0.3 More about the CLR process

1. The range of experiences feeding into CLR

In CarbonLite Retrofit, the focus of attention is on the needs of an individual building and its occupiers – where the owner makes the final decisions.

The CarbonLite Retrofit programme is built on general feedback from many retrofits – the product of hard-won prior experience by those who have been retrofitting buildings over several decades.

CLR also includes the results of monitoring and analysis of specific schemes that went well and, importantly, those that did not! This wisdom is invaluable.

The experts who contributed information into each Module of the course are listed, but the experience of many others has also informed the course.

2. More about the certification process

The detailed pre-retrofit design and construction checklists and the recording of design strategies, targets and as-built evidence that take each project to certification give all those involved in a project an assurance that energy, moisture and comfort performance have all been carefully considered.

Working through a comprehensive scheme like CarbonLite Retrofit to achieve moisture-robust delivery of a chosen energy target ensures that clients, designers and builders clearly identify the performance and comfort criteria at the beginning of project – and are all signed up to them. As the design and on-site work unfold, everyone is working together towards this goal. CLR acts as a discipline firstly for the briefing and design stages, then as the project progresses, for the on-site work itself.

With a specific energy target in mind, reviewing all elements of the design against this target before work starts, highlights areas of potential weakness and allows solutions to be considered in advance. Not all projects will be modelled in PHPP or SAP. However with the growing number of PHPP trained professionals in the UK, the ability to model and track changes in the model will become increasingly attractive to retrofitters and their clients, particularly for larger buildings, flats, maisonettes, or retrofit solutions for specific building types within, for example, a Housing Association portfolio. Careful use of SAP (not RdSAP) is also to be encouraged wherever possible for the same reasons.

3. Keeping a project on track

Once the project is under way, reviewing decisions and necessary changes against the targets keeps the project ‘on track’ even when unexpected issues arise (as they inevitably do) and the stages are recorded – which not only gives assurance to the client, it also helps with learning and with the sharing of that learning. And at the end, the performance of the ventilation system and the airtightness can be demonstrated at completion by third party commissioning and testing.

For example, a standard approach to loft insulation, where fibrous insulation is laid between and over the existing ceiling joists, would be picked up as unlikely to provide the level of vapour or airtightness (and or wind-tightness) required in the CLR standard – and may result in thermal underperformance and potential moisture problems e.g. overly humid attic spaces.

With a performance standard in mind, an airtightness line would be determined; the existing airtightness (for example of the ceilings) would be looked at, and a strategy arrived at to improve it if this was required. The placing of roof and/or ceiling insulation in relation to wall insulation would be carefully considered to minimise thermal bypass and thermal bridging at the eaves junction.

It is the little details like this that are so important to the ultimate performance of a building – without this attention to detail the performance gap won’t be closed.

4. Mainstream energy efficiency approaches and the performance gap

The issue of the performance gap in new building has become too big for the construction industry to ignore and in 2014 the industry – and government-sponsored Zero Carbon Hub – published a detailed set of recommendations on tackling it.¹ Design_vs_As_Built_Performance_Gap

Subsequently, in 2015, the UK Government signalled the end of the “Green Deal” for England and Wales, set up in 2013 to facilitate occupant- and energy company-funded low energy retrofit.

Although there were several political reasons for ending the scheme, there was also concern about the poor performance of some of the retrofits that had been funded² – the energy, comfort and moisture performance gaps in retrofit all being of concern.

If and when anything replaces them, there will be considerable pressure for better attention be paid to the quality of retrofit, to the energy and moisture performance, and to the need for an integrated approach considering, for example, indoor air quality as well as energy saving.

Developing the required ‘across the sector’ design and technical understanding – and a ‘virtuous feedback loop’ to improve retrofit quality and outcome is what the CarbonLite Retrofit Programme is all about.

5. Closing the loop

CarbonLite Retrofit participants are encouraged to arrange on-going engagement with their retrofit projects and clients post-retrofit. Where possible this should include monitoring and/or performance data collection, shared either via the AECB Low Energy Buildings Database, AECB discussion forum or via contributing to new CLR case studies. This is an essential element in anyone’s professional development, and if the results are shared, then the entire retrofit community benefits.

The Low Energy Building Website is a record of many AECB members’ (and others’) achievements to date. Among the 200 (and increasing) projects listed are 88 deep retrofits undertaken as part of the Retrofit for the Future programme, a large competition-based programme of whole-house retrofit and post-completion evaluation and monitoring, and a mine of valuable information.

[edited 7.10.20] Please note that the CLR project certification system is not currently available. When funding permits it will be built off the LEBD. The intention is that each project certification starts with a design stage entry (effectively a whole house plan) in the LEBD, this entry can be set to be publically viewable when complete. Making design stage entries visible is strongly encouraged.

The evidence submitted at the next certification stage, the ‘as built’ stage, is not publically visible being available only to the design and build team and the building owner (or tenant).

Over time as the certified CLR project database is populated, the AECB will publish anonymised results indicating the level of ambition relating to these projects and where possible will link to measured results held on the Low Energy Buildings Database. Certifiers and their clients keen to share as-built evidence in the form of CLR case studies should contact the AECB.

Monitoring can include records of; thermal comfort (e.g. temperature and humidity monitoring, post-occupancy surveys etc.), air quality (e.g. via CO₂ or humidity monitoring), records of energy use, and where moisture risks have been identified, monitoring of conditions within the fabric is also strongly recommended.

The monitoring equipment illustrated below is based on wireless technology, but wired systems also exist.

Now discontinued, the AECB previously offered discounts to members buying the Omnisense Remote Monitoring System (pictured above).

Reporting results and sharing solutions is all part of a rigorous, questioning approach, which is essential if we are to deliver real rather than paper results – and avoid the dreaded performance gap – or gaps. The discipline of comparing others’ approaches to your own, and discussing what each could learn, is the way that knowledge is built and consolidated.

The image below shows the range of information that can be combined to analyse a project, or an aspect of a project. An in depth understanding of monitoring data and the retrofit approach taken gives the opportunity to assess the long term success and robustness of that particular approach.

Certifiers and their clients keen to take advantage of the AECB data analysis service or simply share access to project monitoring data in the form of CLR case studies should contact the AECB.

6. Retrofit Risks: no-one can know everything

The course is intended to inspire confidence in all those involved in retrofit work, and to create a knowledge platform to openly discuss challenges and risks. The CLR project certification system requires risks to be clearly identified and described.

Often risks can be identified in principle, but cannot be quantified, either because there are more factors than can be analysed realistically or because budgets simply do not extend to cover the costs of advanced software analysis or material testing.

The limitations of ‘free’ industry standard risk assessment methods are covered in the course. This should not be taken to suggest that these methods are of no use, indeed they are often a crucial starting point, but simply that they have limitations, and are not a substitute for thinking through individual situations using the concepts and principles taught in this course.

Examples of risk might include:

• Energy, comfort or financial (savings) ‘performance gaps’
• Noise or nuisance from heating or ventilation systems
• Decay of materials
• Poor Internal Air Quality (IAQ) from poorly designed and or executed ventilation systems
• Poor IAQ from mould growth and spore release

At the end of the day it has to be left to owners, advised by the project team, to decide where to balance out any potential risks from the retrofit proposals against the fuel savings, greenhouse gas reductions, and improved comfort conditions achieved.

The CLR approach to risk is to encourage a transparent and evidence-based conversation between all those involved in retrofit, making use of the precautionary principle, understanding risks in a broad context, from the viewpoint of building owners, occupants and neighbours – and to society as a whole – and keeping these risks in perspective compared to benefits. The project certification system also helps by prompting clear thinking about risk: capturing both strategy and detail relating to avoiding, reducing and managing risk; and ensuring ‘residual risks’ are recorded and communicated to the building owner and / or occupants.

We hope that as a result of the confidence arising from a deeper understanding of risk, retrofitters and their clients will be able to make better, more informed decisions with responsibilities and liabilities more clearly identified and fairly distributed.