Greenhouses do an amazing job in summer months of containing heat and creating the best conditions for growing. But as the days get shorter, the sun lower and the cold sets in, every greenhouse owner has a decision to make about how to care for plants over the winter months. Using bubble wrap as insulation has been growing in popularity, and, with a few helpful tips, can be a relatively easy and affordable way to both extend the growing season and protect plants in winter.
Why should you consider using bubble wrap for greenhouse insulation?
Tender and less-hardy plants won’t survive the lower temperatures and reduced sunlight of our British winters without a helping hand. A greenhouse offers some protection from wind, ice and potential snow, but without addressing the issue of warmth, all the care that has gone into growing and tending for your plants could be undone. Greenhouse gardeners are left with the choice of either adding heat or insulating.
Traditionally, plants have been insulated using fleece or burlap, and more recently with horticultural fleece, a readily available plastic alternative to natural fleece.
A greenhouse offers us the opportunity to maintain a higher temperature throughout the space, and some gardeners use electric or oil heaters to heat their greenhouses. This, of course, comes with ongoing costs and maintenance, leading many to lean towards insulation, for both financial and environmental reasons. And of course, many will choose a combination of both.
Bubble wrap as an insulator is a lower-cost way of containing precious heat from sunlight during the day, and stopping temperatures from dropping quite as much overnight.
Why is bubble wrap a good greenhouse insulator?
Bubble wrap insulates in the same way as double-glazing. The air pockets in the wrap create a buffer between the outside and inside temperatures. They heat up from sunlight during the day, and then slow the transfer of heat out into the cold nights. Just like in a double-glazed house, this insulation helps to contain the heat, retaining valuable degrees in heat.
Choosing the right bubble wrap for your greenhouse
If you’ve decided insulation is your preferred option, the first step is choosing your bubble wrap. Packing wrap, while cheap, will not be up to the task. It’s not made to withstand the elements, and the bubbles have not been designed with insulation in mind. It’s recommended that you invest in horticultural bubble wrap, which is more durable and has larger ‘bubbles’, so is significantly more effective. It has been made to withstand the cold and UV from sunlight, so it can also be reused for several seasons.
Before buying your bubble wrap, make sure you have your measurements ready. The best way of holding the heat is to have as few joining sections as possible, and rolls come in multiple widths. In general, the wider the better, so that you can cover more of the wall in one go.
Preparing to bubble wrap your greenhouse
The best time to wrap a greenhouse is just after a big autumn clean, which may take place in October, at the end of your growing season. This means you can make sure that dirt and any pests have been removed before it goes up. It’s also a good idea to make sure the greenhouse has been aired out and has dried properly after the cleaning, because the bubble wrap will be covering your vents, and you won’t want to trap in excess moisture.
Ideally, you’ll want someone on hand to help as you do it, especially when it comes to the roof panes – but if you do have to complete the task on your own, items such as bulldog clips or masking tape will be helpful to have on hand.
How to insulate a greenhouse with bubble wrap
When you’re ready to install the bubble wrap, remember that minimising the number of joins and cuts will make the insulation more effective. As much as can be covered by a single, long, continuous sheet, the better, to reduce heat loss in the gaps.
Starting with your large roll, go horizontally at ground level from one side of the door, all around the walls and back to the other side of the door. This will be the easiest option for lining the lower portion of the glass. Fix the bubble wrap as you go with sticky tape, or with plastic greenhouse pegs that attach to your frame.
For the upper section and roof, think again about how to approach it with minimal cutting of the bubble wrap. This is where helping hands can make a big difference, as you may want someone to hold up sections while you fasten others. You will need to make some strategic folds to fit the shape. As much as possible, fill every corner and surface area with the wrap, to avoid heat slipping out. And again, make sure to fasten as you go.
Impact on Plant Growth
Insulating with bubble wrap can help to extend the growing season in the autumn, for some plants by up to six weeks. For the hardiest of plants, it can even extend growing longer than that. And for more tender plants, it may not offer extended growing, but will help to protect them from the harshest of winters.
However, alongside the benefits of bubble wrapping your greenhouse, you should also be aware of some of the drawbacks of insulating with bubble wrap. These are by no means reasons to avoid it, rather things to keep an eye out for, so that you’re ready to protect your plants.
Do you get condensation?
Having insulated your greenhouse, it’s important to remember that you have just covered up your vents and windows. As the winter progresses, you’ll want to keep an eye on condensation and moisture levels. If you do need to air your greenhouse out for the health of your plants, remember you’ll have to let the heat out along with the moisture, so you may want to use a heater to restore that lost heat.
Does the bubble wrap block out the light?
Another issue is reduced sunlight. While translucent, the bubble wrap will mean less sunlight getting through, and in low-sun months, this may not be ideal for all the plants you are trying to protect. To mitigate for this, you might want to consider lighting options in the darkest of months.
Cost Implications
The outlay for your bubble wrap will come in one go, at the start of the winter – and the cost will depend on the size of your greenhouse. But the good news is that one outlay will save on those fluctuating heating bills throughout the season. And because the wrap is durable, if you’re careful when removing it in the spring, you can reuse the same bubble wrap in future years.
Generally, bubble wrapping your greenhouse will be come out as more cost effective than using fleece to individually wrap plants, but this will depend on how many plants and the size of your greenhouse.
Pros and Cons of Bubble Wrapping your Greenhouse
There are a range of reasons that horticultural bubble wrap is increasing in popularity as insultation for greenhouses:
- Cost effective, compared to using a heater or other forms of insulation
- Can be reused for multiple seasons
- A one-off job to install to insulate the space, instead of wrapping plants individually
- Can extend the growing season, as well as protect plants through the winter months
Some things to be aware of are:
- It’s important to get the right, horticultural bubble wrap that has been purpose-made and can withstand the elements
- When you install it, you need to plan ahead to measure, and keep them number of cuts and joins to a minimum
- The bubble wrap will block your air vents and windows, so keep an eye on condensation
- While translucent, the bubble wrap will still significantly reduce sunlight, so you may need to add lighting for some types of plants
Will bubble wrap be the right insulation for my greenhouse?
All in all, horticultural bubble wrap can be a great way of insulating a greenhouse for winter months. If you’re ready to keep an eye out for excess moisture and add light if need be, it can help protect your plants through the cold, and even extend the growing season. It is durable and effective, and if taken care of, can be reused across several years.
Our advice for smooth installation is to get the preparation right, install after a good clean and be ready to get creative to fold and fasten, to fit the wrap right into corners of your space.
