Insulate or not?

[Stuart Hill]

Hi All, 'tis me again, that novice greenhouse owner!!

many thx for your advice on my other thread but this one is a purely technical question....

last year (my first as an owner of a greenhouse) I used some 4" thick insulation boards, left over from the bathroom re-model, underneath my growbags to, in my mind, insulate them from the cold concrete base. I'm now in the middle of the Winter clean-out and was wondering whether to bother again?
The only change this year has been the drilling of several drainage holes through the floor and sides of the concrete base (greenhouse floor was water-tight), putting weed matting down to stop these holes getting clogged-up, and then I am going to cover the floor with gravel to help when I damp-down. I am only looking this year to grow better tomatoes (although I was still harvesting up until last week), try cucumbers, melons and some early veg in containers. (carrots, spuds and maybe start beans and peas ready to transplant outside).

sorry to ramble on so much but.... so many questions and no-one else to ask!!

Thx in advance.

[Bigmallly]

I can only speak personally as I've fancied building one but would they be any use for making a hot bin?

[Potstubsdustbins]

Another way to look at it would be that the concrete base will act as a 'heat store' warmed by any sunshine we get that will help with cold nights. I certainly leave my concrete base exposed.

[unclefudgly]

Above are both great points, and I do something similar in my polytunnel. 500 litre black water tank at front of polytunnel to catch what little sun there is and store it as a heat sink, then I now keep Novembers regular manure delivery inside my polytunnel to rot down over the winter. I also have started to grow as much green stuff as possible over winter, again to just get some extra green heat.
This year I am also going to insulate with 1m wide large bubble wrap all round and taped to fill the gaps. The whole point is not to heat it but just to stop it frome getting below about 3-4c if possible.

[Nicos]

Personally, I'd use the insulation underneath the same way again....especially as you are putting down chippings.
Once the concrete cools down it'll drain the heat out of the soil in the tubs, so yep...I'd insulate again between the two.
Well...that's my theory!