Lessons Learnt from Building Performance Evaluation of Retrofit Projects: Session 2, Moisture Risk Assessment and Analysis

00:00:00:03 - 00:00:35:16

Speaker 1

This project, Historic England has funded three discrete packages of additional detailed research by way of onsite testing, which were carried out by specialist consultants. These included the testing and evaluation of air tightness testing methods, fabric testing of thermal properties and moisture and risk assessment and analysis. Having received an overview of the project and its initial findings in the first of these webinars a few weeks ago today, Valentina and Spyros are here to present detailed project findings on the evaluation methods for moisture risk assessment and analysis.

00:00:37:01 - 00:01:06:05

Speaker 1

So, a little about our speakers. Dr. Valentina Marincioni is technical director at the UK Centre for Moisture in Buildings and lecturer in Building physics at the University College of London. She is an expert in building physics and moisture in buildings with particular focus on internal wall insulation. Her research focuses on the integration of building physics, predictive modelling and monitoring for the reduction of moisture related issues in building.

00:01:07:03 - 00:01:45:13

Speaker 1

Her work includes the development of frameworks and tools for moisture, safe construction, the assessment of energy and hydrothermal, performance of traditional and historic buildings, and the development of innovative building fabric solutions. Spyros Efthymiopoulos is the doctoral researcher at the Department of Civil, Environmental and Geometric Engineering at UCL. He is a graduate of environmental design and engineering. Spyros is involved in the research related to indoor mould growth testing and benchmarking. As his research experience on the topic of indoor air quality,

00:01:46:08 - 00:02:08:13

Speaker 1

he's recently become a member of the Inter Disciplinary Research Team for UCL, which focuses on the holistic low carbon retrofit of historic buildings. His Ph.D. thesis is looking at benchmarking indoor mould levels for the UK building stock. So without further ado, I will hand over to Valentina and Spyros for today's webinar.

00:02:09:17 - 00:02:58:04

Speaker 2

Thank you, Hannah. So yes, I'm Valentina Marincioni. Very good to be here. Thank you for the introduction. That's it's great to be here and present the lessons learned from the building performance evaluation of retrofit projects, particularly. Today we talk about moisture so moisture risk assessment and analysis. The team today, Spyros and I, but the team has been a larger team composed by made of Toby Cambray from Greenguage Building Energy Consultants and Kostantinos Megagiannis from QODA.

00:02:58:11 - 00:03:03:08

Speaker 2

So it was great to have this team working around this.

00:03:06:14 - 00:03:27:13

Speaker 2

So briefly about the UK Centre for Moisture in Buildings. Our aim is the development of a moisture safe built environment in the UK. We work in a rigorous and transparent manner, together with partners from academia, government, industry and the public to substantially improve the way moisture risk is understood and managed in the UK.

00:03:32:16 - 00:04:09:01

Speaker 2

Why moisture balance? We need moisture balance because we need durability and health of occupants. We know that overall 27% of households reported the presence of some damp or mould patches in the walls or ceilings in their home. And this comes from the follow up survey commissioned by Baz in 2021. This is a lot larger than the 4% that is claimed in as the outcome of the English Housing Survey.

00:04:09:09 - 00:04:34:01

Speaker 2

And this is a lot more what we find in our work in the UKCMB, but also at UCL, as I'm also an academic, as Hannah was mentioning and a lot of our research is around mould and moisture in buildings. So the result of that is that the NHS is paying £1.4 billion a year to treat those people who are affected by poor housing.

00:04:34:06 - 00:04:56:06

Speaker 2

And this is only related to first year treatment costs and not counting for the follow up costs. So enough to after one year. So this is a serious problem that we need to solve. Particularly, we are aware that in in historic buildings there is more awareness of moisture risk. So it's a great place to be and to start from this analysis.

00:04:56:15 - 00:05:28:15

Speaker 2

So talking about potential causes of moisture imbalance are moisture excess because of course we can also have an environment that is too dry and moisture excess can be found as a consequence indoors. As you can see on the left hand side, at the surface, as you can see here or within the fabric so if there is moisture excess within the fabric that can show also at the surface level.

00:05:31:06 - 00:06:26:12

Speaker 2

So what we need is an integrated approach. The way we have done, we have to tackle this issue in this exciting project was to look at four main aspects of moisture analysis and bring them together. And today we'll talk about two of the aspects, particularly the fungal testing and hygrothermal simulations. But to be able to have a full picture of what we and what we were looking at in our in the buildings that we tested, we also carried out building inspections and reports from occupants using a number of techniques, fungal testing, as I mentioned, using quantification, fungal, biomass, species identification both for indoor and outdoor surfaces, but also in situ monitoring of temperature and humidity, particularly

00:06:26:12 - 00:06:57:08

Speaker 2

focusing on critical areas such as the loft and the interfaces. So the last part that we consider is hygrothermal simulations. They can help with the design, but they can also help unpicking what are the factors leading to moisture damage? So we've used the simulations in two occasions, so we've used one dimension of simulation for the design and two dimensional simulations for combined with the survey in the assessment.

00:06:59:10 - 00:07:27:01

Speaker 2

So the first part of the work, as I mentioned, was the detailed analysis of five retrofitted buildings within the project led by CIBSE and Studio PDP, funded by Historic England. And our focus was on the activity sampling, on fungal testing and then the hygrothermal simulation. I’ll leave the floor to Spyros Efthymiopoulos to talk about the fungal testing and I’ll see you soon.

00:07:27:16 - 00:08:05:04

Speaker 3

Hi, it's very nice to meet you all. Thanks. Very nice to be here. So about the fungal testing as we all know, there are some adverse health issues that are the outcomes of indoor fungal growth. And the World Health Organization has reported an increasing trend in the occurrence of dampness and fungi. And because there are these health issues and the damage to the building fabric, it has increasingly been reported as an issue in the news as well.

00:08:05:04 - 00:09:14:14

Speaker 3

We have the recent unfortunate death of Awaab Ishak, a toddler that lost his life due to unfortunately mould growth in the in the house that he was living. But also, we have many other reports about issues from mould growth problems regarding damages, asthma occurrence and many different health issues. So in order to tackle and understand the extent and the history of mould in the property we have developed over the years, a protocol, a sampling protocol that involves the air sampling and surface that involves air sampling and surface sampling and with air sampling we are trying to quantify and identify the species, the fungal species in a room to understand the extent of the issue

00:09:14:16 - 00:09:53:14

Speaker 3

with the quantification and also understand the history and the risks that might come from the fungal growth, from the identification of the species. And we have the surface sampling, which relies essentially on species identification to understand whether visible mould on surfaces are active, because sometimes we may see mould on surfaces, but this might not be active. It might have been taken over by other species like bacteria.

00:09:54:01 - 00:10:43:04

Speaker 3

And also, we want to see if those visible signs of mould affect the background contamination levels and also the results of the air sampling which can show the background contamination levels. So for that purpose, we've developed a protocol, a rigorous, reproducible and robust protocol to assess the fungal growth in different houses. And regardless of the typology of the house and the furniture and the levels of dust and all these biases that can affect the sampling we have developed a methodology that relies on activation, which means we are trying to re suspend particles from places that are accessible, interior surfaces that are accessible.

00:10:43:13 - 00:11:38:01

Speaker 3

And so essentially what we are doing is we re suspend as many particles as possible from the easily accessible interior surfaces, and then we collect the samples through filtration on filters, and we analyse them to quantify the fungal biomass and also identify the species via biochemical assays. So in terms of what we are doing with the activation and we use mechanical means like a leaf blower and we are trying to re suspend dust and fungal particles from all the locations in the room and that may be contaminated by mould or there might be some dust with mould growing in it.

00:11:38:15 - 00:12:21:09

Speaker 3

And we have different locations, for example, locations behind heavy furniture or visible locations like the walls and the floors and the ceilings. But we also have some hidden locations such as sinks or inside air conditioning units, which we don't want to disturb because often they might lead to an over estimation of the fungal burden because they are locations that do not probably affect the fungal contamination in the room, but they do contain an elevated fungal burden in there.

00:12:22:04 - 00:13:07:06

Speaker 3

So with tested active properties, about five properties using the sampling protocol and the and the swab testing. And for the majority for the for half of the cases, the fungal levels and the allergen level. So the quantitative results seem to be very good. So we've classified our findings into five categories from A-plus to A, B, C and D and with A, we have classified the cases with lower fungal levels.

00:13:07:06 - 00:13:40:17

Speaker 3

And with D, we have the cases with higher fungal or allergen levels. And we also have an indicator in our results that is called the FAI indicator is the fungal to allergen index. It is essentially the ratio between the fungal levels and the allergens and it shows us some it gives us an indication of whether there is a hidden source perhaps in the room, but it really relies on the fungal level and allergen levels number.

00:13:40:17 - 00:14:21:04

Speaker 3

So the first property that we tested, we found out that the risk was medium. So the fungal levels were a bit elevated compared to other houses that we've already tested. However, there was no visible mould or any water damage in the rooms that we tested. With BED we have we note the bedrooms and within LR we note the living rooms and the BD on the end of the case means before depressurization.

00:14:21:04 - 00:14:51:12

Speaker 3

So we test that. We've done some air sampling before and after depressurization of the rooms to see if there are any differences in some of the rooms that we tested. So as you might note, in the second property, the risk was deemed minor. We did on air sampling tests in the living room of the property and also in the bedroom. And in the bedroom

00:14:51:12 - 00:15:20:14

Speaker 3

we repeated the test before depressurization and after depressurization and the fungal levels did not change and the allergen levels remained also the same, meaning that the property two and also property five do not have a risk or the risk is going to in general minor for fungal growth and it means that also we believe that they are very well ventilated.

00:15:21:08 - 00:16:23:07

Speaker 3

So the risk becomes smaller. And in cases three and four, we had some different results. In the third property we tested the bedroom and the living room. In the bedroom we found that the risk was high for mould growth, though there was also no fungal visible signs of mould or or any any water damage. So we suspected that for property three, the bedroom might have been either affected by the dust levels or perhaps due to the some mould in the loft or because of some mould due to the outdoor environment.

00:16:24:02 - 00:16:52:14

Speaker 3

So the they might have increased the levels of multiple properties, but there was no visible mould. And in terms of the identity, like the species that we received, there was not a lot of that and the levels were not as high as in the other cases. And we had also property four that we tested and we found out that the risk was deemed high.

00:16:53:06 - 00:17:29:10

Speaker 3

And I think this is one of the important properties because in Property four, in the living room that we tested, we received a report that there was water damage in the past. There was a leak and it might have affected not only the living room but also the the walls and the gaps between like the gaps between the walls and the floor level.

00:17:30:05 - 00:18:38:13

Speaker 3

So we did some, as we say, densification to understand and the history and what are the risks and where they might the fungi might be coming from. So for property one was that we had a high risk for the bedroom. We saw that the dominant fungal species was Cladosporium Sphaerospermum, which is a common type of fungi, especially in the autumn and sorry, in the spring and the summer months. The DNA copies were a little elevated, but because the Cladosporium is a species that is often found in the environment and the quantitative results were not as sorry.

00:18:38:13 - 00:18:47:04

Speaker 3

Bear with me everybody. I think we may have just lost Spyros’ microphone and just see if we can get it sorted out.

00:18:50:00 - 00:19:19:03

Speaker 3

Hello? Can you hear us, Eros? Yes, I think he just temporarily dropped out there for a moment. If you could just go back a few sentences. Yeah. So what I was mentioning about the identified species is that in property one, we found Cladosporium Sphaerospermum were to be the dominant fungal species. And the DNA copies that we found for that species in property one were elevated.

00:19:19:03 - 00:20:30:07

Speaker 3

But because the quantitative results were at high but not very, very high, we suspect that it was either that the elevated levels of here might have been either because of the dust levels or because of a hidden source that we couldn't identify visually during our inspection. So therefore, property one, we would have adjusted them extra level of a fungal test and a little bit more detail test to see if the risk is actually is actually something alarming or not for property two and five, the levels of fungal of the fungal copies where not as high and the species that were found there was mainly Aspergillus Versicolor. It's a very common species.

00:20:30:07 - 00:21:08:07

Speaker 3

It's also used in many cases as a moisture indicator. But because of that low DNA copies that we received from that we got from this particular species, it doesn't ring any and it doesn't raise any concern. But a very interesting result was from Property four, where there was a report for the water damage. So before the in the living room, we the data that we got from the species identification, the levels of the gold were not very high.

00:21:08:07 - 00:21:38:02

Speaker 3

So you can see the DNA copies where about 951 and we had some certain species like Cladosporium and Aspergillus, which are very common in the environment. But we also have an extra species which is called Wallemia Sebi and it's often an indicator of moisture damage and can contaminate woodwork and wallpaper and, and these kind of materials.

00:21:38:02 - 00:22:25:07

Speaker 3

So after the depressurization at the fungal copies increased and not just 10% or 20%, it was almost triple the ones from before the depressurization and also the Wallemia Sebi had the percentage in the identified species levels and was increased. And this actually raised a small concern that after depressurization we might have had some re suspension from from Wallemia

00:22:25:08 - 00:23:01:11

Speaker 3

Sebi that particles that were hidden under the floor where the leakage basically might have travelled the water from the leakage might have travelled. And these are the results from the air sampling before and after the pressurization on the three properties that we tested. And you can see that in the property. In the fourth property, we have a rapid increase of the DNA copies and that was essentially what raised our concern.

00:23:02:14 - 00:23:45:05

Speaker 3

And another result that was kind of different was the swab testing results. So from the swap testing we could get the DNA copies of the 16 targeted species that the 16 species that we targeted and only for property three, we got higher DNA copies from the loft that we said would be assumed and we might have suspected it to affect the bedroom in Property three.

00:23:46:02 - 00:24:36:17

Speaker 3

But also in a property. In another property we found very, very elevated DNA copies, but only on a very hidden location. So we don't expect it to have affected the results of the of the air sampling in many in any way. So in general, from the fungal testing and what we would say is that even if there is no visible mould in the room, growth might still exist and potentially due to a hidden mould source or the level of dust or the existence of plants, etc., and leaks occur.

00:24:37:03 - 00:25:11:02

Speaker 3

And I think that is one of the main issues that raised some concern in our cases. And it was like leaks. The leaks occurs even in best practice retrofits. So these leaks can affect rooms even after they have been remediated, or if the water damage has been remediated and even if treated in general, passport damage can affect the interstitial fungal growth.

00:25:11:17 - 00:25:41:08

Speaker 3

And another thing is that often moisture moves to areas that are far from the source and this can affect internal mould levels. In the longer term, we might not be able to visibly, visually see it, but it might be there. And if moisture accumulating is not able to escape or dry out, then the mould levels might become elevated.

00:25:42:07 - 00:26:00:08

Speaker 3

So I'd like to leave Valentina also to tell you about internal insulation and condensation risk on that point, and I will happily take the questions in the end. Thank you

00:26:00:08 - 00:26:39:12

Speaker 2

Spyros. Thank you very much. So the second part is about condensation, risk. I'm aware that last week there were a number of participants who were interested in condensation, so I thought OK, it was worth dedicating some time to this issue. So I just want to mention what is condensation risk? So when we are particular, this is an issue that we associate with internal insulation because we are creating we are changing the balance of a walls, we are existing wall would be then a lower temperature and there are some risks associated with this.

00:26:40:04 - 00:27:12:17

Speaker 2

So one is the first is the risk of interstitial condensation and mould growth. Another risk is risk of wood rot for the for any embedded timber which is there. So it could be either some elements of timber within the masonry or joist ends and so on. Another risk is a risk of frost damage on the external surface because it's exposing the external wall to colder temperatures can lead to higher risk of frost damage

00:27:13:08 - 00:27:41:13

Speaker 2

and then last but not least, a reduction of dry on of drying. So this reduction of drying also depends on the type of insulation that we have. And that's why hygrothermal risk assessment can be very valuable. So one thing that is very important when we talk about condensation risk analysis is that it's not just condensation. As you can see, there are so many other phenomena and such an interaction of different factors.

00:27:42:00 - 00:28:11:11

Speaker 2

So this why we tend not to use the term condensation risk analysis, although that's something that we're used to in the past, particularly for a simpler, more modern type of construction. Now we talk about hygrothermal risk assessment. So, hygrothermal risk assessment often, the type of risk assessment that we normally do to support design is a one dimensional hygrothermal simulation, for example, using WUFI.

00:28:13:03 - 00:28:39:09

Speaker 2

And these simulations are based on the British standard 15026, which will be updated shortly. And the criteria of assessment are different. And this criteria depends on the type of construct that you have. So in our case, we are looking at hygrothermal risk assessments for internal insulation. So some criteria of assessment that we consider it's interstitial condensation and mould growth.

00:28:39:09 - 00:29:16:16

Speaker 2

And often we can see the mould growth before considering interstitial condensation because mould can occur at a lower levels of relative humidity and water activity. Then another criteria is related to wood rot in joist ends and frost damage on external surfaces. So these are examples. So we are not just looking at condensation, but we are looking at the number of unintended consequences that might arise from change in the balance of this one.

00:29:16:16 - 00:29:47:07

Speaker 2

Okay. So if we have a look at the two properties, so as I mentioned at the start, we had we consider the fungal testing on a larger number of properties, but then we focus on two properties which had internal wall insulation. And also we want to have a look at what is the value of hygrothermal risk assessment, but also we wanted to check whether there are any, any unintended consequences arising after ten years.

00:29:47:13 - 00:30:32:07

Speaker 2

So first thing, we collaborated with QODA on preparing a number of hygrothermal risk assessment reports and QODA have provided the report for properties one and two. And this is what my standard risk assessment should have been done. So following the criterion, following really assessing the potential unintended consequences for that specific type of building. So if we look at the first property which is here on the left, we talk about the front facade because this the back and the rear of the property is extended slightly.

00:30:32:09 - 00:30:57:03

Speaker 2

So we've looked at the front facade. So for condensation risk, it was found to be not likely frost damage as well. The two likely risks where mould growth at the interface and wood rot at the joist end levels. So however this was subject to brick type, so different brick types leading to different to higher or lower different the extent of risk.

00:30:57:03 - 00:31:32:15

Speaker 2

Let's see. So the second part of this analysis was to look at the more detail, brick information. So part of our work was to carry out some Karsten tube testing and some visual also some visual analysis of the bricks that were there. And we have measured a range of of water absorption of bricks. And therefore, we have advised the the consultant on the type on the range of water absorption for the brick.

00:31:33:09 - 00:32:08:14

Speaker 2

So if we were using that range, so if we had some information on the on site, on the site of the assessment, we could have had a more focused type of answer. So after this analysis, the result of the analysis for mould growth risk and wood rot were found to be low. So again, for example, this is a good example on how hygrothermal simulation can support design, but property two also gives even more a more striking example.

00:32:08:14 - 00:32:38:02

Speaker 2

So again, looking at the front in the rear, the risk of mould growth was likely. As we can see here in both cases. So in this case, it was 60 millimetres of aerogel and the vapor control layer and the mould risk was likely. Wood rot was likely but subject to brick type and timber type. So again, in this case, something could have been done by knowing that knowing more about the properties of the brick.

00:32:39:13 - 00:33:07:07

Speaker 2

However, as the mould growth risk is likely in this case, what could have been done was to choose another system. So it's not in this slide, but we have carried out more simulations. And for example, we've carried out simulations with wood fibre insulation and the on the wall and the mould risk was reduced. So it was not likely in the rear.

00:33:07:17 - 00:33:46:12

Speaker 2

So much less mould growth risk and a lot more mould growth risk on the front, subject brick type. So these samples shows the we can use hygrothermal risk assessment to support design and the result actually, we don't know how the designers decided for the solution, but the result in property number two is was that aerogel was used to in areas with only brick but in the areas with timbers the choice went to using wood fibre.

00:33:46:12 - 00:34:15:05

Speaker 2

So wood fibre was installed in the intermediate floor area. And as is seen from the simulation, the risk was lower. So again, useful an example on how hygrothermal risk assessment can help. So just to give you another view after that, after the desktop analysis, we went onsite and we had a look at property one and property two.

00:34:15:15 - 00:34:43:07

Speaker 2

So we had done a fungus test. So and the visual inspection. So in this inspection of property one, we found no visible mould but from the fungal analysis, we found medium to high fungal levels. And then we had we also found moisture damage on the wall that suggested further tests were needed. In Property two, we found no visible mould and low fungal levels, no moisture damage.

00:34:43:07 - 00:35:06:06

Speaker 2

And also we have measured the moisture content of joist ends at the end of the wetting period. Normally we consider the wetting period between being between October to March more or less, and that's when the moisture content is supposed to be the highest of timber joists. So the joist on the intermediate floor were 11 to 18%.

00:35:06:06 - 00:35:48:11

Speaker 2

So just one was 18% and the other five joists were around 11, 12%. And on the ground floor we had three joists and we had 16, 20%. Normally we can see that 20% as our criterion. Others consider even higher. So at the end of the wetting season, this seems to be a sensible, fairly safe level. But again, further tests were needed in in property one and this is what we've done so in collaboration with Greengauge, we went onsite again and we carried out further tests to that property.

00:35:49:10 - 00:36:23:16

Speaker 2

So there were some visual. So our visual inspection identified, salt efflorescence and the selected efflorescence was at ground floor level. Also we had the, the residence mentioning that the was there was a moisture, a history of high moisture in the sleeper walls; so the wall that was found to be under the stairs. So that was a sign for us to look into the interaction between the wall and the floor.

00:36:23:16 - 00:37:03:14

Speaker 2

In this case, there were a couple of points that we want to mention. One was that there was a replacement of the suspended floor and they decided to install a solid floor with a concrete slab and EPS. And this might have exacerbated the push of moisture to the wall. But also the recent history of maintenance has identified patches of cement based repointing and poor workmanship and also possibly a fairly like the black surface, if it's likely to be fairly vapor closed.

00:37:04:12 - 00:37:40:17

Speaker 2

So the so this is at the bottom of the of the wall. We were going to find that there might be issues of the result of a efflorescence. We've seen this with the visual inspection and they might be exacerbated by the floor and the concrete, the cement base, repointing. So the concrete in the floor and the cement in the repointing. Again, in this case, the issues was the ability to at the junction make it to the junction.

00:37:40:17 - 00:38:15:17

Speaker 2

The second part, we've had a look at the side of this building, and there was moss and there was significant damage at high level. We have identified there was there was a gutter leaking and probably it's been leaking for a long time. And we and we also have identified that there were some areas with original lime pointing where there was where we can find some moss growing.

00:38:16:05 - 00:38:46:00

Speaker 2

And then areas with the cement based pointing as well. Here, we suspected a frost damage because we have high moisture levels higher than we would have high water level water will be higher than we would have on in a normal case because the gutter has failed. And therefore we have decided to run further tests on to looking at two dimensional hygrothermal simulation.

00:38:46:13 - 00:39:34:16

Speaker 2

So what we what Greengauge has done in this case, they have focused on frost damage of the surface and they have looked at whether the damage was exacerbated by cement pointing or whether the internal one installation might have led to the damage on its own. And the result was that the damage was primarily exacerbated by inappropriate cement pointing, because also and this is supported also by the visual inspection, what the damage was, the spawling was closer to the cement based pointing and the internal insulation as there was a thick insulation in that case that might have increased the risk, but to a lesser extent than the cement.

00:39:34:16 - 00:40:04:08

Speaker 2

So I just want to give some general remarks before leaving. So again, in that case, we have found both salt crystallization and frost damage and therefore to minimize the risk of salt efflorescence and frost damage, maintenance and the remediation of water damage are key. As we have identified cement pointing might have led to higher risk both of frost damage and salt crystallization.

00:40:06:00 - 00:40:35:02

Speaker 2

But furthermore, to avoid and to reduce the risk of frost damage and the risk of frost damage always increases if you if you if you expect the wall to be a lower temperatures but to reduce the risk of frost damage it's best not to over insulate. And last, but not least on this, we need to pay attention to the interface between elements, particularly in these cases identified between the ground floor and the wall.

00:40:35:02 - 00:40:36:00

Speaker 2

Thank you for listening.

Detailed testing: moisture. CIBSE – Studio PDP Retrofit revisit