Keeping a greenhouse warm over night using hot water?

[Kristen]

Yup, "Backups" are good Particularly with things like Beans where sow & plant early get away OK in a mild Spring, and in a late-Spring year the backups will do instead.

Having a strategically timed village fete is a handy outlet for Backups in mild Spring years ... and for feeling Virtuous

[Scarlet]

Having a strategically timed village fate is a handy outlet for Backups in mild Spring years ... and for feeling Virtuous

Hmm, I get a bit broken hearted when I give plants away because my pots are gone too

[Kristen]

Hmm, I get a bit broken hearted when I give plants away because my pots are gone too

Oh yessssss .... plastic vending machine cups for all "backups" in case they are fete'd ?

[Shadylane]

Transfer them into other things like yoghurt pots, margerine tubs, tin cans, homemade pots etc. I avoid giving pots away - I'm tight like that.

[Penellype]

When I sow early I do so in very small amounts - just 1 or 2 tomatoes, 4 cabbages, a pinch of lettuce. The idea is that I can get something going early, I can see if the seed is still viable, I can re-sow if only a few germinate, and if I am lucky and they grow well I have less of that variety taking up valuable propagator space in March. I've always got an idea of where the crops are going to end up, although it doesn't always turn out exactly like that.

With reference to the water barrels heating the greenhouse, I came across this the other day https://www.youtube.com/watch?v=rUj-5k9YqGQ. Only trouble seems to be that you need a huge number of barrels to make much difference, which takes up a lot of room. But you don't need to start with actual hot water.

[unclefudgly]

Well now that you mention it, I added a 500 litre black water tank at the front of my polytunnel to act as a heat sink. I doubt it has any effect at all during winter, but if the days get hotter and it heats up enough, then it will help to keep temperature dropping on cold snap nights later on.
I.ve also got a huge pile of manure rotting away in there as well, anything to stop temperature dropping below zero.

[Kristen]

I think it would be interesting to see how much your tank heats up during a nice sunny day. 5 degrees, say, on a 500 Litre tank is something like 3kWh - not to be sneezed at. Maybe you will get more than a 5C uplift?

[rary]

M.451, just to let you know that I have sown some sunflower seeds, I have installed a stove in my greenhouse, basically to keep me warm, as I have a number of old fire brick in the garden I placed them around the fire to act as a heat sink it looks as if it works ok as the lowest temperature last night when we had a hard frost was 3.5c the seeds were up through on Tuesday, they must have been very good as mice decided to eat the lot, they are all gone this morning So it`s not just the cold you need to worry about just (ps I will not be putting out any beer traps or they might hold a party)
pps. I also installed a CO alarm in the greenhouse

[Kristen]

mice decided to eat the lot

Sorry to hear that - so annoying. You've reminded me to start bating the mouse traps in my greenhouse, thanks

[Penellype]

There are mice in the greenhouse I use - I found when I started peas off last year that a tray covered with a propagator top was enough to keep them out until the plants were big enough to survive (ie when they got too tall for the top).

[Bohobumble]

mice decided to eat the lot, they are all gone this morning So it`s not just the cold you need to worry about just (ps I will not be putting out any beer traps or they might hold a party)

Yep, they did that with my broad beans the blighters, had to re-sow, now I use traps in there to keep the red kite restaurant stocked with dishes of the day (my shed roof).