Frost/wind protection

I was planning on building some kind of temporary cold frame type contraption for the back garden. I have a few young vulnerable plants in pots that I was going to overwinter in it. Then in the spring I can disassemble it.

However I have a very large plastic tub that I got from work. In the summer we fill it with water and it keeps my son occupied for hours. In the winter I just turn it upside down until the following summer.

I have some tri-wall clear poly carbonate sheets and this year I was thinking of leaving the plastic tub the right way up, putting my vulnerable potted plants in it, and placing the polycarbonate sheet on top and securing it with bricks.

The plants will be protected from any wind, and no frost will be able to settle on the vulnerable leaves.

I plan on having the polycarbonate sheet on a slight slant so rain water and any snow melt can drain off. I also plan on circling the tub, once the sheet is on, with several layers of stretch wrap (cling film) which I can also get from work. This will cover any gaps and pretty much make it water proof.

Does this seem like a feasible idea?

 

Sounds feasible but you will need to ventilate it on most days.

 

That was my main concern. If I wrap it with stretch wrap then that pretty much makes it water tight and air tight! If I don't wrap it then rain will inevitably leak in, but on the plus side, so can air for ventilation.

If rain leaks in then a pool is going to develop in the bottom of the tub.

How about ditching the stretch wrap idea and putting some lats of wood in the bottom for the pots to sit on, so they're raised and the plant roots can't get waterlogged?

Without the stretch wrap will frost be able to get in and ice up the inside?

 

If water gets in and freezes, the tub can crack. I loose watering cans like that every winter

Do you have a table or something like that to cover one end so that you can leave a ventilation hole?

 

Condensation is the main issue to solve; I'm also wondering whether the tub is opaque or clear plastic? If it's opaque and has tall sides, will the plants inside be getting enough light, even with the lid off?

 

You Probably don't want to do it but I'd drill some holes in the bottom, I dont like the shrink wrap idea to be honest.
The shrink wrap has no insulation value.

 

This is a picture I've just taken just to give you an idea of the set up. The purpose of the wood framework is to simply give it more height. When it rains heavily the rain leaks in through the gaps between the wood/tub/top sheet and then pools in the bottom, hence my idea to shrink wrap around the top and make it more waterproof, but of course that's my ventilation hampered then too!

The tub cracking, even in the coldest temps is not an issue one bit. These things are bomb proof, they're made of thick wall heavy duty HDPE.

Drilling a small hole in the bottom for drainage is doable I suppose, I can simply plug it up in summer when I fill it for my son.

Will it matter a great deal if the light isn't fantastic. After all, the plants are dormant through winter, do they really need bright light everyday?

What I don't want to be doing really is building something specially for protecting the few plants I'm putting in there, when I have this tub which is ideal, though may need some tweaking.