Understanding the Environmental Performance of Historic Buildings for Conservation

Speakers: Sophie Godfraind, Tobit Curteis, Jessica van der Drift

Sophie

Thank you Jess, and good afternoon everyone, and thank you for joining us. So today I'm really pleased to welcome our special guest speaker, Tobit Curtis. Tobit is the author of our recent guidance, understanding the Environmental Performance of Historic Buildings for Conservation. He has, for over three decades, been developing environmental survey and monitoring techniques for historic buildings. Over to you Tobit.

Tobit

Thank you, Sophie. Um, and Jess. And, uh, great to see so many people here today. Um, there's quite a lot to, to run through, so I'll spin through some of these slides quite fast, but if questions come up, please do add them to the chat. Uh, and we'll try and pick them up at the end. And if we run out of time and there's no time afterwards, do feel free to to, to email Sophie or I and we can see if we can answer them directly.

Um, now, um, some of you might, uh, be familiar with the 2014 Practical Building Conservation Environment book, which I worked with colleagues on for Historic England, English Heritage as it was at the time, um, which looks at the environmental performance of historic buildings, collections, all of those things that we have to deal with with, um, environment and conservation. It's a big and very useful book, but it is not exactly user friendly for the, uh, the building professional, the people commissioning these sorts of, uh, pieces of work and surveys.

So the aim of the guidance, which has recently been published is to look at the practical application of all of those techniques, which are discussed back in the PBC book, and to turn this into a, a practical tool that you can use as owners, as professionals carrying out this type of work, as those commissioning it. That was the, the, the, the idea, um, behind it.

Now, for simplicity sake, you all have seen the, um, the document itself. I'm going to, I've structured this very much along the lines of the table of content. So you can see the, the progression, the same basic structure and methodology that we use in addressing this type of, um, environmental performance assessment for conservation. And I would like to separate out environmental performance assessment for energy and for conservation. These are two parallel and related, but slightly different things.

We're talking about conservation here. So, um, I will just start with the absolute basics that we're all familiar, that different types of building have different types of microclimates. Some have thin walls and are are inefficient. Some have thick walls and small windows. They all perform differently. They create an environment within them, which varies. Um, as occupants, we tend to change the environmental conditions in a building to make ourselves comfortable primarily and not necessarily for the conservation of the building or the collection in it. Um, if you are tackling and changing environmental performance in buildings, it is very important to understand how all the different factors interacting to create those conditions, uh, work together and therefore, which ones you need to change and how that will impact on everything else. And just to reiterate what I said earlier, this is what this document is aimed at giving you the, the, the basic knowledge, uh, for, and also the references of where to go, where to follow this up, uh, if you need to get into it in more detail.

So, as I said, there's a lot to get through. And so I'd split it up into these six sections, which broadly follow the, the main document. So if we start with the, um, ah, we've lost all our coloring, Jess, um, but we can go through that nevertheless. Um, if we go through the, the series as it's laid out, let's start with what is the building environment and why does it matter?

Now, there are lots of different, um, ways that this is, is presented. My own approach is that the building environment is the conditions to which the historic building fabric and the collection, I should say, is exposed. And in our context, this is largely moisture, heat, and light building environment is the greatest agent of deterioration next to mechanical damage. I think we tend to sometimes look at this stuff as if it's sort of quite benign and, and has little effect. In fact, next to things being knocked down, things being knocked over. Building environment is the thing which causes most of the damage that we as building professionals will be dealing with. It also has a direct impact on energy efficiency, both cost and energy use, as well as the comfort of those using the building. So it's becoming more and more relevant from that point of view. And as has been noted, we tend to manipulate building environment for our comfort rather than for the conservation of the, um, of the building or the collection.

Jess

I'm awfully sorry to interrupt. I've uploaded the wrong slides when we made the amendment earlier, would you like me to swap them over to the other, the other version? It shouldn't take long.

Tobit

If you could do that super fast, that would be, That's okay.

Um, while you're doing that, I think it's, it's worth, uh, just sort of thinking about where we are likely to come across building environment. because it's one of those things when people start talking about it, um, they've already answered the question is, is this something we have to be concerned about?

Now, most of us with in developing historic buildings, conserving, repairing, historic buildings, changing heating systems, resurfacing, historic buildings, all of these, all of these things have a very significant building environment element to them. But the issue is perfect, Jess. That's the one. Um, the issue is that people often don't recognise it as such, and therefore these questions don't tend to be asked until rather too late, um, in the project. So at the end of this, I'd very much like you to be all going away thinking, ah, right, this is a building environment question. Let's ask this at the beginning of our project, and then we'll be in a better position and we will establish the risks.

We will know how to control them. So back to where we were. Um, historic building environment is driven by the weather for the history of human construction building envelopes. The structures around us have been mere buffers between the internal and the external conditions. The weather does something and it's gently reflected by what goes on in the building. Now, in the middle of the 20th century, we decided that it would be a much better idea if we built much more what we thought of as substantial structures, which totally separated inside conditions from outside conditions. Um, and we put a big machine in to try and modify the conditions on the inside. Well, didn't work very well, hugely inefficient. We're now having to live with the, the consequences. But for our, um, our, from our point of view, we're dealing with traditional building structures, and these are buffers.

The principle driving factor for a building environment in an historic building is the external weather. And for us, the key parameter is water. Now, I've said vapor, liquid, and ice. Of course, in, in the climbs we are in here in England, we're often dealing with the first two, not the ice. But it's important to think of the whole cycle.

Um, let's see, why does it matter?

Well, poor building, uh, environment can result in damage to the historic fabric, the furnishing collections, uncomfortable conditions, and poor energy management. That pretty much covers it. If you get environment wrong, you have a damaged building, which is uncomfortable to use and unsafe to put sensitive artifacts in.

So let's have a look at a few of those deterioration issues. Um, chemical deterioration, um, I've, I've just put a few, uh, snapshots of, of particularly significant examples in, but just to, to show the, the range of impacts that the environment in a building can, uh, can have.

Um, some of you will be familiar with the problem of underside, lead corrosion in a historic building. Often historic church roofs, which came into, uh, being in the mid eighties when we started changing heating and insulation under lead roofs. Uh, this is, uh, uh, uh, precisely an effect of, of poor building environment causing materials which had been absolutely fine beforehand to deteriorate swiftly and dramatically.

Stained glass, I mean, most people, many people look at stained glass and assume glass is, is stable and not really doing much. Of course, those of you who are familiar with it will know just how unstable, particularly some early, some medieval stained glass are, that it's soluble, that it's chemically reactive. Um, if you introduce poor environmental conditions, pollution, condensation, you end up with the sort of damage that we are looking at here. Um, microbiological deterioration, um, moulds growth of one sort or another, they're certainly disfiguring. And on the whole, we are dealing with either buildings which are architectural works of art or works of art within them.

So the aesthetic impact shouldn't be, uh, underestimated. But more importantly, most of the micro organs, no, excuse me. Most of the microorganisms we are dealing with, um, have damaging materials produced as part of their life cycle, be it alkaline or acid. Um, they also have physical connections. The building, the high moisture digging in. They're, they're causing a loss of cohesion. So it's not simply an aesthetic impact that the microorganism has is a chemical and a physical one as well.

Microorganisms, bigger things, pests. Um, if the conditions are conducive to the growth of particular types of pests, beetles in this case, um, they will very happily use a lot of our collections as nutrients. Um, they will eat them, um, on the right hand side there. In some cases, if there is significant liquid water and contaminant spores, you'll have outbreaks of things like, um, dry rot.

So there's a whole range of orga, uh, of, of, of biological and microbiological, uh, deterioration issues, which are directly linked to the building environment, dimensional response, different types of material, expand and contract and move in a different way as a result of changes in temperature and humidity.

Um, wood, for instance, um, over time continues to expand the contractors as, uh, the moisture content of the cellular structure varies.

Um, paint layers, which are very flexible, often when they're first applied, chemically change, become more brittle, and so over time aren't able to move in the same way as timber substrates.

And so that environmental instability, which was fine on day one by day 501, is causing flaking delamination loss of cohesion Broadly. Those, uh, uh, that, that's a sort of, um, overview of some of the key deterioration issues that, um, we will be looking at later on.

Um, and I wanted to leave this first section with this slide, the building performance triangle. It's something that, um, some of you all know my colleague Robin Pender, with whom I, I wrote the Building Environment book. It's something that Robin introduced me to. And I think it's a very useful way for us building professionals to think about the impact of what we are doing on different aspects of the, uh, the estate we are caring for. The point that it makes, and I think this is very visually, is that the effect of people using the building, the effect of the building envelope and the effect of the building services are all interacting. If you change one, you will have to change or you, or you will produce poorer conditions for the other. So always, when you are looking, particularly the end of this, um, this talk, when we're talking about changing conditions, it's very important to think of the impact all the way through between people services, envelope, right?

The next bit I wanted to look at is trying to understand the environmental parameters, what they are and what they do. I suppose it's into, into two sections.

So let's have a look at the understanding bit. First, just looking at the, um, the parameters we were talking about. Temperature first of all, um, a lot of our, uh, a lot of our buildings, a lot of our, our materials are quite insensitive to temperature.

Stone doesn't react vastly. Um, a a lot of the, some, some of the timber we're dealing with doesn't react vastly to, to, uh, temperature. It does react to, to moisture, but that's something we'll come onto. But one thing which I think is useful is seeing that how different materials react to particular parameters when they are all part of the same structure. And I think this example of leaded lights and stained glass is a good one. Um, the masonry and the glass itself has very little reaction to temperature. The lead cames, on the other hand, have a very significant reaction to temperature. And because all are part of the same structure, they push against each other, they distort. This can lead to structural failure or simply distortion, which will eventually lead to structural failure as you see in the window on the right.

So temperature in and of itself is a significant issue, but probably the most, um, the most significant for us is water, liquid vapor condensation. I've, I've left ice out of, of this for the time being, but we can certainly pick up in the, the Q and A if that will be useful. Liquid water, first of all, where does it come from?

Well, liquid water ingress through building defects, holes in the walls, water actually coming from the sky as rain striking the building running down, and then penetrating through groundwater and drainage water, not getting away from the base of the building. Water table, standing water, is that actually interacting with your, your building, your footings, groundwater surface water? When water drains away from the surrounding land, is it actually getting away or is it tracking back into your building because of the surface topography because of the ground drainage? All sorts of ways that that can get back in.

Internal surfaces, so many examples of failing, burst, cracked water, pipes, foul or, or, or supply, um, which then feed water gently into the building envelope and cleaning. Um, there are a horrible number of cases of simply introducing buckets of water as part of a cleaning process and not realizing how much is absorbed into the building and how much the fabric will react.

On the left hand side, we've got that picture of some dry rot. Again, dry rot generally needs a liquid water source. It's rare, not impossible. It's rare to find, uh, water vapor and condensation causing it. Um, of course, so many of our buildings are, are contaminated with the spores of dry rot and the nutrients there. All you need is, is the water and the temperature to allow 'em to grow.

But possibly more significantly on the right hand side. The issue of salts. All of our buildings are contaminated with salts of one sort or another. They might be original building materials, which were never washed or cleansed. There was no understanding of this or need to at the beginning. Um, those of us who deal with churches will know that most of us, if we're buried in church yards, will turn into nitrates, and then we will be absorbed into the surrounding soil. And those of us who are holy enough to be buried close to the church will then be absorbed into the footings and come out on the internal walls, causing damage to the stone and wall paintings, um.

Introduced materials. In the 19th century, there was a huge amount of, of, uh, development, intervention repair, some of which stopped the buildings falling down, but a great deal of cement and other contaminant materials full of sulphates were introduced into our building. So we'd have these very, um, contaminated, saturated, uh, buildings. Um, all that we need then to cause salt deterioration, dissolution crystallization and loss of cohesion around the porous structure is fluctuating moisture conditions. So that's why it's so, so important.

Um, for, for us as, uh, architectural conservators. Water vapor, um, buildings, as I said, introduce a buffer between the internal and external conditions. So you would expect far more stable water vapor conditions on the inside and the outside. However, we change that. We undermine it with ventilation, with doors being opened simply with the way we heat buildings and, and the, the way water vapor works. And that can have a significant effect on sensitive, particularly organic, um, materials.

Um, on the right hand side, there is a detail of the wonderful Grand Sutherland tapestry in, uh, Coventry Cathedral showing the way in which the, um, textile has expanded and contracted in relation to variations in moisture content.

Um, where is this moisture coming from? Well, there's outside. It is penetrating through the poor conditioned building structure. It's damp air blowing in through doors and windows, um, also from the inside. Um, we can have evaporation from, as I said, washing of floors. We can cook, we have bathrooms, we dry laundry, we walk in with wet shoes. All of those introduce water into the mix, which then evaporates into the internal microclimate, resulting in the instability which can cause this sort of damage.

And then condensation. Now condensation is really the interface between the, uh, the, the vapor question and the, uh, liquid question. Warm air can hold more water vapor than cold air. And so as you reduce the temperature, um, it will hold less and less. Now, if you introduce warm moist air into a building where the walls are cold or the glass is cold and that air touches them, it will drop in temperature until the air can no longer support the water and it will condense on the surface. That's how condensation happens.

And then light. Um, with light, we have to consider the visible light. That's the spectrum that our eyes are sensitive to and that we see things in. We have to consider UV radiation, which is not something that we can see, but we can certainly see the effects of it.

Um, and then we have to consider heat. Now in these two slides on, on the left, uh, this is a Roman blind, um, which has been in daylight for about 10 years. And you can see that in the exposed area, the, uh, organic colorants, the pigments, have broken down in various levels depending on the extent of the, um, exposure.

On the right hand side, uh, you have, uh, a book showing bleaching on the, on the spine, again, as a result of exposure, both to visible light and UV radiation. Now, on the right hand side, you can also see physical deterioration of, of that book. Um, this is something which is also characteristic of, of, um, UV radiation. It causes a breakdown in organic molecules, some organic molecules, which can lead to structural failure of this type Heat again. Here we have the whole of the, um, gram Southern tapestry, and you can see from sunlight, um, coming in crossing how there is a heat pattern which pans across the whole of the tapestry, um, causing, as we'll see later on, variations in moisture content, um, in, in humidity, which caused the expansion and contraction leading to those defamation.

Jess

Hi, Tobit. Awfully sorry to interrupt. I think we've lost sound at our end. Can anybody hear me?

Tobit

I'm back again.

Jess

You're back again. Fantastic. Okay, I'll stop.

Tobit

Sorry about that. Wrong slide.

Um, so yeah, this one showing an 18th century monument with, um, direct sunlight striking it, resulting in differential heating and cooling on individual elements, which will affect the, uh, condensation patterns, which will affect some of the, uh, other deterioration, salt deterioration.

So simply by exposing a, a, a, a non-photo sensitive monument to daylight, you are having heat fluctuations, which lead to, uh, specific types of, of deterioration. So it's worth thinking about the source of light as well as the, uh, impact. Um, the lux, the visible light element, uh, and the damage caused by it can result from artificial light on the whole these days. The, uh, visible light, uh, the, the heat, uh, element is only a daylight thing is we're now using LEDs. But think of what the risk is. Think of if it's heat, light, uv, and then evaluate the risk depending on your, your lighting source.

Right. Um, understanding the inherent building environmental performance. Let's have a look at a few charts. Um, you'll be familiar with some of these terms, I'm sure. Um, the key ones I want to consider are absolute humidity, relative humidity and temperature. In most of the slides that I put up with, you've got charts in, you'll have grey as the external conditions and colours as the internal condition. So in this slide, you've got, um, at the bottom, you've got temperature, red, inside grey, outside at the top, you've got relative humidity, grey outside, blue, inside, nice little church in the west country. Um, you can immediately see the difference between unstable external conditions and more stable internal, um, conditions.

Now, let's go on to this. So what do the terms mean? They're often misused and misunderstood, which is why I think it's worth looking this in, in, uh, in detail, ambient temperature, the temperature of the air, obvious surface temperature, the surface, the temperature of the, um, surface of the physical material. That's obvious as well. But these two things are often sort of pushed together as if they are the same thing, they're really not.

Um, ambient temperature, air temperature can change very swiftly. Indeed, surface temperature is often very slow to change, particularly if that surface happens to be attached to a very large medieval stone wall, which has a huge thermal mass. So one of those, the first of those could be a swift changing thing. The second is often slow. If bright sunlight falls on it, maybe the surface temperature will change slowly as well. But they are two different things.

Now, when we talk about humidity, when people talk about humidity, generally what they mean is a parameter called relative, um, humidity. And relative humidity is complicated, which is why it got so wrong so often.

So we'll start with the simpler one, absolute humidity. Absolute humidity is the actual amount of water vapor molecules in the air in a particular space, irrespective of temperature. Now, if I have a look over at my dial on my wall, I can see the relative humidity here is about 58, and the temperature's about 18. So the absolute humidity must be about 12. That means if I've got a, a glass box of air from my office, which is a cubic meter, there will be 12 grams of molecules of water bouncing around in that. If I increase the temperature of that box, the air in my office, I'll still have 12 grams of water bouncing around in my box. If I drop it, I'll still have 12 grams of moisture. It is irrelevant to what the temperature is. This is physical water vapor molecules.

Now get onto relative humidity, the amount of water vapor molecules that the air is actually holding as a percentage of the number it could be holding at that temperature. That's the key thing. Warm air can hold more water vapor than cold air. And so if I take that box, which at the moment according to the dial sitting on my desk will be about 58% relative humidity, and I increase the temperature, it could actually hold more water vapor, but there's no more water vapor in that glass box. And so the relative humidity will go down. And if I make the air colder, the air won't be able to hold as much water vapor, still the same number of water vapor molecules going around. So cooling it will drive the relative humidity up.

Now moving on to dew point, thinking back to our condensation, if the relative humidity goes up and it gets so cold. So if that air touches a cold surface and it can't hold that water vapor anymore, we hit a hundred percent and it condenses. And that is the dew point temperature.

Now, just to illustrate this, and I appreciate, I'm labouring a point, but it's something which is really important in understanding and controlling this stuff. This is just really to illustrate what a building might be. Now, our buildings aren't made of glass and they're not sealed like a glass box, but just to give the impression, if you have those 13 grams of water in that glass box and you decrease the temperature, the relative humidity goes up, and if you increase the temperature, the relative humidity goes down.

I think I probably laboured the point enough, but I hope that that's clear. Because it affects everything else that we, we do with this. Um, water vapor buffering involves actually stopping molecules coming from one space to another, opening windows, opening doors, whatever it happens to be. Temperature buffering is something totally different. Uh, you don't need to have air exchange to, to gain or lose temperature. It helps. You can do it. But as you can see with this thin walled, um, little building in Stratford-upon-Avon with a heater on the inside, it's thermally very inefficient. And so a great deal of heat is radiating out from that building just because of the thermal in inefficiency of the lath and plaster, not because there's any air leaking or out, doesn't just have to be timber.

Um, lath and plaster, Um, timber post walls, um, this is the side of a cathedral, um, with a wall about 1.5 meters thick and a gurney stove on the inside that's losing heat as well. But again, this is due to to to radiation of the heat. It's not due to air exchange or air loss, which is what would be needed if you want to, um, destabilize your absolute humidity, your water vapor from inside to outside.

So why do we care about this? Well, a lot of our work involves modifying the building environment. That's why we are trying to understand what it does and how to evaluate it. Now, mostly we are trying to create, or for most of history, we've been trying to create improved thermal comfort.

Um, back in the 20th century, uh, a smart engineer introduced the idea of design temperatures. Um, and this was, uh, oversimplification, I know, but broadly at a particular temperature, things are comfortable at another temperature. They are not comfortable. This is a huge and very unhelpful oversimplification, uh, and has caused an enormous amount of problems for, for historic buildings.

Comfort is associated with a whole range of things. Air velocity, air temperature, humidity, surface temperature, clothing, heat loss through convection and conduction. All of these things affect how we feel. If you are sitting in a, uh, a building at 18 degrees centigrade, fair enough for a design temperature, and it is very humid because there's a lot of water in the walls because the gutters are leaking, you will be uncomfortable. If you are sitting in an air mass of 18 degrees centigrade on a very cold pew or standing on a very cold floor, you'll have different temperatures across your body and you will feel uncomfortable. If you are sitting at 18 degrees centigrade in a draft, you will feel uncomfortable. Comfort is to do with a whole range of things.

It's very important that when we're trying to improve comfort for our clients, be that through heating systems, insulation, reducing, uh, air leakage. We understand what all those different things are and also what they do. We’ll come onto what happens if you over, if you reduce air exchange in, um, in an unplanned way later on.

But think of comfort as a whole series of, uh, environmental factors and think about the ones we can safely change and the ones where there is significant risk. Of course, historically, people have known this, uh, without doing too many measurements. That's why you see in plenty of, um, uh, medieval manuscripts, textiles hung against walls to reduce radiant heat loss to the cold thermally, massive building or panelling or as you can see here, shutters. These are all things which are put in place, yes, for decorative reasons, but primarily to modify the way that the building envelope provides internal, um, environmental conditions for comfort.

In, in the 19th century, many of our churches, there were very simple, uh, ways that people address this with door curtains and, and the like. I mean, this is just one example I'm putting up of course, in the 21st, 20th, 21st century, we didn't like the look of them, so we took them away and a lot of our buildings became less comfortable as a result.

But I just want to make the point that people have been trying to modify buildings in a fairly, uh, sensitive and passive way throughout the history of buildings. This is not a new thing, we're just doing it in a different way. Um, internal ceilings, medieval churches on the whole were built without ceilings.

Then in the 17th and 18th century when they were finding its rather cold and draughty, they put lath and plaster ceilings in. Then in the 19th century when they thought they preferred the architectural space, they took out the, uh, lath and plaster ceilings and it got cold again. And then, uh, this is a case study. In fact, this will be, uh, published case study at some point soon. Uh, a ceiling was put back into this very important, um, church with 11th century wall paintings, Hardman in West Sussex. And you'll see when you'll see the published data, it immediately improved the stability, the efficiency of the building. In this case, it was for conservation reasons. It could just as easily have been for comfort reasons.

Moisture, we feel uncomfortable in wet buildings, both because of the moisture in the air, but also because, um, wet walls are thermally less efficient than dry walls. Um, and if we start to need, want to change this, we start to really need to understand where that discomfort is coming from, where that heat loss, where that air exchange is taking place.

So let's have a look at, at roofs. because I want to get us onto the knotty subject of insulation. Everyone's very keen on insulation these days. I was even asked recently if insulation is good or bad. I don't have a moral position on insulation. It's just a tool that we use to change things. So insulating a, a lath and plaster, uh, vaulting at a church, you can see from th it works very well indeed keeps lots of heat in. Let's have a think about this though. When you have heat leaking into your roof, you look at your electricity bill and you think, gosh, how incredibly inefficient and expensive that is, why don't we insulate at the ceiling and keep all that heat in there?

So you insulate at the ceiling, you keep all heat in, you see your bill, go down, you think great! What was that heat actually doing? That heat was escaping. Now that's already a pejorative term. That heat was going into your roof and it was heating up the back of your lead or your tiles and it was increasing the dew point temperature and it was, sorry, it was reducing the dew point temperature and it was reducing the amount of condensation you are going to get on your lead or your tiles. We've seen what condensation does on lead already. So by putting in your insulation, you are making that roof space colder, which means you are increasing the risk of condensation on the underside of your lead or your tiles.

Are you happy with that? I don't know. Maybe it's a good thing, maybe it's a bad thing. Maybe it doesn't matter. But it's very important that you understand it. And in most cases, it's very important that you understand the level of ventilation, probably additional ventilation you will need in your roof space in order to allow evaporation, in order to counter the possibly damaging effects of reducing the temperature of your roof space. So these things all have knock on effect and it's really important in any of these changes that you think the whole thing through. Don't just stop at the, oh, the insulation saving us money.

It's, and what happens next? Um, I mean, this is insulation is a particular, um, bug bear of mind because it does tend to, to stop it at the, it happens on walls as well. I mean, this is an illustration, um, of, of what might happen in a traditional wall with plaster on the inside.  There is heat on the inside of the building. It's been lost to this thermally massive wall. Um, and so we put insulation in front of it. We keep the warm air on the inside. We keep the wall cold and oh goodness, at the interface between the insulation and the wall, it drops below dew point temperature and you're getting condensation on your plaster underneath your insulation.

This happens a lot. It is completely predictable. Now you can predict it with clever. We type, uh, calculations or other modelling techniques. Um, or you can just anticipate it from basic assessment of the building. You don't necessarily need to go to to, to great detailed study to work this out.

Water vapor and heat pass through open apertures. We use apertures to get in and out of our buildings. Um, installing porches, secondary doors. All of a sudden there is a whole new approach to this. And many of the, the, the, the, the, the, the glazed porches in particular, but often the, uh, solid ones are becoming architecturally beautiful. We are dealing with buildings which are important, which are listed, which are often beautiful. We need to take this into account in our interventions.  But there's a whole raft of new designs coming through at the moment, which are very effective in terms of environmental performance, but are also elegant and sensitive to the building.

Internal compartmentation, we use our, I've used church examples here because they're a very good example of a big open building, which is actually used for lots of different things. Uh, we use our buildings for different things in different areas with different people. I'll come back to this in a moment. If we have them all open as a single space, it makes thermal efficiency and heating. Far, far harder.

Shutters. Most buildings you go into that have shutters, you'll find them, um, painted, closed, you can't use them again. They are incredibly efficient. Um, I was staying in an Airbnb with, with rather nice shutters, hence these, um, images, um, they are already there. They're extremely efficient. If you have a thin pane of glass, you can imagine what the thermal efficiency is. If you put half an inch of timber in front of it, it increases massively. And they are flexible. You can use them at night, you don't use them through the day.

So a lot of these traditional systems, which we've dismissed because we've been relying on carbon-based energy, are starting to come back into fashion. And this is a very good thing. Blinds on the outside awnings. This picture of, um, in the late 19th century of Buckingham Palace, look at the lower level of windows there.

We're all starting to be concerned rightly so, about the effect of climate change and overheating of our historic buildings. Well, this isn't a new thing. The Victorians were perfectly well aware of this, and therefore these things were built into our buildings. Now they've mostly been stripped out and are lost, but we've now got brise soleil. We are introducing this with different words and, and, and different designs. But it's the same basic thing that's been looked at for, you know, well over a hundred years. 200 years.

Light control measures. Um, there isn't time to go into these in any detail, but there are reasonably elegant ways with our historic buildings where you can control visible daylight, you can control UV with blinds, with filters. There's a whole series of materials that you can use to do this both sensitively and effectively heating. Um, one of the biggest changes we make is through heating, convective and radiant. It is important that we understand where we want our heat to be and how it is to be used, whether it is general, whether it is local, whether it is conservation heating, which is intended to change the, uh, relative humidity rather than the temperature.

But understanding how heating systems, how heat distribution and projection works is hugely important. I tend to, when I'm dealing with churches and other open buildings, use this approach to, to the type of heat we need in each area. Who are we heating? Is it, is it toddlers? Is it an elderly audience sitting down for a long time? Um, what are they doing? Are they just visitors walking around? Are they in a three hour concert? Um, when, how long are they there for? How long is the duration? Um, where, which parts of the building it's all used differently? It which risks do we need to control?

It's a useful way of just thinking through the effect of heating both on people, what is needed and the risk to the building, air exchange and, um, and ventilation.

Um, often we use air exchange to modify the internal conditions in the building simply by opening the windows and letting air move around. Um, we need to separate our air movement and air exchange. If we exchange air in slide between inside and outside, then we will have far, far more unstable conditions inside.

Does this matter?

Well, maybe if you're in a big stone barn, it doesn't, but if you've got lots of 17th century panel paintings there, it does. Maybe you just want to mix the air within the building because you have some damp corners. Well, that can be done with fans, it can be done with passive systems. But understand how ventilation and air exchange works.

I wrote this for the, um, diocese of Oxford and then updated it for the, the C of E last year. It's a good general guide, I think, to how the, how the systems work, where the risks are. I think the, um, the link will be in, in the notes afterwards. Good and bad ventilation to go back to that old chestnut. Um, there are some places where ventilation generally is far better than it is far worse. Under pews, close to the ground roof spaces, those sorts of things. Although it's uncontrolled and it destabilizes conditions on the whole, the bene, it is more beneficial than not.

So there are some broad rules of thumb and mechanical systems. We change performance with mechanical systems. They never do quite what we want them to do. Did you know there's a lot of heat kicking outta the back of most dehumidifiers, which if you put them against, um, some rather nice medieval books will do no good at all. Um, and then control with h-ex systems. Again, no time to discuss this today, but understanding how these mechanical systems actually work, what the real impact is, is something that's terribly important that, that we on the design side do, and then work with our m and e colleagues to make sure that the the machine actually does what we want.

Fine. Um, a couple of slides just to pick up on the point that many of us will be asking these questions When we're involved with a building which is changing. A historic building which has had one particular, um, uh, role for its entire life.

Huge barn in this case now being turned into a conservation studio, rather beautiful one. Um, church, which has been used in a particular way now as a concert, uh, venue. We need to understand how these changes are going to impact on the historic fabric and collection as well as the comfort. And it's these sorts of projects where building environment in this sense often comes up, which is why I flagged those.

Now just to finish up, what I will do is quickly run through the type of steps that take place in a building environmental performance assessment to make the point that some of it's high tech, some of it's really not. Some of it needs to be done by specialists. Some of it doesn't. Some of it can easily be done by a competent architect. They are the building professional. Most projects require simple tools.

I'm often rung up to ask if I will do environmental monitoring for someone. Well, I can, it's expensive. It takes a long time. Why don't you tell me what you need to know? And I'll tell you whether the expensive longtime tool is what you want.

Most of the time it's looking at buildings, it's reading them. It's understanding how the systems work and spotting where the issues are. How good is good enough. People love decimal points in data. Um, this is a slight misquote of the, um, economist, um, John Maynard Keynes. I would rather be vaguely right than precisely wrong for most of our work, not all, but for most of our work, having things going in this, the right general direction is much better if we understand how we're using that data than having very, very accurate data and getting completely missing the point. So don't over obsess with how accurate your your tools are.Understand your building best, right?

The basic methodology. Understand how the building would originally have performed. Understand how it is performing now, why has it changed? And in parallel to that, if we are making changes, what will those do? The first step is always macro.

Now I'm not suggesting ground investigations for everything, but I am suggesting you take into account whether your building is sitting in low lying flooded country in Lincolnshire or sitting on top of a crag in Staffordshire. Is it surrounded by a woodland or is it sitting by the sea? These will affect its basic environmental performance. And then history. We come in for the blink of an eye of a building to look at problems and hopefully tell them how to be solved.

But of course the building has been changing from day one since it was built. Is the deterioration we're looking at now, uh, new? Has it actually been going on the whole time and we're just seeing the next iteration? When did it start? Has it suddenly changed linked into the fact that this is now open to the public? There's a new heating system in.

So look very much at the long-term history, both of the building and the deterioration you are looking at, understand the materials. Brick works differently to stone, which is works differently to concrete. Understand the structure. How are things loaded? How are they connected to the ground? Look at the internal surfaces. You are often brought in because the internal surfaces are are deteriorating.

This is, um, the Archer Pavilion at at rest park. Again, there will be a case study published on this. Understand the patterns of deterioration. So you can link what's going on on the inside to the outside, understand the damage to the outside. Again, link those patterns to what's going on inside.

This is all basic visual assessment. There's nothing technically clever about this. The clever bit is trying to link everything together and work out what you are actually seeing in terms of cause and effect.

Rainwater disposal. So much of this is to do with rainwater disposal. Rain hits the top of the building, it needs to get to the bottom and it needs to get away without coming back into the building. And particularly with climate change and changing, um, volumes and speeds of rainfall events. This is becoming particularly, uh, important.

If you do then need at that stage, mostly you can actually answer your questions. But if you do then need to go further, you can start doing more technical assessments. Look at the patterns of deterioration. We've already talked about that. Then thermal imaging.

Thermal imaging is very useful because it looks at temperature variations, which are caused by a number of things. They might be caused by different materials, but they might be caused by water evaporation. When you sweat, you lose energy. That's why you sweat. You cool down. Buildings are the same. If you have water coming up at the base of the wall, it evaporates out, it cools. So thermal imaging can be a very useful way of looking for moisture, but there's a lot of other things that affect, uh, temperature.

So one has to be very careful about this. Separate out liquid water and water vapor. Is it condensation? Is it liquid water leaking in? Go through those processes that we talked about earlier to separate those things out. Liquid water has very characteristic and often very localized patterns, whereas water vapor and condensation tend to be far more general.

Electrical capacitance, moisture meters, there is no such thing as a moisture meter. It doesn't exist. There are things which measure electricity or electrical characteristics, which is affected by moisture. Electrical capacitance sensors tend to be, uh, fairly surface based. Electrical, uh, sorry, microwave sensors can look at change far deeper in the, uh, structure. Compare all and you'll see patterns, or at least hopefully you'll see patterns which will back up your physical assessment if you really need to know. And the risk is high. If you don't get this right, then you can do core sampling. Then you can do gravimetric readings, looking at actual moisture content. But it's time consuming. It's expensive. And most importantly, it's damaging. Mapping those however, will then correlate with your liquid water sources. Give you a far clearer idea and a very fixed idea of where the water is coming from. And if you want to monitor it, you can use, uh, dowel method. You can use a similar gravimetric system to look at water change and drying over time. So there are ways of doing this. I'm mapping that again, salt activity. And then finally, environmental monitoring.

Environmental monitoring tends to be misused as a term for environmental survey. Everything we've talked about up to now is environmental survey monitoring is specifically evaluating and correlating long-term patterns between two different factors. So when the weather changes outside, what happens inside? When we have a service or concert, what happens? When we turn the heating on? What happens? It's that correlation over time, which it will tell you about which the other, uh, the other survey techniques won't. So that is a bit of a galloped through.

But if I can leave you with these final thoughts. Um, understanding the building environmental performance allows you to understand the conservation risk. I think that's self-evident, but I think sometimes it needs to be pointed out that just to go back to the point that next to mechanical damage, environmental deterioration is the greatest form of long-term damage to our, our buildings. When you are doing these sorts of surveys, it should be done early in the project. These things need to be done at RIBA one or two. By the time you get to RIBA, three or four people have already designed the project. And then you come up with things which say, well, it's not like this at all. There's that risk. It has to be redesigned. So early in the process, the initial assessment is always low tech. You are using your eyes a tape measure and maybe some drawings. Um, when you have worked out what you think is going on, you can then use the high-tech tools. You don't monitor buildings in order to find out what's going on. You work out what's going on first and you monitor to confirm, to refine occasionally to prove you wrong as well. But it's that way around.

When the deterioration is complex, you develop a model of deterior, uh, of, of, of the, of the, um, deterioration technique in your mind. And then you use these tools to refine it. And finally, for those of you who are commissioning this stuff, ask for information. Tell someone you've got this sort of deterioration in your building and you want to understand why. Don't ask them to do thermal imaging. Don't ask them to do environmental monitoring. Tell them what you need to know and then discuss with them the best tools to do that.

So to go back to where we started, this was the 2020, uh, 2014 Building Environment book. Here we have the guidance. Again, links are in the notes. Thank you all very much, Much wonderful.

Jess

Thank you so much to really, really interesting, as I'm sure everyone will, will agree with me. Um, unfortunately we do only have three minutes, uh, left today. Um, so we've made a a note of everyone's questions and we will answer them and probably put them in the Heritage Connects Knowledge Hub. I will share that in the chat now and in two minutes. Do want to answer one very quick question and then we'll have to let everybody go?

Um, Margo, if you want to put your question in the chat, we'll make sure that we have um, uh, an answer for you as well.

Tobit

Uh, let me see. Good questions. Um, okay, I think there is a theme running through these questions. Here's one, and I think it probably captures it.

Timber panelling is timber panelling, adequate insulation for historic buildings. Um, I would turn around and say, what are you trying to achieve?

All of this goes back to identifying what it is you are trying to achieve in the building and then looking at the tool which will allow you to change the building performance to, uh, to achieve that. So is timber panelling adequate installation for historic buildings? Yep. Some cases it's fantastic. In other cases it's entirely inadequate. Um, and what goes on behind the panelling? Um, so this, this is all very, um, question specific.

The, the most, most of the mistakes I see made in this are because the question hasn't been thought through properly. You are trying to change something now. You might be trying to change it because you are conserving it. You might be trying to change it because it's gonna have a change of use. Maybe it's becoming domestic, whatever it is. And so looking at the, the reasons that it is not adequate, now looking at the tools that are open to you to make those changes and looking at the risks associated with those, that's always the process.

I'll go through these questions in, in much more detail, but just skimming through. I think that is a theme that probably runs, um, through many of them.