Webinar on Retrofit Fundamentals

00:00:00:10 - 00:00:25:05
Speaker 1
Good afternoon, everybody, and thank you for joining us today. So briefly, we’re explaining some of the fundamentals of historic building retrofit and hope to clarify what we can consider when improving energy efficiency of historic buildings. I'm joined by my colleague Joanne Williams. She's building surveyor for historic adaptation here at Historic England. Joe will be on hand to answer your questions in the chat and will join me later for the Q&A session.

00:00:25:06 - 00:00:48:06
Speaker 1
So thank you all for being here. We'll begin with a question to get an idea of what you already know about historic building retrofit. So, Matt, if you could bring up the first question, please. So we just want to get an idea of what your current knowledge level of historic building retrofit is. So we have an idea of who we're talking to today.

00:00:49:03 - 00:00:54:15
Speaker 2
Hannah, I’m so glad we don't seem to have too many experts in the field. That's interesting.

00:00:54:24 - 00:00:57:24
Speaker 1
So we would have been able to go for a cup of tea if everyone was already an expert.

00:00:58:05 - 00:01:08:10
Speaker 2
And now I'm just thinking exactly the same, although I don't know if you noticed in the chat, we've actually got some people here from Canada and America, which is really exciting. Oh, yes.

00:01:09:02 - 00:01:16:00
Speaker 1
I did see yeah, I did see somebody from far away Nova Scotia or something like that. I thought I saw a couple.

00:01:16:01 - 00:01:29:10
Speaker 2
They've probably got a lot of snow right now, so you might come on a retrofit course why not? Not I. Oh, really interesting people. We have an awareness and a good understanding of currently leading.

00:01:31:06 - 00:01:40:16
Speaker 1
Fantastic. Someone's decided they're not an expert anymore in the last minute. Oh, yes. They say, Oh, brilliant.

00:01:42:19 - 00:01:45:24
Speaker 2
So I think that's everyone.

00:01:46:02 - 00:02:19:21
Speaker 1
I think that's everybody. Yep. Fantastic. Thank you, everybody. That's really interesting. So we're all sort of about middle ground at the moment on our sort of knowledge and awareness of retrofit. So we'll continue. So the UK climate is changing and we can all see and feel the effects of this around it. This diagram from the latest Met Office report that was published in July 2022 looks at how key UK variables in the most recent decade decade to 2021 compared to the average over the last 60 years.

00:02:20:12 - 00:02:42:24
Speaker 1
The technical conservation team here at Historic England have long acknowledged the potential impacts of this on our heritage assets. For over a decade, we have supported a program of research to inform the evidence based advice and guidance that we provide to government and the public. More recently, this work is concentrated on the effect added insulation has had on the heat and moisture behavior of building elements.

00:02:43:09 - 00:03:04:09
Speaker 1
This has informed a range of guidance that you can find on our website. It's easy to assume because historic buildings have been around for hundreds of years, they'll be able to withstand all future threats posed by the natural environment. Recent research has suggested that rapidly changing climates will intensify this threat and create new has. It's based on historic buildings and their inhabitants.

00:03:05:02 - 00:03:29:07
Speaker 1
But in this time of climate crisis and with the added pressures of cost of living and the conflict, we must find ways to save energy, cut carbon and make our buildings resilient and improve the quality of life for occupants whilst preserving what is important about our historic buildings. Firstly, a point of clarification. When we talk about historic buildings, we're generally talking about those of traditional construction.

00:03:30:02 - 00:03:59:16
Speaker 1
Traditional buildings have permeable construction, which both absorbs and readily allows moisture to evaporate. Examples include those consisting of solid brick, stone or earth external walls and pre 1919 timber frames with any infill. Traditional construction excludes modern cavity wall, prefabricated and modern timber, steel or concrete framed buildings. Historic buildings have a role to play in the changing climate that we see today.

00:04:00:11 - 00:04:31:01
Speaker 1
It's widely acknowledged that the most sustainable building is one that already exists. Studies have shown that making energy efficiency improvements to existing buildings is at least 4% better in lifecycle carbon terms than if you were to demolish and replace. In some cases this can increase in any 60% better historic buildings also offer us many opportunities to learn from the past, highlight solutions that can be adopted into the future and demonstrate how they were constructed to be resilient to the environment.

00:04:33:12 - 00:04:56:07
Speaker 1
So what is retrofit in its simplest form? Retrofit refers to the addition of new technology or features to an existing building. However, in this time of climate crisis, the retrofit of buildings has come to encompass so much more. It is used to refer to the improvement of an existing building to ensure it's responsive, resilient and well adapted for our changing climate.

00:04:57:05 - 00:05:30:02
Speaker 1
This may include the repair renovation, refurbish cement and or restoration of the building alongside upgrade of existing services and the addition of new low carbon technologies. Retrofit can be deep achieving significant reductions in energy consumption or focus on soft retrofit measures and still achieve meaningful energy use reductions regardless of where we scale. A retrofit says a good retrofit will successfully reduce energy consumption and carbon whilst improving the health and comfort of its occupants.

00:05:30:15 - 00:05:58:17
Speaker 1
A poor retrofit, however, may fail to realize the anticipated energy, carbon and financial savings and increase the risks of problems like moisture, mold, growth, fire risk and overheating. Many homeowners are understandably at a loss of where to begin and what to do for the best, particularly when their home to be retrofitted is traditionally constructed, designated or both. We now have our next polling question.

00:05:59:18 - 00:06:05:21
Speaker 1
So if you could bring that up for us, that would be wonderful.

00:06:10:00 - 00:06:40:19
Speaker 1
So as I'm sure you're already aware, when you're planning any retrofit or advising a client to do so, it helps to be aware of some of the fundamentals. And here's a few headlines with a reminder. So the first of which is damp fabric is cold fabric. And I think we had a question if Matt can hear me, he can bring it up.

00:06:40:19 - 00:06:40:23
Speaker 1
Okay.

00:06:42:15 - 00:06:44:20
Speaker 2
Well, this would be totally awkward if we’ve lost Matt

00:06:45:20 - 00:07:00:17
Speaker 1
Oh, there we are. He was getting a cup of tea because he's an expert. So the question is, how much quicker does damp building fabric lose heat compared to dry fabric? Why not? No one's dry off damp.

00:07:02:04 - 00:07:03:06
Speaker 2
Although there is one now.

00:07:03:09 - 00:07:06:21
Speaker 1
Oh, this is very interesting.

00:07:06:24 - 00:07:09:21
Speaker 2
This is this is not actually what I expected. Certainly.

00:07:10:10 - 00:07:14:00
Speaker 1
I expected the people to assume it was the other way around. So, yeah.

00:07:14:00 - 00:07:20:08
Speaker 2
I think that's really interesting.

00:07:20:08 - 00:07:23:04
Speaker 1
Hmm. Yes.

00:07:24:18 - 00:07:29:04
Speaker 2
You know, I don't know. I'd like I know the answer, but I don't know. I think.

00:07:30:18 - 00:07:31:00
Speaker 1
That's.

00:07:31:00 - 00:07:32:15
Speaker 2
True over the years, you know, the reason that.

00:07:33:02 - 00:07:38:05
Speaker 1
People are jostling for they're so young, it's like, oh, I think that seems to be everybody.

00:07:38:13 - 00:07:39:12
Speaker 2
I think is.

00:07:40:14 - 00:08:08:22
Speaker 1
So thank you all for participating in that. That's really brilliant. So damp fabric loses heat 30% faster than dry fabric. Most of you thought it was more than this, which is interesting. So yes, it is slightly better thermally than you might imagine. However, it's still not good. So damp fabric has the same effect on us as on a building's ability to stay warm, as wearing damp clothes would have to have on us.

00:08:09:14 - 00:08:40:12
Speaker 1
And quite often people don't realize this say the most significant risk of any retrofit measure is that of increased moisture accumulation. This can be a surface or interstitial condensation or moisture accumulation within the building fabric. Beyond its capacity to readily manage this increased moisture can cool the fabric, increase heat loss and energy demand. It can give rise to mould formation with the associated health impacts, the occupants that we've all become critically aware of recently.

00:08:41:08 - 00:09:13:08
Speaker 1
So maintenance and repair of a building is vital. It's essential that any building is repaired and allowed to dry naturally and fully, especially before fabric upgrades are undertaken. Whatever measure is undertaken, it's important to ensure the continued and adequate ventilation is maintained to ensure good levels of indoor air quality. So quite a lot of people don't necessarily understand that a lot more heat loss occurs through infiltration losses or drops than people might imagine.

00:09:14:07 - 00:09:55:20
Speaker 1
Older buildings can lose around 15 to 20% of the heat by drafts. A UCL study has proven that fabric upgrades are not essential to the transition to low carbon heating, nor are they essential for any low carbon heating system to be sized correctly and operate effectively. However, it showed that the reduction in infiltration losses are of vital first step on the route to domestic energy efficiency and alongside with installing effective heat pumps more effective than fabric insulation measures at reducing energy demand.

00:09:55:20 - 00:10:25:18
Speaker 1
So contrary to popular belief, fabric upgrades are often not the most cost or carbon efficient, efficient measure. We've got another polling question for you now. If Matt is able to bring this up and that is, what percentage of the energy consumption do you think can be saved through maintenance, renewal and conservation focused refurbishment alone?

00:10:25:18 - 00:10:28:14
Speaker 2
Honestly, you know, this one's like we've we're in the middle now.

00:10:29:01 - 00:10:35:10
Speaker 1
Which is quite. Yes, yes. Yeah. This is really a skill. This is fantastic.

00:10:36:00 - 00:10:43:12
Speaker 2
I've also just just given the winner, of furthest participant who is currently in Germany. But he is actually from Australia.

00:10:44:01 - 00:10:51:18
Speaker 1
Oh, fantastic. I might say not physically furthest.

00:10:51:18 - 00:10:59:19
Speaker 2
Not yet, no. Well, he would be if he was still over in Australia. Fantastic. I think that's everyone.

00:11:01:24 - 00:11:09:12
Speaker 2
How do we have to stop it now. I think to saying can you read a little bit slower to me then. Yeah, that's why.

00:11:09:12 - 00:11:40:07
Speaker 1
Thank you. Yeah. No I will, I will say thank you everybody. So yes, so a study by James Ritson and hopefully they'll be a link put up for it you to find it. Um, if not, we can share that with you. So this study has shown that maintenance, periodic renewal, conservation focused refurbishment have the potential to save between 30 and 50% of carbon emissions.

00:11:40:07 - 00:12:12:05
Speaker 1
Along with this, up to 40% of energy savings. So this study found that the most effective benign intervention was the improvement of hot water and heating systems, rather than the more accepted methodology of installing insulation measures. In addition work by Freya, Robert Wise has modeled a number of soft retrofit scenarios and shows that they have significant energy and carbon reduction potential.

00:12:12:23 - 00:12:50:22
Speaker 1
Soft retrofit measures include behaviour change and non fabric additions that are often considered outside the scope of retrofit projects. This work also found that already SAP, which is the software behind EPC rating tools, overestimates energy use for the case study buildings by an average of 66%. It suggested that the use of these tools is likely to lead to retrofit measures that are in reality, never achieve the expected savings and are not at present appropriate for modelling the energy and carbon of heritage buildings.

00:12:52:15 - 00:13:27:20
Speaker 1
This research was presented in an earlier technical Tue recording, of which is available on our website. Through the link provided. Insulation upgrades have their place, of course, and are of benefit. However, these studies collectively demonstrate that many measures can be undertaken first and provide a meaningful improvement in energy efficiency of historic buildings. Repair, draft proofing and soft retrofit measures are the easiest, lowest cost and lowest risk place to start when trying to reduce energy demand in older homes.

00:13:31:18 - 00:14:04:00
Speaker 1
So if you are considering thermal upgrades to be made to the fabric of the building and it's possible to do so without negatively impacting the building's significance, they are best focused on the element which stands to provide the maximum relative improvement. For example, a Georgian townhouse will have relatively more glazing than a solid wall, so secondary glazing may give the best overall thermal gain in this scenario, whereas a detached house will likely have more walls and window.

00:14:04:01 - 00:14:41:24
Speaker 1
So appropriate wall insulation may provide the biggest overall gain in thermal improvement here. In addition, the nature or regional variation of construction type needs to be considered. For example, a Victorian terrace will likely have thin brick, solid brick walls, which would bring much bigger benefit from being thermal upgrade graded. Sorry. Whereas thick, solid walls of a Devon shear farmhouse are now known to give a higher u-value than previously assumed, and the addition of insulation would likely not provide substantially thermal improvement here.

00:14:43:10 - 00:15:14:18
Speaker 1
Be mindful also that in some cases exposed solid walls can provide thermal mass, which can function as a useful heat sink to buffer and regulate internal temperatures during the summer. So concealing this behind internal insulation could have negative impacts that you are not expecting. In considering all of these factors. The most cost efficient measure can be identified for each property and then carefully designed and appropriately detailed.

00:15:14:18 - 00:15:55:03
Speaker 1
So ensuring thermal continuity of any fabric intervention is dramatically more important than maximising the thickness of any insulation. This prevents concentrated cold spots where moisture and mould growth can occur. Bear in mind that the impact of thermal bridging is proportional to the more you insulate, the bigger the impact of any thermal bridge becomes. If internal wall insulation is to being investigated, do you consider that it has been proven that just 45 to 50 millimetres of a natural fibre insulation will be beneficial and just 60 to 75 millimetres is the optimal thickness to achieve maximum return on your investment.

00:15:55:16 - 00:16:20:21
Speaker 1
Beyond this, there is a dramatic diminishing return. This also ensures that the external wall of the building does not cool too much and begin to take moisture at a level beyond its ability to manage it. Internal wool insulation is a high risk of thermal bridging and moisture accumulation. It needs to be very carefully considered and detailed if it is to be proposed.

00:16:21:14 - 00:16:53:19
Speaker 1
Finally, use compatible and appropriate materials. The permeable nature of traditional construction needs to be accounted for when considering fabric upgrades, with the exception of below ground areas. Natural permeable material should be your first choice. Bear in mind that construction types thicknesses can vary across an existing building or phases thereof. Materials and details must be compatible with the existing fabric being upgraded and junctions carefully considered.

00:16:54:22 - 00:17:24:17
Speaker 1
The type of insulation that is appropriate for use in each retrofit needs to be carefully considered to reduce the space heating or cooling demand and ensure thermal comfort isn't changed. That is, to provide a steady thermal temperature with minimal soil, steady internal temperature with minimal fluctuation. Every material not only has thermal conductivity value as also known as u-value, but has a unique, unique density and specific heat capacity.

00:17:25:09 - 00:17:50:24
Speaker 1
These three values will determine its thermal diffusivity, which is how quickly heat can move through the material, or how well it stores heat and its thermal effusive beauty, which is how quickly a material transfers heat to another. These factors all need to be taken into account as they impact the material's ability to buffer internal internal temperature changes. And this can be really useful.

00:17:52:05 - 00:18:22:02
Speaker 1
As noted before, the specific construction type to be insulated plays a role in the decision. But so too does the building's orientation amount of solar radiation and its occupancy patterns. This is where understand the exact building to be retrofitted and taking a whole building approach becomes critical to getting a retrofit right. First time. So where to start? Any retrofit needs to respond to the particular building to be retrofitted.

00:18:23:07 - 00:18:55:21
Speaker 1
It is important that a whole building approach is taken rather than implementing isolated single measures with no prior prior planning. A whole building approach is one that seeks to save energy, sustain heritage significance, and maintain a healthy indoor environment through understanding the building and its context. Most of all, it deals with specific situations as opposed to generalities. Opportunities and constraints can vary widely depending on the building's content.

00:18:56:11 - 00:19:28:08
Speaker 1
The optimum solution in one case may be quite different from another, even if the buildings appear similar. Therefore, for a building and site specific approach is needed one which considers the interrelationship between the occupants, the fabric and the services of the building, and aims to find a bespoke, balanced solution. Taking a whole building approach also helps to highlight and resolve uncertainties, reconcile splitting aims and manage the risk of unintended consequences.

00:19:29:17 - 00:19:55:06
Speaker 1
To do this effectively, you first need to know a few things about the building. To be retrofitted and undertaking a pre-retrofit assessment is a critical first step. I will give you a short overview of the key aspects of this. So firstly, the energy performance of the building and therefore its options will be affected by its unique context.

00:19:56:02 - 00:20:33:12
Speaker 1
Thus you must you need to establish if the building's context condition both through death based assessment and site survey. Firstly, establishing the regulatory and statutory context of the building is important. Its location orientation, the site topography are also important to understand to determine the building's climatic or microclimate conditions and its level of exposure. Level of exposure to elements varies regionally, locally and even between the different sides of the same building.

00:20:34:04 - 00:21:15:09
Speaker 1
A building in an exposed upland area or close to the sea will need a different approach to one in a sheltered inland or open site in urban settings. Exposure can be much influenced by the proximity of surrounding buildings. Establishing the building form materials, construction types and any variations in these and different phases of the building. A critical, a thorough onsite building survey should establish condition and pre-retrofit, repair or maintenance needs alongside the existence of any previous interim interventions.

00:21:15:09 - 00:21:57:01
Speaker 1
Their impact and appropriateness. Understanding the age type and condition and efficiency of existing building services alongside the extent of existing ventilation provision is also vital. If the owner occupier is willing and able. A thorough building performance evaluation can greatly a decision making. This could include elements such as thermography, air tightness testing, relative humidity, temperature and CO2 monitoring as climate change seen as more extreme weather and natural hazards.

00:21:57:09 - 00:22:29:12
Speaker 1
We need to ensure we are creating not only energy efficient homes, but resilient buildings. Retrofit measures must be suitable for the particular building and its unique environment now and in the future. A hazard is something that does not directly cause harm, but has the potential to cause harm or loss. Some climate change hazards need to be considered include increased humidity, increased intensity and frequency of rainfall, and more frequent flood events and the risk of ground swell.

00:22:31:01 - 00:23:03:05
Speaker 1
Higher wind speeds and more wind driven rain, more sunshine and solar radiation with hotter, drier summers, increased risk of ground shrinkage and increased risk of overheating. Risk is the probable in likelihood of harm or loss occurring if the hazard is not managed. A building may be impacted by a variety of different hazards to different levels of risk, depending on the site's exposure and vulnerability.

00:23:03:05 - 00:23:29:16
Speaker 1
So understanding the different hazards and opportunities and managing risks of harmful impacts will help us make the right choices when planning any retrofit. The Good Homes Alliance has a useful tool to assess overheating risk of existing buildings. A link to which should hopefully be put in the chart fully say we also need to know how our building is used.

00:23:30:14 - 00:24:15:11
Speaker 1
We all use homes in different ways. The amount of energy we use varies to the number of people in a house. The indoor temperature we find comfortable and the services and equipment we will use have significant effect on how much energy a household consumes. Establishing the existing energy demand. An energy use intensity of the building is important. Understanding the occupants, expectations of thermal comfort and preference for heating strategy will inform decisions on appropriate services and controls in each retrofit case, the occupancy level and patterns and the activities that take place in the building may increase moisture load and need to be considered.

00:24:17:02 - 00:24:28:08
Speaker 1
The average home generates 21 pints of moisture every 24 hours, and moisture accumulation needs to be accounted for and managed in any retrofit design.

00:24:30:12 - 00:24:54:02
Speaker 1
Understanding the client's budget needs and wants is critical to planning and phasing any appropriate retrofit. You need to understand what they can afford to invest now and what they might be able to invest over a longer period. Is there more need? Is there need for more space in the home and all their existing plans to extend on new spaces?

00:24:55:08 - 00:25:25:01
Speaker 1
What is the motivator for retrofit? Is it simply the aim to reduce energy bills and avoid fuel poverty? Is there an awareness of and a want to reduce operational carbon and embodied carbon within the building and the project? It has been demonstrated that most successful retrofits are more often than not those that engage with the owner occupiers and address their needs.

00:25:26:23 - 00:25:55:20
Speaker 1
Finally, it is critical that the information gathered in a pre-retrofit assessment is used to make a whole building retrofit plan. On our website, we've listed the options for retrofit measures in order of priority, considering their benefits, costs and technical risks. This is increasingly referred to as an energy efficiency hierarchy. The Centre for Sustainable Energy has a useful graphic that illustrates this principle, which is shown on the slide.

00:25:56:23 - 00:26:31:19
Speaker 1
All retrofit should prioritise occupant and building health energy conservation, which is the top of the pyramid and should be addressed first. Can be achieved by actively reducing energy use through behaviour change or soft retrofit measures such as installing curtains and rugs. The second tier on the hierarchy energy efficiency can be achieved by simply referring repairing defects so that fabric remains dry or undertaking measures such as draft proofing and insulating, not upgrading or installing heating controls.

00:26:32:04 - 00:27:14:14
Speaker 1
Installing secondary glazing or replacing old heating systems with new low carbon alternatives. Upgrading insulation sits in this bracket to perhaps discuss. These are higher risk measures which require specialist planning design an informed integration if they are not to risk unintended consequences that might negatively affect the building or its occupants. The final stage in the hierarchy is installing renewable or low carbon energy sources such as photovoltaics, by reducing energy demand through the first two stages of the hierarchy, the amount of energy needing to be produced will have also fallen.

00:27:15:08 - 00:27:53:22
Speaker 1
This means that any system could be smaller and cheaper than if it had been installed without first addressing the other factors. The key thing to remember is that retrofit can be phased to suit any budget savings from early energy efficiency measures can fund later placements of heating systems, fabric interventions or renewable energy installations. Phasing should consider and time with the need for replacement of services or building elements, along with any plans to extend or upgrade the building that the homeowner may have.

00:27:53:22 - 00:28:25:05
Speaker 1
So. Updated Your home page has a wealth of information on the repair and upgrade of old homes. This includes a new section dedicated to energy efficiency in your home. You can see the Web address here, and I think there's a link in the chat where you can find listed the options for retrofit measures. The London Energy Transformation Initiative, or LETI for short have a useful site, a free online guides and information.

00:28:26:04 - 00:29:01:11
Speaker 1
This includes one pages and a climate emergency retrofit guide, which includes explanation of this process for making retrofit plans that say. In conclusion, there are many different options to save energy and cut carbon, to make our buildings resilient and to improve the quality of life of its occupants. Always preserving what is important about the historic building. It's important to weigh up all of the impacts and costs of each measure before deciding which to pursue.

00:29:02:14 - 00:29:30:15
Speaker 1
It's important to identify appropriate options for the particular building and its occupants now and in the future. Make a retrofit plan to implement measures using the energy efficiency hierarchy, which can be phased to suit any budget and need to look first at repairing the building. Reduce infiltration losses and install low carbon heating, particularly if they're historic features to consider.

00:29:31:00 - 00:29:54:18
Speaker 1
As this alone can make a vast, energy efficient improvement. Thoroughly considered and target any fabric upgrades and carefully design them in all cases. Retrofit will increase moisture risk, so it's imperative that we ensure adequate ventilation is still provided.

00:29:58:14 - 00:30:04:06
Speaker 1
So thank you for listening. I hope this has been useful and we'll move on to the Q&A.