How to insulate your greenhouse

A greenhouse is a gardener’s sanctuary, providing an ideal environment for nurturing plants year-round. However, maintaining optimal temperatures within the greenhouse can be challenging, especially during extreme weather conditions. Proper insulation is essential for regulating temperature, conserving energy, and protecting delicate plants from harsh elements. In this article, we’ll explore practical strategies and tips for insulating your greenhouse to create a stable and nurturing environment for your plants.

1. Assessing Your Greenhouse:

• Before implementing insulation measures, assess your greenhouse’s current condition. Identify areas where heat loss occurs, such as gaps in the structure, poorly sealed doors and windows, and thin or damaged glazing materials.
• Determine your climate zone and typical weather patterns to understand the specific insulation needs of your greenhouse.

1. Choosing Insulation Materials:

• Selecting the right insulation materials is crucial for effectively regulating temperature and humidity levels within the greenhouse.
• Common insulation options include:
  • Bubble wrap: Lightweight and inexpensive, bubble wrap can be applied directly to the interior surfaces of the greenhouse to create an insulating barrier. Opt for UV-resistant bubble wrap for longevity.
  • Polyethylene foam: This versatile insulation material can be used to line walls, ceilings, and floors, providing thermal protection and moisture resistance.
  • Fiberglass or rigid foam board: These rigid insulation materials offer excellent thermal resistance and can be installed between framing members or attached to the interior surfaces of the greenhouse.
  • Thermal curtains or blankets: Installing thermal curtains or blankets along the walls and roof of the greenhouse can provide additional insulation during colder months, while allowing for ventilation when needed.

Why bubble wrap a greenhouse?

The purpose of adding bubble wrap is to provide a layer of insulation. But it is best not to go for the average packaging variety, and instead go for horticultural bubble wrap.

Horticultural bubble wrap is not only extra thick but the bubbles themselves are larger and it is these bubbles, or air pockets, that provide insulation. Double glazing works exactly the same way, creating an air pocket between two panes of glass to slow down the transfer of heat and cold. The idea with bubble wrap is to retain any valuable heat in the greenhouse during the day and prevent the greenhouse from being affected by frost at night. This insulation can increase the temperature inside the greenhouse by one or two degrees, so it’s certainly a viable solution to keeping your greenhouse warm this Winter.

How to bubble wrap a greenhouse

This is best done after the annual clean. Make sure all the glazing is clean, nooks and crannies are clear, and a general purge of dirt, pests and disease has been done. Give the greenhouse a chance to air and dry after cleaning. It is important to reduce the moisture inside as once the greenhouse is wrapped, you will lose access to your windows and vents.

Choosing your bubble wrap is important. Packing bubble wrap will offer little insulation and will deteriorate when exposed to the elements and sunlight. Proper horticultural bubble wrap is thicker and treated so that it withstands UV damage, meaning it will last 2 or 3 seasons. It is important to consider the longevity whilst we all do our best to reduce our single-use plastics.

Now for the fun part. The best way to bubble wrap the greenhouse is to use long continuous sheets, cut and join as little as possible to reduce heat loss. I’ve found this works best by wrapping horizontally with long lengths from one side of the door, around the greenhouse to meet the opposite side of the door frame starting at ground level. You can secure the bubble wrap as you go with sticky tape or with little plastic greenhouse pegs designed to clip into the channels in your greenhouse frame.

You may need to finagle the wrap a little when it comes to wrapping the roof, this is where it helps to have a willing assistant.

What to watch out for

There are pros and cons to this method of insulation, and the most obvious con is that anything covering the glass will reduce the light coming into the greenhouse. The bubble wrap acts as a diffuser stopping direct sunlight and in favour of a much softer (weaker) light. If you live in an area where sunlight is very reduced in the colder months, this is something to consider to ensure your plants get the appropriate amount of light and you may decide to employ any means of lighting.

Another consideration is that once wrapped, you will lose the ability to access the vents and windows. This means air cannot circulate as well and excess moisture cannot leave the greenhouse. This could cause problems with build-ups of condensation which in turn can harbour moulds and encourage disease, so you do have to be vigilant. You can open the greenhouse door to vent the moisture, but it is at the detriment to that hard-won heat.

If you are unsure of the benefits, there are alternatives to wrapping the whole greenhouse. You could try dividing the greenhouse and insulating only one part, or even use bubble wrap to insulate just one staging bench, creating a micro-environment within your greenhouse. Or clever use of propagators or cold frames within the greenhouse can help offer some protection on a smaller scale.

1. Sealing Air Leaks:

• Addressing air leaks is essential for preventing heat loss and maintaining a consistent temperature within the greenhouse.
• Use weatherstripping or caulking to seal gaps around doors, windows, vents, and other openings. Pay special attention to areas where different materials meet, as these are common sources of air leaks.
• Install automatic vent openers with weatherstripping to ensure proper sealing when vents are closed.

1. Enhancing Glazing:

• Upgrading or augmenting the glazing materials of your greenhouse can significantly improve insulation and energy efficiency.
• Double or triple-glazed windows: Replace single-pane windows with double or triple-glazed alternatives to enhance thermal performance and reduce heat loss.
• Insulated polycarbonate panels: Install insulated polycarbonate panels to replace traditional glass or acrylic glazing. These panels provide superior insulation while maintaining excellent light transmission for plant growth.

1. Adding Thermal Mass:

• Thermal mass refers to materials that absorb and store heat, helping to stabilize temperature fluctuations within the greenhouse.
• Incorporate thermal mass elements such as water barrels, concrete blocks, or stone pathways into the greenhouse design. These elements absorb heat during the day and release it at night, moderating temperature swings.
• Position thermal mass materials strategically to maximize their effectiveness, placing them near sunny areas where they can absorb solar radiation.

1. Monitoring and Adjusting:

• Regularly monitor temperature and humidity levels within the greenhouse using a thermometer and hygrometer.
• Adjust insulation measures as needed based on seasonal changes and weather conditions. For example, you may need to add additional insulation during colder months and remove or adjust it during warmer periods.
• Continuously assess the effectiveness of insulation materials and sealing techniques, making adjustments as necessary to optimize energy efficiency and plant health.

Conclusion:
Insulating your greenhouse is essential for creating a stable and nurturing environment for your plants year-round. By implementing a combination of insulation materials, sealing techniques, and thermal mass elements, you can regulate temperature and humidity levels while conserving energy and protecting delicate plants from extreme weather conditions. With proper insulation, your greenhouse will not only provide a comfortable and productive growing space but also serve as a sanctuary for cultivating lush and thriving plants.