Automatic vents

Does anyone have recommendations for automatic greenhouse vents? (The sort of thing that contains a wax which expands as the greenhouse gets warmer, which in turn drives a piston that opens the window).

I'm thinking I should enquire how wide they will open the window, and what weight etc., but I'd appreciate hearing about any good / bad experiences.

Thanks.

 

I have Bayliss ones, they have worked well for years.
Even managed to buy a new cylinder off them when one of mine did go on the blink, which was much cheaper than buying a new one.
http://www.baylissautovents.co.uk/

 

Bayliss, are about the best.:thumb:

 

Follow up on this:

I didn't buy any, in the end - also didn't paint the greenhouse white either

I'll try another Summer before I decide, because I think it may be that as I have a large greenhouse the airflow is sufficient to keep the temperature down without too much fiddling with the vents

I have been very carefully opening vents on the leeward side - so that I get convection, rather than draught, and I reckon if they were automatic (i.e. the vents opened themselves on both sides) the effect wouldn't be so good. But I may get bored of having to rush out to the greenhouse when I have forgotten and see the sun blazing down ...

 

Yup. I'm creating the "low down" vent by opening the door a bit ... but a louvre would be good, and I certainly think that automating that would make good sense.

But I have roof vents on both sides, and in practice I only want to open them on one side (except on exceptionally hot days, but even then I didn't find the greenhouse getting too hot this Summer) - and if I fit automatic vents I won't get the choice - they'll all just open anyway ...

... if I was away for a while during the Summer I can't see much harm in just leaving the roof open, day & night. Its the cooler months that might be a problem.

But I think we are both saying "Automatic vents with manual override" is what we need!

 

Just to add that although Bayliss is one of the original and more reliable manufacturers, I have three Jempvent openers in use, they were bought three years ago and retailed at £14-99 from a large discount store close to where I live, as yet they have been very reliable. I also agree with what has been said about manually managing ventilation but as a safeguard an auto vent can save small seedlings from frying when there is nobody around, it only takes an hour or so of sun on an otherwise cloudy day and the temperature will rocket. Even established plants can be damaged by large temperature fluctuations so I'm a big fan of automatic vents.

 

Thanks bobj, but what I actually want is to be able to close them on one side of the greenhouse (leeward side), and open on the other.


I'm pretty sure what I want isn't available, and is basically a pipe-dream. if I forget to open the greenhouse it opens by itself, but if I do open one side I don't want the other side opening ...

... sounds like I need electric motors to do the opening, and some fancy control box. Which would be totally daft for a small greenhouse like mine ...

 

"Good luck with it anyway"

You mean Good Luck with remembering to get up in good time and tootle down to the greenhouse to open it up before a) I forget and b) the sun fries everything?!! ... luck is definitely what I need.

As a cheapie-alternative I have been thinking about a temperature alarm, which I think would work fine for when I forget and am at home (which in my case is a fair-bet)

 

Kristen, what I would do in your situation, is fit a manually, sorry, womanly,:dh: operated,louvre vent low down opposite the door. And fit an auto vent to the most sheltered roof vent, leaving the other for you to adjust with.:gnthb:

 

I tend to find on windy or cool sunny days the vents on the windward side open less even if the vents are adjusted to open at the same temperature.

Not up on other makes than bayliss, but with these the air flows directly over the temperature control cylinder, that way, once the vent starts to open on the windy side the airflow cools the cylinder and keeps that vent almost closed.

Vents on the leeward side dont get this cooling so open greater.

 

now why didn't I think of that? Sounds like the perfect emergency solution.

I've got about 4 vents on each side, so having one of them automatic would be fine, and fitting it to the East side would be away from the prevailing S.W. wind 99% of the time.

The jobs-a-good'un, thanks.

 

Kristen, how big is your greenhouse?

 

30' x 10' (and another which is 12' x 10', but not yet erected)

Piccies: http://kgarden.wordpress.com/projects/greenhouses/

 

"they are probably not for you."

Nonsense. Sounds just like my shade of green ... "mean green"!

Good advice John, thanks. I wouldn't have though of replacing the glass with plastic in the vents.