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Greenhouse vent suggestion???

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Greenhouse vent suggestion???

Postby chinookgardener » Aug 25, 2010 2:15 am

Hi there,

I have recently purchased a polycarb greenhouse that is 8x8x7. Even with shade cloth it is getting way to hot and I need to add additional ventilation in addition to the ceiling vent and door window (I do have a tiny fan as well). Looking at ventilation units online is depressing as they are so expensive - someone I know recommended using a bathroom vent instead...do any greenhouse owners have any suggestions?

Thanks!
*I apologize if this isn't in the correct forum...still figuring this site out...

Kira
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Re: Greenhouse vent suggestion???

Postby Eeyore » Aug 25, 2010 3:34 pm

I can't see why it wouldn't work. I had a small greenhouse and on hot days I would leave both doors open so the air would blow through and cool it down.

I'll move this to Garden Projects.

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Re: Greenhouse vent suggestion???

Postby OGrubber » Aug 25, 2010 4:56 pm

Hi Kira, Welcome!
I have a couple of 24 by 96 poly houses so have a pretty good idea of how much heat is generated, even early in the season.

The bathroom vent might just do the trick for you but I'm thinking you'll probably need more than one in each end - your poly-house is free standing, or at least both ends ventable, yes? Hopefully angled into your prevailing winds as well.
I would go with 3 or 4 [or more!] in each end - the type with their own fans - and wired or pluged in seperately, and as close to the top as you can get them. these fans aren't meant to be running all day so I suspect you'll get some burn-out which is why I suggest they are run separately - would make replacing much easier. If you put them in both ends, then you can take advantage of the wind to draw air through from one side or the other.

Alternatively, you could also build a framework at either end to hold a large box fan [the household floor model types, and again, as close to the top of the poly house as possible] which can be slipped out to turn the right direction to either draw or blow depending on the wind direction.... this would need an outside "hatch" to close up for winter and inclement weather.

I hope I've been helpful, or at least given you some ideas towards the options you have.
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Re: Greenhouse vent suggestion???

Postby chinookgardener » Aug 29, 2010 12:04 am

Thanks so much for your suggestion!

I think the large box fan may be a little more in my price range, I can always invest in the other fans next year when my budget is a little more. I have 2' x 4' vent on top with an automatic opener, and a big window in the door...would I place the vent blowing out or in? - I wouldn't say it is in a spot that gets lots of wind.

I'm finding it very difficult to keep my greenhouse from getting too hot. I have the shade cloth (70%), and I can only go out there and mist the plants so often - it's too small to invest in a misting system. It's actually harder to keep it cool than warm...good thing our summers are so short (or non existent this year in Calgary).

Cheers

Kira
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Re: Greenhouse vent suggestion???

Postby OGrubber » Aug 29, 2010 10:05 am

chinookgardener wrote: I have 2' x 4' vent on top with an automatic opener, and a big window in the door...would I place the vent blowing out or in? - I wouldn't say it is in a spot that gets lots of wind.


The best scenario would be to blow the air through. Draw in the cooler outside air from one end and push the hot inside air out the other end - a complete air exchange. This also would create better air circulation around your plants.

If your vent and window are at the same end then I would push the hot out - you may still have a "hot spot" at the other end though.

Just a thought about your mention of misting; not such a great idea. You could end up creating perfect conditions for white mold, damp-off, and any number of other nasties. Better to just water well in the morning and only if necessary, again in the evening, leaving plenty of time for the leaves and stems to dry before dark.
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Re: Greenhouse vent suggestion???

Postby otnorot » Oct 14, 2010 9:38 am

Lee Valley sells a vent control that automatically opens and closes a vent/window according to temp.
Page 52 in their online garden catalog.
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Re: Greenhouse vent suggestion???

Postby houseinthecountry » Jan 15, 2011 8:42 am

Hi all,

Rather than starting a new topic I thought I'd ask here...

I'm interested in buying a small greenhouse - the ones you see for sale in the $600 range.

Just wondering about what others think who have them. Good? Bad? Easy? Hard?

Mainly I am a rampant seed starter all winter, and by early spring I've run out of room. I also don't really have a place to harden them off well. I thought a greenhouse would be the way to go.

Any ideas would be great.
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Re: Greenhouse vent suggestion???

Postby B_BQ » Jan 15, 2011 10:00 am

We downsized about 5 years ago. My previous home had a 10 x 10 greenhouse, which I left behind! :cry:

I really missed the greenhouse when we moved here, and the 2nd year decided to pick up a plastic one, which sits against the side of the house. I find it invaluable for the shoulder seasons, (Spring and Fall). I start tomato seeds in the basement, under grow lights, and the little greenhouse is great for getting them hardened off gently before putting them in the raised bed.

I'll go and have a look for a pic of it. I love it!

~BBQ
This was taken just a few weeks ago showing how little snow we had at the time.
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Re: Greenhouse vent suggestion???

Postby houseinthecountry » Jan 15, 2011 10:46 am

THanks BBQ If you have the choice to keep your small one, or go back to your 10x10, which would you choose? I have the space for either, though a sunny location is a bit of a trick.

Do you have yours on the south side of you house?

I'm jealous of your no snow... we've been hammered here, have been under a thick, deep blanket since early December sometime.
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Re: Greenhouse vent suggestion???

Postby B_BQ » Jan 15, 2011 10:59 am

No doubt that I would choose the 10 x 10 - more space to move around and actually spend time in it! So, if you have the space then go for the larger one.

This space was the only place I had to put the greenhouse, as it is not free-standing. It's location is not south but more north! It gets a little bit of not-so-hot sun first thing in the morning, and then hotter sun late afternoon/early evening. Not an ideal location, but it's OK.

It has a window to open and also a circular vent on the door.

It's not a very strong structure, but as it's attached to the ground and wall with anchors it's done very well for the past 3 years.

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