What is a Greenhouse and How Does a Greenhouse Work?


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I know a greenhouse is a great place to grow plants, but that’s about all I know. I thought it might be helpful to look into exactly why a greenhouse is such a great environment for plants.

What is a greenhouse? A greenhouse is a closed structure made of transparent materials. These materials allow gardeners to regulate the climate conditions inside the greenhouse and create the perfect environment for growing plants all year long.

After finding out exactly what a greenhouse is, I decided to look further into what sort of options were available to me for creating my ideal greenhouse. Here’s a look at what I found.

How Does a Greenhouse Work?

I’ve been thinking lately that a greenhouse might be a productive adventure for my family, but I don’t really know how they work. I know the basic concept of harnessing the sun’s rays, but there must be more to it than that. 

How Does a Greenhouse Work? A greenhouse works by harnessing the sun’s rays and setting up the best environment for growth. An ideal environment means maximum plant growth and production. A greenhouse does this by allowing you to control the following.

  • Temperature
  • Humidity
  • Light

I’m sure you’ve figured out that a greenhouse doesn’t just control temperature, humidity, and light on its own, you have to have the right set up. I’m going to tell you what you need to make sure your greenhouse works exactly as you want it.

Types of Greenhouses Available

There are three types of greenhouses to choose from when it comes to setting up your perfect garden. 

  • Lean-to
  • Detached
  • Ridge and furrow (gutter connected)

Lean-to:

This option is probably the most used among home gardeners. A lean-to greenhouse is built against the side of another structure. It has a sloping roof and shares a wall with the other structure, think build on to garage or house.

The wall the greenhouse is built against actually helps moderate the temperature in the greenhouse. It absorbs the heat during the day and then puts it off, back into the greenhouse, during the night when it’s cooler. Here’s a look at the benefits of a lean-to greenhouse.

  • Smaller
  • Fairly easy to put together
  • Lower cost
  • Convenience

Detached

Detached greenhouses stand on their own, although it might be connected to another greenhouse or work area by a corridor. Quonsets are the most popular choice for a detached greenhouse. These are small greenhouses made of arched rafters with solid end walls. Here’s a look at the benefits of a detached greenhouse.

  • More creativity with design
  • More flexibility with location
  • Can choose any size

Ridge and furrow

Ridge and furrow greenhouse are used most often commercially. They are connected at the top by a common gutter. Usually, there is no internal wall under the gutter. Here’s a look at the benefits of this type of greenhouse.

  • Less expensive when you need a lot of area
  • Less heating cost per ground area
  • More energy efficient for large greenhouses

Think about your goals for your greenhouse to decide which type of structure is the right one for you. It can be overwhelming at first, but you’ll be grateful later that you took the time to figure it out. 

Best Greenhouse Materials to Use

Greenhouses are made of many different materials, starting with the frame. The greenhouse frame is generally made from one of three main materials. Here’s a look at the materials and a little bit about each.

MaterialPros of MaterialCons of Material
AluminumVariety in style, long lasting, can manipulateMore expensive
SteelFairly affordable, durable, strongDifficult to work with
WoodNatural insulation, pleasing appearanceCan deteriorate quickly

Once you figure out what greenhouse frame is best, you need to decide what greenhouse covering you want. I know, I know… another decision, but the most important factor with the covering is that it is transparent. Transparent materials allow the sun to get into the greenhouse and have the maximum effect. These types of coverings are used most often.

  • Glass
  • Fiberglass
  • Double sheets of polyethylene

Glass

Using glass as your greenhouse covering allows for the most light to get in, around 90- percent. It will also last longer than any other greenhouse covering. On the flip side, it’s the most expensive type of covering and also doesn’t allow for any flexibility in shape.

Fiberglass

 A fiberglass covering is more affordable and lighter than glass and still allows about the same amount of sunlight to get through. It also transmits less heat, helping to keep your greenhouse slightly cooler in the summer.

On the other hand, fiberglass begins to break down over time. When this happens, the amount of light that gets through decreases.

Double sheets of polyethylene

This plastic is made up of two layers of plastic with a layer of plastic webbing in the middle. The extra layer in the middle helps with insulation. This type of covering is also fairly affordable.

The downside is that the amount of light that gets through is about 10-percent less than glass or fiberglass and it wears down and yellows quicker than the other options. 

A critical component to all the materials used in a greenhouse is a ventilation system. A greenhouse will not operate without either a natural or mechanical ventilation system. 

The ventilation system allows air to circulate throughout the greenhouse rather than sitting stagnant. It also helps regulate the temperature and humidity, which is something you’ll need to pay attention to when it comes to creating the perfect environment.

Here’s a look at how each ventilation system works. 

Natural VentilationMechanical Ventilation
Install roof and side vents in greenhouseHot air risesHot air flows out roof ventsCool air is pulled in side ventsFan can help circulate airInstall exhaust fan at roofInstall special shutter opposite fan on groundExhaust fan blows hot air outCool air comes in through shutter

What Makes a Greenhouse Work?

Now that you’ve seen the different materials used to build greenhouses, it’s time to get the 411 on how those materials come together to make a greenhouse work.

Remember, a greenhouse is a structure that allows you to regulate the climate conditions and grow the best plants you can any time of the year.

The frame of the greenhouse isn’t as important to how it works as the covering materials. As I mentioned, the covering materials have to be transparent. The main idea of a greenhouse is to harness the sun’s heat energy. Transparent materials allow you to do this.

Here’s a look at how the greenhouse works.

  1. Sun enters the greenhouse through transparent covering
  2. Heat energy from the sun warms the plants and air
  3. Transparent walls trap the sun’s heat inside
  4. Warmer temperatures allow for higher rates of photosynthesis

Photosynthesis is how plants grow. This is when plants use sunlight to break down carbon dioxide and water and turn it into glucose or sugar for growth. When the greenhouse is too cold (or too hot), photosynthesis doesn’t happen at the same rate and may even stop completely.

Dealing With Seasonal Changes in a Greenhouse

Since a greenhouse is a structure that traps heat, you’re probably thinking that there may come a time when it gets too warm. Depending on where you live, you would be right.

As the seasons warm up or cool down, you’ll need to make changes to your greenhouse to make sure it’s still performing the way you want. Some of these changes are easy and inexpensive, while others might take a little more time and money.

You can look for signs on your plants that it’s too hot or too cold, but that’s taking a more reactive approach. If you want to be proactive and ensure your plants always have the ideal temperature to grow, invest in a thermometer.

Here’s one on Amazon that measures temperature and humidity.  ThermoPro Thermometer 

Here are some ideas for lowering the temperature in the greenhouse in the hot summer months.

  • Shade cloth
  • Portable AC unit
  • Misters
  • Evaporative cooling system
  • Moving plants so that ones that like more sun and are in the sun and ones that prefer shade are in the shade
  • Placing plants so that larger plants can shade smaller ones

In colder winter months, you’ll have to do the opposite and warm up the greenhouse. Check out these options.

  • Portable heater
  • Water barrels around greenhouse (they retain heat during the day and put it off at night)
  • Heat lamps above plants
  • Soil heating cables under plant beds

If you consider everything we’ve talked about, then your greenhouse should operate just as it is designed: to provide a structure where you can grow plants in just the right environment. Happy growing!

Eyerly Family

The Eyerly Family is a family of 8 that loves gardening. Over the past several years we have been applying what we learn about gardening to our own 16x16 raised back yard garden. Our garden is very prolific and we grow a wide variety of vegetables which we love to eat! Click here to learn more about the Eyerly Family.

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