How to Windproof Your Greenhouse

, written by Ann Marie Hendry gb flag

Temporary repair on a wind-damaged greenhouse

If, like me, you garden in a very windy location, you’ll know what havoc it can wreak. Twice I’ve had panes of glass blown out of my greenhouse. Both times I was fortunate enough to spot the problem quickly and temporarily patched the gap with a sheet of plastic-covered cardboard, preventing further problems. I was lucky – while buying replacement glass I got talking to a lady who had lost almost every pane out of her large greenhouse, and not for the first time!

On both occasions the glass blew out on the leeward side, which should have been relatively sheltered. That seemed odd, so during the next storm I decided to go out and observe what was going on. Imagine my surprise as, fighting to stay upright against the wind, I witnessed two panes, one above the other, billowing outwards from within, barely held in place by the S-clips that joined them!

Keeping Wind Out of Your Greenhouse

Once wind gets inside a greenhouse it will do its best to force its way back out again. It rarely leaves the same way it came in. As more air is channelled in the pressure builds up until, inevitably, something has to give. Glazing clips pop off, and panes are blown outwards.

The most obvious way for wind to gain entry is via a missing pane of glass, so replace any that have already been blown out as soon as you can. Most good glazing companies keep standard sizes of horticultural glass in stock, but if you have unusual sizes or need toughened glass or polycarbonate then you may have to order it. Cracked glazing can be temporarily fixed with glazing repair tape but, again, it’s best to replace it as soon as possible as the repair could fail during further high winds or under snow.

When I installed my new glass panes I doubled up on W-clips (the ones that hold the glass into the frame) all round; the number of clips that originally came with the greenhouse was nowhere near enough! Silicone sealant can be used to secure the glazing clips in place for additional strength.

Some greenhouses can be fitted with bar caps to hold the panes in. These seem to be the most secure option, so it’s worth checking if they’re available for your model. Unfortunately they’re not made for my greenhouse, so instead I taped each pair of overlapping panes together with glazing repair tape, inside and out, as this seemed to be the weak point.

Glazing repair tape holding panes together
Glazing repair tape on both sides of overlapping panes offers extra protection against wind

Wind can creep in through the tiniest of gaps in a frame, so it’s important to block them up. If you look carefully you may find that the frame doesn’t meet perfectly at the corners or at either end of the ridge. I used tape inside and out to cover the holes because that’s what I had handy, but silicone sealant would be a more permanent solution.

If your greenhouse door has a lock or catch, make sure it holds the door very securely shut. Otherwise, a heavy brick wedged against it should stop it from blowing open.

Make sure any rubber glazing strips and seals around the door, windows and other vents are in good condition, and replace if necessary. Windows and vents must close snugly. I have found that sticking a strip of foam anti-hotspot tape (intended for polytunnel use) around the frame of my greenhouse’s roof window vent gives it a much better seal and stops it rattling in the wind.

Foam tape helps make a better seal when the roof vent is closed
Foam tape helps make a better seal when the roof vent is closed

In some cases a whole greenhouse can become airborne, especially lighter ones with polycarbonate glazing. Avoid this by making sure that it’s well anchored down. Mine is bolted to a metal base, which sits on soil but is deeply concreted in at each corner. It has never moved.

Greenhouse Protection from Wind-borne Missiles

So that’s how to keep the wind out – but what about flying objects? The most obvious thing is to tidy up your garden before a storm. Put away or tie down garden furniture, plant pots, children’s toys and gardening tools. The ease with which wind can hurl heavy objects about is astounding, but even quite light wind-borne objects have the potential to smash glass.

That doesn’t stop things blowing in from elsewhere however, so in some cases you may need to physically shield your greenhouse. In areas where winds are really ferocious, some gardeners surround their greenhouses with slatted wooden fences, wind netting, or hedging to filter the wind and deflect wind-borne objects. There is a downside to this as it can also reduce the amount of light reaching plants inside, but if your greenhouse is in a serious wind tunnel or on a very exposed hillside, a wind barrier may prove essential.

Temporary repair to greenhouse
Make temporary repairs to damaged greenhouses to keep the wind out until you can buy replacement glazing

Once the strong winds have died down, take some time to check over your greenhouse. Occasionally glazing clips can jiggle loose and end up behind the glass, so make sure they’re all still in their correct position, securely holding down the glazing. Cover up any gaps left by broken or missing panes until you can buy replacements. Sheets of plastic, tarpaulin, or even an old blanket is better than nothing as a temporary wind-blocking measure.

What other methods do you use to protect your greenhouse from wind? Drop us a comment below and share your tips with us.

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Comments

 
"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

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