Buying Your Dream Greenhouse

My greenhouse is from BC Greenhouse Builders

Thinking of buying a greenhouse? Wondering what you need to know to make sure you get the greenhouse of your dreams?

1. Questions to ask yourself
To build yourself or to buy a kit? Do your research as there are pros and cons to both. Check out the greenhouse kits that are on the market, what they have and why. Consider how you would implement these accessories into your home made version. Looking cute and charming is not enough, you need it to function well, also.

What materials to build your greenhouse from? This depends on your budget, your climate, and what you want to do in the greenhouse. Will an unheated coldframe or hoophouse work for your purposes, or do you need a heated greenhouse?

Do you tend to get lots of snow? heavy wet snow? high winds? extreme cold? extreme heat? Do you need it to be sturdy? What kind of a frame will you require to hold up to the conditions? Pvc, aluminum, steel, or wood? The pitch of the roof is a consideration, too. If you tend to get snow, you want it to slide right off. Curved ones let in more light, steep ones allow for gutters.
Realistically, please do not go with pvc, it just does not hold up. Note that those inexpensive greenhouse kits from box stores often do not stand up well to high winds or heavy snow loads, have been known to blow away. If you choose one of those, please anchor it to the foundation really, really well.

What are you planning to grow in the greenhouse? 
Is it for spring and summer use, starting seedlings and extending the season? Year round vegetable growing? Over-wintering tender plants in winter, like citrus trees, fuchsias, and pelargoniums? Growing orchids and other hot house plants? The warmer you want your greenhouse to be, the better insulation value you want it to have.

The insulation value and the amount of light that gets into the greenhouse is determined by the covering that you use for the greenhouse. This is your most important decision. Will your walls and roof be glass, poly sheeting, polycarbonate, or fiberglass.
- Glass is very pretty, lasts the longest, but is not insulating and does not diffuse light (so one has to worry about sunburnt plants). It breaks the easiest out of all the options.
- Poly sheeting is the least expensive, diffuses light, and insulates quite well, but has a short life span and needs replacing every 3 to 5 years, and can tear/rip.
- Fibreglass retains heat well, diffuses light, and is fairly inexpensive, but is hard to seal as it undulates. The coating will begin to wear off in about 6 years, then yellows and looks dirty.
- Polycarbonate insulates the best, diffuses the light, and lasts a long time, but it does not look as pretty as glass does.     

I use my greenhouse year round. 
In spring, I start seedlings and maintain a temperature of 8°C to 10°C. 
In summer I grow tomatoes, peppers, melons, etc.. and try to keep the temp below 30°C. 
In winter, I maintain a cool greenhouse, meaning that I keep it above freezing to happily house my citrus trees, tender perennials, and hardy annuals (5°C to 7°C), but not hot enough to actively grow tropicals (13°C and up). 
Therefore, it was practical for me to go with poly-carbonate rather than glass. It retains heat better in winter and diffuses the sun's rays in summer, so saves me money on both heating and cooling. Also, is safer as I have a lot of large trees around.  

Both my hoophouse and greenhouse (in the picture above) have steel frames to withstand the weight of the heavy, wet snow we get here on the coast. They both also have sloping sides so that the snow slides right off, mostly with no help from me. 

Long side of greenhouse faces south to capture as much sunlight, as possible. 

2. Location, Location, Location

When considering the placement of the greenhouse on your property, think about how much light it will get both in winter and in summer.

You want a minimum of 6 hours of sunlight in the winter, when the sun is low in the sky. So, right about now, mid-winter, is when you want to be watching your yard to find that best spot. Is it shaded by the house? Tall cedar trees? Leafy deciduous trees may or may not be a problem.

In summer, you want 6 to 8 hours of direct sunlight on the greenhouse.
At my last house, I had tall cedars on the east and alders on the west. Therefore, in winter, I had 7 to 8 hours of sunlight as the leafy trees lost their foliage, thus giving me a longer day when I needed it most. In summer, I had 6 hours of good sun right on the greenhouse, with spotty sun afterwards, as the sun went behind the alders. Perfect!

If possible, keep the longest side of the greenhouse facing south, to best take advantage of the sunlight.

Propane heater on the left and exhaust fan on the right hand side

 at the back of my greenhouse.  

3. Ventilation & Air Flow
Good air flow is critical for a healthy greenhouse, not only to let out the excess heat, but also to prevent humidity and condensation build up in winter. High humidity can cause fungal issues and plant diseases.

Pretty much all greenhouse kits will all have some vents on the roof, this is a good start. They let out the excess heat in summer to keep the greenhouse from becoming an oven. You will want these to be the kind that automatically open as the heat builds up inside.

In addition to these vents, you also want through ventilation. Having a window or vent at the back of the greenhouse, opposite the door, helps draw fresh air into the greenhouse. To do it again, I would put a door on both ends of my greenhouse and leave them both open all day long, as most commercial greenhouses do. It is an economical and easy way to move the air around.

An exhaust fan is optional, but such a lifesaver. It moves the air around, maintains an even temperature in the greenhouse, and refreshes the air in just minutes. In winter, manually turn on the fan to suck out the stagnant, humid air and draw in fresh air through the louvered vents in front. In summer, have it set to automatically go off at a certain temperature, forcing out excess heat. You can go away for the weekend and not worry about the greenhouse cooking your plants.

Additionally, a small circulating fan inside the greenhouse is really important. It moves the air around in the greenhouse, and when pointed at your seedlings, makes them stronger, sturdier, stockier, and prevents them from succumbing to damping off disease. 

If you choose not to install an exhaust fan, a circulating fan (or two or three) is critical to keep your greenhouse healthy. You will use it/them in both winter and summer to move that air around. Keeps your plants from cooking in summer and getting mildew/diseased in winter. Place the circulating fan by the open front door to pull in the fresh air and force out the humid/hot/stale air through the back window/vent/door. 

Sometimes you want to work in the greenhouse after hours... 

4. Power Source

From the above, you can see that a power source to the greenhouse is pretty helpful. Especially in our humid climate. What else, besides air circulation, would you use power for?

You will need it to heat the greenhouse now and again, even if you're not doing so year round. If you have power, you can plug in a temporary heat source, a small fan heater or a space heater, when needed. We may have a cold snap in spring while you have your tender seedlings in there. You may wish to over-winter some tender perennials, hardy annuals, citrus trees, or other plants which do not require heat all winter long (in our temperate climate), but do need to stay above 0°C degrees.

You also need power to start seeds. Bottom heat to get them germinating and grow lights for the grey days. What is the point of the greenhouse if you are still mucking about in the house?

You may want a light or two so that you can play in the greenhouse after it gets dark outside. Maybe you want to do some seeding after the kidlets go to bed? Or perhaps some twinkle lights to make it pretty :)

 The water from our first greenhouse was collected from the roof of the greenhouse, 

into a huge cistern that was set into the wood, out of sight.  

5. Water
This seems pretty obvious. One needs water to grow anything. Consider adding a hose bib inside the greenhouse. But... maybe you prefer to collect water from gutters into rain barrels instead? That is an awesome idea. However, in the middle of summer when drought season hits and we have no rain, you still want easy access to water, a water bib close enough that you can fill up those water barrels. Nothing gets old faster than running back and forth with a gazillion watering cans.

I chose to go with cement steppers for the floor of my greenhouse. 

They soak up the heat during the day and release it at night. 

They also look good and are easy to keep clean, disease and weed free. 

Other things to consider... 
Gutters. Add gutters to your greenhouse to capture water into a cistern or water barrels.

Flooring. This depends largely on your budget and the look that you want. You will want a floor that is easy to keep clean, weed, disease and pest free. Cleanliness is crucial for a healthy greenhouse.

-Concrete is easy to sweep, keep clean and weed free, quite practical. It is hard on the legs and feet, and has no drainage, unless you add a drainage pipe or gutter. It retains heat, which you may or may not want.
- Stepping stones, like mine in the picture above, or bricks. Easy to keep clean and weed free, very practical, looks good, and has drainage built in between each stone. However, it is also hard on the legs/feet, and retains heat.
- Gravel. Great drainage and a fairly inexpensive option. Looks tidy, easy to keep weed free, as long as you add several inches of gravel, not just a skim coat.
- Gravel with a stepping stone or brick pathway. Looks great, is relatively inexpensive, has great drainage, is easy to keep clean of weeds, pests, and diseases.
- Sand or soil. I highly recommend not to do this. Is really hard to keep clean, and very prone to growing weeds. The conditions are optimum for weeds to grow quickly, and pests may be living and multiplying in those weeds.
- Heavy duty landscape fabric. Inexpensive, has great drainage, softer under your feet, is easy to keep clean and weed-free. It comes in wide sheets so that you may not require any over-lapping of seams, depending on the width of your greenhouse. See picture below.

Heavy duty landscape fabric floor. 

The Greenhouse Interior.... The Accoutrements.
Once you have the shell of a greenhouse, you'll need to think about what kind of accessories to add to get you going.

Potting table, or work table of some kind. Ideally place this on the north side of the greenhouse, so as not to create shade.

Benches or shelves for smaller plant pots. Large pots are great on the floor, but if you have plants in all stages of growth, you will want to get them up off of the ground.

Built in beds or in ground beds. This may be a practical solution for you, depending on what you are growing in the greenhouse.

Hooks to hang things from, accessories and baskets, either flowers or tomatoes.

The rest will come about as you grow along. You will figure out how you want to store your soil, what tools you need, how to organize things, what you need from day to day ... bins, pails, boxes, watering cans, etc...     

If your days are long and hot in summer, you may want to look into getting some shade cloth. 

Shade cloth will save you loads of money on cooling the greenhouse. 

Building a greenhouse is a big investment, 

but one that you will enjoy every day as an avid gardener. 

Worth every penny. 

Happy Growing!