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"I thought it was to the glass on the lee side being sucked up away from the greenhouse frame. Similar to how an aeroplane wing works. The air has further to travel over the pitched roof and so the pressure is lower outside than air pressure inside the greenhouse. Therefore the glass will try and lift."
Graham Silcocks on Friday 6 November 2015
"When I reglazed my greenhouses in polycarbonate I also drilled the alloy frame so I could run some galvanised wire on the outside of the panels. This prevents the panels from bowing outwards and popping out of the W clips.It's worked so far!!"
Keith on Friday 6 November 2015
"Hi Graham, I think you're right in saying that the air pressure inside the greenhouse is higher than that it is on the leeward side outside, but only if air is getting in somewhere. I haven't lost a single pane since taping up every tiny gap I could find in my greenhouse frame, and the panes no longer try to bow outwards during a gale (and believe me we've had some strong winds recently!) so it works for me. I wonder if any gardeners who are also physicists are reading who could give a definitive answer? Keith, that's a clever idea!"
Ann Marie Hendry on Tuesday 10 November 2015
"Further to Keith's comments regarding re-inforcing polycarbonate with wire - I installed a 10 x 6 aluminium frame with polycarbonate panels July last year. One week in and a force 4 removed several panels which I had to retrieve from neighbour's gardens - W clips alone did not do the trick because of flex in panels. I ended up drilling pairs of holes in the frame top and bottom of each panel - fixing brass eyelets into the holes then running plastic coated garden wire inside the flutes of the panels and tensioning the wire by twisting at the top. The brass eyelets allow the wire to slip though and the panel won't flex - effectively laced tight into the frame. This all worked fine through numerous winter storms and I felt pretty smug until this morning, when I found the greenhouse completey demolished by Imogen (recent storm), but with all the polycarbonate panels still in place. The aluminium frame had twisted and sheared in many places, so it is now beyond repair.My advice to anybody who lives in an exposed position is not (as I did) to go for the cheapest option. The original greenhouse cost IRO £400 + a huge amount of work to build it, re-engineer the ill fitting parts and re-inforce the panels as described . I am now looking at around £1800 (installed) for a timber framed/toughened glass replacement - guaranteed 10 years, which might just see me out!"
Jay Butler on Tuesday 9 February 2016
"Wise words Jay! Good luck with your new greenhouse. Embarrassingly, after writing this article I suffered more lost panes in my greenhouse. I couldn't figure out why they'd come out at first, but on close scrutiny I discovered that my 'temporary' fix of tape over a small gap in the frame had blown off! No other panes were lost, despite days of high winds, so that got me thinking. The panes had blown out on the sheltered side of the greenhouse, presumably creating an escape route for any air that was forced inside and preventing further damage. The back of my greenhouse faces into the prevailing wind, so since I replaced those panes I now wedge the door open a crack every time we have a gale (which is frequently at the moment!), and I'm pleased to say that this is working so far."
Ann Marie Hendry on Tuesday 9 February 2016
"I have come to the conclusion that at very exposed sites 10mm polycarbonate screwed all round at 300mm intervals or closer to a wooden frame using 'penny' washers is about the best solution. We have a small-holding in the Peak district and the down-side to this idyllic location is the extreme exposure in windy weather. In the early days one of our telegraph-pole and corrugated iron barns went off down-wind, took a section of the farmhouse roof off and landed in a neighbour's field so we were forewarned before ever contemplating a greenhouse!Although it's not as aesthetically pleasing as glass, polycarbonate is amazingly tough. One of the doors did get pulled right off in a gale but was found up against a hedge about 100 yards away scratched but intact and reusable. "
Colin Mill on Monday 25 April 2016
"It sounds as though Colin in the Peak District has to take things very seriously indeed. For my part, I am happy to report all three of my greenhouses (10x8, 8x6, 6x6)are still intact. It's worth mentioning that they are at the windward side of the house with strong winds off farmland. My only caveat is that one door in particular has to be secured as it is a flimsy fit and will blow off given half a chance. However it has not broken despite being airborne a couple of times. Polycarbonate has paid dividends in terms of safety."
keith Jamson on Monday 25 April 2016
"Keith - I'm perhaps overly cautious as, prior to the flying barn incident, I worked for some years at the summit of Great Dun Fell where 120mph gusts are not unknown. It left me deeply impressed by the power of the wind. There is of course another benefit of a well-sealing greenhouse - better heat retention on windy nights. As part of controlling the greenhouse we now record temperature and humidity in and outside the greenhouse and it's clear that on windy nights the greenhouse quite quickly converges in both temperature and humidity with the outside suggesting we still have too much leakage. I'll pay greater attention to sealing with our next greenhouse and perhaps try to use the rainwater store as a heat reservoir to help cool it in the day and warm it at night."
Colin Mill on Tuesday 26 April 2016
"Colin I think you are absolutely right to be so cautious! Mine are lightweight alloy frames and because of the negligible weight of the polycarbonate they are prime candidates to go flying. Planning regs mean they have to be moveable so I have them weighted with bricks around the skirt and tools hanging on the interior. However I don't think that would be any where near enough if I lived where you are."
keith Jamson on Tuesday 26 April 2016
"Thanks for posting this! This is a big help for us who does not know anything about the materials being used on windows."
Nicholas Bastow on Tuesday 28 June 2016
"I have twinwall polycarb glazing held in by plastic quadrant strips. They bowed out like crazy and popped-out in quite low winds. So I drilled through the frame and polycarb, top and bottom, centrally. And bolted using standard greenhouse (square) nuts and bolts. Don't overtighten and cause the panels to bow inwards."
Graham "Taf" Parsons on Friday 29 July 2016
"Storm Doris is causing havoc and I've had to watch my new (5 months old!) greenhouse get pulled apart piece by piece today. Went outside to try and fix it but far too dangerous, will let the storm do it's worst then repair and take note of some of your suggestions. May also try bubble wrapping the exterior next winter as we get strong winds often."
Mark Sandon on Thursday 23 February 2017
"Oh no - so sorry to hear that your new greenhouse has been damaged Mark. It's so frustrating when this happens but it is a good idea to leave the clear up til tomorrow, a greenhouse in a gale could be very hazardous. "
Ann Marie Hendry on Thursday 23 February 2017
"I am about to purchase a smallish greenhouse but have hesitated awhile after reading the above messages concerning wind damage. If you have a prevailing wind or, as I am, live in a valley and wind funnel, is it any use angling the greenhouse so that the wind is not hitting one end full on but is divided by the corner?"
Tim Hayward on Friday 19 January 2018
"I should think that's got to help. Any sort of windbreak you can come up with sounds worthwhile too."
K Jamson on Friday 19 January 2018
"Thank you, very kind to reply so quickly. The greenhouse would be partially sheltered by a hedge, at least."
Tim Hayward on Friday 19 January 2018
"That's exactly what I did with mine Tim. I think it does help somewhat, but I still lost panes a couple of times. The door faces away from the wind, and since I started wedging it open just a crack when it's windy (about 2 years ago now) I haven't lost a single pane. I reckon you'd get the same effect if you had a vent on the side that faces away from the wind and left it open slightly."
Ann Marie Hendry on Friday 19 January 2018
"I think a wind-break is a good idea. There is a lot of info on the web about getting the density of the planting right - too solid, it seems, is counter-productive. As I have mentioned before, we are on a very exposed site and have, since the greenhouse, added a fruit cage and I'm convinced that despite being only moderate weight netting it does reduce the wind inside the cage and for a small distance down-wind. Certainly, there are companies that sell netting as wind-break so there may be something in it and at least it could be put up while you wait for any hedge to reach a useful height."
Colin Mill on Saturday 20 January 2018
"We are looking at putting an 8 x 24 green house not far from our house (on the downwind side) to get the protection that the house would give it. After reading everyone's comments, I'm wondering if it's best to have the doors nearest the house like I'm planning on doing or whether I should have the back end face the house and then crack the door open when there's strong wind - what do you think, everyone? Thanks!!!"
Jenise on Monday 19 March 2018
"Hi Jenise. Most greenhouses also include one or more louvre vents instead of glass panes on the walls. Having the door facing the house is bound to be much more convenient, so my advice would be to make sure you have at least one louvre vent on the side of the greenhouse that doesn't usually get buffeted by the wind. Open it lightly to allow air to escape when there are gales forecast. Oh, and make sure the door closes tightly!"
Ann Marie Hendry on Tuesday 20 March 2018
"I live in Sunderland in the northeast and get my fair share of gales in the winter. I had gave up on glass a few years ago and had replaced the sides with poly carbonate sheets. At least its a lot safer. This year i have extended my greenhouse from 8 x 6 to 12 x 6 by adding a 4 x 6 new section. This new section came with the poly carbonate glazing and when assembled and attached to my existing green house it was evident that it was a wee bit too flimsy. I purchased a few lengths of aluminium flat bar from B n Q and cut it down to approx 10 inch lengths. I then attached these to the top and bottom of the frame by drilling through the new flat bar, through the poly carbonate and fixing with self tapping screws. Theory is that this will prevent the poly carbonate sheets flipping out and is a lot stronger. I was pleased with the result so bought more flat bar and repeated on the rest of the green house. I am by no means an expert but below are all the things i have done over the years to help prevent that horrible sound of breaking glass.- As many glazing clips (W) as you can get your hands on.- Replaced sides with poly carbonate rather than glass.- Filled any gaps with silicon.- Attached extra aluminium strips to top and bottom of the poly carbonate sheets ensuring they are secured to the frame.- Attached an eyelet to my sliding door so it closes firmly to the frame with no gap. I use a pad lock to lock the door shut.- If there are severe gales forecast i shrink wrap my green house. I have never had a problem even if we have had really bad storms once i have done this. I then remove the shrink wrap when the gales have dropped off."
Dave on Tuesday 18 September 2018
"Fantastic tips Dave, thanks! I had never considered shrink wrapping...interesting technique! If it works, it works..."
Ann Marie Hendry on Tuesday 25 September 2018
"I live in Nova Scotia Canada. My wife and I are just contemplating a greenhouse. The one we are looking at is totally polycarbonate as you all suggested. I will be tying it down with twist in spikes and have also thought about the flat bar that Dave has suggested. Hurricanes are pretty common where we live but I will place it sort of in the sheltered area against a tall pine grove. This should help. Will let you all know how we make do with the 8X12 poly house."
Rick on Wednesday 20 February 2019
"Good luck Rick!"
Ann Marie Hendry on Wednesday 20 February 2019
"My brother ran engineering in a hotel in Bermuda. When a hurricane approached all the windows on the leeward side were opened . During the 'eye' his team went out of the shelter and reversed the process. I have a polytunnel on extremely windy hill. I have polycarbonate which is currently strapped together with a truck tarpaulin rachet strap. I will screw metal straps to the tunnel this week so I can take the strap off and start spring seeding without having to crawl in through the door ! Gap at rear adjacent to high hedge. "
lynne morgan on Monday 18 March 2019
"Interesting to hear about your brother's experiences in Bermuda Lynne. Thanks for sharing!"
Ann Marie Hendry on Tuesday 19 March 2019
"I've had a few of my toughened glass panels fly off during the worst of storms, some landing a couple of meters away in the field next door, but luckily (and fingers crossed) they've all survived.The glazing clips don't last long so I purchase a length of 10mm diameter plastic rod, drilled a 5mm hole through the middle and cut them at 12mm in length. Using self tapping screws, I fixed them along the frame work, securing the glass panels in place with 8 per panel where I can.A photo might be better to describe what I've done. Let me know and I post a link."
Alan on Monday 17 February 2020
"Great idea Alan, thanks for sharing!"
Ann Marie Hendry on Saturday 22 February 2020
"please help - my pollycarb greenhouse is so noisey. The panels rattle and pop in and out in any wind and is unbearable in high wind. Its my first greenhouse and iv got it in a sheltered spot? Can anyone tell me how i can stop the movement / noise - thanks"
Jen Cameron on Sunday 13 September 2020
"Hi Jen. You may need to add more greenhouse clips to keep the panes secure. Alternatively you could try applying a bead of silicone sealant around the edges or use some clear polytunnel repair tape."
Ann Marie Hendry on Tuesday 15 September 2020
"I converted my glass glazed greenhouse to twin wall poly carbonate. The problem with the long panels is, as others have mentioned, that the panels bow out and 'ping' off the W clips. I found that by cutting 25mm x 16mm square electrical trunking into 24.5" lengths (without the capping) I could wedge these 'bars' between the aluminium rails half way down each panel to stop the bowing."
Ken on Thursday 18 March 2021
"Hi Ken your trunking suggestion sounds interesting---how has it held up to storm Arwen please?"
Ali on Saturday 4 December 2021
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