A Case Study in Mitigating Overheating: Kensington Palace State Apartments

Good morning, everybody. Thank you so much for having us today. My name is Lynda O'Sullivan. I'm Senior Project Manager for Historic Royal Palaces. We manage the unoccupied palaces, including the public side of Kensington Palace. We have been working with Ingleton Wood and Historic England to look at mitigating overheating within the palace, both currently and in the future.

I'm gonna give you a brief bit of architectural history on Kensington Palace, and then I'm gonna talk about the challenges that we face. I'll hand over to Sarah from Ingleton Wood, who is going to discuss the modeling process, and then it'll come back to me for some thoughts on the outcomes of the research and what we will do with that information. So, just a brief introduction to Kensington Palace. There has been a property on this site since probably the 1700- sorry, the 17th century. George Copin built a Jacobean house here, which was then purchased by William III and Mary II for £20,000 in 1688 after the Glorious Revolution. And they immediately commissioned Christopher Wren to start making alterations.

He initially built four pavilions, one on each corner of the building, and then carried on building to the north in the early 1690s, and then built the South Range, which is the one that we are focusing on today. in the later 1690s. By about the 1730s, we have the footprint of the palace that we now have today. So, you go from the kind of image on the left, which is a concept of what the Jacobean House might have looked like, to the image on the right, which is a drawing from the early 1700s. So, this is the King's Range, the South Range. It was constructed by Wren in 1695.

We have the state rooms on the second floor, we have royal residences on the first floor, and then we have more domestic accommodation at ground floor level. the building is constructed of load-bearing masonry walls, with a mixture of gray and yellow stocks and window dressings in red "Rubbers". We also have some central pilasters, which are quite nice, although not as fine as the orangery to the north of the site. And then we have, a Westmoreland slate hipped roof which survives intact, with a central pediment and decorative urns to the top. So, Kensington Palace State Apartments today sit within the heart of West London. It's worth noting that, originally, when the property was purchased, it was in the countryside.

We have the Royal Parks to the northeast and the south of the palace, and then we have the Royal Household Apartments to the west. We house precious collections and interiors, both those belonging to historical palaces, the Royal Collection Trust, and other generous loans. And we have evoked the open picturesque landscape of the early 1700s. The palace is open five days a week to the public during the winter, and seven days a week during the summer. And we have approximately half a million visitors a year come through, plus those people who nip in just to use the facilities. the grounds are open and free of charge, and then there is a fee to purchase a ticket to come in further.

So, the challenge that we face. The impact of climate change is now becoming apparent. Between 1960 and 1990, and then again between 1990 and 2020, we can demonstrate a one and a half degree rise in temperature. And that's just in the later 20th century. Our buildings are obviously heavily used by members of the public, and you can now start to really feel that at times it's becoming increasingly uncomfortable for visitors and staff. And we have to be mindful of the collections that we have during the peak hot weather.

The scale of their palaces and collections, and the access to the public, whilst it is quite large, and it is quite complex, what we wanted to do is explore passive options that could also be translated into opportunities for people with perhaps slightly simpler or domestic-scale buildings. Up until now, the majority of the studies that have been undertaken on historic buildings are necessarily domestic. Most of the building stock in that era is of a domestic scale. But there is potential learning that can be scaled down and made available to a wide range of people. It is worth noting that because of the complexities associated with fire protection, security, and environmental protection, that we're not able to just open our windows and leave them open overnight, or let in agents of decay that would affect our collections, dirt, pollution, dust, pigeons. So, we have a slightly complicated arrangement with respect to how we can ventilate and what we can do and what we can't, which is interesting.

So, I just wanted to also make a couple of comments on the experience of heat. The experience of thermal comfort is dynamic. As you move through spaces, not only throughout our buildings and landscapes, but through your lives, your body adapts to temperatures, and it also adapts to what you are doing in those spaces. Whether you are sitting at your desk typing or whether you are at the gym or working out, your body adjusts in order to be able to deal with the temperatures and the experiences that you are in at the time. It's not just restricted to the base temperature. Your experience of heat also relates to humidity, air quality, and air movement, and they all impact the capacity of the body to adapt and self-regulate.

The experience of heat comfort is also complex. It relates to how you felt temperature yesterday and where that sits in within the kind of environment that you've experienced at that time, which is one of the reasons why a heat wave in March is so much more uncomfortable than a heat wave in June. If you've had a buildup of warm weather coming up to a point and then slowly going down again, your body has acclimatised and is much more able to adapt. And heat stress, which is when your body is no longer able to adapt to the environment around it, is when people start becoming unwell. People's individual capacity to be able to adapt to temperature can depend on their age, their gender, their fitness, and physical conditions. So, it's important to understand that overheating is not a line in the sand.

It is a range of experiences, and relates to a wider range of environmental factors than just the temperature at the time. So, with increasingly uncomfortable temperatures, when we have heat waves in the summer, Historic Royal Palaces have worked with Historic England to commission an overheating study to understand the impacts and possible options associated with passive mitigation. We would like to improve the internal environments for not only our visitors and our staff, but also considering how those affect us now and in the future. So, the two key questions are: how do passive measures improve summertime conservation conditions and occupant comfort? And how would any mitigations impact the building throughout all seasons? And these actions were then moved down to: does the building comply with TM 52, which is the CIBSE technical standard with respect to overheating?

How do the internal conditions vary throughout the year? How does the building react under future weather scenarios? And how effective are the selected mitigation measures to the internal environment? overheating analysis was undertaken using dynamic thermal modeling software, which is an IES system. And that was recommended by Historic England, who I think have done similar research on some other buildings in central London. And we conducted the iterations of the models using the following passive measures: external shading, two types of window blinds, both light and dark, passive solar control film, smart solar control film, which we have done research at Hampton Court with respect to tapestries, natural and passive ventilation, and mechanical ventilation.

And those were considered against weather files for 2020, 2050 and 2080. I'm gonna hand over to Sarah now, who's going to discuss modeling. Thank you, Lynda. Hi, everybody. So, as Lynda mentioned, unfortunately, the public display areas of Kensington Palace, particularly those facing south, as shown in this image here, are becoming increasingly uncomfortable over those summer heat wave conditions. So, as Ingleton Wood, we were appointed as sustainability specialists and thermal modeling specialists to look at really understanding this issue that the palace is facing, and how potential solutions can be implemented.

So, to begin our appointment, we wanted to get a good understanding of the building itself, and all of the kind of nooks and crannies that often make up a heritage building, being that they are of quite different construction to modern buildings. So, to that end, we appointed MK Surveys to carry out a Matterport Survey, which essentially picks up a very detailed point cloud of the entire area of the palace of interest. And it tells us about things in detail, such as the ceiling heights of every room, the thickness of every wall, and of course, elevations and plans. So, in kind with all of the information that HRP had available about the plans and drawings of the palace, we were then able to build out an as accurate as possible thermal model using IES. So, this is an image of what our model looks like in terms of the 3D geometry. It is using the software IES, which is a 3D building physics and building assessment software that allows us to look at either thermal or energy modeling in detail.

And for this study, we were really interested in the thermal performance of the building. So, we took a lot of time making sure that the building was as accurate and realistic as possible in terms of any inputs that would affect how it holds heat and how people experience heat in the building. So, for example, we spent some time getting to understand the constructions of the building, the floors, walls, roofs, and windows, and assigning U-values, either based on direct calculation or from accredited measurements of similar constructions. Similarly, we assigned wall thicknesses to each and every wall within the palace based on what is known about how thick they are, because this will affect the inner volumes of each room, and this will affect how much air is moving through each space in the palace. So, we really wanted to get each of those geometries correct. Also, windows and doors were set to be open on the specific profiles that were acceptable to palace operations.

So, there are constrictions around the galleries and display areas, as well as security. So, the windows and doors are opened on specific schedules, and we wanted to reflect the natural ventilation as it is as well as possible. So, I just wanna go into a little bit more detail in terms of the model setup to kind of explain how we got to a trustworthy baseline model, which has then gone on to be useful to HRP in quite a few ways and quite a few follow-on studies. So, as I mentioned, we assigned those U-values and wall thicknesses, window and door operational profiles, but we also wanted to assign how many people are in the palace on a given summer day or throughout the year. So, we were able to obtain visitor entry data from the client, and we assigned people moving throughout the palace as they would be expected to on the visitation route. So, sort of the number of people per room and how much time they're spending in each room was assigned in as much detail as possible.

And also, the amount of heat that those people are expected to be generating based on what activity they're doing in that room. So, for example, for staff in the palace who may be sitting at a desk, they probably won't be radiating as much heat as a person who's in a gallery and idling around on their feet. so those kind of public, people gains for each person in each space were assigned as well. The lighting and other internal gains were assigned in detail as well. So, the palace has already undergone a LED upgrade to low-energy lighting. So, these are emitting pretty low levels of heat, about five watts per meter squared.

And we also assigned computers and tech and the heat emissions that come from those to spaces that are relevant to have those, such as the staff offices. We also spent some time getting to understand how the palace is currently set up to mitigate overheating or to kind of help towards this problem. So, there were a few measures that are already in place, and we had those in our baseline model as well. For example, there are dark-coloured internal blinds already throughout a lot of the palace, and these are drawn to certain levels. So, we really reflected the way that those internal blinds may be absorptive of heat that comes in due to their dark colour, as well as how much sunlight they are blocking. similarly, there are solar films already on the windows, and these reflect a certain amount of light, so that sort of mitigation of sunlight entering the space was reflected too.

And the same for mesh blinds, which are also there for security and for mitigating those aggressive sun rays. The air permeability was assigned for a leaky building of similar sort of construction from CIBSE Guide A. And really, all of that is to show that we think that the time spent getting to really understand such a complex and unique building as this one was really worthwhile in terms of being able to trust and develop our model from there. So, this is showing the baseline performance of our model. So, the way that our model is predicting temperatures will be in this King's Gallery space, which is quite an important space for visitors and for overheating currently. So, what we're seeing here is temperatures predicted between May and September.

In the blue, those are measurements from the King's Gallery in 2023, and in the lighter blue or green, those are what our model is predicting the temperatures to be. So, the important thing here is that the ranges of temperatures are predicted to be very similar, with peak temperatures around 31 or 32 Celsius, and trough temperatures overnight going down to 17 or so Celsius. So, this tells us that our model is pretty accurately performing similarly to how the actual building is. But importantly, it isn't lining up perfectly, and the reason for that is just due to the model using sort of a representative year weather file rather than exact data for a particular year, as we have in the measurements. So, from this baseline, we wanted to start testing out what interventions can be put in place to help keep these peak temperatures down. So, I'll briefly explain some of the metrics that I'm gonna be using for the rest of this study just to explain some of these terms in advance.

But Lynda very helpfully explained that human thermal comfort is dynamic, and it isn't solely dependent on air temperature. There are quite a lot of factors that affect how we hold heat and how stressed we feel in terms of heat, And one of the big ones is the amount of direct sunlight that is on us. And we look at that in our model through solar gain. There's also impacts of the air speed, so how much air movement there is through a space, the humidity, and the thermal mass or radiant heat from surrounding objects or even other people. So, throughout this study, we looked at air temperatures and solar gains. So, those will kind of come up as key metrics.

We also wanted to understand the way that the palace is performing in terms of how overheating it is currently and predicted to in the future. So we used CIBSE's TM 52, which is an adaptive and dynamic thermal comfort assessment methodology, to really understand how people are feeling in a space and predicted to feel in the palace. So, firstly, once we had our model set up and calibrated, we wanted to assess how the building is performing currently, and sort of understand where some of these complaints may be coming from. So, under the 2020 weather file, this is the results for TM 52 compliance. So, I'll briefly run through the three criteria for TM 52, and sort of what they're telling us. Criterion 1 is an annual average indicator of thermal comfort.

So, it has to do with setting a limit on the overall number of hours that can be above a certain comfort threshold for temperature. So, you can see that in the current weather file, the current performance of the palace, it is not failing any rooms for that Criterion 1. So, the overall annual performance is not failing. Then we have Criterion 2, which deals with the severity of overheating within any one day. And here is where we can see that the palace is already struggling a little bit in some rooms, particularly those, unfortunately, that are on the public display route, and that are southern-facing. And this has to do with high heat events and the way that people are feeling during heat waves.

So, this kind of tells us or aligns with what people are reporting experiencing in the palace already. Then we have Criterion 3, which sets an absolute upper limit for how warm a room can be based on that dynamic comfort threshold. And here, again, the palace is not yet seeing any issues. So, then we had a look at, in a future weather file for the year 2050, how is the palace predicted to perform currently? So, you can see that by 2050, unfortunately, more rooms are failing two out of three criteria for TM 52 resulting in an overall failure. And these rooms, again, are typically on the southern facade and public-facing.

There's also significantly more rooms that are failing Criterion 2 under this condition, meaning that there are more rooms being affected during heat wave events. And importantly, the weather file that's chosen for TM 52 studies happens to be one that represents a sort of moderate summer, not necessarily one that is severe heat waves. So, this is kind of a better case scenario for how people might be experiencing the space in 2050. Then we have, looking forward even further, to the year 2080. And by this time you can see that the majority of spaces assessed are in fact failing TM 52, and some of them are failing very severely. So, this really tells us that the sooner we can intervene to be helping to passively mitigate these extremes in temperature, the better and the more long-term those interventions can be.

Importantly, one of the rooms that is failing the most severely and is a very important space for visitors to spend time in is called the King's Gallery. And so, this will be a space that I will hone in on as a sort of representative example for how our interventions are performing. So, from that baseline understanding of the model, we started to look at the changes and interventions that Lynda outlined for us earlier. The first one we tested out was changing those dark-coloured internal blinds, which are absorptive to some degree, to a lighter-colour internal blind that will reflect back a little bit more of the sunlight so that it doesn't enter into the room. And what we see here, I'm showing the temperatures in blue and red, and you can see that there is a minor peak temperature reduction of a quarter to a half of a degree Celsius. So, not a huge temperature reduction.

And correlated with that, there is a 0.75 kilowatt reduction in solar gain shown in the black and green in the King's Gallery. So, this measure on its own isn't coming across as super strong, and a person in this room may not notice this minor difference. However, in conjunction with other measures, this may be an effective additional factor. We then looked at the existing solar films and the potential to improve those solar films to make them more reflective of sunlight, so to reduce their G-Value. So we, looked up what films might be available and found that a G-Value of 0.4 might be achievable for this type of window. So, in improving the G-Value to 0.4, you can see in the black and blue curves that we get a more significant reduction in solar gain.

About two kilowatts. And this is correlating with, in the green and the red, a temperature reduction of up to one degree Celsius. So, while one degree might not seem like a large number, when we're talking about peak temperatures and the amount of time people are exposed to heat, that kind of temperature change can be quite helpful, particularly when it's coupled with a reduction in the sense of heat being on them from sunlight directly. So, this measure, we think, is quite effective. So, the next step that we took in the study was actually based on historical photographs and renderings of the palace that show that at some point in its history, there actually already were external awnings on the southern facade. So, you can see here in this photograph that we have these sort of dropdown and kick out awnings or external blinds that were keeping out some of the sunlight.

So, we were curious to understand how this measure could perform and help the palace to stay cool if they were to be implemented. So, to that end, we added in to our model physical external shades following the design and and historical evidence for what was previously in situ, and we used this to assess those same metrics. And what we found is that this measure is the most significant at reducing the solar gain massively, by about 80%, from seven kilowatts all the way down to two kilowatts. So, that's a very massive reduction in sunlight hitting people in the space, which is great. And this is associated with, again, the most significant temperature reduction in the space of, again, up to two Celsius. So, combined, this measure could help people feel more comfortable in this space for longer.

So, this is just a brief summary slide of what the study has shown us so far, comparing the peak temperature reduction for these various measures. So, you'll see the baseline in black, a minor improvement from those light-coloured internal blinds, a little bit more for the solar films, and the most significant measure being those external blinds. And again, potential combinations of these measures may be more effective than any single measure on their own. So, as I've mentioned, I think spending the time to really calibrate this model and understand this building has allowed us to use it to answer lots of different questions and go in lots of different directions for study. And one of those that we were curious about was the potential for additional natural ventilation through windows and roof lights. And so, we tested out a model iteration where we allowed more free area on the windows to be openable, and this is shown in the yellow and green area.

So, that would be the areas that are open for ventilation. And what we found is that allowing for additional natural ventilation through those portions of the windows in the current weather file is quite effective at reducing those peak temperatures by about a degree or a degree and a half. And this is a very interesting finding, but it needs to be taken in consideration that natural ventilation may not be something that can be unregulated at the palace due to the collections, as well as, over time external temperatures are only predicted to warm, so natural ventilation can only ever be as, as cooling as the air outside is cooler than inside. So, this measure may not be a great long-term solution, but it was an interesting finding for us. So, one other aspect of this is that I've been speaking about these future weather files as though they are certain, and the future is not defined, it's not certain yet, and it fully depends on our collective behaviors now and how much emissions of CO2 go into the atmosphere in the coming decades. So, we wanted to understand, along with HRP, what impact potential future weather files may have and how the building can be adapted to whatever future may come its way.

So, I'll just briefly explain this language of RCPs and weather files. And RCP 8.5 is known as the business-as-usual case. So, an RCP is a Representative Concentration Pathway. It aligns with a certain amount of carbon dioxide emitted into the atmosphere. And this condition is the one if we don't curb our emissions as a planet. And we see the most severe temperature increases of up to four degrees by 2100.

And again, this is correlated with more and more extreme and intense weather. Then we have the medium emission scenarios, RCPs 4.5 and 6.0, which align with some degree of mitigating our emissions in the coming decades. And this is associated with moderate increases in temperature up to 2.2 degrees by 2100, and again, moderate changes in those extreme weather patterns. Then there's the ideal RCP 2.6, which is the extremely ambitious mitigation of our carbon emissions pathway, which would see a lower carbon future and a pretty minor increase in temperatures and change in weather. So, we took two of CIBSE's available weather files to really understand the way that they reflect these different Representative Concentration Pathways, as well as what types of weather they are reflecting. So, the medium emission scenarios shown in weather files one and two here align with RCPs 4.5 to 6.0.

So, they're kind of, if we do curb our emissions pretty well. Then there's the high emissions scenario which reflects RCP 8.5, and this is our high emissions business-as-usual future. But importantly, CIBSE allows us to look at different kinds of summers. So, the DSY stands for design summer year, and this is sort of the pattern of weather that we expect in a given summer. So DSY1 reflects a moderately warm summer, nothing too intense, not a scorcher as we'd expect. Whereas DSY2 does reflect a summer with a more intense, short, very high heat spell.

Then we have DSY3 which, again, is a warmer than usual summer, reflecting a longer, less intense warm spell. So, as a study, we wanted to understand how the building will perform under these many different potential weather scenarios. So, this is just comparing the weather files so that we could understand how they are each causing the palace to perform. And on the right-hand side, we're looking at peak internal temperatures, and on the left it's the number of rooms failing TM 52 under a particular weather file. So, you can see that DSY2, that short, very intense weather file, very intense heatwave event, is the one under a high emissions future that's causing those most intense peak temperatures and the highest number of failures of TM 52. On the other end of the spectrum, the medium emissions future is a much more manageable potential increase in temperatures and peak temperatures around 31 Celsius, with a much smaller number of rooms failing TM 52.

We did the same comparison for the 2080 weather files, and the trend is very much the same, where this DSY2 and DSY3, which have those more intense, warmer than average summers, are seeing pretty significant numbers of rooms failing, and really kind of unmanageable peak temperatures. So, I won't have a ton of time to go into even more results from the study, but to these different weather file results, we were able to also assess the effectiveness of each of our interventions and rank which ones are the most effective, finding ultimately that when we can keep out the solar gain in the first place using those external awnings, that really is one of our most effective measures for mitigating this overheating. So, I hope that this conversation so far has allowed us all to think about that, while we certainly need to continue mitigating our emissions, we need to be improving our RCP as much as possible by using clean energy and being as efficient as possible. We also do need to be considering how we adapt to the fact that the climate is already changing and it will continue to change. Whether that means looking at how we can build resilience to floods, if that is our main climate hazard, or in the case we've looked at to get today, how can we passively mitigate overheating as best we can? So, the main takeaway that I want to leave you all with is that we really do need to be taking proactive steps to understand the climate hazards upcoming for our buildings, understand the unique risks and vulnerabilities of each building, and then we need to be not afraid of taking actions that will maybe change the look or the usage, as things have always done over time.

We can embrace change and we can allow our buildings to evolve and adapt to the future and the usage that they are needing in the future. So, I will hand you all back to Lynda for the final part of the presentation, but if you have any questions, I will happily answer them at the end. Thanks. So, just to kind of round that off, the data's been really interesting and it's been a really exciting process for us at Historic Royal Palaces. I think we need to be clear that given the likely increase in temperatures, we do need to think about the implementation of mitigation, programming cost for an implementation, and considering whether further steps need to be taken. I think, given that the climate is heading in a particular direction, whether we need to do something now or whether we need to do something in the future, we do need to do something, because the status quo probably can't continue to be maintained in the medium to longer term.

The most impactful option available to us would be to install solar shading externally. And as you can see from this photograph and the one in the next slide, we have both physical and photographic evidence of there being external shading at Kensington on this range historically. The latest photograph we have of evidence of that is from 1950, which shows it across the first floor, both on the south and on the east elevation. So, we're not quite sure when that was taken down or whether or not there were other interventions at other periods of time. We can see - currently we have a scaffold up on our south elevation, and we can see hinge pintles across all of the second floor windows where they are operational. So, that's quite interesting, because I have no photographic evidence of external shutters being installed, so it must have been something that was fairly short-lived.

Obviously, for most people that type of evidence may not be available. We're a very photographed and recorded building. So, it's good to be able to kind of see other examples elsewhere. We know that there were three suppliers of external blinds on Kensington High Street in the 19th century, and a significant one up at Bayswater. So, these were not uncommon features, even if they are fairly rare in the UK now. One of the things that is interesting about the visitor experience that we talk about with our operations team is that in order to be able to get to the palace, you have to have crossed the quite warm park during those heat wave conditions.

So, you've already got to Kensington as a visitor or a member of staff, you are already quite hot. Then you head into the palace, and you go off on your route. But unlike, say, larger properties such as Hampton Court, where you might go off on a route and then come down to a cool outside space before going off on another route, at Kensington we are a smaller property, or at least the proportion of the palace which is open to the public is smaller, and therefore your route is more intense. Your experience is more intense. You spend the majority of your time in internal spaces rather than cool external courtyards, which would've been available to residents historically. So, we may look to introduce cool moments rather than trying to introduce and cool down the whole building.

Looking again at the external environment, we may try and explore opportunities for allowing people to be cooler before they enter the property, if they've come across the park or walked across from Kensington High Street, so that when they come into the building they have those moments of cooling down before then heading off on the route. So, whilst this study has been really helpful in offering us opportunities to consider how we might cool those spaces specifically on the south elevation, they do fit into our wider operational and kind of visitor experience vision that we'll be looking at as we move forward towards the summer. One of the interesting things that I've realised is, again, as I mentioned at the beginning, Kensington used to be in the countryside, and we think there's between a 1.1 and a 1.8 degree increase in temperature associated with it now being in an urban environment. So, the change has already happened. One of the things that people say is, you know, hasn't it always been this way? Yes, we can see evidence of people having mitigated this in different ways throughout the past, but it hasn't always been as hot as it is now, and we need to consider how we use our building sustainably for future generations if we would like to still make it accessible to the public.

I can see lots of questions coming in the chat, so, it'd be great to give people an opportunity to, to ask their questions. So, thank you very much to Historic England for helping us with this research and providing some really fantastic technical advice from Joanne, Hannah, Caroline, and Morwenna. And again, thank you to Ingleton Wood for their support in producing this model, and really looking into it in depth and how we can protect the building for future generations. That was amazing, Lynda and Sarah, that was absolutely fab. And even though I've worked on the project with you, it's still amazing what you come out here at the end of it, isn't it? Which is really good.

And you're right, we have had so many questions in the chat, so I'm just going to have a look at my little chat thing. Don't worry, you can both take a glass of water. So I'm just going to go from top to bottom because we've got a few. Did you examine the impact of overnight purging? We did look at overnight purging. There was a, there was a slight extension to the original modeling brief that we put together.

We have a number of roof lanterns, and we have looked specifically at whether or not we can improve the internal conditions by purging at nighttime. We do need to look in detail at both the security and the conservation discussions that go with those. We we're not able to just generally leave windows open, so we have to think about those in detail, but we will be looking at those and we hope to improve. One of the interesting things at the minute is that the elevation continues to heat up internally until 11 o'clock at night, even though the sun goes round off of the roof from about six o'clock in the evening. So obviously where that temperature is building up in the day and then it's working its way through the building, it's not having the opportunity to actually purge from the building until about two o'clock in the morning. So we do - yeah, I think it would be beneficial, but we do need to consider how we manage that, from an operational perspective.

Okay. You definitely don't want bats or pigeons going in at night. No, and there are lots of pigeons in Hyde Park. Yeah. Not what you want. That's really interesting that it keeps heating up until 11.

That's, that's really significant. Do we know if that's to do with the U values of the walls or is that to do with the fact it's in an urban heat environment? What, do we know why that is? I'm not 100% sure. I'm looking, I'm looking at Sarah and hoping she's got a response to that. Oh, you're still on mute.

Sorry about that. Yes, I think one of the factors there would certainly be the thermal mass of the walls, just the amount of heat sink that this very simple solid brick construction can be, it would just kind of mitigate or mediate through to the cooler side. And that will take hours and hours, so quite interesting. So a massive shame that it wasn't made of really, really thick stone and you probably wouldn't have had that issue. But that's what's interesting isn't it, is you can't necessarily say what's working for you and what happens in that time is actually going to be the same for a building that's next door that could be of completely different construction. And I think that's a really important thing that we need to think about.

Yes, and I think coming back to the kind of all year perspective is really important as well. If we put solar film on our windows, then we are going to lose nine months of free energy coming into the building. And you know, most of these buildings didn't have central heating until fairly recently. And although admittedly they would've been managed at a lower internal environment, we don't really want to be suddenly cutting that off through the winter and then having to replace that with mechanical heating, which has a cost and a carbon impact. So the option to have something which is flexible, so internal or external blinds is better for us than having something that once installed is permanent, because that gives us the flexibility to manage the building and energy requirements accordingly. It's great.

It's all those like connecting things you have to think about, isn't it? It's just not that - I know we always say it's not that one solution fits all thing, but it is actually, there's so many other options or issues that could occur just by making one simple decision in some people's mind. Yeah, And I think the scaling up and down is really important actually. A couple of years ago we had an enormous heat wave and my husband managed to grab a, you know, an old sheet and two pieces of 2x1 timber and literally propped it over the kitchen window. And the difference was staggering. So whilst you know, you have a range of buildings, if you can think about, you know, the kind of lower tech solutions that are easy for you at home or in your property then it can be really helpful.

And the surveyor of the fabric for Historic Royal Palaces spends quite a lot of time in Australia and as she says, that's why people have verandas. You just don't let the heat in and then it's much easier to try and control the internal temperatures rather than try and get the heat back out again. Yeah, that's fascinating. It is one of the findings actually of the Technical Tuesday we did last week on overheating. That's really interesting. So let's go on to the next question.

What's the chimney situation in the palace? Chimneys were, yeah, sorry - I would have to ask Sarah if they were included in the model. The State Apartment chimneys, as far as I'm aware, are open and ventilated accordingly. The first floor and the ground floor chimneys, some are open and some are blocked by later, kind of, movements around. But I'm hoping that we kind of modeled those in with the construction of the building at the time. Interesting.

Yeah, I don't think the chimneys were modeled as open, which is kind of ringing a light bulb that that could be an interesting thing to look at and see, see the effect that that could have on purging the heat. Well, there we go. Thank you to whoever that was. That is, that is phase two of this study looking at the passive ventilation options. So another one, and actually I was thinking about this whilst you were talking: Would reducing visitor group sizes, or generally, visitors on warm days be a good way to reduce your emitted heat from people in the rooms? It's an interesting question.

So Historic Royal Palaces receives, we don't receive any regular grants from the government or the Crown. We are funded by ticket sales and by events and generous donations. So our income and our capacity to be able to maintain this building is based on that income that we we gain from tickets. Weather is is notoriously unpredictable, therefore we sell our tickets however far in advance, I couldn't tell you right now, I think the tickets are now on sale for the summer. So we wouldn't really be able to kind of adjust our our levels accordingly. Obviously, we do have circumstances where if there is a significant heat wave we would, we would have to then manually reduce our visitor numbers.

I can think of the pagoda specifically at Kew Palace where above a certain temperature, it's not appropriate for us to be opening that. I think this falls into one of those things we are going to be looking at in the future. And I don't think it's just going to be us as an organisation. I think generally heritage organisations across the board and museums and other public buildings are gonna have to start thinking about this. I would say that post Covid, the situation has improved because we tend to avoid that kind of 10 o'clock opening and a massive two mile queue to get in the door because the domestic population tends to, to book their tickets in advance. And you know, you think, oh well I'll get there for 11 with the post, you know, the trains and you've already booked your tickets.

So there tends to be more of a spread throughout the day because we have a certain amount of tickets available on a half hourly interval. But international audiences do - for which quite a large proportion of our visitors are - tend not to book so far in advance and do tend to book that once they're here. And often have several things to do in a day, So they might choose to come in the morning or an afternoon. So I think group sizes and visitor flow is something that's really important and we are looking at that now across the palace, along with a number of other kind of, as I said, visitor operation options to help people have a good experience when we're here. We'd like to say it's a fantastic experience. Don't not come because you think it's going to be hot.

Just going to say that now otherwise - who'd have thought? Yeah, but who thought Covid actually had some positives? Yeah, yeah. Really interesting. How bizarre. But it is, it's a really important point though, isn't it, about visitor flow and actually how we use our building, but also the income that comes into it.

I won't name the properties that I used to work at, but we had two where the staircases started failing because the footfall had gone astronomically more than it had ever been. And it is that - it's a bit of a concern, isn't it? Because we want people to go into heritage buildings, want them to experience it, we want to bring the money in because you know, they're not cheap to look after, but there's all those consequences we don't think about. Like they weren't built to take, I think one of my properties had about 650,000 a year or something like, you know, they weren't built to take that. And then we've got the question of when it comes to climate change and there are those considerations. And we As an organisation very fortunate in that we have an in-house team of building conservation professionals and then we have, you know, options to bring in additional resource, such as Sarah, who's come to help us with this specific challenge.

And that means that we can monitor and we can consider conservation in the longer term, which for some organisations they don't have that resource available. So, you know, we are hoping that having worked with you on this project, people can kind of take that learning away and think about how it might apply to them. Yeah, that's great. I will move on to other, I could just keep asking you guys questions of my own. What would happen to the discrepancies between your model and actual measured temperatures if you used actual weather data in your model instead of the typical weather file? Sarah, I think that's probably one for you.

Yes. Yeah. It's a good question. I think that it would definitely lessen those discrepancies just given the way that we've gotten the performance to be pretty accurate, we believe. I think that if we were actually inputting the correct external weather for every minute of the day, it would allow those internal temperatures to track much more closely. And I think we'd overall have a little bit prettier graphs when we look at measured versus modeled.

But I don't think the story overall would be too different. Because the weather files from CIBSE are pretty representative of up till now they have until 2020 that are based on measurements. But those are continuing to evolve. So the weather files that we have, at least for the present, are quite good. And then we do have a lot of options for looking at the different future weather files as well under lots of different emission scenarios. Yeah, that's really good.

So what have we got: Was air permeability validated with site surveys? And if so, what was the method that was utilised? It wasn't for this. It wasn't, no, so we are considering doing that on a separate area of the palace and I think that there are, there's a couple of questions relate to that. One, do we need to do that to find that the building is fairly leaky? To which the answer is probably not, but sometimes quantifying what you know qualitatively can be helpful, particularly if you are justifying value for money in an intervention.

If you want to say, you know, we all know that if we keep the heat out, the building will cool down internally, but if we're going to spend X amount of money on that, we want to be able to justify doing so, so we can demonstrate the importance of doing that. And in this particular instance, there was a number of options available to us and we wanted to work out what the best option was. In terms of air permeability, I think Sarah's model had an option for, kind of, very leaky, a little bit leaky, not too leaky. And I think we probably went for the middle. You know, we do maintain the building well, we've recently had a bat survey of the roof, which demonstrated that, you know, the roof is in really good condition and it's well protecting, for the King's Range. So I think we made a selection based on what we thought was the most appropriate.

Yep. And I'll just add to that, that was part of, kind of, the initial calibration and model setup was that as a parameter and testing out a few values that we thought could be reasonable and sort of going in the direction of where the results looked the most real compared to the measurements. And I should say, you know, we are fortunate we have internal measurements available to us because of our collections and the conservation team. So we can adjust all of those factors to get down to a kind of profile that really does reflect reality. And that's the other thing, isn't it? You've got major collections in there, which are normally, I'm assuming most of your collections are still in the rooms that they were originally in.

It's not very often they get moved. So that's, you know, that crux of overheating of going, how are the collections impacted versus how are your occupants impacted? Two very different things. Which is interesting to come back to the ventilation discussions because actually it's the change in environment and the speed of change that's very important to collections, not having a significant change in relative humidity because we've had the windows open and suddenly there's a summer downpour and the moisture levels have gone up incredibly quickly and that means that, you know, there's kind of too much adjustment for those collections to cope with in a short period of time. So often the consistency of environment is as important as the actual environment itself. Yeah, it's that nice little equilibrium, isn't it, that we're all trying to get to.

Right. We've probably got enough time for two more questions. So regarding the solar films, what challenges did you experience with thermal stress on those existing historically glazed windows? Well interestingly, there was an explosion at one of the embassies on Kensington Palace Gardens in the 1990s. So whilst we are fortunate in having the historic windows, the joinery's original in places, the first and ground floor are 19th century, but the second floor is 17th century. Unfortunately we don't retain any historic glazing on that elevation.

We do have UV film, which has a degree of solar reflectant, a small amount of solar reflectance, as standard as most museums would do with collections internally. But it's modern glass, so it's not quite the challenge that it would be. You know, it's, yeah, unfortunately that wasn't something we needed to consider in this particular scenario. No, but what a good excuse for not having historic glass. I don't think I wanted to be a stay on duty that day, but there we are. No, yeah, I used to work in security.

That's quite a scary one actually. Right, last question, sorry to anyone that we didn't manage to get to your questions to. Are there any heritage constraints in terms of installing external blinds? I think there's many heritage constraints because what we don't want to do is to damage the significance of the building in order to be able to protect it for the future. It's one of those constant balance conversations you have often too with fire protection and other considerations. We are looking at the opportunity for external shading and as I've said previously, we have precedent here, which is very helpful.

Historic England are obviously bringing out guidance and, you know, my understanding is your preference would be for external passive options to be considered, you know, significantly before any mechanical options are considered if it's necessary. The detailing of how we install the blinds, how we wire the blinds and get, you know, electrical feeds to all of our windows and then up to the window heads is a very big challenge for us as I would imagine it would be for others. You know, doing so without having to notch joists or getting, you know, creating holes in fabric. How we can support those blinds without damaging the masonry because they are quite heavy when they're up there and the surrounds and the balance boards that you would've seen has historically. And then interestingly, none of our windows appear to be square, either vertically or horizontally. And of course, all modern blinds are of a particular dimension and they need to go up and down at an angle.

And that's a challenge because our windows don't do that. So we're looking at how we could detail that. You know, we are also subject to planning permission and scheduled monument consent. So we have been working very closely with Historic England and we will need to apply to the local authority to do that if that's found to be possible. So it's a challenge, but I think it's the right one because the alternative is mechanical ventilation and the impact of that on the significance of the building would be very big and would, you know, would require a lot of electricity and a lot of maintenance. So this is the right first step for us is to look at those passive options so that we can improve the environment without damaging the building.

And I think that's a really key point, isn't it? Is we have to accept climate change is happening. You know, there's very little we can do to stop it. We've already met the 1.5 threshold that we'd all hoped not to meet, that was met last year, or was it 2024 actually. So what do we do? We need these buildings to continue to be used, if they're not used, they will fall into disrepair.

And it's that option of heavy which in some circumstances will be the only option. You know, we've got modern listed buildings that are high rise and they might need to have it because we can't put external shading on an entirely glass building, could we? Or we've got to find those nice little passive measures. And I think what you've done, both of you, and Ingleton Wood and the wider estate team, you've done constructive critical analysis of your different options. And I think that's, you know, a great thing, Great thing for all of the people listening today to take on for their next projects.