insulating polytunnel?

[Aunty Social]

There is a US gardener called Patrick Dolan (and his cat Oscar) Extending Your Growing Season in Winter: Can Your Garden Survive the Cold?

I thought I'd bought this book but it's another by Lewis Hill called COLD CLIMATE GARDENING. There should be a special section for gardeners located in cold, grey, windy environs: this past year has been like trying to grow veg on JMW Turner's ship in a storm, whilst battling pirates in the form of slugs, caterpillars & rabbits (the rubber snakes saw off the pigeons).

[Small pumpkin]

If you can afford another layer of plastic two layers with an air gap is about the best you can get
just need a small 12v air pump, battery and tiny solar panel to keep it 'inflated'

How do you secure the second skin to the tunnel. If it needs to be loose enough for air to be circulated around it ?

And what size tunnel would a 12v air pump be suitable for?

[roitelet]

How do you secure the second skin to the tunnel. If it needs to be loose enough for air to be circulated around it ?

And what size tunnel would a 12v air pump be suitable for?

Make a frame, tunnel within a tunnel. Bit of a faff but it works. Has to be removed in the summer though.

[MarkPelican]

I suppose it depends on the type of polytunnel, but (when I did it) I put wires on the inside of the support posts and tucked the bubblewrap (bubble side out) underneath the wires. There was a gap between the bubblewrap and the main skin of the tunnel without needing a pump or anything.

[unclefudgly]

I have tried bubblewrap to insulate, and while it does offer some extra protection, I didn't see the benefit I thought I would get. I now try to grow as much green stuff as possible actively growing and generating a small amount of heat, and this does as much as having bubble wrap in helping temperatures stay above freezing in my experience.
I also have a large 250 gallon black water tank at front of tunnel that gets heated up by meagre sun we get this time of year and stores that heat in the water to release overnight.
For me just keeping temps above freezing is ideal

[4Shoes]

How about a mini Polytunnel?

Still on the drawing board

I'm have 2.4m x 1.2m Frames with feet and cloches (Blue Pipe and Polytunnel grade plastic) for the garden. Also use them as a cold frame.

Idea is at the end of the year, bring them into the polytunnel, stack them 4 high and fill with fresh muck to create a hot bed. Cover with cloche and you have a heated mini polytunnel.