Decarbonisation Plan Webinar 3. Understanding your building – surveys and assessments

• Understanding how your building is preforming will shape the options appraisal
• Information from the surveys and assessments will fit into different criteria which will inform the options appraisal

This is the Q&A session from the session – questions asked by the chairs from questions posted in the question chat and from thoughts arising during the webinar. The answers were provided by the consultants Beatie Blakemore and Elizabeth Flower, who presented the webinar.

Accreditation and competence for thermographic surveys

Question: What accreditations or competencies are required for professionals undertaking thermographic surveys?

Answer: Many thermographic surveys are carried out, but only a small number are robust, quantitative assessments. Where accuracy is critical—such as for BREEAM (Building Research Establishment Environmental Assessment Method) certification—a quantitative thermographic survey must be undertaken by a trained, competent professional and comply with relevant international standards. Guidance on required accreditations is provided in the Historic England resources.

The guidance includes fact sheets covering professional accreditations for surveys and related consultancy roles.

Who should undertake fabric condition surveys

Question: Can a fabric condition survey be carried out by a CIAT (Chartered Institute of Architectural Technologists) accredited conservationist or similar professional?

Answer: Yes, provided they can demonstrate competence. Accreditation is important, but experience is equally critical. Professionals who are not formally accredited surveyors (for example, Royal Institute of Chartered Surveyors) can undertake surveys if they can demonstrate relevant expertise and a strong track record in heritage buildings.

How clients can assess consultant competence

Question: Can clients ask to see previous surveys or work when appointing consultants?

Answer: Yes. Consultants should demonstrate competence through case studies, previous work, and client references. This evidence should form part of the quotation and selection process for a Decarbonisation Plan.

Whether all surveys are always necessary

Question: Should every project undertake all possible surveys, or should this vary case by case?

Answer: Survey requirements should be tailored to the building and the client’s budget. While detailed surveys (such as airtightness or U value testing) provide better data, a lighter touch but holistic approach may be more appropriate where resources are limited. More detailed surveys can be scheduled as a later stage if needed.
In the case studies, some surveys were carried out later and did not change overall energy recommendations, but they influenced detailed design decisions such as ventilation strategies. This supports keeping the Decarbonisation Plan strategic and cost-effective.

Carbon footprint of carrying out a decarbonisation assessment

Question: What is the carbon footprint of undertaking a decarbonisation assessment itself?

Answer: While it is theoretically possible to calculate the carbon footprint of the assessment process, doing so would not materially affect decision-making in this context. Given limited resources, priority should be placed on understanding the building and setting out a long-term decarbonisation pathway rather than measuring assessment-related emissions.

Predicting the cost of surveys and assessments

Question: Is there a rule of thumb for estimating the cost of surveys or a Decarbonisation Plan based on building size?

Answer: No reliable rule of thumb exists. Survey costs cannot be calculated purely by floor area. They depend on factors such as building complexity, access difficulties, location, and time required on site. Because of these variables, the study did not include benchmark costs.

The most effective approach is to obtain multiple quotes and compare scope and cost to identify value for money.

Helping clients become “confident clients”

Question: How can clients judge whether a survey has been done properly?

Answer: The templates, fact sheets, and guidance enable organisations to understand what should be included in surveys and plans. This supports clients in reviewing proposals, comparing quotes, and assessing whether the scope and quality of work are appropriate.

Speakers

Beatie Blakemore: Associate Director, Project Lead & Architect at Haworth Tompkins

Elizabeth Flower: Associate & Architect at Haworth Tompkins

Dan Miles: Senior Sector Development Adviser, leading the Sector to Net Zero project, supporting heritage organisations on their journey to net zero at Historic England

Feimatta Conteh: Senior Manager, Environmental Responsibility at Arts Council England and Co- manager of the ACE-HE decarbonisation project

Dan Miles: Hello, hi everyone!

Feimatta Conteh: Good afternoon everyone! So Dan and I are hosting the webinar this afternoon because we had the pleasure of leading the project from Arts Council England and Historic England's side. So hello, I'm Feimatta Conteh, I'm the Senior Manager for Environmental Responsibility at Arts Council, and Dan, do you just want to introduce yourself a little bit?

Dan Miles: Yeah, I'm Dan Miles, I'm the Senior Sector Development Advisor at Historic England. Historic England and responsible for the Sector to Net Zero project supporting heritage organisations on their journey to net zero.

Feimatta Conteh: So Dan and I will be taking the questions that you post in the questions for presenters and asking them of our lovely presenters today, so Beatie Blakemore and Elizabeth Flower from Howarth Tompkins.

And just before I hand over to Beattie and Elizabeth, I was just going to give a quick introduction to the project. And this is the third of four webinars that we've done, so there's a full introduction to the project in the first webinar, and as Jess said, that will be available on the Historic England website in April.

So not to take up too much time, as we said, I'm from Arts Council England and the Environmental Responsibility Team, and we've worked with Historic England on this, and that's under— we had a joint statement of purpose on climate action looking at the overlapping heritage and cultural sectors that we support, The first project we've done under that statement of purpose is looking at how to develop support and guidance around decarbonisation plans.

So, in the project, we worked with 3 cultural organisations in heritage buildings, and then commissioned a multidisciplinary team led by Howarth Tompkins— and you can see all the consultants' logos at the bottom of the slide there— to work with these organisations to develop decarbonisation plans. and then build a suite of resources, templates, and guidance around that.

And I can see that there's just been a link added to the chat there, where you can find all of the resources on the Historic England website. And so these webinars are kind of taking us through decarbonisation planning step by step. And I'll just hand over now to our speakers, Beatie and Elizabeth, who will take us through this next one, which I think is about information about the buildings. I think I've probably got that title wrong. But it's gathering information. So thank you very much!

Beatie Blakemore: Thank you, Feimatta! Thank you!

And I'll make a start. So as you mentioned, Feimatta, this is one of the third of four webinars which are really designed to demystify the process of commissioning a decarbonisation plan and to explain the roles of both the kind of client organisation and consultant team, to explain the steps involved in undertaking a plan, and to introduce the suite of resources that we've developed as part of this Decarbonisation Pilot.

So today, webinar 3, is really all about developing an understanding of your building. So in the last webinar, we focused quite a lot on what the organisation or the client team might need to do to begin to gather information around your building and its use, and how you would go about commissioning and building a consultant team to help you with that.

Today, we're really going to focus on what that consultant team will do with that information and indeed what further surveys and assessments that they might undertake to build their understanding of both the building in its context and how it's used, as well as its energy use. So we're going to talk a little bit about the range of surveys and assessments that a professional team might undertake, why these are needed as part of a decarbonisation plan, and the practical considerations for undertaking those. And then we're going to explain how those are used to benchmark energy use and establish a baseline for any future interventions.

So, this really forms part of steps 2 and 3 of the 6-step decarbonisation plan framework that we put together. And as I say, it's really all about developing this robust and broad understanding of how your building works. And the reason this is important is that it forms part of what we call a building performance evaluation. And this is a process of bringing together, analysing, and interpreting a really quite broad range of information about how the building works currently.

So that includes the building's context, its physical context, as well as its wider managerial and ownership and sort of financial context, how it's used and the different patterns of use from day to day, week to week, and throughout the year. It looks at the condition of the built fabric as well as its services and systems, so all those systems that keep the building warm in winter and cool in summer and keep the lights on. It looks at the energy use across the building and again across the seasons, so how energy is used and where in the building.

And then, really importantly, it also looks at the internal environment, so how the building is experienced by its users. So, looking at things like air quality, thermal comfort, etc. So, this is really important because it's needed to underpin any potential interventions, potential retrofit measures that might be undertaken to improve energy efficiency. These need to be based on a really thorough understanding of the building and how it performs currently.

And this enables any of those subsequent interventions to be designed in response to quite specific site opportunities and constraints, ensuring that measures are appropriate for the particular building in question, that they're proportionate and effective and cost-efficient, and that they're prioritised in a way that makes sense for the particular building and its organisation. It makes sure that those measures account for the building's wider site context, and again, that's not just about its physical context; it's also about how it's owned, managed, and used.

And that needs to look not only at the current issues and opportunities, but also look forward to potential further climate change risks that might be on the horizon. This broad understanding of the building also makes sure that any measures will prioritise occupant health and wellbeing, and the so-called health of the building, ensuring that the fabric remains resilient in the face of future climate change. And really importantly for historic buildings, it also ensures that any measures avoid harm to significance and heritage value. Elizabeth, I'm going to pass over to you.

Elizabeth Flower: So, as Beatie mentioned, in the last webinar, we talked about what information a client or building owner may gather in advance of starting a decarbonisation plan in order to brief the consultant team. But today we're looking at how the consultants will pull that information together and how they'll use it to gain this thorough understanding of the building in its context and how it performs.

So, there are 4 methods that we use to gather data and surveys. Desktop research, collating and interpreting data that we can find readily available on the existing site. Site observations, which can include walkarounds and visual surveys of the building fabric and building services, and also discussions with owners and users. Technical surveys, which include measured assessments of thermal performance or airtightness, as well as many others, and finally computer modelling, so combining measured data on energy use with benchmark information.

So in terms of desktop research and site observations, we'll be looking to gather information on site conditions, statutory context, Building design and construction, heritage significance, current occupation and use, operational challenges and opportunities, and building services systems.

And as I mentioned, there's a slight overlap here with what we discussed last week. Some of this information may have already been gathered by the client or building owner ahead of starting the project, but the consultant team will review the information provided to them and also identify any gaps in that information that need further investigation from them, as well as doing our own research in order to develop this holistic body of knowledge.

As part of the pilot study work, we developed a client fact sheet that covers the information gathering process in a fair amount of detail. And this is available on the Historic Kingdom website to accompany this webinar. But today, I'm going to give a brief overview of each of these areas so you can see how they might feed into the building performance evaluation.

So in terms of site conditions, we'll be firstly looking at the building's location. Is it urban, suburban, or rural? Its orientation, looking at how does the sun path, for example, affects the building? Are there any south-facing facades that are overheating? What is around the building? Is it overshadowed by neighbouring buildings or trees or other structures? And we'll look at its topography and other site conditions, the general lay of the land, any hazards such as contaminants or structural or geological issues. And then how do these affect the building's exposure and also its vulnerability?

So, for example, is the building particularly at risk from the effects of climate change, like subsidence or flooding? All 3 case study buildings that we studied within the pilot were in urban built-up sites like this. However, for more rural locations or those closer to rivers, etc., there may be higher, more kind of bespoke risks.

So, having done this research, the team might produce a series of constraints drawings or site markups that graphically illustrate the site conditions and capture this information really clearly and legibly within the decarbonisation plan to feed into the later steps. They might also identify further site-specific surveys that could be beneficial to get a better understanding of particular issues, like flood risk assessments or geological investigations.

Then, looking in detail at the design of the building itself, we'll be considering its scale and form, and again, relationship with neighbouring buildings, like looking at any party wall conditions, the building's age or possibly ages of different parts of the building, its construction. So we want to get a good understanding of the build-up of external walls, floors, roofs.

And finally, its spatial arrangement. So, how are the different spaces and uses within the building located in relation to each other? And the reason this information is useful is that it allows us to develop more of a detailed and accurate picture of the building's fabric performance, i.e., how well insulated it is in its external envelope. And again, the consultant team will capture and summarise this information within their reports, and also again, they might identify other investigations that could be worthwhile, perhaps further down the line. So possibly opening up walls, floors, or roofs to understand their construction more accurately.

So we'll also be looking at the statutory context of the building, and the purpose here is really to set out what the likely statutory issues are that might affect any future energy-saving interventions. So this will cover heritage designations, including conservation areas, the building, site, or landscape's listed status. Also, local planning policy, so there may be specific local planning targets which may be relevant to climate change mitigation. And also areas of non-compliance with building regulations that are relevant to the specific building that may need to be addressed if future interventions are implemented. In terms of the building's heritage significance, again, we talked last week about the client's role in gathering heritage information about their building, but the consultant's role is really to bring together this existing knowledge and expand, interpret, and summarise it within the early stage reporting.

So we'll look at the building listing entry and try to broadly understand the curtilage of the listed building. Does it cover the whole building, or is it just kind of specific areas? A heritage significance statement may already exist for the building and be provided by the client, but if not, a suitably competent professional, like a conservation architect or heritage consultant, should draft one for the decarbonisation plan to capture where the key areas of historic significance are in the building.

So the diagram in the middle there shows a marked-up plan that we produced for one of the case study buildings. To grade areas of significance and guide where it may or may not be possible to implement any more modern energy-saving interventions. And to understand the significance, the consultant may also need to look at the building's conservation management plan, if one exists, and any historic development maps or original building plans. We'll also look at the building's use and occupation. So the configuration and spatial arrangement of uses, often uses that sit side by side next to each other can affect each other.

So, for example, in one of the case study buildings, we had a very cold, unheated basement-level museum space sitting next to an occupied office space, and these two areas had very different environmental needs and conditions. We'll also look at the types of users who occupy the building and any specific needs or requirements they might have. We'll look at the typical hours of operation, and then any patterns like seasonal fluctuations of use, or perhaps anomalous timings of use, such as out-of-hours events.

And finally, we'll discuss the operational challenges and opportunities raised by the organisation, typically through workshops with the building owners. And these can include issues with the control or function of the services, possible issues with the building condition, so any known areas of damp or water ingress, any known issues with environmental comfort, spaces that are known to be too hot or too cold.

And then on a more positive note, we'd like to discuss any future ambitions. So are there any capital projects on the horizon, or ambitions for increased growth or expanded programmes? And then also, are there any potential funding sources that may become available or fundraising opportunities?

Beatie Blakemore: So, alongside building this kind of contextual understanding of the building and illustrating it graphically through reports, the team will also undertake a series of technical surveys that look at the fabric and the services in a little bit more detail, some of which may already be available. So we talked last week about the fact that some buildings may already have fabric condition surveys, but again, part of what the team will do at the beginning of the project is to identify any gaps in information and potentially undertake those as part of the plan.

So some of these technical surveys include building fabric condition surveys, as we mentioned, services condition surveys, fabric performance assessments that look at the thermal performance of the fabric, and we'll talk about this in a bit more detail later on. U-value tests, thermographic assessments, and airtightness tests and data. And again, as Elizabeth mentioned, with the other sort of information gathering that you might undertake, we have produced a fact sheet that explains in more detail what these building performance surveys include and the sort of practical considerations that you might need to make in commissioning and undertaking them.

So before we go through each of these surveys in a bit more detail, we'd like to do a little bit of a quick poll in the room about what kind of surveys or assessments you may have been involved in commissioning or indeed undertaking. As last week, I think we've got a mix of people in the room who may be sort of client building owners or operators, as well as professional consultants. But let's see how familiar you are with these different tools?

Speaker: Well, so air— oh, U-value tests are coming in really low, and as are fabric performance assessments, but lots of people— we're looking at about 57% of people have taken commissioned building fabric condition surveys. About 19% looking at building service condition surveys, and 14% on airtightness tests and data. We'll give it another 10 seconds for people to cast their votes. The numbers seem to be stabilising now.

Beatie Blakemore: Interesting! So, okay, well, we're going to— it looks like there's quite low levels of engagement with some of the more technical assessments. So we're going to go through these and explain them in a bit more detail as part of this session. So, fabric condition surveys, it looked like quite a few of you— I've gotten the number, I think it was about 50 or 60%— have been involved in either commissioning or having seen a building condition survey as part of the building that you occupy or manage.

But for those who aren't so familiar with this, it's really a visual inspection of the condition of the building fabric. And by building fabric, we're really principally talking about the kind of construction materials that make up the building, and with a particular focus often on areas of external fabric, so the external walls, windows, roofs, etc., and how they're impacting the internal conditions.

And a fabric condition survey is usually summarised in a report. It might include a description of the nature and condition of the different construction materials throughout the building. It should identify any defects or deterioration in that fabric, and it should also start to prioritise and identify the repair and maintenance needs. And you may see a so-called traffic light system where the really urgent repairs might be highlighted in red, which need, you know, dealing with immediately, whereas repairs or maintenance works that are anticipated to be required within the next few years might be kind of indicated in a different colour. So this provides the building owners and managers with a really clear way of prioritising their maintenance needs.

Now, typically, a full fabric condition survey might be undertaken every 5 years or so, but it should really be supplemented with seasonal and yearly inspections of the fabric by those who actually occupy the building. So there are, of course, regular maintenance activities like cleaning gutters and perhaps inspecting roofs that should be undertaken alongside these more comprehensive studies. Alongside the tabulated summary of the fabric performance and/or condition, rather, and repair needs, you might also see in a condition survey a series of photographs, particularly highlighting any areas of defects, and possibly also a set of marked-up plans or elevations which are identifying where those defects have occurred.

So this is a really important document to have to hand as part of your general stewardship and management of a building, but it's also really critical as part of your decarbonisation plans for two reasons. One, that actually the condition of the fabric has a material impact on how energy efficient it is. So a damp building will transmit heat more quickly than a dry one, for example, and certainly a building with significant cracks also contributes to air leakage as well and therefore heat loss. But it also enables you to prioritise decarbonisation works in line with the immediate needs that you may have with regard to looking after your building, and we're going to talk about that in more detail at the next session. So, who might undertake a fabric condition survey?

So, often these are carried out by a building surveyor or a suitably competent architect. Generally, a surveyor should have full access to the building, both internally and externally, and it would normally take around a day to undertake, depending of course, on the scale of your building or site. You may be operating several buildings across a larger estate, in which case this is a significantly larger task, and then it will also take a few days or weeks to pull that into a report that you can review and share amongst the owner's team.

So similar to the Fabric Condition Survey, as part of a Decarbonisation Survey, your MEP engineers might also undertake a services condition survey. So this is quite similar, but it's really focusing on the existing service systems and the age and condition of them across the building. So it identifies the range of systems that you have within the site, and it confirms whether they're working effectively and as designed.

And logistically, this is carried out by a building service engineer, and similarly to a fabric Condition Survey requires full access to all of the occupied spaces, as well as plant rooms and risers, services cupboards, and roof areas, where possible. What's important here is that it really needs to be supplemented by information from the users of the building about how those systems are used and controlled.

So it's not just a visual assessment of what they could— what the consultants can see on site. It needs to be aligned with an understanding of any operational challenges that you might be facing with regard to control, and of course, how the patterns of use, how the building is actually being used, is a really important consideration too.

The MEP engineer, in conjunction with the architect, might also undertake a fabric performance assessment, and this is a really important part of the modelling of energy use across the building. So, by this we really mean an analysis of the thermal performance of the external envelope, by which we mean the roofs, the walls, the windows, and the floors. And this is in order to identify the proportion of heat loss from different parts of the building.

So, as you can imagine, single-glazed windows will lose heat more quickly than a well-insulated wall or roof, and the size of those windows will also have an effect on how much heat loss you're experiencing through that part of the fabric. So it's very important that the team builds an understanding and, and a sort of calculation of the proportion of heat loss through these different elements of the fabric in order to underpin any future modelled assessment of current performance and indeed opportunities for improvement.

So, some of you may be familiar with this term U-value. So, a U-value is a measure of the thermal performance of a particular material or component within the building, and it measures the degree to which that component, a window or a wall, prevents heat from transmitting between the inside and the outside of the building. And as you can imagine, sometimes that might be a single component, like a sheet of glazing, but more often than not, it's comprised of layers of different elements of building fabric, and that needs to be looked at sort of holistically from inside to out.

Now, there are a few ways in which U-values can be determined. They can be calculated using industry data, on the thermal transmittance of each of those material layers that make up a building component. They can also be measured on site with varying tools, such as a heat flow meter, which looks at that temperature differential across the building from inside to out and how heat is transmitting across those layers of fabric.

Now, measuring the U-values on site is a significantly more robust way of assessing the performance of specific building components, as you can imagine. It does come with a cost, and on the case studies that we undertook as part of the decarbonisation pilot, we didn't, for example, undertake measured U-value assessments. We really looked at the sort of industry standards, so we did a calculated U-value assessment of the buildings.

I think it's really worth emphasising here, though that particularly when we're talking about traditionally constructed buildings, industry data has been shown through testing to be, to be on the conservative side in terms of how traditionally constructed buildings perform. By which I mean that, actually, in practice, traditional buildings, such as solid stone, solid masonry buildings, often perform better than what the industry data would suggest. So, you know, if you have the funds to be able to undertake measurements of U-values on site, it will provide a significantly more robust understanding of how the fabric is performing.

Another way to look at the differential performance of different components of the fabric is through a thermograph. Thermographic survey. So this is also known as thermal imaging, and this uses specialised infrared cameras to detect radiation emitted by different objects, and it produces thermal images, these photographs that display those temperature variations across different surfaces. And this can be used to identify heat loss through— as you can see here, through windows are clearly losing heat more quickly than other elements of the fabric, but it can also identify defects, so problems with the insulation or other aspects of the building, and show things that you might not be aware of through the naked eye, such as air leakage, moisture ingress, and it can also be used to look at electrical or mechanical faults internally to the building.

Now, if you look carefully at the image on the right, to the right-hand side of the image, there's a circle shown as AR7. So this is actually showing a crack in the building wall which on close inspection from outside the building was just about visible, but you can see the degree to which that crack is causing really significant heat loss through the fabric, and that's for two reasons. That's one of which is that there's a little bit of air leakage coming through that crack, but the other one, and this is really critical, is that there's moisture ingress coming in through that defect in the fabric, and that's contributing to even greater heat loss.

So this kind of visual survey can be very useful for not only showing the different performance of different parts of fabric— windows versus walls versus roofs— but also to start to identify those problems in the sort of condition of the fabric that might also be contributing to heat loss.

There are two types of thermographic assessment that I want to mention here because they're quite important. They carry very different kind of cost implications for the client, but also very different results. So Type 1 is a qualitative or illustrative thermographic assessment, and this is the type that we undertook as part of our case study plans. And this provides a high-level visual interpretation of temperature patterns across different building fabric surfaces. It can be carried out by a building services engineer or an architect with an infrared camera, and as such, it's quite low-cost.

There are certain things that you need to think about when undertaking this kind of assessment, so it needs to be carried out during the heating season, and there is a certain amount of skill required in interpreting those images to make sure that they're being understood correctly.

So for example, windows can reflect the sky and give misleading results in terms of what they're telling you about the performance of the fabric, so it's quite important that the person looking at those images knows how to interpret them. The second type of thermographic assessment is known as a quantitative survey, and this is a much, much more detailed assessment that's undertaken under controlled conditions, and it enables a numerical assessment of the fabric performance. It's significantly higher cost because it needs to be carried out by specialists, highly trained certified professionals, and because it is logistically complex to undertake, so it requires very specific weather conditions and controlled internal temperatures.

So there's quite a bit of preparation that a building owner or occupier would need to do before the thermographic survey is undertaken. So the first thing to note is that there needs to be a temperature differential of at least 10°C between indoors and out, and typically that means that these kind of assessments can only really take place between late October and sort of March, April, so we're coming to the end of thermographic season at the moment.

There also— it needs to sort of take into account the, the weather conditions before and during the survey, so ideally, and this is not always possible, but ideally you would have overcast conditions in the days leading up to the survey, and that's because if you've had very, very sunny weather consistently recently, the external fabric of the building, the walls, are going to have absorbed quite a lot of that solar energy, and that may give you slightly misleading results about how that bit of the fabric is performing.

And often surveys will be undertaken in— during— after daylight hours, in order again that the kind of sunlight won't affect the results of the images. As a building owner or occupier, the other thing you need to consider and plan for is that the building needs to be consistently heated throughout to a constant internal temperature of 20 degrees for about 3 days before the survey. And that may mean that some spaces that you don't typically heat to the same level as others need to be brought up to that consistent temperature throughout.

And this is to enable, you know, a properly sort of equivalent assessment of the various rooms and spaces. You also need to take things, furniture and objects, away from the external walls before the survey is undertaken so that that doesn't affect the thermal imagery that might be taken from outside the property, and you need to leave internal doors open to sort of encourage that even heating of the space and make sure that all the windows and doors are kept closed.

So a bit like the measured U-value assessments, this gives you a significantly more robust and detailed understanding of where heat loss might be occurring through your building, but it does come with additional capital costs. And for each project, you'd need to weigh up the benefits of undertaking this more detailed survey with any kind of capital constraints that you might have in commissioning your plan. The next really important aspect to consider around heat loss is airtightness.

So we've mentioned this a few times, that leakage from your building, whether, you know, intended or unintended, is a big source of heat loss through buildings. This is also known as infiltration, and it's primarily caused through poorly sealed doors and windows, construction defects as we saw in the thermographic image earlier, parts of the building that may well have been designed to bring air out of the building such as chimneys, flues, and vents, and, and uncontrolled natural ventilation systems, but also of course the mechanical ventilation systems such as extract fans that draw air and therefore heat out of the building at higher higher rates. So just to talk a little bit about the kind of different ventilation systems we might mean here.

So mechanical ventilation systems might include extract grills and fans in bathrooms, or major building systems such as MVHR, which is mechanical ventilation with heat reclaim. Now MVHR is what you want to do in a building like this because it actually reclaims some of that heat. But often a building might, might well be equipped with extraction systems that don't have any heat reclaim, and therefore all of that energy is being lost to the atmosphere.

Openable windows can be a form of uncontrolled ventilation. In a modern building, you might have windows that actually have a sort of automated opening and closing in response to either the internal conditions or the external weather, such as rain. But if you have a manually opening window, that's only controlled to the extent that your occupants know how to manage that.

So a window left open is of course completely uncontrolled and may well be losing heat at quite considerable rates. And then of course we have the completely uncontrolled air infiltration through the fabric, such as cracks and gaps and pores in the building envelope. And new buildings are required to monitor the quality of construction to ensure that the building is as airtight as possible.

But when we are talking about existing buildings, there may well be historic defects in the construction that you may not be aware of that could be contributing to quite a bit of heat loss through, through some of those gaps. So this is important to understand because it really affects the sort of calculations about how much heat might be lost through a building and therefore how much heat is needed to keep it comfortable during the heating season.

So as part of a decarbonisation plan, your team will carry out an airtightness assessment which quantifies how leaky a building is, and this again helps to sort of model the energy needed to keep it comfortable. And as with the U-values, it can either be calculated or measured. So a calculated airtightness assessment would use benchmark data about the nature of the building combined with an assessment of the construction and geometry of the building in question. A more accurate way to understand the level of infiltration of a building is through a measurement on site. Using equipment such as a blower door test, which measures how much air escapes through the building fabric at a set pressure.

And as with U-values, this is considerably more accurate, but comes with some sort of, you know, practical considerations for implementation. So what will be involved with this is that one of the major sort of door openings will be sealed up, and as you can see in the picture to the right, and installed with a blower. All of the other windows and doors in the external envelope should be kept shut and sealed, as should all the mechanical ventilation systems and any drainage chaps in plumbing systems that might be another conduit for air. And then the building is pressurised and the rate at which the air escapes the building is measured.

Now, on the case studies that we undertook for this decarbonisation plan, we did carry out air pressure tests within the three buildings, and it was very interesting because actually they all performed much better than what the industry benchmarks would have us expect a historic building to be.

So, about 50% better in terms of air tightness. So, this was really interesting and surprising at the extent of difference between the calculated and measured data, but not so surprising to the Historic England team who commissioned this, because actually part of the reason these tests are being commissioned is to try and make that industry data more robust and more accurately reflective of what historic buildings actually perform in practice.

So, having done this range of fabric performance and airtightness assessments, the design team should now have a good understanding of where the heat loss is occurring through the building, and importantly, the proportion of heat loss through different elements of the fabric. So this will be illustrated graphically through a pie or a bar chart, such as we're seeing on the screen to the right, which is for one of the case studies that we undertook as part of this plan.

And this tells us where the kind of key risks are in terms of poor performance, but also it helps us to then target our interventions when we get into the kind of options appraisal and starting to propose opportunities for energy efficiency measures, and to importantly quantify what those measures might actually deliver in terms of energy and carbon saving opportunities.

Elizabeth Flower: Thanks, Beatie! So the next step of the process is to really bring together all of the information gathered from the site investigations that I outlined and the surveys that Beatie outlined to understand how much energy a building uses and the sources of that energy— electricity, gas, or oil— to identify how and where that energy is being used within the building. Then to establish a baseline for how that building is performing and compare that baseline to buildings of a similar type.

So the consultant team will request metered energy data from the building owner going back over 3 years, and this can usually be provided by the building's energy supplier on request fairly easily. So this metered energy data will then be tabulated to look for seasonal fluctuations or year-on-year changes. This chart shows the electricity usage of one of the case study buildings over the last 3 years, compared by month.

So the different colours are the different years of usage, and you can see that for this building, electricity usage has remained fairly stable. Except for in the winter, where there's been some reductions year on year, possibly due to the introduction of more energy-efficient lighting, which has reduced electricity consumption in the darker months.

Then this next table shows the gas consumption for the same building, and you can see that as this building has a gas heating system, there's a significant drop in consumption over the warmer summer months. When they're not switching the heating on.

So next, the combined energy data— so both electricity, gas, and any other sources that the building uses— will be looked at in different ways to understand the balance of energy use and to assess this against specific client priorities. So here we're looking at the building's energy use over the last 3 years, compared by utility cost, megawatt per hour consumption, and then also by carbon emissions.

So following this, the building services engineer will then use industry data alongside data gathered from the building surveys, including the U-value estimates and heat loss assumptions, to estimate a predicted operational baseline of energy use, which is the kind of line shown here. So this is what the building ought to be using in terms of energy.

So this graph shows a prediction of the gas consumption over a year for one of the case study buildings, and this is based on real weather data, so how hot or cold it was at certain times of the year, overlaid with typical energy use data for similar use buildings to those set temperatures. Next, this predicted baseline, now shown in a dashed line, is then compared to the actual energy use, which gives context to the building performance.

So in this case, the baseline was calculated to be relatively low due to fabric improvements that had already been carried out during a previous refurbishment project. They had some roof insulation and some secondary glazing, but what we're seeing here is that the building is using much less energy than predicted using the industry data. And the reason that was found to be behind that is that this building is really struggling with their energy bills.

So the building isn't being heated to a comfortable temperature, and staff and visitors are kind of putting up with being a bit cold. The building's metered energy use and estimated baseline are then also compared with other industry benchmarks. So benchmarks are based on buildings of a similar use, but they don't take into account the age or spatial characteristics of the building. Here, you can see the case study building highlighted in the dashed red line has lower energy use than expected in comparison to the industry benchmarks.

And as I mentioned, this is due to the fact that the building isn't being heated properly or also used to its full potential. If the building was heated effectively, we'd expect to see the metered usage to be much closer to the calculated operational baseline, which is the second column in that graph. And this gap between the predicted and the actual energy use is something that a decarbonisation plan should seek to address.

So ideally, we want to suggest any interventions that also resolve thermal comfort issues or problems with energy bills, as well as providing the energy efficiency. And this may mean that the building's energy consumption increases a little bit, in order to provide proper heating, but that additional energy comes from more renewable sources. Also, it's worth noting that heating the building properly might enable it to be used more intensively, which itself would improve its overall sustainability.

So we're not necessarily looking for a downward trajectory in energy use alone. We're also looking to improve the efficiency of the overall use of the building and its long-term resilience, as well as efficiency in energy terms. But we'll talk about this a bit more in the next webinar.

So, at the end of the information gathering and assessment process, we know how a building is used and if there are any plans for changes in the future. We'll have a good understanding of the heritage significance and architectural characteristics of the building. We understand the condition of the building fabric and building services. We understand how much energy that building uses and where that energy goes.

And in the next and final webinar of the series, we'll explain how retrofit interventions are then selected, appraised, and prioritised as part of the final decarbonisation plan. So please do come along to that. And I'll now hand back to Feimatta and Dan to take some audience questions.

Dan Miles: Hi everyone!

Feimatta Conteh: Hello, that's brilliant! I thought that was a wonderful webinar. I learned a lot through that. We don't have a huge amount of time, we've got about 10 minutes, so I think it's probably worth just saying that if we don't have time to answer all the questions in the webinar, if there's things we need to get back to, we can share the questions and the answers on the webpage with the webinar recording. We might not have time to address all of them, but actually to save me having to pick one, I'll hand over to Dan if you want to ask a question of Beattie and Elizabeth.

Dan Miles: There were a couple of questions here looking at the accreditation body, sort of competence of people undertaking these types of surveys. Would you be able to give a bit on that?

Beatie Blakemore: So this was specifically around thermographic surveys, wasn't it? Yeah, I mean, I think what we were trying to sort of emphasise today is that a lot of thermographic assessments are undertaken in the building industry, and very few are of the kind of highly regulated quantitative type that we think really brings those kind of very robust results. So there are certain instances in which you need to undertake a quantitative survey using a competent professional.

So if you are doing a project that requires BREEAM certification, you need someone who has received specific training in undertaking, preparing, undertaking, and interpreting thermographic data, and there's an international standard that that process needs to adhere to to achieve BREEAM accreditation. So I think that if you were to look at the resources and fact sheets that we have on the Historic England website, we ought to have some more information there about the specific accreditations that might be required.

Elizabeth Flower: Yeah, I was just going to add to that. We definitely have it captured in the surveys fact sheet that Beatie provided a link to, but also a specific fact sheet on professional accreditations across surveys but also other consultancies. So yeah, please do look there.

Feimatta Conteh: And I guess off the back of that one, there was a question that was in the chat which I think related to this, and I think it was about the fabric condition surveys, could that be carried out with— and I don't know this acronym from before— a CIAT-accredited conservationist? I don't know if you've come across that professional role before, because I think you've said, you know, who should carry out the building fabric condition survey, so I wonder if a conservationist might be a relevant professional.

Beatie Blakemore: Yes, yeah, and I think the key thing here is competence. Competency, as well as accreditation. So, I mean, you know, there are lots of instances of architects who aren't necessarily actually conservation architects but have a body of work behind them in undertaking heritage assessments that demonstrates their competence in looking at and understanding a heritage building.

So that's when we're talking about sort of heritage assessment, but similarly for undertaking condition surveys. I think the key thing here is around the experience of the team that you've employed and ensuring that if they're not covered by a professional accreditation, such as a sort of RICS surveyor, that they can demonstrate through their past experience that they have the skills, understanding and knowledge to know what they're doing in undertaking these surveys.

Feimatta Conteh: And here's a very non-building professional question, just kind of from me. So if you were a client in that situation and you were commissioning somebody, could you ask to see some of the previous surveys they've done so you can sort of see whether it will provide you the— okay.

Beatie Blakemore: Yes, and in, you know, securing quotes, quotations from professionals for undertaking a decarbonisation plan, you would expect them to demonstrate their past experience through case studies, possibly client references. So you would want to sort of see that evidence that your team has the requisite skills to undertake this kind of work.

Dan Miles: I'm just having a look at one of the questions. We've got probably a couple more minutes. And this is a question I— this is— sorry, Beatie Elizabeth, this is a slightly horrible question. It's one that I always think about. But when you look at these sort of types of projects, you know, if you had all the money in the world, you would undertake all the different types of surveys, but we don't.

So the question here is, do you recommend each project require to carry out all of these surveys and assessments you've mentioned, or could this depend on case-by-case basis? How would you start thinking about what is appropriate in terms of what you're trying to do in this context?

Beatie Blakemore: Yeah, it's a really good question, and it's one we sort of covered last week in the webinar, too, around tailoring the scope and complexity of the decarbonisation plan to the specific client in question. And, you know, as with all things, it often comes down to budget, doesn't it?

So, if you've got a very constrained budget, it's all very well us saying, well, look, you know, the infiltration tests and the U-value tests, they give you much, much better data to work with. But if you are a client body with really limited funds, it may well be better to do a lighter-touch survey that is still holistic in its scope and gives you a really good understanding of and brings together how the building is used, the contextual pressures, you know, calculated assessments of its energy loss and energy needs.

But you at least have a really robust document, and that can then recommend that in order to sort of drill down into the future opportunities for change, you might then commission some of these more costly and accurate surveys as part of the next step. So I think it really, as always, depends very much on the specific circumstances of, of the building.

Elizabeth Flower: But yeah, and to give a bit of context to that, on the case studies where we carried out the airtightness testing, we actually started developing the plans based on kind of industry standard data and then carried out the airtightness test retrospectively. And what we found was, although there was this big difference in the findings about how leaky the buildings were, the ultimate finding from the survey didn't change the recommendation for energy improvements across the building.

But what it would do is change the design of future ventilation systems. So like Beatie said, that survey, even if it comes further down the line can still add benefit in terms of that detailed design, but while keeping the decarbonisation plan kind of early and strategic and high-level and more cost-effective.

Feimatta Conteh: Yeah, I know when we've done presentations about this before, Dan, you flagged that around kind of airtightness testing in terms of, you know, and Elizabeth put it really well there in terms of the design of future installations. So there's questions come in which made me go, oh man, we missed a trick in the project, which is what's the carbon 'What is the carbon footprint of carrying out a decarbonisation assessment?' We could have been measuring it with the project— sorry, we didn't— but any comments on that? Because I think it's quite an interesting question.

Beatie Blakemore: So I assume that this is around the actual activity, the sort of services undertaken.

Feimatta Conteh: Yeah, so I guess if we were doing it, we would have logged all the travel that happened in the project, all the subsistence, you know, in my world of doing carbon footprinting of projects and stuff. So yeah, we didn't do it in this project, but have we got any ideas, or is there any work being done in that?

Beatie Blakemore: Well, you know, it's interesting. It sort of comes back to this question of sort of when is measuring really valuable to decision-making. And yes, in an ideal world, we'd all have a very precise understanding of the carbon footprint of all our activities, particularly if you can use it to change behaviour. And drive change.

But I think my sort of off-the-top-of-my-head answer to this question is that I don't think that would necessarily materially change the core purpose of this particular piece of work, and therefore it's probably not, not the priority. If you're— if you've got limited funds and you want to sort of place your focus where it can be most valuable, you're probably better off really doing the work on the building. In terms of building that understanding of the building and setting out the kind of long-term decarbonisation path for that.

Dan Miles: No, I think it's funny, when we chose that, we selected the different buildings, and even as part of the project, we were talking about, you know, some of the case studies being public transport and sort of all that side of things, to minimise sort of travel costs and travel carbon. Probably one last thing, and I don't think it's one we can answer, but it's a really interesting question, and it's something that we are still thinking about and trying to do, and it's a difficult one, and it is looking at the cost of completing these types of surveys. And I know that we spoke to you about this at the beginning, and Feimatta and I were going, just give us a rough estimate, these type of costs, but it's not as simple as that.

Feimatta Conteh: Yeah, the question there is, is there a rule of thumb, a way of predicting what budget a building owner should set for this work, there's a question saying, is it interesting to know a rough cost for different building sizes? And I guess, Dan, the question to us, interesting to know what the cost of completing all the surveys on the case studies were, but I guess because it was a public tender, we could share information about the cost of the overall project. But we can put that in the answers afterwards. But if Beattie and Elizabeth have anything on the $64 million question, how much money should people put aside for this.

Elizabeth Flower: So with the condition survey, as you said, we did explore it within the pilot study, and we went to the surveyor and asked this exact question. And the conclusion really was that you can't cost a condition survey purely based on area. It's much more complex than that. It's the time that it takes to visit the site, the complexity of the site, difficulties with access. There's lots of other factors that go into that cost than a kind of per square metre rate. It also will vary based on kind of geographic region within the UK. So there's so many factors that go into it. To give accurate kind of costing benchmarks, it just would be too difficult. So that's why we didn't do it within this study.

Dan Miles: But it's a really valid point. I still think there's some sort of matrix out there that you can put in number of windows, times area times how many staircases you need to go up and how far away from a train station. But we'll think about that for another time.

Elizabeth Flower: I think with most things, it, you know, comes down to getting a number of quotes that you can compare and contrast yourself to make sure you get the cost-effective price.

Feimatta Conteh: And I think what's something that this project supports, you know, for clients out there, because Dan, we always had this phrase, isn't it, of supporting people to become confident clients. So people are looking at the fact sheets and the templates and seeing what should be in the different surveys and things.

When people are getting quotes, they can kind of use that as a reference to see, because one of my questions— I know we haven't really time for it— is like, yeah, how would a client know that the survey has been done properly and has covered everything that's needed? But maybe we can answer that in writing after this because I noticed we're just past the hour.