How to Insulate a Greenhouse and Save Money

If you’re a greenhouse owner, you know that keeping the space warm and efficient can be a challenge. The main loss of heat from greenhouses is from draughts and through the structure. However, with some simple tips, you can save money and improve the efficiency of the heating you choose. If you haven’t yet decided which greenhouse heater to purchase, we suggest reading our guide on selecting the best heater.


Here are some ways to insulate a greenhouse effectively and keep your plants safe in winter. 

how to insulate a greenhouse

1. Seal Cracks, Replace Broken Panes, and Ensure Vents and Doors Fit Snugly

Before you start any insulation project, you need to make sure that your greenhouse is in good repair. Check for cracks and gaps in the structure, and replace any broken panes. Also, ensure that the doors and vents fit snugly to prevent draughts.


2. Add a Layer of Bubble Polythene to Insulate the Greenhouse

Adding a layer of bubble polythene to your greenhouse is an effective way to insulate the space. However, keep in mind that every layer of plastic cuts out a significant amount of light (about ten percent). This will impact on growth. This also applies to double-glazing, which reduces light transmission.


3. Use Transparent Mastic to Seal Quickly and Easily

Transparent mastic is an easy and quick way to seal gaps and cracks in your greenhouse. However, make sure to use a flexible material, otherwise, panes can break when the structure flexes in the wind.


4. Renew Seals on Doors and Ventilators

Renewing seals on doors and ventilators can help prevent heat loss. However, sometimes taping plastic sheeting over leaking areas is required. Take care to leave some facilities for ventilating.


5. Screen Off Part of the Greenhouse to Limit the Area to Be Kept Heated

In large greenhouses, screening off part of the greenhouse with polythene and battens to limit the area to be kept heated is possible. This will save on heating costs.


6. Use Roll-Down Blinds or Thermal Screens to Protect Plants from Frost

Additional internal protection from frost is possible by draping fleece over plants in cold snaps. However, covering the whole greenhouse at night with roll-down blinds or by using thermal screens suspended above head height is much more effective (but there is the drawback that they have to be deployed each evening and rolled back in the morning).


7. Choose the Right Temperature to Save Fuel

Choosing the right temperature can help save fuel. A minimum of 3ºC (37ºF) is sufficient to sustain many tender plants, but it is a bit risky if they get damp, and most greenhouses have cold corners. The lowest practical temperature is 7ºC (45ºF), and 10ºC (50ºF) will give greater peace of mind. However, alert gardeners can use fleece and other means to protect plants at these fuel-saving temperatures.

snow greenhouse insulation

8. Use Snow to Provide Natural Insulation

Snow can be an effective insulator for greenhouses during the winter months. It can create a barrier around the greenhouse that prevents heat from escaping and cold air from entering. When piled against the walls, snow can provide significant insulation and reduce the need for heating.

However, it’s essential to remember that wet and heavy snow can cause damage to the greenhouse roof. The best type of snow for insulation is light, fluffy snow. Fluffy snow has more air pockets, which can trap heat and provide better insulation. 

It’s important to keep in mind that while snow can provide effective insulation for greenhouses, it may also reduce the amount of light that plants receive. Therefore consider removing snow from the sunny side of your greenhouse. 


9. Use Leaves, Straw or Hay as Eco Friendly Insulation  

By placing leaves, straw or hay against the walls of your greenhouse, you can create an extra layer of insulation that will help keep the greenhouse warm. This is a simple, eco-friendly and cost-effective way to keep greenhouse warmer during the winter months.


10. Use Containers of Water to Give Off Warmth as They Freeze

Containers of water placed in the greenhouse to give off warmth as they freeze (latent heat of freezing) are advocated. However, the ‘temperature lift’ they provide is negligible, and by the time the water freezes, the plants will already be damaged. 


With the cost of water being measured by the meter these days, it’s a smart move to take advantage of the free rainwater that falls from the sky. All you need to do is install a down-pipe kit and a water butt to collect the rainwater.

Rainwater is a better option for your plants as it doesn’t contain any chemicals that tap water may have, and it has the ideal pH balance for your soil. Not only will using a water butt save you money in the long term, but it will also help keep your plants healthier, (and warmer if installed in the greenhouse).


11. Use Compost pile as Source of Warmth

By placing a compost pile inside the greenhouse, you can create a steady source of warmth that can help keep the plants healthy and comfortable. As the compost breaks down, it produces heat, which can be used to heat the greenhouse. The heat produced by the compost pile will be released gradually, potentially maintaining a sufficiently warm temperature for the plants to thrive.


12. Utilizing Chickens to Warm up your Greenhouse

Chickens or other poultry can be utilized to help warm up a greenhouse during the day, particularly if the greenhouse is large enough to accommodate them. Creating a designated section for the chickens or other poultry within the greenhouse allows their body heat to increase the temperature, which can be beneficial for plant growth.

When considering using poultry to warm up a greenhouse, it’s important to ensure that the designated section is adequately ventilated to prevent moisture build-up and to keep the bedding clean and dry. Chickens and other poultry can produce a significant amount of moisture, which can lead to increased humidity levels that may not be ideal for plant growth.

Chicken – heated greenhouse can help maintain a warm and healthy environment for your plants, but it’s important to consider the potential risks. Poultry can be destructive to plants, as they may peck at leaves or scratch at soil, which could lead to damage. To prevent this, it’s best to keep the poultry in a separate section away from the plants.

greenhouse insulation

Problems when Insulating a Greenhouse 

Damp and Associated Moulds and Rots

Damp and associated moulds and rots can be very damaging in winter, no matter how carefully plants are watered. On sunny days, ventilate freely to shed surplus moisture. In fact, you may have to use a little heat to dry the house out, but it preferable to do this than lose plants. To prevent the formation of mould in your greenhouse, we suggest using an electric fan heater to aid in air circulation.


Reduction of Natural Light

Certain crops, such as winter lettuce and alpines, require ample amounts of sunlight and can be negatively affected if the insulation causes excessive shading. It is recommended to avoid using materials like bubble wrap for plants that are sturdy enough to endure the cold as they benefit from exposure to light.


How to Maximize Light in the Greenhouse

Natural light is an essential component of greenhouse gardening. It provides the energy needed for photosynthesis and helps your plants grow strong and healthy.


Here are some tips for maximizing natural light in your greenhouse:

  • Clean your windows and roof regularly to allow for maximum light penetration.

  • Use reflective materials like aluminium foil to direct light towards your plants.

  • Use light shelves to increase the amount of light reaching your plants.

How to Keep Patio Plants Safe and Healthy During Winter

During winter, patio plants don’t need a lot of light but must be protected from freezing. It’s ideal to keep them at a minimum temperature of 7ºC (45ºF) since they don’t need to grow to survive. Insulation is recommended to maintain this temperature. However, for plants that need to grow, a compromise is needed. For instance, installing bubble polythene to the sides or the north facing roof and gable ends can provide some insulation without blocking too much light. If you’re raising seedlings or keeping a collection of orchids, compromising on insulation is a practical approach.


It’s also crucial to consider purchasing a greenhouse heater for the coldest period of winter. We suggest reading our guide on selecting the best heater  to chose the best greenhouse heater for your needs.  



In conclusion, insulating a greenhouse is essential for greenhouse owners to maintain an optimal temperature for their plants. Draughts and heat loss through the structure are the primary reasons for heat loss, and there are several ways to insulate your greenhouse effectively. The best method depends on your greenhouse’s size, location, and the types of plants you are growing. These methods include sealing cracks, adding a layer of bubble polythene, renewing seals on doors and ventilators, using roll-down blinds or thermal screens to protect plants from frost, choosing the right temperature to save fuel, using snow, leaves, straw, or hay as eco-friendly insulation, utilizing compost pile or chickens to warm up a greenhouse. However, greenhouse owners should also keep in mind the potential problems when insulating a greenhouse, such as dampness, which can cause plant diseases and poor plant growth.




Q: What are the primary reasons for heat loss in greenhouses?


The primary reasons for heat loss in greenhouses are draughts and heat loss through the structure.


Q: How can you insulate a greenhouse effectively? 


You can insulate a greenhouse effectively by sealing cracks, adding a layer of bubble polythene, renewing seals on doors and ventilators, using roll-down blinds or thermal screens, choosing the right temperature to save fuel, using snow, leaves, straw, or hay as eco-friendly insulation, utilizing compost pile, or chickens to warm up a greenhouse.


Q: What is the best method to insulate a greenhouse? 

The best method to insulate a greenhouse depends on your greenhouse’s size, location, and the types of plants you are growing.


Q: What are the potential problems when insulating a greenhouse? 


The potential problems when insulating a greenhouse are dampness, which can cause plant diseases and poor plant growth.

Leave a Comment

Your email address will not be published. Required fields are marked *