Webinar on How Climate Change is Increasing Lightning and How to Protect our Built Heritage

00:00:00:00 - 00:00:29:23
Speaker 1
Welcome to today's Technical Tuesday webinar on how climate change is increasing lightning storms. This is a follow up and refresher webinar on lightning protection and a look at how climate change is impacting and changing our weather patterns. I'm Geraldine O'Farrell, as already stated, one of the senior building services engineers and the author of Historic England's Guidance on lightning and surge protection for Historic Buildings.

00:00:31:06 - 00:00:59:08
Speaker 2
And hello, I'm Caroline Cattini-Dowe. I'm the Building Services Engineering team leader and Historic England's principal engineer and I'll be co-hosting, with Geraldine today. And just to get started. As we all know, we're very aware that major storm events are becoming more frequent as climate change impacts our weather map. Now, this in turn is causing changes in the frequency and patterns of thunderstorms in the UK.

00:00:59:08 - 00:01:23:03
Speaker 1
So on that basis, here is a brief overview of the issues and topics we will be covering today. The first will be how and why does climate change impact or whether to produce more thunderstorms. This will be followed by a quick explanation of what lightning is, then evidence of changing weather patterns, a quick look at current trends in insurance claims resulting from lightning strikes

00:01:23:13 - 00:01:55:08
Speaker 1
And finally, a quick reprise of Historic England's online guidance. Our planet is on course for a three degrees Celsius temperature increase by the end of the century unless World governments succeed in cutting emissions. The effects of global warming on weather systems are already apparent, with erratic rainfall patterns developing around the world. As the CO2 in our atmosphere increases and temperatures rise, the land surface also warms up.

00:01:56:07 - 00:02:24:11
Speaker 1
This, in turn produces strong updrafts of air that are more likely to produce the right conditions for thunderstorms. Also, this climate change is making the air warmer due to the increase in seasonal temperatures. This will in turn allow the air to hold more moisture and both these factors can boost the chance of a thunderstorm. All of this may also result in stronger storms with the increased risk of flooding.

00:02:24:11 - 00:02:48:18
Speaker 1
Predominantly, higher temperatures are now experienced further north in the UK areas, where the frequency of lightning storms has changed but not quite as may be expected. The map on screen is the result of 12 years work carried out by the University of Portsmouth to help weather forecasters, local councils and members of the public better prepare for extreme weather events.

00:02:50:01 - 00:03:20:05
Speaker 1
This map shows where the greatest density of lightning events are occurring in the UK, and as the study states, thunderstorms can be difficult to forecast. But if you have an awareness of when and where the risk is greatest, you can plan for these events. One of the many interesting findings is that in Scotland, the north west facing coastlines are now experiencing the storm activity in winter rather than in summer, when it is more common.

00:03:20:05 - 00:03:44:07
Speaker 2
So although we might know what might be the contributing factors to lightning storms, there are still very complex systems and they play an important part in the transportation of heat and energy across the globe. Thunderstorms also pose a potential risk to heritage buildings. And in the webinar, we will explain how to protect a listed building or scheduled monument without marring its appearance.

00:03:44:07 - 00:04:04:06
Speaker 2
We have lots of town tapes, air terminals and other protective paraphernalia. And we're also going to show how indirect strikes can impact a building and its contents, especially that equipment with sensitive electronics. And that's whether you have a lightning protection system or not.

00:04:04:06 - 00:04:36:04
Speaker 1
So what is the impact? What impact is global warming having on the frequency of lightning storms across the world and in the UK? Well, unfortunately, even with research and statistical evidence, it does not paint a clear picture. The Met Office has had a system in place to detect and locate the source of thunderstorms since the 1940s. This is done via observation stations, as you can see on the screen, volunteer your observers as well as from its lightning location system.

00:04:37:12 - 00:05:06:01
Speaker 1
The map on the right hand side indicates the distribution and quantity of these stations around the United Kingdom. And you can see they're fairly well covered. The lightning location system is otherwise known as the Met Office, RTD net or a rival time difference network system. This is an automatic lightning location network consisting of around ten lightning out station sensors located across Europe.

00:05:06:21 - 00:05:16:11
Speaker 1
Together, they are used to determine the location and time of lightning strikes across a wide geographical area.

00:05:16:11 - 00:05:37:24
Speaker 2
Recently, we've experienced a lot of very hot summers and the ten hottest on record are now shown on the screen on the slide, and you'll see that three of the four hottest on record have been in quite recent years. And what I want you to note is the locations of where the three hottest are. And this is quite significant and could be a result of our changing climate.

00:05:38:16 - 00:05:55:22
Speaker 2
Now, as we stated earlier, with the warmer temperatures we're all experiencing, the frequency of thunderstorms is changing in certain parts of the UK and we're now seeing many more parts of the Midlands and the North of England experiencing more such events.

00:05:55:22 - 00:06:26:11
Speaker 1
However, just to confuse see more between 1989 and 2019 has been an overall reduction in storms. This reduction is not evenly spread over the UK as the south of England is seeing fewer storms but the north is experiencing more. Lightning storms are becoming more frequent in the center and east of the Midlands and with some areas of North Yorkshire, Manchester also impacted. On a worldwide scale

00:06:26:12 - 00:07:08:20
Speaker 1
researchers at the Worldwide Lightning Location Network revealed that the number of strikes recorded during the summer months in the Arctic between 2010 and 2020 have increased from 18,000 to more than 150,000. At the same time, temperatures above latitude, 65 degrees north have increased by 0.3 of a degree Celsius, making intense thunderstorms more likely. Concentrations of storms is also changing. In 2022 between the 14th and 18th of August, there were 26,718 lightning strikes.

00:07:09:06 - 00:07:48:18
Speaker 1
This is more than half of all UK lightning strikes in the past 12 months, which in itself was a total of just under 50,000. And with more intense storms comes greater rainfall. In High Beach in Essex, 66.4 millimeters of rain fell in just 3 hours on one day this summer just passed. As we have had been having unseasonably hot weather, the ground was not able to absorb the water and this is when localized flooding can occur and wreak havoc to buildings and infrastructure.

00:07:48:18 - 00:08:16:11
Speaker 2
And you can see on the screen here, places like York, Ironbridge over the River Severn and Heatherslaw in Northumberland, they've experienced recently flooding some of the images there on the right hand side. With more intense rainfall like that seen in High Beach, mentioned by Geraldine on the previous slide, comes a greater chance of flash flooding and flooding is also a major risk factor to heritage buildings and the contents, which in themselves could be of heritage value.

00:08:17:10 - 00:08:41:11
Speaker 2
So the warmer it gets, the more water in a cloud can hold and the more likely you are to get lightning storms. And so it becomes this vicious circle, as it says on the screen, in the text there, every one degree say you are likely to get a substantial increase in thunderstorm occurrences. However,

00:08:42:07 - 00:09:08:14
Speaker 1
nature being what it is, unpredictable, the relationship between climate change and lightning is not entirely clear cut. Although there have been increases in temperature across the country, we are not seeing storm increases everywhere. As previously stated, it would appear that the increasing frequency of storms is only apparent in the Midlands and North England and nobody is entirely sure why.

00:09:09:19 - 00:09:28:11
Speaker 1
This is the reason behind the Met Office statement saying that they need to study their data further before being able to come to any firm conclusions. There is still a lot to uncover about thunderstorms and even now we don't entirely understand what goes on inside a thundercloud.

00:09:28:11 - 00:10:00:16
Speaker 2
So if the Met Office needs to study their data, can we gain insight by looking in interpreting insurance claims resulting from lightning strikes? When looking at claims statistics kindly supplied by the Ecclesiastical Insurance, we can see that overall claims have actually fallen. But those insured on heritage policies have risen in quantity and also value. Now, is this a direct correlation between the age of the building and its fragility, vulnerability or something else, like a lack of appropriate protection on those buildings?

00:10:01:22 - 00:10:25:17
Speaker 2
The evidence provided doesn't actually allow us to make hard and fast conclusions. But what is of interest is that the use of surge protection to buildings appears to be on the increase by virtue of the decrease in the number of claims made for vulnerable electronics that are not automatically protected by having a lightning protection system. And surge protection used to be a bit of a dark art 20 years ago.

00:10:25:17 - 00:10:48:05
Speaker 2
But with the reduction of claims, it seems to indicate that more of these devices are being installed into the electric distribution system, which is a good thing. So can we come up with any plausible reasons as to why this might be? Well, we're not trying to be Vague here, not intentionally vague, but thunder storms, as Geraldine said, are of unpredictable behavior.

00:10:48:18 - 00:11:16:03
Speaker 2
They don't always do what we expect them to do, going on past experience, for example, they don't always strike the highest points of a building, and they sometimes don't hit the tallest structure. Also for heritage building, if struck and damage is likely that the repair cost will be far higher as any repairs will have to be on a like for like basis to the same standards and using similar or the same materials and will probably take longer to complete.

00:11:16:03 - 00:11:31:18
Speaker 2
And as I said previously, the reduction in claims for electronic equipment such as computers, systems, fire and intruder alarm installations could be down to just the better understanding for the need to install surge protection devices.

00:11:31:18 - 00:12:06:06
Speaker 1
So let's have a quick re-examination of Historic England's advice on this. A publication was reissued in 2019 to bring our guidance in line with BSEN 62305 parts 1 to 4. This version is now applicable to all heritage building stock and not just churches as it was previously. On screen are links to the recording of the original webinar that took place in 2020, which goes into far greater detail than today's event will be able to.

00:12:06:17 - 00:12:34:04
Speaker 1
And there is also the free downloadable PDF of the guidance. These will be quite easily found on our website also. So what is lightning? Well, it's a powerful force of nature that most of the research into has been carried out in the United States as part of their space program. US rockets tend to be rather tall, pointed objects that would attract lightning.

00:12:34:15 - 00:13:05:01
Speaker 1
And the US historically has had a lot more storms than the UK. Lightning is a very high electrical discharge to earth or to an adjacent cloud amounting to millions of volts and thousands of amperes. It is caused by static that builds up inside the cloud due to the action of frozen raindrops bumping and rubbing against each other. The electrical current that occurs makes the surrounding air very hot and it quickly expands.

00:13:05:16 - 00:13:26:08
Speaker 1
And this is what we experience as thunder. And because sound travels slower than light, we get the delay between seeing the flash and hearing the sound. As dangerous as it might seem, there is only a tiny chance of being hit by lightning. And if you are caught out in a storm, there are ways to mitigate your risk even further, as we shall see in a minute.

00:13:28:06 - 00:13:51:09
Speaker 2
That lots of different forms of lightning, as you could see in the illustration on the screen, most of us think of the first time when we when we think of thunderstorms, but discharge does not necessary always go to ground. It can travel from cloud to cloud or even cloud to the air. And it's more likely to go to ground when it's actually raining.

00:13:51:09 - 00:14:17:04
Speaker 2
So, having seen the previous slides, I'll just give you a quick you can take that time because we've got a poll question. So looking at the photograph here and it's not very serious, this poll, so don't worry too much about it. Now, this is a photograph that was taken over Guildford in Surrey in 2019. And what I want you to do is, is guess what you think, what type of lightning this is.

00:14:17:13 - 00:14:42:16
Speaker 2
And I think Matt is going to bring up the poll. It reminds you of what they all say. We got cloud to air, ground to cloud lightning or intercloud lightning. Oh, we have a run away lead here. I think there's some people that know they think.

00:14:42:16 - 00:14:44:15
Speaker 1
As we said, it wasn't very serious this.

00:14:46:12 - 00:14:56:07
Speaker 2
Yes, you're quite right. It is intercloud lightning. And you can just see that cloud. And I sort of where that lightning is. Excellent. Very good.

00:14:57:12 - 00:15:34:03
Speaker 1
Paying attention. I oh, yeah. Well done. So. Okay, the British Standards, the Historic England's guidance is based upon, as stated before, is BSEN 62305. Now this standard is made up of four parts and the interrelation between these four parts is shown on the left hand side of the screen. Standards on lightning protection have been around for about 130 years, dating from Queen Victoria's time, and she had protection added to her servants dormitory in the stables (got her priorities right) at Osborne House on the Isle of Wight.

00:15:34:13 - 00:16:01:14
Speaker 1
Now the latest standard considers the modern use of technology in electronics and allows for appropriate protection of these. So here is an example of what a lightning strike can do to a building. Now, I would add that we have permission to identify the church involved and show the building after the storm. This church had only one down tape and one air termination connected to a single earth pit.

00:16:02:00 - 00:16:38:02
Speaker 1
Now this for quite a while was considered sufficient to protect the building and was in fact our standard guidance. This case involved a direct hit to one of four pinnacles of top of the tower. I gone too far. Okay, this is the next pole. Sorry. My fault. So again, not very serious. What does our audience think happened?

00:16:38:02 - 00:16:50:19
Speaker 1
You have all the options on screen.

00:16:50:19 - 00:16:52:01
Speaker 2
Good enough. A runaway lead?

00:16:52:13 - 00:17:14:09
Speaker 1
Yeah. Well, actually, our audience are pretty much right. The the main answer is D did a lot of damage and C is also technically correct. The lightning struck and damaged the church so. Yeah, absolutely. So I'll move it on.

00:17:14:09 - 00:17:36:04
Speaker 2
Okay. So you can see this is the from that from the pole from Geraldine’s previous slide. The photograph shows extensive damage to the stonework in those top images, the roof and the interior balcony, level two. Now, what happened in this case was the lightning struck one of the other finials that did not have air termination and down tape.

00:17:37:00 - 00:17:59:20
Speaker 2
And this then was blown apart, which sent the stonework through the roof and into the church interior below. So why did the lightning seem arbitrarily, arbitrarily, to strike another finial and not the one with the air termination in it. Well, that's because the construction of the church had a metal rod running down the center of each of the finials to support the stonework.

00:18:00:10 - 00:18:32:08
Speaker 2
And it was that metal that the lightning chose to strike rather than the lightning protection. Now, because there was no earth rod connected to the metal work there was in that finial, there was no way to dissipate the energy from the lightning to ground. So what happened? It blew the stonework apart and caused all this damage. So it must always be remembered that lightning strike locations can be completely arbitrary, and especially where the lightning protection system is not designed appropriately.

00:18:32:08 - 00:18:51:06
Speaker 1
So we have another example on screen. This is the resulting damage from a side flash to a church in Northamptonshire. Some of you may wonder what that is, what I mean by that. Well, again, as shown on screen, we can see that the metal work, that metal work has been used to support the stonework of this decorative feature.

00:18:51:24 - 00:19:10:14
Speaker 1
It's circle for you so that you can see it more clearly. Here the strike has jumped from the highest section of metal work, probably the lightning tape that you can see on the left hand side to a lower section. Now, this might have been caused by a high resistant joint or ineffective bonding of the metal work somewhere else.

00:19:11:02 - 00:19:21:02
Speaker 1
And is this sort of occurrence that is most likely experienced at high level with a lightning discharge at its highest.

00:19:21:02 - 00:19:48:03
Speaker 2
Now, just as a quick aside, it's not just heritage buildings that need protection. Rare and older trees also do, so in a collection at Kew Gardens the trees are protected by their own down conductors. And as you can see in this image, which was kindly shared by the Royal Botanical Garden, so you can see those down tapes on there for those special trees that have been protected.

00:19:49:13 - 00:20:08:01
Speaker 2
Now, this next poll was probably a bit of a giveaway, given what you've seen on the previous slides and what we're talking about. But what do our audience think this strange looking photograph is an image of? I think Matt is going to just bring up the poll now. There we go. So do we think it's burnt fungus? Burnt thatch.

00:20:08:01 - 00:20:08:18
Speaker 1
Burnt tree Interior?

00:20:08:18 - 00:20:11:11
Speaker 2
I wonder what made you think it might be that?

00:20:11:22 - 00:20:33:24
Speaker 1
Yeah. No, that's a few for burnt fungus. If you’ll llow me to say, it looks a bit like one of my pasta recipes, but slightly overcooked. But there’s no meat balls Matt. Yeah. It's certainly an interesting image isn't it. It certainly is. Yeah.

00:20:35:01 - 00:20:39:11
Speaker 2
Yeah, I think so. Yes. The burnt tree interior. Quite correct.

00:20:40:06 - 00:20:45:15
Speaker 1
Yeah.

00:20:45:15 - 00:21:08:22
Speaker 2
And just to carry on with the tree theme on the screen are some interesting images of damage that lightning strike could do to a tree. And the damage really does vary depending on where the tree is struck, how vulnerable it is, what we mean by vulnerable in this case is how healthy the tree's, how old it is and any unforeseen disease, and it may have etc..

00:21:09:20 - 00:21:35:00
Speaker 2
And you can see, as the photographs indicate, burn in is a very common result of splitting a tree, causing it then to collapse, which could cause further damage of other things as well. So protection is vital for ancient trees and those with tree protection orders as well, which is in line with what Kew is doing they're taking to protect their most important specimens.

00:21:35:00 - 00:21:54:21
Speaker 1
So you might think that we've straight away from the main message of this webinar, but it is important to consider the other things that are vulnerable in thunderstorms, and that includes us. As hinted at when we were on Slide 14, a very small number of people get struck by lightning every year and most survive, I hasten to add.

00:21:55:19 - 00:22:10:14
Speaker 1
But we don't expect people to go around with a Faraday cage draped around them unless they happen to be in their car, and that does it for them. So without a lightning protection system to intercept, conduct and disperse a strike, how do we protect ourselves?

00:22:12:21 - 00:22:32:12
Speaker 1
Well, here on screen, we have a person walking along, minding their own business on the right hand side when they get caught out in a thunderstorm. Now, I'm sure we all remember the adage about not standing under trees to shelter from a lightning storm. And hopefully by now you can see and understand why. However, you can still be in potential danger

00:22:32:12 - 00:23:09:06
Speaker 1
just as buildings are to a remote strike to ground. With structures, this discharge can enter through metal pipework, cables, taking the services which take the services into the building. Now this sort of indirect event can be protected by the installation of surge arrestors. With people the potential difference or PD stand between a difference between our feet are shown on screen as V1 and V2, when in contact with the ground can be enough to cause a current to flow through your body.

00:23:09:06 - 00:23:32:13
Speaker 1
Smaller images show the type of damaged clothing worn by people who have been struck both directly and indirectly, as well as the obvious scorching. You can see tracking marks on the soles of the shoe and a rather dramatic hole in the hat. So what should you do to protect yourself as much as possible if, say, you cannot get back to your vehicle, which provides protection?

00:23:33:13 - 00:23:53:24
Speaker 1
Well, little tip here. The best way to limit your risk is to place your feet together and curl up into a smaller ball as you are able. This limits the potential difference between the parts of you that are in contact with the ground and hence the current you might experience.

00:23:53:24 - 00:24:16:04
Speaker 2
And just to reassure you all, the Royal Society for the Prevention of Accidents states that only about 30 to 60 people get struck each year and only about three of those prove fatal. However, depending upon whose statistics you refer to, the risk does vary as showed on the screen, the British Medical Journal considers the risk to us all as being even lower, so nothing to lose sleep over.

00:24:16:04 - 00:24:23:00
Speaker 2
Just remember the tip given by Geraldine previously.

00:24:23:00 - 00:24:47:21
Speaker 1
So to round up, let's have a quick look at the key components that make up a lightning protection system. So we'll start at the top with air terminations. These can be generic metal terminations like the one on the right hand side of the screen, or they can be other parts of the building utilized as the air finial, such as a wind vane or a flagpole mount.

00:24:47:21 - 00:25:16:10
Speaker 1
Depending upon the type of installation these can be connected to downed tapes or to a roof termination network. This in this section involves the down conductors that link the lightning protection system at the top of the building to the earth pits at ground level. This is where clever installation methods are needed to disguise the route down the building and to protect the building services from damage and staining.

00:25:18:02 - 00:25:45:24
Speaker 1
To prevent staining and to aid colour matching, it is probably best to use PVC covered tape or rod. Tape is normally 25 by three millimeters and rod is normally eight millimeters in diameter. The cross-sectional area is the same. You can see on screen the different colours that are commonly available. Now, the image images on the right hand side of the screen show two common mistakes.

00:25:46:19 - 00:26:12:05
Speaker 1
The first photograph shows the route taken by a down tape that could so easily have been removed over, slightly undisguised, by one of the rainwater down pipes shown to make it less obvious. There is a sketch of this in our guidance. The far right image shows the result of using bare tape and you can see the green staining that is leached out of the copper.

00:26:12:05 - 00:26:34:19
Speaker 2
So before we go on to earth pits let's look at some rather old and totally wrong installation methods that's been employed in our images on the screen. And you see the first shows the tape installation being run in turn you this one on the left hand side and you can see that test clamp at ground level. It's been located behind the back of a cupboard rather unhelpfully.

00:26:35:09 - 00:27:00:10
Speaker 2
And the test camp is basically that's where you disconnect the joint between the down conductor and the earth system and it's there for you to take your resistance readings to check that the system is still reading on the ten ohms and in second installation you can see that they've decided not to relocate the external luminaire. No. Instead the down tape is jumping over the luminaire which is the lighting has got to do that.

00:27:00:10 - 00:27:12:08
Speaker 2
It's just going to go straight through that. Luminaire And then lastly, this image on the right we've got, there is a long horizontal tape which is very, very bad practice because if someone was standing by that

00:27:12:08 - 00:27:12:16
Speaker 1
wall,

00:27:13:00 - 00:27:32:12
Speaker 2
under that horizontal section of tape, any strike would just jump from the tape to the individual standing underneath it. And because they're offered low resistance, pass for the lighting. So it really is all those three images, a very, very poor practice.

00:27:32:12 - 00:27:58:09
Speaker 1
So finally, the Earth electrodes and the Earth pit chambers that they are accessed from. Here on the right hand side, we see the interconnections between the Earth pit, the test clamp and the down tape. And this is taken from our guidance again. However, if the ground conditions do not allow for the driving of earth rods a copper mesh, the middle image can be installed instead.

00:27:58:14 - 00:28:18:02
Speaker 1
Instead, this method may require a large area of mesh to be laid to obtain the appropriate resistance readings. The depth at which this is laid is far shallower than driving sections of 1.2 meters sections of Earth rod into the ground.

00:28:18:02 - 00:28:38:06
Speaker 2
So in an ideal situation, situation with just wrapped buildings up in a Faraday cage, the built in equivalent basically of cotton wool. But as we know, this is not possible with heritage buildings. We certainly will want to do that. So a network of tape tapes would just disfigure the appearance of most heritage buildings and not an acceptable solution.

00:28:38:13 - 00:29:00:07
Speaker 2
So we need to come up with an entirely different approach. Although the earthing and bonding of incoming services and the lightning protection system, which is shown on the bottom of your screen, remains the same for any type of building, heritage or new, the form of external protection must be different. So we have to take a different approach to that to still be compliant.

00:29:00:07 - 00:29:30:15
Speaker 1
So Historic England has always, for as far as I've worked for it, advocated what is known as the tower only system of providing a defence to the building without covering it in down tapes. Now, this form of lightning protection is still in the present British standard and allows its use to suitable buildings employing only two down conductors. However, a risk assessment must be carried out to determine the size of the protective angle you are permitted to use.

00:29:30:15 - 00:29:42:23
Speaker 1
And you can understand what I mean by protective angle from the small black and white sketch on the bottom of the screen.

00:29:42:23 - 00:30:08:01
Speaker 2
So this brings us to the end of our presentation now on climate change and its impact on lightning storms frequency. Plus a refresh on our guidance. How best to protect your heritage buildings from a strike. The really however always remember to check whether you will need planning permission listed building consent or scheduled monument consent in cases of places of worship, the appropriate authorization from the denominal body before you start work.

00:30:08:01 - 00:30:13:22
Speaker 2
So it's always worth remembering that. Just a reminder if it.

00:30:13:22 - 00:30:32:04
Speaker 1
Thank you all for listening, Caroline. And I hope that you found this interesting. Our email addresses are on screen. Please feel free to contact us about any issue you might have either on this topic or any others concerning building services. And we will help in any way possible.