenhouses are excellent for expanding your food selection year-round and can be done on a budget.

I have been playing with simple greenhouse operations for a few years. However, the goal has always been to produce food locally for longer. Your first greenhouse will empower you to feed yourself. 

The Greenhouse Planning Stage

Start at the end and work backward when considering how to build your greenhouse or what materials you’ll need. Here are some questions you’ll need to answer:

• What do you want to grow?
• What is your budget? 
• Is it possible to find used gear?
• How much do you want to grow?
• How much space do you have available?
• What are your light sources?

The key to all successful building projects is knowing what you consider a success and finding a way to make it happen. For this article, we will focus on budget-friendly greenhouses and the essentials you need to succeed. These small-scale structures are perfect for an urban backyard or a larger-size semi-rural lot.

Greenhouse Materials

When considering materials for a greenhouse, three in particular come to mind:

• Polyplastic (potentially fibreglass reinforced).
• Glass.
• Polycarbonate.

Choosing poly for the structure will likely be the most cost-effective option. For most people, glass can be a budget buster. However, I suggest using only sliding glass doors if you can access used building materials. They are typically double-pane, provide insulation, and can often be found for free or at a low cost second-hand. Glass panels can be constructed into a wooden frame and make for a great greenhouse structure. 

Most DIY people will decide to go with a small premanufactured kit with a polyplastic roof. If you are in an area with many trees, I’d suggest using the fibreglass-reinforced poly option, which is easier to repair if damaged. My experience with polycarbonate greenhouses is they are simply not worth the investment. You’ll watch it fly across your yard in the first big windstorm. At least, that’s what happened to me. 

Potential Problems with Greenhouses

The primary issues you will face in your greenhouse are temperature and humidity control. You will, of course, need pest control and will have to handle various diseases, but you can only handle those once you have conditions in specification. Most greenhouses come with vents to remove heat from the space. Some of these are passive with gas dampers, and others need manual intervention, such as side vents that grower opens and closes themselves. Regardless of your greenhouse type, you must address venting. Hitting very high temperatures in your greenhouse in the summer will result in lost flowers and drastically diminished food production. Temperature and humidity monitoring is essential. I also recommend heat and water sources for added humidity.

We have succeeded in cooling the greenhouse in the summer by using direct evaporative cooling and misting water into the air.

Bringing warm, dry air inside and misting water into it prevents the greenhouse from overheating. I suggest using a small RV-style pressure pump and a dehumidifier. When the temperature gets too high, the misters turn on and cool the space.

We light our greenhouses for winter operation, which helps with the heat but doesn’t provide enough warmth. So we use a small wood-burning fireplace.

We built a hearth around the fireplace and put a table in the building. With this addition, we can heat the greenhouse and have a fun spot to hang out on colder evenings when you want to be outside, but it’s just a bit too chilly.

If you run your greenhouse all year in Canada, expect to use a lot of wood! However, the experience is worth the time to keep the greenhouse warm. A couple of words of caution to people running a greenhouse 365 days a year: bugs suck! If you do not have a very good indoor pest control plan, you will likely be attacked by aphids. Don’t get me started. We could beat them back, but not after the damage was already done. If you don’t have proper pest control throughout the winter, I recommend letting the temperature in the greenhouse drop below freezing to kill off some of the nasty bugs. Otherwise, you’ll start hating aphids as much as me.

Final Words of Advice for your Greenhouse

Get creative, look online, and see what you can build that fits your location. Greenhouses are an incredible way to create food security and grow plants how you like. Most importantly, it’s a lot of fun to be in a warm greenhouse at -15°C outside, wearing a T-shirt, enjoying all your plants and artificial light.