How To Insulate A Greenhouse

When the weather starts to turn and the nights grow long and cold, it can often spell disaster for the unprepared gardener.

This is particularly true of those plants that require hotter temperatures and rely on a greenhouse to maintain ideal growing conditions.

Protecting your beloved plants and crops from the chill and ensuring their survival can seem daunting and even scary, as plants can deteriorate quickly when temperatures drop even slightly, undoing months or even years of work.

In this guide we’re going to look at how to insulate your greenhouse to protect your plants and your hard work from the onset of winter.

Why Insulate a greenhouse?

Quite simply, because your plants may die if you don’t do so. Certain plants require much more warmth and humidity than others, and typically these plants are grown in greenhouses. 

However, during the winter months, it’s not possible for greenhouses to sustain the correct conditions passively due to lower outside temperatures.

This means that your plants will be vulnerable, unless you insulate your greenhouse to help your plants survive the changing conditions.

The best way to protect your plants from winter damage is by using a heated greenhouse. This will keep them warm enough so they don’t suffer frostbite, but will also allow you to keep the temperature controlled so it doesn’t get too hot.

However heated greenhouses can be expensive, and even if you’re lucky enough to have one, insulation is essential to improve its efficiency.

How To Get Your Greenhouse Ready for Winter

The first step is to ensure that all lights in your greenhouse are working properly.

If you don’t have any light bulbs left, then you’ll need some new ones. This will be especially important if you have fluorescent lighting, which needs to be replaced every year.

Next, check the temperature settings on your heater. If they aren’t set correctly, you could end up with frost damage to your plants.

Finally, consider adding a heat mat underneath your pots and pans to prevent them from freezing during winter months.

Learn Your Greenhouse Climate Zone

The USDA has created a climate zone map that helps gardeners determine which plants will thrive best in certain areas.

This tool allows you to select a location based on the average temperature, precipitation, and sunlight hours so you can judge how your greenhouse will perform at different times and how to structure your preparations to take advantage of these changing conditions.

Bubble Wrap

Bubble wrap is one of the most effective ways to protect your plants from the elements. It provides insulation, keeping them warm during winter months and protecting them from frost damage.

It’s also cheap, easy to work with and readily available which offers a host of advantages to gardeners of all levels.

Weatherproofing Tape

Keeping water out of your greenhouse is critical. You can use weather tape to seal joints and gaps in panes of glass, helping to keep water out and warmth in, which will improve the overall efficiency of your greenhouse significantly.

Internal Curtains

The best way to protect your plants from frost damage is by using internal curtains. These are specially designed plastic sheets that fit inside your greenhouse and prevent heat from escaping.

They should be positioned so that they cover the floor of the greenhouse, however they shouldn’t obscure the walls or ceiling as this is where the little passive heat the greenhouse generates will come from. 

Cover Fabric Frost Cover

Covering your plants in frost cloth is another prudent step to take to protect your crops. This will protect them from the freezing temperatures outside and keep them safe until spring arrives.

It’s important to remember that this material needs to be kept dry at all times, which is why using them with a greenhouse is so effective.

Hoop Tunnel

The hoop tunnel is a greenhouse structure used to protect plants from harsh winter conditions. It consists of a series of hoops made out of wood or metal that are placed around a garden bed. These hoops act like a protective barrier against extreme temperature fluctuations. 


If you want to keep your garden healthy during winter, mulch!

It will protect your soil from freezing and provide nutrients for your plants, and this can be used in your greenhouse too to add some additional insulation to the plant pot at the top, without smothering or stifling the plant itself.

Use Insulating Pots

The best way to keep your plants warm is by using insulated pots. These come in different shapes and sizes, but they all contain some sort of insulation to prevent heat from escaping.

They’re usually made from polystyrene foam, which is lightweight and easy to transport.

Fan Heater

A fan heater is a simple device that uses fans to circulate warm air around a room. They’re usually mounted on the ceiling and come with thermostats so they automatically adjust the temperature according to the ambient temperature.

Double Glazing

A double glazed window will reduce heat transfer by around 50% however most greenhouses are single pane. It’s also important to choose windows that fit properly and seal well so they don’t let any air through which will lower the temperatures inside the greenhouse significantly.

Thermal Screens

A thermal screen is a great way to keep your greenhouse warm during the winter months. They come in many different shapes and sizes, but all will provide some degree of insulation from the outside elements.

Base Cladding

The base cladding is the first layer of material applied to the exterior wall surface. It should be made from materials that will provide protection against water penetration as well as keep the cold earth from sucking warmth out of your greenhouse.

A Helpful Video on Greenhouse Insulation

Final Thoughts

Insulation is an essential part of keeping your greenhouse warm throughout the winter months. If you do nothing else, make sure you insulate your greenhouse thoroughly before winter sets in. 

You may find yourself spending more money than you expected when you start looking into how to insulate a greenhouse, but it’ll be worth every penny to protect your hard work and ensure everything survives until the springtime.

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