Polytunnel doors and cold weather.

[Camile]

Hi everyone,

I was wonderring what I could do to lower the heat loss in the polytunnel.

So far the doors are about 2/3 polythen (bottom) and 1/3 windbreak mesh (top) ..

I'm keeping the doors closed at all time otherwise the birds would wreck it all ..

I thought there was some sort of polythen blind coming with the doors, but it doesn't, so I was wonderring if I should make some sort of blind, or polythen panel to cover the top part of the part for those long winter nights ?

I intend to leave some barrels with water in it so the diference in temperature won't be too big but that may not be enough, just a p lus me think..

Thanks,
Camile

[maggienetball]

We nail a large piece of thick plastic (left overs from the actual tunnel plastic) over the door that is rarely used. We nail it to the outer frame rather than the door which reduces the draft too.

In the winnter we completely cover the door that faces the prevailing wind and use the sheltered door.

For the other end that we use all the time, we nail the same type of thick plastic across the top and down one side and then hook the other "loose side" over a nail when we've finished in there. A bit of a pain as we have to duck under a little in order to get in but no great hardship and it does the job completely at zero cost.

When the wind gets up to gale force we have to renail a bit of it after the storm. Still no big deal really.

We also cover tender crops with fleece in the tunnel when the weather gets really wintery. It always seems to do the job for us - but then down here in sunny Torbay we rarely see anything much worse than -3!!! Hellish winds though.

The other thing we always do before "shutting up for winter" is to thoroughly clean the tunnel interior walls and the gravel, turn and feed the soil and remove clutter. This is to stop unwanted bacteria and diseases building up or lingering over winter. By keeping the draft out and the heat in we're also preventing the diseases/bacteria being killed off naturally.

There are organic and chemical yunnel cleaning solutions available.

Hope this helps.

[hedgewizard]

DON'T KEEP THE DOORS CLOSED - low temperatures in the autumn are far less dangerous than getting a runaway fungal infection in there! Yes, make film covers for the upper part of the doors, but leave them WIDE open during the day and close them an hour before sunset; the only time you don't open the doors during the day is if the temps are forecast to stay below freezing. Get them open first thing in the morning, as the air in the tunnel is generally colder than the air outside once the sun is up.

[maggienetball]

I don't think I agree with you hedgewizard.

I have used a polytunnel for a number of years and read a few books on the subject and have never been advised to keep them open in winter. Gardening Under Plastic, suggests just my methods for winter use.

I did mention in my post about diseases and bacteria and that you should clean the tunnel thoroughly to prevent these.

However, if you leave the doors open (except at night) then the inside temp may be barely above the outside (you need to allow for windchill also) and there wouldn't be much advantage to growing indoors.

My olives, lemon and other tropicals that I overwinter in the tunnel would not benefit from the "doors wide open" method either, and I doubt that they would survive the winter.

I would continue to support my method of closing the doors and preventing drafts in winter. I am thorough and methodical and have not had any polytunnel disease problems as yet (although I am sure that I, like anyone else, will get some one day).

I would suggest Camile, that you use trial and error. Try out some winter veggies in the tunnel with the doors open and see whether you get much success. If you try with the doors closed, please ensure you clean the tunnel thoroughly as the summer diseases are killed off by the cold and by keeping the tunnel (or greenhouse or cold frame) warm, nature cannot do her thing - so we have to do it for her!

Good luck though, and let us know how you get on.

[Camile]

Good morning,

Thanks for the tips guys ..

so far I'm leaving the doors closed but as I said, I have the top part of the door with mesh , , and I think I'll cover it up completly as it makes more sense to me indeed .. and our weather might be harsher than hedgwizard ..

so far I've planted radishes, lettuce and spring onions and it's growing nicely (still seedlings stage though) ... even though we had some frost already ... butu we have more or less the same weather than you maggienetball

I've planted spuds in bucketts too .. and I have a few strawberries plant that are blooming in there ..

and the tunnel has been up for less than 3 weeks so I don't think I would have summer diseases yet .. and when the time comes I'll ask how to thorougly clean the tunnel ...

Thanks again,
Camile

[hedgewizard]

Actually Maggie, Gardening Under Plastic says the same thing I do (I just checked - you made me doubt myself!) on page 15.

If you've got away without a fungal infection so far, well done - but the day you get one it will spread quickly if ventilation is poor. A friend of mine lost his entire spring planting that way, for the same reasons you mention.