Greenhouse Basics- What you Need to Know

It seems like years that I yearned for a greenhouse, dreaming of the day when I could grow my own chemical-free lettuce, tomatoes and cucumbers year-round- avoiding the sky-high prices of out of season produce all the while enjoying flavorful, organic veggies, If only I had known ahead of time what I was in for! Before you jump in building your own, here are some greenhouse basics- what you need to know!
greenhouse-basics-what-you-need-to-know

DIY: Greenhouse Basics 

We worked together, my spouse and I, to erect this modest 8’x16′ greenhouse, reclaiming old fencing that used to contain goats in the field as simple shelves that allowed for maximum airflow.

b101-diy-greenhouse-1

The floor, reclaimed limestone bricks, and paver stones laid out in a pattern created by our eldest son who reveled in the fact that he’d already designed this on his game in Minecraft and how spectacular it would look in “real life” when he was done.

b101-greenhouse-floor

In all, it took the boys about 2 hours of their time, but to me, it was a timeless moment. We filled the gaps with pebbles for drainage, because I  also installed a self-watering spray system.

The area between the limestone bricks is filled with paver sand, to ensure the bricks don’t shift creating a falling hazard.

b101-greenhouse-floor-filled-in

Paver sand contains a polymer that activates when it’s wet and then becomes firm when it dries. It doesn’t wash away or rinse away as play sand does.

b101-greenhouse-floor-paver-sand

The shelves are the perfect width to hold bags of mulch, soil or individual plant pots. 

b101-greenhouse-reclaimed-shelves

Choosing the Building Materials

For both the roofing and the sides we used white (& clear) corrugated panels. Corrugated roofing isn’t particularly “Cheap”, but it will last 10-15 years if it’s taken care of properly.

We chose this particular material because it lets in the proper amount of light, will last and more importantly can withstand the occasion Hurricane, High Winds and Hail that we have a tendency to receive seasonally in our area.

The installation of an automatic fan is necessary to ensure proper airflow and humidity levels.

b101-diy-greenhouse-fan

We decided to repurpose a couple of old gutters we had lying around to plant strawberries.

Things to Consider Before Building

When I was busying myself “dreaming” of having a greenhouse… I neglected a few key points of consideration, such as:

  1. How difficult would it be to maintain the temperature in the building?
  2. How Hot would it get during the day?
  3. How cool would it get at night?
  4. What is the Optimum temperature for plants to grow?
  5. Should the greenhouse be clear or opaque?
  6. What is the optimum humidity level in the greenhouse?

Well, dear reader, let’s just say in the 2 short months of having a greenhouse, I’ve gotten quite an education.

Temperature, Hot, Cold & In-Between

We purchased an inexpensive thermometer/ hygrometer combination, which gives both the temperature as well as the humidity level at a glance.

When choosing the greenhouse materials, take into consideration how hot your area gets. For instance, in MAY in South Carolina, it frequently hits 90°F outside, with relatively LOW humidity. What this means is that the inside temperature of the greenhouse can easily reach 128°F by 11 am, effectively cooking the plants inside.

When picking out the materials, we opted to build the sides with white corrugated panels, meaning the light filters through, but not glaringly so and the roof was alternated white and clear panels, as some vegetables require full sun. A mistake on our part, because had we the opportunity to start anew, the entire roof would be diffused without any clear panels.

Most common vegetable plants thrive best at about 75-84°F.

It didn’t make much sense to me to install an air conditioner in a greenhouse, particularly since most air conditioners also remove moisture/humidity- which is actually helpful. So, we opted to build our own air conditioner, otherwise known as a swamp cooler.

This simple device lowers the temperature to about 85°F in the greenhouse and also provides additional moisture in the air for the plants, preventing the soil from drying out too quickly.

Directions to Build Your Own Air Conditioner

When we first planted our seeds, it was relatively warm during the day, hitting temperatures of about 70°F, however, temperatures plummeted at night to only 36-40°F those first few days, making it difficult to keep the soil warm in the greenhouse. This was remedied with a couple of plant pots and a few tea-light candles.

b101-diy-greenhouse-heater
View How to Make your Own Greenhouse Heater

Greenhouse Basics: Proper Humidity Levels

The humidity level in a greenhouse in important for several reasons, if it’s too low the soil of the plants dries out too quickly, resulting in wilted plants. If it’s too high, fungal diseases such as Botrytis or powdery mildew spread like wildfire, wiping out tender young plants.
A general rule of thumb for most seasons is a humidity level of 50-86%.

°FHumidity
50°83%
61°89%
68°91%
86°95%

It is important to have good airflow in the greenhouse, so be sure to install a fan in both the front and back to help circulate the air properly. If you want to have a successful greenhouse experience, keep those key questions in mind when creating your own!

About Liss 4076 Articles
Melissa Burnell, known to her friends and fans as "Liss," grew up in Southern Maine, now residing in sunny South Carolina. As a busy Wife, Mother of two sons, an avid photographer, and self-employed entrepreneur, Liss understands the value of both time and money.

12 Comments

  1. good info. is it hard or expensive to make a swamp cooler? i would definitely need this.

    would a couple of low watt lights be bad to use at night to generate heat instead of tea liters?

  2. i, too, have dreamed of having a greenhouse. i don’t think it would be feasible to try to grow plants year-round here in northern michigan, but it sure would help get things growing earlier in the spring and keep things growing longer in the fall.

  3. Florida is always humid and hot except for about one month a year. LOL Thank you for the info on the pit falls. I wanted to build a green house to keep chickens out of my plants.

    Didn’t think about it getting to hot.

    Very use-full info. :springsmile:

  4. Love the info. I have purchased several supplies already to build my dream green house. After reading im glad i havent began building.

    I need to tweek a few things first.

  5. I enjoyed the information there was definitely somethings I had not considered when I was planning my green house but now I know where I need to make adjustments. thanks

  6. A greenhouse like this is relatively light in weight for it’s size. In areas of the country prone to high winds and severe thunderstorms, make sure the greenhouse is securely anchored to the ground or concrete footings. You don’t want to come out in the morning and find your greenhouse in the neighbor’s yard.

  7. We built a greenhouse using a recycled carport, recycled windows and leftover lumber from building a deck. The top of the carport is perfect due to the diffuse lighting. We built it over the septic tank to utilize the heat in the winter.

    The floor is formed concrete blocks in case we need to get to the septic tank (the clean out/septic over flow is on the outside of the greenhouse).

    The windows required some simple framing, thus the left over lumber. I spent a little extra on some 1/4″ acrylic sheets for the few areas above and below the windows due to the nasty hale storm we occasionally get. Prior to pouring the floor, we buried a barrel on the low end of the slope to recycle the run off from the yard and greenhouse watering.

    Added some inexpensive solar watering pumps and it’s practically care free.

    The greenhouse is built against our home, thus the windows essentially make up the other 3 walls and a long piece of acrylic blends the roof edge to the carport edge.

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