[lovemyveg]

I am very confused with the question of greenhouse insulation for winter.  I thought that large bubble wrap polythene sheets would be better for this, but after some investigation have been given to understand that the small size bubbles would be best.  At Two Wests and Elliot http://www.twowests.co.uk/TwoWestsSite/product/HTS.htm their "heatsheets" are just 10mm.  I am not sure what the difference between this and bog standard bubble wrap is (it is not too badly priced).  Other links have also advised on the small size bubbles in preference to the large.  Can anyone throw some experienced light on this subject and where can I find this insulation at a reasonable price?  Or is it better to buy the "heatsheets" if this is a better product?

[Ice]

Sad, I know, but I just worked out how much my greenhouse would cost with this material and it came to £160.    I'll stick to bubble wrap thanks very much, one layer on the walls and two on the roof of whatever is cheapest.

[DD.]

11 squid inc. postage for 50 sq m.

Does loadsa greenhouses:

LINK

[lovemyveg]

Thanks DD for the link to the bubble wrap I have had a look at this and its an excellent price.  Are we saying then, that there is no value in getting the large bubble wrap for extra insulation that the same result will be got from the small bubble wrap?  Thanks again

[DD.]

Small stuff's fine & at this price you could do a double layer.

[lovemyveg]

Small stuff's fine & at this pride you could do a double layer.

Brilliant,  I am now off to ebay to order.  Thanks for your invaluable help.  What a great Forum with such helpful, happy people.

[pushrod]

 Can i politely ask why you want insulate your green house and if you are going to heat it?

[DD.]

Same reason as you insulate your home!

[lovemyveg]

Can i politely ask why you want insulate your green house and if you are going to heat it?

The reason for using bubble wrap to insulate the greenhouse this year is that last year I bought a paraffin heater - used it once, as the gallon of paraffin cost me £8.50 and lasted 48 hours on a very low wick.  So that is still in the box in the garage.  I bought the remaining greenhouse plants into the porch attached to the house and overwintered them there using the central heating in the house, leaving the greenhouse obsolete.  This year it is the turn of the bubble wrap - with no added heating (I have not got electricity in there and will not use the paraffin again).  So hopefully this will do the trick and I will not be overwintering as many plants as last year.  If I had costed out the rearing of plug plants bought last September, the plants would have been more expensive than buying in a 5 ltr mature plant bought from an expensive nursery.

[pushrod]

Same reason as you insulate your home!

You spend many £100s heating your home in winter. The insulation in your home is to try and reduce the heat flow out of it.

Lovemyveg, the reason i ask is because a lot of people mistakenly think that with a layer of bubble wrap against a 6mm pane of glass they are going to keep their green house warm through the winter - they won't.  Insulation just reduces the rate of transfer of heat meaning that with your insulation it might stay a degree or two warmer for an hour or so longer. However during the course of the night or a cold spell the outside and inside temps will still equalise, they just take a little longer to do it.
If you had a rare collection of plants that were frost tender then the insulation might reduce your heating bills by 5%, but as you already know paraffin heating gets expensive and the money spent on that can be better spent buying bigger plants in the spring. It really is not worth spending a lot of money trying to keep a few pelargoniums and tender fuschias.
Where your greenhouse can be useful is in stopping the roots of slightly hardier plants getting trapped in waterlogged soil that becomes frozen. It can do that without the insulation.

Money spent on shading is probably a better investment to try and stop some of the damaging high temperatures that you can get.

[lovemyveg]

Thanks pushrod for your reply.  Last year was my first one with a greenhouse and I did attempt to overwinter the pelargoniums from my window boxes, but will not be bothered to do this again.  I also had bought 20 bearded irises that were too small to go into the garden at the time, so again tried to overwinter them until the Spring.  That was the first lesson - do not buy plants late in the year to overwinter.  I agree totally that it is worth buying established plants in the Spring rather than plug plants to grow on.  I managed to get shading for the greenhouse from a car boot sale, so have used this on the south facing side of the greenhouse during the "summer" which has worked well.  I do understand that without heating in there I cannot keep any tender plants, but there are a few large plant pots that will do better in there on the staging, than outside.  I will also put the lettuce in the greenhouse.  Last year I grew winter lettuce outside with a fleece cover and they did remarkably well, so I shall experiment with them in the g/house as well.

[NigelB]

Mine's full of cacti of every shape and size... I used to go to a lot of trouble burning up energy in the form of paraffin and electricity trying to keep it warm in winter... Then later, I double-skinned it with bubble-wrap at great cost too....... All of it a waste of time, energy and money....
What I came to realise, is that cacti,  amaryllis, and a few other types of what I considered to be 'soft' plants are happy enough for short spells at, or even below, freezing temperatures as long as their roots are dry..
Cacti certainly benefit from a dry spell in winter... It triggers their flowering mechanism and I've had cacti flowers every summer since I've left them dry and unheated in winter...

Here's what I've learned in the 15-or-so years I've had my greenhouse....

They can stand cold...
They can take it wet...
BUT, they can't do both cold AND wet or they'll rot.

Greenhouses are rarely frozen for long... A very cold night with clear skies will usually give a sunny start to the day, warming the greenhouse enough so the plants don't become damaged..... And if the skies are cloudy, then temps tend not to drop too low anyway....

So, in short, I've learned not to throw money at the greenhouse in winter and it does just as well now, if not better, then when I was trying to heat it.....
Oh, and some plants simply aren't worth the trouble of trying to keep over winter, just re-sow in spring.
Hope this helps.

Nig.

[pushrod]

As you found out lettuce can be remarkably hardy -  under fleece sounds good and they will probs do better there than in your greenhouse, but good luck with them. I grow mine in the ground inside cold frames but the problem is that you can get green fly in there overwintering with them so i might have a go at your lettuce/fleece idea. ( I did have a lot of success with cabbages and cauliflowers under fleece and keeping butterflies off).
IMO the  problem with greenhouses is the sudden fluctuations in temperature, the warmth can trick plants into new growth too soon. If your green house is kept warm over winter it can also help pests survive as well!
I think your big pot plants will survive better in your greenhouse from not being battered from the wind and waterlogging than they will from having a layer of bubble wrap on the glass if you get my meaning.

Edit: agree totally with your views Nigel - you posted while i was replying to lovemyveg.