Would this work?

[Bohobumble]

Jay-ell & Bohohumble - its time for you to join this http://www.growfruitandveg.co.uk/gra...s%27+club.html

I joined, now what?!

[Kristen]

It might well ultimately end up the same as outside but the heat differentials should mean it'll cool down slower, hopefully meaning that any cold periods are minimised inside before sunrise.

Yup agree with that, although it is the absolute lowest temperature which is critical for anything tender - Tomatoes and the like.

it can't hurt my onion seedlings!

Actually I wonder if it is a bit warm for your onions? Its not something I know much about, this time of year I grow mine under lights and with heat so a different method, but my recollection is that they are best kept "cool" after [some initial heat to encourage] germination? 15C or something like that?

[Bohobumble]

[ATTACH=CONFIG]53167[/ATTACH]

Let's see how that goes, will transport my onion seedlings there tomorrow

Thanks all for your comments!

Thanks for the 'like' there VC, I can tell it was for the three trays of radishes I put in there

I should really sow some more today for your challenge!

[veggiechicken]

I joined, now what?!

Answer some of the questions and show us just how nutty you are

[Penellype]

Wow! sounds like you're making the best of it tho, can you seal the edges of the polycarbonate with glazing tape (WEATHER PROOFING GLASS/WINDOW REPAIR TAPE 20M X 50MM: Amazon.co.uk: Garden & Outdoors) to keep drafts out?

I could seal some of it but not the places where triangular pieces of glass are missing, some of them several square inches in area. I just have to work with it - I daren't mess with it too much as several more windows have serious cracks in and pieces of glass could well fall out. The roof panes are mostly sound so I don't think anything is going to fall on my head, its just the sides that are a bit ropey. Its much better than no greenhouse at all though

[Bohobumble]

I'll dig mine out, and the logging thermometer, and stick it in my greenhouse for a few days to see.

Any results as yet there Kristen? I'm keen to see if you note any interesting effects with your logging equipment!

[Kristen]

Sorry, not managed to find the blow-away yet. Need to do it soon otherwise we won't have any more cold temperatures this year to do a proper test against ...

I'll check if Manageable knows where it is A good chance as its Le Weekend

[Kristen]

Erected the Blowaway and put some Loggers in it a few days ago. Could do with some cold temperatures for a decent test ...

I'm leaving the blowaway zipped up during the day so the day temperatures will be MAX and it will have as much heat as possible into the evening, so real-world tests might not have quite so much heat-buffer to play with.

That said, its in a large greenhouse, which is ventilated, so I don't think the heat gain from direct sun will be huge (compared to if it was in a small greenhouse / shut up perhaps. We'll see



Loggers under a pot on top shelf, under a pot alongside (just above ground) an another outside (under a pot, natch!) on the North side out of direct sun

[Bohobumble]

Nice greenhouse! What shrubs do you have growing there?

As it happens my cheapy pH meter from China arrived today, it's also got a light meter (and moisture) it's rather sunny here so will nip down to see what light differential there will be.

It is nowhere near as swish as your loggers so please do share any data you get, it'll be really interesting to see? I wonder if the lack of soil in the blowaway will make any difference too.

Now to find the superglue to stick my thermometer back into it's markings.... I have a nifty way of calibrating as I don't have a cold

[Kristen]

What shrubs do you have growing there?

They are box cuttings, over-wintering - there are quite a few in there, here's another photo "standing back a bit"



There is some Chard (blinking small though!) between the pots, on the left, which will hopefully make a Spring crop - the Box plants can go out when that comes up ... and then Sweetcorn will go between the Chard, where the pots are now ... and then Peppers between the Corn as it is harvested ...

it's also got a light meter

I've got a light meter somewhere (Gadgets R' Me !!) although not sure useful for this experiement. I suppose I could measure light inside blowaway, and inside greenhouse, and compare / see the loss.

I wonder if the lack of soil in the blowaway will make any difference too.

Yes, good point. Might be worth trying again with a large-ish container of water in there.

[Kristen]

OK, some results ... bit of a cockup, but perhaps more useful data as a result.

I put the logging thermometers:

• On the top shelf of the Blow-away
• On the top of a pot say on the greenhouse border
• Outside the North/Shaded end of the greenhouse, on a brick.

All covered with a pot so that they were not in direct sun.

Result: Blow-away fell to a LOWER temperature than the greenhouse! However, I think this is because its thermometer was up (relatively high) on the shelf, and the one on the pot, stood on the greenhouse border, had the benefit of warmth rising from the soil.

But I think it shows that the temperature in the Blow-away falls just as quickly as the greenhouse itself, and (by itself) provides no additional insulation benefit.


(Click for larger image)

Some additional thoughts:

• The Blow-away was kept zipped-up all day, so it got hotter than would actually be the case. The greenhouse vents were opened on warm days.
• There were no pots / soil / thermal mass in the Blow-away, which might heklp.
• The Blow-away is a small volume so could be heated cheaply, relative to the whole greenhouse.
• Measurements are shown to 0.1C, but the thermometers are probably not accurate to 0.1C

More detailed article on my blog with a break-out image for one day and tables of falling temperatures / lag to outside etc. etc.
https://kgarden.wordpress.com/2015/0...ng-protection/