Author Topic: Greenhouses  (Read 8183 times)

RobsVeg

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Greenhouses
« on: July 16, 2007, 17:28:02 »
Hi There

I want to buy a greenhouse so I can have it heated in the winter to try and extend my range of produce through the year but I am not sure whether to go for traditional glass or polycarbonate, is there a difference with them retaining heat or any other problems which makes one or the other better or worse. Any tips or pointers would be appreciated as I have only ever used the tiny PVC type before [just to get things going for the allotment].

Thanks very much

SnooziSuzi

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Re: Greenhouses
« Reply #1 on: July 16, 2007, 17:34:46 »
I have a glass one but as panes are broken I am replacing with polycarb and I'm not noticing any difference, except maybe that the polycarb isn't as thick as the glass so it was whistling and rattling in the winds a couple of days ago!

I'm sure that polycarb would dull over time, but glass smashes, so it would really be down to a personal preference.  Oh, and polycarb is cheaper to replace than glass I have found!

HTH :D
SnooziSuzi
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allaboutliverpool

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Re: Greenhouses
« Reply #2 on: July 20, 2007, 05:42:16 »
Life is never as simple as it looks.

On an allotment I would go for anything but glass if you are subject to vandalism.

In a garden in view of the house, glass, which looks ok.

Heating is the big problem. Glass haemorrhages heat especially in metal frames and requires laborious lining with bubble-wrap each autumn.

Polycarb, the sort that goes on the roof of conservatories, because of its air cells is the best for insulation, thus cheaper to heat.

In an ideal world I would have a lovely cedar greenhouse with toughened glass, big enough to have a separate section that can be insulated and heated; just like the ones you see on telly.

Because of the lower translucency of polycarb, unless you have particularly surceptible plants, it is not necessary to shade it at the height of summer.

You choose....... ???



« Last Edit: July 20, 2007, 05:45:46 by allaboutliverpool »

euronerd

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Re: Greenhouses
« Reply #3 on: July 22, 2007, 11:29:55 »
There were some posts earlier in the year about this, and something came up that isn't generally thought about: when we were having strong winds the polycarb greenhouses simply took off, whereas traditional ones, due to the sheer weight of the glass, tended to stay put.

Geoff.
You can't please all of the people all of the time, but you can't upset them all at once either.

cambourne7

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Re: Greenhouses
« Reply #4 on: July 22, 2007, 16:16:57 »
What about a heat sump?? i seen that on its not easy going green?

How does the greenhouse heat sink work?
Some details are in the book, but half the adventure is working out for yourself and thereby customising you solution. All you need is:

The heat sink is imploded glass - we used bottles from various parties and the local pub - imploded courtesy of Krysteline www.krysteline.net
Big hole - we lined it with polystyrene that came as packaging
Pipes were standard waste pipes for under sinks etc
Fan was a small 12V computer fan from a market £1.20 - in a box made of scrap wood
A 12V deep cycle leisure battery
Small 11w solar panel and charge controller
Old chimney cowl for the air to be pushed out the glass

Air sucked down from the apex heats the broken glass under the floor. Fan runs 24 hours a day. As the greenhouse cools the cooler air is still pumped through the glass, but when it comes out through the cowl, at floor level, the glass has warmed it so a constant supply of warm air is now being pumped through.


Tee Gee

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Re: Greenhouses
« Reply #5 on: July 22, 2007, 16:37:13 »
Quote
due to the sheer weight of the glass, tended to stay put.

Not quite right euronerd.

Polycarbonate flexes more in high wind than glass and as a consequence the glazing clips  become undone and the sheets take off.

The other thing is; I seem to recall from my college days is that roofs are not blown of with the wind as such they are basically sucked off.

What happens is; when the wind blows over the roof it creates a vacuum on the leeward side of the roof, this causes the normal air pressure in the building to become greater than that out side, so the roof is blown off from inside the building due to the unequal air pressures!

Now I never thought when I did my studying that  I would ever need to use that bit of information  ;D


cambourne7

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Re: Greenhouses
« Reply #6 on: July 22, 2007, 17:32:19 »
who says you never learn anything??

Robert_Brenchley

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Re: Greenhouses
« Reply #7 on: July 24, 2007, 09:43:57 »
Sucking off is dead right, it's always the downwind side that goes first. Lots of cracks around the eaves does a lot to reduce the likelihood. My mother had the roof of a house in Cornwall done with fibreglass stuff; a lot of people were having it done at the time. It went over the slates and sealed it up so it was guaranteed not to leak. All very well, but it sealed up all the holes. A few years later there was a bad gale, and the roof, which had stood 150 years of Cornish winds, landed in the back garden, still in one piece.

Lavender lover

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Re: Greenhouses
« Reply #8 on: July 25, 2007, 19:07:18 »


I bought this ketter greenhouse a few months ago from my catalog [Empire] [also avalible from studio]
Hubby laid it on a wood base sunken into the ground so it sits level. Inside is a bed of sand, weed guard and then stones. The whole greenhouse is screwed on to the wood and is going nowhere in any weather.
It is only plastic but it looks pretty which was the most important thing for me as it is in front of my living room window and can be seen all the time.
Electric has been laid underground before it was put up.
Its pretty, children friendly, football friendly, easy to clean, ready shaded and was not too difficult to put up.

SnooziSuzi

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Re: Greenhouses
« Reply #9 on: July 25, 2007, 21:35:22 »
That's a nice tidy greenhouse, LL  ;D
SnooziSuzi
Acting my shoe size, not my age!

RobsVeg

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Re: Greenhouses
« Reply #10 on: July 28, 2007, 12:25:40 »
Hi All

Sorry I haven't been back sooner, busy busy. Thanks for all the advice and tips,didn't think I would get a scientific explanation about the wind but it's certainly something to think about, I'm still deciding which way to go but I do have to agree with SnooziSuzi - that IS a very tidy greenhouse.

Thanks again everybody.

 

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