Greenhouse Insulation: How and When to Do it?

Undoubtedly, a greenhouse makes a property look aesthetically more appealing. However, the primary reason for installing a greenhouse is to protect the plants outdoors from harsh components in all seasons.

For example, in winter, you want to keep your crops or plants in good condition instead of letting them suffer in chill temperatures outdoors.

A greenhouse will keep your plants warm and protect them from snow, rain, or wind. Good insulation offers a controlled environment, ensuring perfect humidity and temperature for plants to grow.

Plus, you can adjust the light level, humidity, and temperature based on the plants you want to propagate, including the delicate indoor seedlings.

Also Read: Greenhouse: Definition, Uses, Types, How it Works

Moreover, besides saving your lawn babies, you can significantly minimize your energy expenditure. So while winter is around the corner, you must ensure your greenhouse receives sufficient light. How? Let’s find it out!

When Is The Right Time To Insulate Your Greenhouse?

When Is The Right Time To Insulate Your Greenhouse?

In winter, you must ensure that your greenhouse is warmer than the outside temperature. This will enable the less hardy plants or crops to survive in the chilly months.

In addition, and as already mentioned, it should receive sufficient light for proper insulation during the darker, shorter winter days.

Why Should You Insulate A Greenhouse?

Greenhouses usually remain 2 to 3 degrees C more than the temperature outside, enough for plants to survive in mild frost. But survival becomes challenging when the temperature escalates substantially. This calls for insulating greenhouses.

Like many others, you can also set a best greenhouse heater in the winter. But insulating a greenhouse can save much on your electric bill and protect your plants. 

A properly insulated greenhouse maintains 5 to 6 degrees C above the outside temperature, catering to all plant needs under extreme conditions.

How Do You Insulate A Greenhouse?

Don’t worry if your greenhouse needs to be warmer to protect your plants from freezing temperatures outside. Below are a few practical and budget-friendly ways to make the greenhouse cozy.

1. Insulation With Bubble Wrap

Insulation With Bubble Wrap

Firstly, block the drafts before insulating. If you find gaps in the frame or crushed panes, replace them. Also, check whether or not the vents and doors fit tightly.

Secondly, seal off your greenhouse with an inner plastic layer. Besides securing the gaps, the plastic lining will decrease the rate at which heat gets away. However, you can use old bubble wrap – an affordable material with good insulation.

Bigger bubbles are a more popular greenhouse growers’ choice as more light can penetrate them, offering better insulation. In fact, you will even find specialized big horticultural bubble wraps to be UV-stabilized. As a result, they tend to be more durable than the ones used for online packaging.

Secure the bubble wrap to the greenhouse’s frame from the interior. If it’s an aluminum frame, use greenhouse clips for fastening. On the contrary, you will need a staple gun or drawing pins to stick the wrap to a wooden frame.

Well, make sure to insulate the root too. However, let the bubble wrap hang loosely across the door as you have to go out.

Pros and Cons of Bubble Wrap Greenhouse Insulation


  • It is cheap and efficient
  • You can easily install it
  • The material is accessible.


  • It can often shield the light that plants require.
  • They will require replacement every alternate season.

2. Insulation with Thermal Foil

Insulation with Thermal Foil

Next, insulate the northern part of the greenhouse with a pocket-friendly thermal insulation foil. They are pretty efficient at keeping plants warm in winter. It consists of two layers of silver foil with a bubble plastic between them. This will help in reflecting heat to the greenhouse.

First, clean the greenhouse windows and then attach the thermal foil to its northern side. Use tape, greenhouse clips, and staples to secure it. Next, you can measure the greenhouse, cut the foil accordingly in small chunks, and set them one by one.

Pros and Cons of Thermal Foil Insulation


  • It prevents heat loss all year round.
  • It reflects heat inside a room to keep it warm.


  • The material shields substantial light from reaching the plants
  • It can be expensive.

3. Insulating with Polyethylene Plastic Covering

Insulating with Polyethylene Plastic Covering

Another effective way to insulate greenhouses is with polyethylene plastic. However, you can use this material covering only one season. So it won’t keep your plants warm for the next winter.

  • First, clean the greenhouse windows to let sufficient light reach the plants, despite the plastic covering. 
  • Then, cut the plastic sheet according to your greenhouse size. You can cut the material into smaller chunks as it will be easier to attach. 
  • Cover each greenhouse area with staples, tape, or nails for proper insulation.

Pros and Cons of Polyethylene Plastic Covering


  • Polyethylene is a highly efficient light transmitter
  • It can save cost up to 40% compared to other alternatives
  • It enables better airflow inside the greenhouse.


  • The material is prone to wind damage.
  • It becomes less effective over time and, thus, needs frequent replacement. 

4. Insulate With Thermal Jugs

Insulate With Thermal Jugs

Using thermal mass, you will require one-gallon jugs, black paint, and bleach. First, paint all the empty jugs black so that the water stays hot for a long time. Then, add a tablespoon of bleach to the water to avoid molding the jugs. However, it’s better to label the jugs, so you don’t confuse them with normal water.

Keep the jugs in the plant pots and on all sides of the base. The jug water will draw up the sun’s heat rays throughout the day and set the heat free back during the night, keeping the plants warm.

Pros and Cons of Thermal Mass With Water Jugs Insulation


  • It is cheap and easy-to-install
  • These jugs will keep the greenhouse warm.


  • One-gallon jugs may heat up slowly. 

You can also use 55-gallon jugs instead of one-gallon for more efficient insulation. But it can be expensive.

5. Insulating with Compost

Insulating with Compost

This process seeks a separate chamber or composting area in your greenhouse for execution. You can pile cement blocks or bricks to keep your plants and compost separately.

For compost, you can add field waste and food scraps. In addition, you can even put your pet’s poop or droppings in the compost. The microbes emit heat that helps to keep a greenhouse warm.

Besides providing a place to eliminate added waste, composting is good for our environment. So here are the advantages of composting –

Pros and Cons of Insulating With Compost


  • It’s a natural way to insulate the greenhouse and keep plants warm
  • Compost helps in saving the environment
  • It’s an ideal place to eliminate waste
  • Compost is also healthy for plants.


  • Compost typically emits a foul smell that might be distressing for you.

6. Insulating with Space Heaters

Insulating with Space Heaters

Space heaters can also be a good choice as they operate decently to warm up winter plants and are easy to install. Just set it in your greenhouse and leave your plants to enjoy the warmth. 

But the downside is that it can cost a lot if it keeps operating throughout the winter. Space heaters consume a lot of energy and, thus, can be pricey. With that in mind, it is better to use a space heater as a convenient option when you are in a pinch. 

They are effective on freezing nights or when you are busy enough to set up jugs or heat lamps.

Pros and Cons of Insulating With Space Heaters


  • They are easily accessible and easy to install
  • Space heaters can effectively keep plants warm.


  • Space heaters can be costly if they run consistently
  • They only warm up the air but not the plants
  • You will need other insulating methods like bubble wrap or plastic to contain the heat in the greenhouse.

7. Insulating with a Good Greenhouse Foundation

Insulating with a Good Greenhouse Foundation

Most people overlook this factor, but a greenhouse foundation is important. When the outer ground freezes, it moves into the greenhouse via ground structure with freezing temperatures. Heat loss can occur up to 15% from the ground during this process.

However, please don’t make a greenhouse foundation with wood, cement, or concrete, as they cause poor insulation. Instead, you can use peat rock, gravel, or dirt.

You can surround the greenhouse with insulating soil to encourage ground insulation. On the other hand, foam or Styrofoam board are suitable options to insulate your greenhouse’s external border by inserting them vertically down to nearly a foot.

Pros and Cons of Greenhouse Foundation


  • It can hold onto the heat inside the greenhouse
  • It protects the plants with raised beds
  • Inexpensive
  • Greenhouse foundation prevents heat loss to the topsoil.


  • It can bestow a negative impact if not set up properly.

Other Convenient Ways

You can also insulate your greenhouse in a few additional ways –

  • Thermal screens and blinds are handy for greenhouse insulation at night. 
  • You can place the plants inside cold frames and cloches for added protection. 
  • Cut out empty plastic bottles at the bottom and put them over plants. They will act as mini cloches. 
  • Even a blanket of snow can aid in insulation due to the insulating properties of snow. But you have to remove the snow from the roof’s sun-kissing side to let the sunlight reach the plants in the greenhouse.

Wrapping Up

Greenhouse insulation is as important as employing a heater to warm up your house in winter. However, insulating your greenhouse has many advantages, like offering the necessary heat for your plants and saving electricity costs a lot.

An insulated greenhouse keeps the warm air enclosed to help the precious plants sustain during freezing months and all year round.