Autovent Temperature?

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Pimento

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Autovent Temperature?
« on: April 13, 2012, 22:05 »
Hello all,

I've just got my first greenhouse on the plot. As I can't get up there everyday, I'll definitely need an autovent, and soon! I'm a bit fuzzy, though, about temperatures. When do people think I should set it to open? I'll be having just-pricked-out seedlings in there - half-hardy annuals as well as veg.  The lottie's very exposed, and gets no shade at all really. So I need to ventilate really well (and shade too) - but at the same time keep the gales out!

All advice greatly appreciated, and thanks in advance!

Pimmy.




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JayG

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Re: Autovent Temperature?
« Reply #1 on: April 14, 2012, 11:51 »
You've summed up all the conflicting variables rather well, and it does seem to be a bit of a juggling act at times, especially with the weather being the most unpredictable variable of them all!

I don't think it's possible to quote an exact figure for when the vent should start to open, partly because you could waste a great deal of time actually trying to achieve it by trial and error - mine probably starts to open at around 23C, and is fully open at 30C, which is about the maximum I would really like to see in there.

Even with partial shade down one side of my greenhouse I've seen the temperature above 35C, so the door has to be opened as well (my greenhouse only has 1 vent)

Leaving the door permanently wide open isn't a great idea either, because temperatures will fluctuate too much and any strong winds could cause structural problems, especially if the door faces into them.

I would think that for yours shading is an absolute necessity, the balance between the autovent and minimum amount of door opening for keeping the temperatures stable will be mainly down to trial and error and keeping an eye on weather forecasts (a max-min thermometer will help you keep track of temperaures in your absence.)
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Pimento

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Re: Autovent Temperature?
« Reply #2 on: April 15, 2012, 06:18 »
Thanks, JayG, that's helpful. Apart from frying or freezing little plants, a main concern is having the window open too wide at too low a temperature and letting potentially-damaging winds in. it's a very old greenhouse - hopefully the door will stay on if I leave it open! :D

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davel831

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Re: Autovent Temperature?
« Reply #3 on: May 20, 2012, 08:22 »
Quote
Even with partial shade down one side of my greenhouse I've seen the temperature above 35C, so the door has to be opened as well (my greenhouse only has 1 vent)

Leaving the door permanently wide open isn't a great idea either, because temperatures will fluctuate too much and any strong winds could cause structural problems, especially if the door faces into them.


This is very much the probelm we have in our greenhouse.. we fitted a autovent and try to keep the door to a minimum opening as we too are very wary of wind damage....

it is a trial and error but this is the probelm we face with small greenhouses..  I am also very wary to spray plants in the greenhouse to avoid diease and fungal probelms


cheers dave  :D



edit to clarify quote
« Last Edit: May 20, 2012, 10:05 by mumofstig »
Dave

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Pimento

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Re: Autovent Temperature?
« Reply #4 on: May 20, 2012, 09:32 »
Hello Dave,

I'm definitely in the same boat. Although I haven't even fitted the autovent yet as on my chilly old plot it hasn't even been warm enough!  :(  Middle of May and night-time temps in there are still between 2 and 5 degrees, and it hasn't been above 18 in the daytime. Boo!

What we have had, though, is some fierce gales in the last week, enough to really rattle the door frame, so I'd have been loathe to fit the vent anyway until the weather's a mite more summery.

So yes, it's definitely going to be trial without, I hope, too many errors...

Best wishes,

Pim.

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mumofstig

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Re: Autovent Temperature?
« Reply #5 on: May 20, 2012, 10:09 »
You are best to fit your autovent while it's cold -they are difficult to fit when it's warm and sunny as they'll be trying to open as you fit them  :blink: and that's no fun I can tell you!

But if it is cold they won't open,  so there's no problem with them being fitted now.







edit for typo
« Last Edit: May 20, 2012, 10:19 by mumofstig »
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Pimento

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Re: Autovent Temperature?
« Reply #6 on: May 20, 2012, 10:13 »
Thanks for the advice, MoS. The only problem is that if I fit it and we suddenly get a warm day, I wouldn't want it opening with the wind levels we're currently having (that's the allotment, not me personally   :lol: )

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davel831

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Re: Autovent Temperature?
« Reply #7 on: May 20, 2012, 18:46 »
pim
      i am thinking of getting a louve then replacing the bottom of pane of glass on the door then open it slightly then when temps gets up the autovent will open then we have a cool air flow!!

cheers dave ::)



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