Lessons Learnt from Building Performance Evaluation of Retrofit Projects: Session 1, Overview

00:00:00:07 - 00:00:25:09

Speaker 1

And good afternoon, everybody, and thank you for joining us today. I'm Hannah Reynolds, architect for a historic building retrofit at Historic England. And I'll be chairing today's webinar. So to ensure energy efficiency and carbon objectives are delivered without unintended consequences. We must understand what truly successful retrofit looks like. For this, it's essential that the success of our interventions be judged by their performance over time.

00:00:26:05 - 00:01:03:03

Speaker 1

The BPE Retrofit Revisit Project led by CIBSE and Studio PDP, evaluated a range of domestic retrofit projects several years after completion to assess outcomes. Gather lessons and help us continuously improve retrofit practice. As part of this project, Historic England funded three discrete packages of additional detailed research by way of onsite testing carried out by specialist consultants. These packages included testing and evaluation of air tightness testing, fabric testing of thermal properties and moisture risk assessment and analysis.

00:01:03:10 - 00:01:27:03

Speaker 1

Historic England also sat on the project steering group. In today's seminar, which will be the first of two. The project leads Julie Godefroy and Marion Baeli will present an overview of the project and its initial findings. The second webinar, which will take place on the 29th of August, will present detailed project findings on evaluation methods for moisture risk assessment and analysis.

00:01:27:11 - 00:01:51:15

Speaker 1

We hope you'll be able to join us for that session. So a little about our speakers. Julie is co-lead for the Retrofit Revisit project. She is a chartered engineer and works as head of Net zero Policy for CIBSE, where she leads the work on climate action, including net zero carbon building standards, policy works and collaboration with other institutions.

00:01:52:06 - 00:02:19:07

Speaker 1

She has been involved from early master planning stages to post occupancy evaluation and has worked in most sectors with a particular interest in housing and heritage buildings. Marion is an architect and author who places her passion for low energy design at the centre of her work. Part of the Westminster Design Panel and UK Passive House Trust Board and former NLA expert panel member.

00:02:19:13 - 00:02:46:15

Speaker 1

She approaches sustainability with a pioneering attitude. Her book, Residential Retrofits 20 case studies followed the delivery of the award winning Princedale Road Project, which was the first certified passive house retrofit in the UK. And this work leads on from that study. I will now hand over to Julie and Marion to give today's presentation.

00:02:49:07 - 00:03:01:03

Speaker 2

Thank you, Hannah, and welcome and thank you to all of you for attending. Can you hear me? Alison? Yes. And that's someone. Yes.

00:03:01:07 - 00:03:02:16

Speaker 3

We can hear you loud and clear.

00:03:03:17 - 00:03:26:16

Speaker 2

Great. So this is really an overview and you will see that some of the more detailed findings. We're still working on a little bit, but there is plenty to unpack. Can hopefully you'll find something of interest. I'll hand over to Marion to present the project, but we will go back and forth and we look forward to your questions in the second half.

00:03:28:06 - 00:04:05:01

Speaker 3

Thank you, Julie. I just wanted to clarify also the title of Back to Retrofit for the Future was a a an initiative from the Technology Strategy Board, a government body at the time which was trying to ascertain what was the best way to retrofit property in the future. But the future is now and so we need to reassess what we thought the future was going to be and whether this is suitable for now and and for a further retrofit.

00:04:05:01 - 00:04:43:00

Speaker 3

So on the whole UK housing stock. So the reports from Retrofit for the future in 2012 looked at one hundred project aiming for an 80% carbon reduction in operation. On the back of that fantastic R&D initiative. I took 20 of these houses and did a further in-depth study looking at their construction, detailing the specification, as well as two years of post occupancy evaluation.

00:04:43:11 - 00:05:16:13

Speaker 3

And I wrote this book, Residential Retrofit 20 Case Studies. As Hannah has mentioned. The objectives for these revisit roughly ten years later, ten years after the original retrofit has been delivered, is to understand what has stood the test of time is is there any lessons that we need to extract from this experience and review for the retrofit as of now?

00:05:17:00 - 00:05:46:01

Speaker 3

Is there anything that has changed? Is there any failures of successes that we need to take forward? The particular interest of this building performance evaluation exercise focuses on moisture, insulation options and moisture and combustability but also degradation of original solutions such as air tightness. And that is just a few aspects and we'll go into further details on on the other aspects.

00:05:46:11 - 00:06:20:08

Speaker 3

We also looked as an objective at the building performance evaluation techniques and whether they were the most appropriate and the most practical. What can be learned in a relatively short and non-intrusive manner? Where are most more specific or detailed techniques useful? And how can some techniques be used and developed further? So we'll go through that throughout the presentation.

00:06:20:15 - 00:07:00:05

Speaker 3

The project needs are, as Hannah mentioned, CIBSE and Studio PDP is a coordinated that's an R&D exercise with the financial support of UK. R I Innovate UK and Historic England. There's been also a huge amount of in-kind contribution from many others and we'd like to thank you to everybody for their passionate support in this exercise. The project partners are the be building performance evaluation evaluators on the left hand side.

00:07:00:11 - 00:07:31:14

Speaker 3

So roughly one evaluator per property. We also have the BPE testing and experts who looked at the air tightness, the performance measurements on site of of within each of the properties. And we also have a very generous steering group who've dedicated some of their times to look at our reports and comment on the findings from the entire team.

00:07:32:00 - 00:07:44:09

Speaker 3

So thank you to everybody involved. Now I'm going to hand over to Julie, who is going to talk to you about the core scope and the detail scope that we chose to carry out on these properties.

00:07:45:08 - 00:08:14:09

Speaker 2

So on the properties, essentially, we applied the same building performance evaluation package, which we called the core one, and then we selected a few for more detailed tests. In terms of the core scope, we really wanted something that was comprehensive enough so that we didn't just look at, for example, energy use people's feedback or moisture insulation, but really gave us a rounded view of building performance.

00:08:14:09 - 00:08:42:05

Speaker 2

So we applied a user surveys from Soap. It's similar to the BUS, the building U study survey, but it's got additional questions. So it's it complies with the British standards 4101. We did an energy audit based on a year of energy bills and one months of more detailed monitoring. In that same month, we also did monitoring of temperature, relative humidity and carbon dioxide.

00:08:42:05 - 00:09:09:02

Speaker 2

To give us a view of the internal environment. And through this, we applied the Build Test Solutions method to obtain a SmartHTC, smart heat transfer coefficient and a mould risk indicator largely based on moisture and temperatures. In addition, we did airtightness testing on all homes using both the blowerdoor test and the pulse flow pressure test. So that was done on all of them.

00:09:09:09 - 00:09:53:03

Speaker 2

In addition, on some of the homes that will come through. There was an independent witness of the airtightness test, as Hannah said. We also looked at fabric performance in more detail, both in terms of thermal performance. So U-Value measurements using plate U-VALUE and built air solution heat 3D measurement some thermal images, some indoor independent experts providing advice and a whole moisture package which combined physical measurements as well as WUFI modelling and we'll talk to you a little bit about it today, but the next webinar will tell you much more.

00:09:53:03 - 00:10:15:15

Speaker 2

The way we selected the case studies. As Marion said, there were many from Retrofit for the future and we were also aware of other projects that were outside of Retrofit for the Future, which may qualify. Essentially, we wanted retrofit that had happened more or less ten years ago so that if there were issues that were to develop, probably they were already identifiable.

00:10:17:04 - 00:10:43:11

Speaker 2

So it's the case for all our case studies except one which is a phased retrofit, which did start more or less ten years ago. We also wanted them to be best. So our example of practice at the time, we didn't want to review projects that everybody knew were probably suboptimal. So window replacement are very elemental approach and we did want homes that had been evaluated it at the time of the retrofit.

00:10:43:11 - 00:11:14:00

Speaker 2

So but we had a comparator. Then, obviously we needed availability of data, residents engagement and in terms of the home characteristics, we wanted a good mix, i.e. pre and post 1919 internal and external insulation approaches and then other interesting characteristics such as the type of insulation applied. And that's an overview and Marion can tell you a bit more about these case studies.

00:11:14:10 - 00:11:41:01

Speaker 3

Yes. So this is the list of the case studies that we are looking at into in this R&D project. In green on the left hand side, you will see the name of the project that were in the original book that I published ten years ago, and they were part of the retrofit for the future program. So there is extensive data from the time because they were all monitored for two years.

00:11:41:01 - 00:12:07:17

Speaker 3

So we have great data and you have also in white some other projects as Julie mentioned, some are we have one listed building and we have a step by step and we also have One, Wilmcote House which is a multi tenancy, large scale apartment block. It was important for us to also look at this, this archetype of building.

00:12:08:09 - 00:12:38:12

Speaker 3

You could see the pre 1919 and post 1919 project also and the reasons why we we chose these particular projects, whether there is a good mix of internal wall insulation, external wall insulation, etc.. So we try to be as representative as the UK housing stock, as possible and you can see here the illustration of the the front facade of these properties.

00:12:38:12 - 00:13:07:10

Speaker 3

So you can see on the bottom right hand side One, Wilmcote House with the multi tenancy block which is has been very interesting to to look at and then the mix of various ages and strategies, internal wall insulation or external or 1960s Victorian or Georgian. So good mix of property types. The findings Hannah mentioned at the very beginning this two sessions.

00:13:07:10 - 00:13:49:04

Speaker 3

Today's session is on fabric performance and testing technique and the second one will be on the 29th of August by Valentina Marincioni from the UK Centre of Moisture in Buildings and Spyros Efthymiopoulos from the UCL as a doctoral researcher. So join us also for the 29th of August. Now to the key findings that of the of this of this research. In air tightness you'll see on the right hand side graph the grey bars are the air tightness results post retrofit.

00:13:49:04 - 00:14:33:12

Speaker 3

So before any retrofit measures were implemented. In purple, the air tightness achieved post retrofit at that time. So roughly ten years ago and in green, the air tightness results that we have observed this year in 2023. So you could see the slight variation in some of the of the properties, which is interesting to see. In eight homes, the average air tightness has worsened by about a value of one metre cubed per hour per metre squared at 50 Pascale There is a slight increase in two projects, which is quite interesting.

00:14:34:08 - 00:15:03:09

Speaker 3

It's always to be taken with a pinch of salt because it might be the result of a slightly different kind of measurements or equipment or testing methods, methodology and another one was also the result of testing another property within the Wilmcote House. So we, we, we're not comparing exactly like for like even though the apartments are absolutely identical.

00:15:04:11 - 00:15:29:02

Speaker 3

But overall, you can see that all the homes perform very well against the the average housing stock and against the pre retrofit. So it's not unusual, as you might know, to have an air tightness of roughly 15 for, for example, a Victorian house that's not being retrofitted. And the benchmark for newbuild housing you might know is around three.

00:15:29:02 - 00:16:07:00

Speaker 3

So you could see that these retrofits are still well below these values. So this is really positive even ten years on. On air tightness techniques. So there's been two techniques used in this R&D. One is the Blower Door test, which is the most commonly known where you fit a fan within the entrance door. And the other one, which is more recent, which is called Pulse which has also been used to enable this R&D to learn some lessons of technologies and equipment that are best suited for these BPE exercise.

00:16:07:00 - 00:16:33:16

Speaker 3

And you could see that the two measurements up relatively close to one another. So that's quite encouraging to see that the Pulse is of interest. So we had the feedback from some of the evaluators that it was faster to implement in some cases, but not all of them. The only, I say, commentary that we need to make on the pulse technique as well.

00:16:33:16 - 00:17:01:09

Speaker 3

It's very quick and easy to take measurements. It is does not offer the options of finding the leaks, such as walking around with a smoke gun and see where the smoke goes through the fabric. So it's worth noting that and particular restriction with the Pulse testing, but overall quite a close, close alignment. And Julie is going to talk to you about the energy use results.

00:17:02:09 - 00:17:26:10

Speaker 2

Thank you. So similarly to the airtightness graph here, you can see for most of the homes, the energy use before the original retrofit and the retrofit revisit, there's one home where we are still interrogating the data but very broadly speaking, you can see that in many cases energy use is very similar to what it was in the original retrofit.

00:17:26:10 - 00:18:03:05

Speaker 2

So there's been no marked increase. There's a couple where it is different. And again, we're trying to understand the causes a little bit more. Sometimes it's different occupancy patterns, people working from home, much more etc. You can also see lots of question marks and that's that's endemic in the industry. There are some issues with metering of onsite systems, which means that in many of these homes which do have renewables, we do not actually know the total use by the building because either BPE export is not measured.

00:18:03:10 - 00:18:28:14

Speaker 2

So we don't know how much of the BPE output is used by the building and how much isn't or there's just no metering at all. And that's often the case with solar thermal. So some question marks, but at least comparable data with pre with the original retrofit. And largely speaking, you can see that the homes now still perform really quite well compared to the national average.

00:18:28:14 - 00:19:09:15

Speaker 2

Many of them even compare very well against the LETI recommended targets and there's no huge increase across the board. So the savings in energy use are holding well. We have been limited in the analysis of the thermal part of energy, which obviously is a lot of what all these retrofit measures are trying to address. We hope to have a little bit more detail in the final report, but there is no doubt that there are restrictions, again, as in many homes, to identify specifically what is the heating part of energy use. In order to do that

00:19:09:15 - 00:19:34:09

Speaker 2

obviously, we've looked at airtightness, as Marion has said, but we also applies the build test solutions to SmartHTC measure. So what is it essentially it's it's a new method relying on smart meter data and temperature data are monitored over at least 12 days. And essentially it gives you an HTC similarly to what a co-heating test would do.

00:19:34:09 - 00:19:59:14

Speaker 2

The co-heating test, as we know, are quite expensive and disruptive. Residents have to be out of their homes, etc.. So we're very interested in this as a measure of thermal performance in many cases we could compare with a design HTC which is provided by SAP or PHPP and in about half of the homes there's very good agreement with the design between the design HTC and the SmartHTC.

00:19:59:14 - 00:20:37:04

Speaker 2

value measured. In three of the homes is a large difference. And at the moment we're still analyzing whether that comes from actual physical difference or degradation in the installation. For example, the message itself. An HTC is quite global so we have to unpick all the components. But again, the homes as a sample perform very well against the average stocks so the built test solution ratings that you can see here nine of the homes are either rated good or excellent.

00:20:37:04 - 00:20:39:07

Speaker 2

Julie So he could I just interrupt you a second?

00:20:39:13 - 00:20:40:15

Speaker 3

A couple of our.

00:20:41:17 - 00:20:42:16

Speaker 2

Delegates are asking.

00:20:42:16 - 00:20:43:08

Speaker 3

About.

00:20:43:11 - 00:20:45:17

Speaker 2

Yes. Sorry!

00:20:46:13 - 00:20:57:07

Speaker 3

Some about Alexa, just asking about some of the initials that you're using, some of the acronyms, and maybe could explain some of those as you go. We've just been asked about HTC and HLP. Sorry to interrupt you, Sorry.

00:20:57:07 - 00:21:36:03

Speaker 2

No, of course. So HTC, sorry about this. I really don't like it when people do that. So I'm sorry I did HTC Heat Transfer coefficient, HLP is the heat loss parameter Essentially it's normalized to the floor area, the HLP compared back to the HTC. We also thanks to Historic England funding carried out U-VALUE measurements both using the sort of traditional plate u-value measurement as well as a new built a solution method called Heat 3D and that's based on essentially infrared radiation.

00:21:36:03 - 00:22:14:15

Speaker 2

So like thermal imaging across the wall, you can see the intersection here. And again, the interest in this method is that it's cheaper, quicker, less disruptive than the traditional plate u-value measurement. I have to say here that at the moment we could not get that many comparative points between plate U-VALUES and heat 3D measurements and the uncertainty margin in Heat 3D is plus or minus point one watts per metre square per Kelvin, which when we're talking about really well insulated walls like this means that it's very difficult to reach a conclusion on the comparison.

00:22:14:15 - 00:22:45:01

Speaker 2

So I think this one, even if we do a bit more analysis, is going to remain as a ‘for further research’ theme in our report. On temperature. So we measured temperature over at least a month in most rooms in all of the homes. In one home, there was a problem with the sensor installation, but in all of the others, essentially there's a range across the home of temperature between -18 and 21 degrees as an average temperature.

00:22:45:15 - 00:23:15:08

Speaker 2

And you can see here the energy use across the homes and the temperature measured. We could potentially see that there's a general trend that the homes that were a little bit cooler. So in the 18, 19 degree range seemed to consume a bit less. And those that were a bit heated, a bit more consume a bit more. The sample is so small that there's always going to be quite a bit of noise with them in the data.

00:23:15:08 - 00:23:40:10

Speaker 2

So I think there's a little bit of a trend, but not necessarily that strong. We have to note that most residents rated the homes very comfortable in the winter. It wasn't the case in the summer. We didn't do any monitoring, but it is one of the few things where residents did say that sometimes homes are not comfortable. And to finish on the indoor environment.

00:23:41:05 - 00:24:16:14

Speaker 2

We also looked at relative humidity as well as carbon dioxide and ambient mould. So much more in the field of air quality for health. They were quite good relative humidity levels in eight of the nine homes. So very much within the recommended bands and the analysis of mould risk associated with RH and temperatures. RH, relative humidity, from BTS is that generally speaking, the mould risk from these parameters was quite low in one home rise

00:24:16:14 - 00:24:48:10

Speaker 2

of humidity was high and that is attributed to insufficient ventilation. Similarly, the CO2 levels are pretty good in most of the homes. Separately, UCL did some mould spore, sampling in five homes. And that's quite interesting because even in homes that had been rated quite well for temperature and relative humidity, some of them were identified as having relatively high fungal or allergen counts.

00:24:48:10 - 00:25:35:07

Speaker 2

And I'll tell you a bit more about this before the webinar in two weeks by Valentina and Spyros, because that leads me to the bigger investigation on moisture. So I've mentioned so far ambient moisture, but we also looked at fabric degradation. Four of the homes were selected for this kind of tests, some of them in air brick, some of them in joists or in features such as and junctions between walls and floors where retrospectively going back to the retrofit ten years ago, people thought maybe actually this is a risky detail and we would want to see how this is performing now as well as details where we saw insulation may have degraded.

00:25:35:07 - 00:26:04:07

Speaker 2

It's very interesting for us to look at all these measures all together because they have to, although they each tell us slightly overlapping things and they look at slightly different parameters. But to summarize before the longer webinar by Valentina, the temperature and RH monitoring and the associated built air solution mould risk score is just capture one type of risk which is surface condensation and mould from internal conditions.

00:26:04:14 - 00:26:42:05

Speaker 2

And it seems to be quite useful for ongoing monitoring to see whether a problem might develop by comparison, the mold analysis, it's really about the overall outcome, whereas they may be created from and it can capture other risks such as fabric degradation or insufficient condensation, which you wouldn't get from your internal RH measurements. We also asked residents whether they had observed mould, but obviously that is very, very partial in terms of what you capture and the fabric moisture content on the right.

00:26:42:05 - 00:27:18:10

Speaker 2

And again, that is an outcome but specifically on fabric. So the type of technique that you want to apply all depends on whether you're doing a diagnostic, ongoing monitoring, whether you know there's already a problem or not. Finally, on maintenance, we do want to flag up that this is a recurring trend across most of the case studies. Generally speaking, we found that many homes hadn't had much attention to maintenance of the envelope and there were several issues, for example, with cement pointing.

00:27:19:04 - 00:27:47:12

Speaker 2

But none of them really were specifically related to the retrofit is just general maintenance of the homes that need to be addressed. Whether it’s retrofitted or not. As expected, we also found some issues on systems, especially because many of these homes have quite complex and innovative systems. Solar thermal and very one of the arrangements at the time, on the other hand, mechanical ventilation with heat recovery.

00:27:47:12 - 00:28:03:02

Speaker 2

So MVHR has held it very well in most of the homes where it was installed. And that's quite remarkable because at this time MVHR was quite new. I'll hand back to Marion.

00:28:03:14 - 00:28:30:12

Speaker 3

So, on user feedback. So this is the SOAP survey on our homes. SOAP is a questionnaire that is handed out to the occupants, which is quite expensive but is able and is is tailored to retrofit in particular and is able to really get some, some fantastic feedback from the occupants. So about nine houses out of ten were very positive.

00:28:30:12 - 00:29:07:05

Speaker 3

One was rated poor. Not all of the reasons why some of the criteria is were sort of ranked not very highly is not always related to retrofit measures, but it could also be about the spaces the common parts, etc. depends on various property configurations. But overall there was a great or excellent satisfaction in particular with the comfort in winter time and the low energy bills.

00:29:07:05 - 00:29:41:15

Speaker 3

There is two feedback which is quite key, which is about the level of controls of the system from the occupants. And there's been quite a few issues with controls that were just too difficult to operate and this is really a big challenge for an MEP manufacturers is how to make MEP system controls much more intuitive. Some of the properties have resolved this or tried to have the occupants manage their systems with a building user guide as a poster.

00:29:42:12 - 00:30:18:13

Speaker 3

And just definitely a good, a good lesson to try to roll out in other properties. The other criticism was some issues with summer comfort and particularly in the top levels of some of the properties and in on moisture and fabric degradation. As Julie mentioned, maintenance is really an absolute number one measure to to look after throughout the life of the building.

00:30:18:13 - 00:30:58:17

Speaker 3

And it's fundamental for retrofits and building fabric to be maintained in good condition, of course, but also not affects the energy performance of the building. So in this property that you see on the screen, there was a leaky gutter for many years. And because the property is super insulated in this particular case with sheep's wool internally, the brickwork is therefore positioned in the coldest part, exposed to a cold environment in winter and is not getting warmed up by the movement of air from inside to outside because the insulation is preventing the heat to reach the brickwork.

00:30:58:17 - 00:31:33:10

Speaker 3

So having a cement cement pointing instead of lime pointing the brick had no space to expand under extreme moisture in the winter and has it broken down, as you could see on the photographs. So the maintenance of simple aspects such as gutters is really important. There's been a few more issues with fabric on another project. This one is about phenolic insulation boards which have bowed and compressed over time.

00:31:33:17 - 00:31:56:02

Speaker 3

And this has happened in that property which has used these phenolic insulation all around on the outside of the building fabric. So this is something also that we need to be conscious of. It doesn't mean that the house no longer performs, but it just means that the material might not be as long lasting as we might have expected.

00:31:56:07 - 00:32:19:14

Speaker 3

It's worth saying that the in this particular case, the insulation has been exposed due to the remedial work for a failing balcony above. So any time that you can do a little bit of destructive access in the building, fabric can open up some lessons that we might not otherwise be able to to see. So it's a great moment to learn.

00:32:21:11 - 00:32:25:07

Speaker 3

And now we're going to go through the summaries with Julie.

00:32:26:13 - 00:32:47:08

Speaker 2

Hello. And it will be a whistle stop because as you can see, there's really quite a lot of material and we don't want to repeat everything. We also want a lot of time for Q&A, but looking back at the scope that we applied, what did we learn? So the SOAP retrofit, I see someone has asked about the acronym.

00:32:47:08 - 00:32:58:06

Speaker 2

It is actually an acronym which I just forgot because no one uses it. It's developed. SOAP is the name of the company who has developed it so that.

00:32:58:07 - 00:33:00:01

Speaker 3

Some of the parts of it.

00:33:01:06 - 00:33:35:13

Speaker 2

Yes, some of all parts. Thank you. So all findings on this is is very easy to apply. It seems quite well suited. It's got an online platform, though, and some residents did struggle with that. So paper surveys are always still useful as a backup. But apart from that is very similar to the Building Use Study survey, except that it's British standard compliant and the use of energy use of energy bills over here, we do very much think that it is a useful data, even if it's simplified.

00:33:35:13 - 00:34:09:02

Speaker 2

However, in some cases and it's quite striking in many homes actually the evaluators did spend quite a lot of time trying to get the data from the residents and even from the suppliers. We did not always get it in full, even on properties that had smart meters. This was compounded, as I've said, in cases where there were on onsite renewables, where very often it's difficult to get a full picture and the lack of heat monitoring of some sort.

00:34:10:17 - 00:34:40:06

Speaker 2

On the other hand, the approach to do more focused period of one month, that was very useful. It allowed us to get at least some manual readings and on the internal environments that was very useful to capture a lot of the trends and verify them against residents feedback. Airtightness testing, as Marion has said to the results across both methods were quite consistent with what industry has already said about these methods.

00:34:41:01 - 00:35:08:06

Speaker 2

Smart HTC seems promising, even if we do need a bit more analysis on the sample is relatively quite small and the mould risk indicator based on the one months of monitoring, again, that seems promising but probably more for ongoing monitoring and be aware that it's only capture a some risk factor. You could still fair well against it, but have other sources that contribute mould in the environment.

00:35:09:09 - 00:35:39:02

Speaker 2

In terms of the detailed techniques, as I've said on the U-Value side, it's a bit inconclusive at the moment. Potentially, we could have done a bit more thermal imaging on some of the construction details that we considered risky and on moisture. Valentina and Spyros will tell you much more, but roughly speaking, the methods seem to be quite useful at providing some additional detail compared to the general performance.

00:35:39:10 - 00:36:12:15

Speaker 2

findings, but Valentina will tell you more in two weeks when you attend. I've just talked about techniques, but in overall performance, have the retrofits passed the test of time? We think they really have. Certainly on the fabric side, it's been very effective. Still an air tightness and thermal performance, some issues with services as we could expect ten years on, but maybe less than personally I expected, considering many of them were so innovative.

00:36:12:15 - 00:36:40:02

Speaker 2

Comfort is very good across many of the home with that slight caveat on summer comfort in some of them and energy largely speaking, they're still very well performing homes and quite similar to the original retrofit. They are important notes there is that it wouldn't be the case in all retrofits. These were considered best practice retrofits. They were well funded.

00:36:40:10 - 00:37:10:00

Speaker 2

There was a lot of attention to the design, to the overall installation strategy, to the construction. So this is not your average retrofit. And we do expect that this in part or in large part why they're still performing well. On the other hand, we also want to say that we did not just within these best practices retrofits. We did select homes where in some cases we thought there may be a problem and we want to understand more.

00:37:10:00 - 00:37:32:11

Speaker 2

This is something we did ten years ago that people are now a little bit worried about, and that's especially the case in the moisture investigation. So the fact we haven't found problems is still positive because in some cases we were not sure whether we would find them. So thank you very much from all of us and to Historic England for spending of this.