It’s time to break out the bubbly! Don’t get excited, not that kind of bubbly – I’m talking about horticultural grade, UV stabilised bubblewrap. This stuff is great, with large bubbles to trap the warm air, and it should last at least three years.
It’s so easy to put up, simply measure the size of your panes of glass, cut the bubble wrap to the appropriate size and then fix on using strong tape. Leave the roof of your greenhouse so that plenty of light can still get in.