Everything has frozen over in my PVC greenhouse!

[Digitalis]

I've got lots of cuttings and various other stuff in pots in my PVC greenhouse. I have insulated it with polystyrene, bubble wra, fleece and cardboard.

However, today I have checked it over and all the pots and compost are frozen solid. :(

Do you think the established cuttings will be ok?

I've also got some young festica glaucus in there.

[Digitalis]

[rdm51]

 Afraid your going to be very lucky if anything comes though that.
My Polycarbonate greenhouse has bubble wrap, two layers of fleece and three layers of newspapers covering my fuchsia cuttings, plus an electric fan heater keeping the inside of greenhouse just around 5 above freezing
so this could work out to be a costly cold snap for me.
The temp here in the outskirts of Glasgow has not gone above freezing all day and the forcast looks like this could last for a week or more.
We have a a covering of snow but think we have missed the worst of it so far, Sunday not looking to promising.
Bob

[teejam47]

i have put most of my pots on poles attached to the top of the greenhouse and the floor. I have then wrapped them in fleece and also some in fleece and plastic i.e. a large circle pulled up around the pole and then tied at the top. I am using parasene but this is too expensive for too much use and so am experimenting with t lights ( be very careful) at the base of the poles inside the upright tunnels.
So far so good Terry

[Vinlander]

If you need to prevent frost  then water tanks used as heatsinks are much better than insulation alone because this is an active process not passive - the latent heat of fusion is an immense amount of heat that is only released as it freezes. Metal tanks will respond faster because the heat has got to get out.

It works better than heaters too unless you need to maintain it a lot warmer, say above 5C - which is very expensive!

People in New England have been using this technique for centuries in much worse winters than ours.   

A single oildrum or similar should protect a shed-sized greenhouse.
                                                                                                                                                                                                                                                                                                                             
Cheers.

[chriscross1966]

If you need to prevent frost  then water tanks used as heatsinks are much better than insulation alone because this is an active process not passive - the latent heat of fusion is an immense amount of heat that is only released as it freezes. Metal tanks will respond faster because the heat has got to get out.

It works better than heaters too unless you need to maintain it a lot warmer, say above 5C - which is very expensive!

People in New England have been using this technique for centuries in much worse winters than ours.   

A single oildrum or similar should protect a shed-sized greenhouse.
                                                                                                                                                                                                                                                                                                                             
Cheers.

Even more effective if you paint it black

chrisc

[Vinlander]

Hi chriscross1966 - you have a point.

But if you actually do the classic experiment with the cube and the IR sensor, then you find that a rough surface is more important than its shade of grey - though a dark surface does help. This isn't what it says in the textbooks - but they were written before lazy technicians started painting the cubes instead of blackening them... Paint is plastic, and therefore an insulator - it interferes with convection too.

The old experiments also ignored the fact that blackening inevitably adds roughness - it was never supposed to be real science - just a teaching aid...

I would recommend roughening first and then using the old-fashioned smoke blackening technique (carbon black is a good conductor) you can also smear with burnt cork.

All this is in my previous, more comprehensive message in "Edible Plants/Dwarf Beans winter challenge" - which also seems to address most of the outstanding questions about the possible downsides of heatsinks raised in "Under Glass/solar greenhouse heat sink".

Key point from that - drain the water before the time you would expect a frame or greenhouse to consistently warm up without a heatsink - whenever that is in your area.

I must add that getting heat into a water tank is important but it's less of an issue than getting it out - because if you don't have enough daylight hours for it to seep in (most of deep winter) then you are relying mainly on latent heat - which is already in there.

Cheers.