Rule logic tree of archetypes for onsite installation

• Currently, retrofit installation relies upon a high level of acquired knowledge. For example, understanding of suitable material interactions and combinations, or the requirements for air flow and cavities in the property. This means that retrofit measures are often found to cause unexpected issues when installed. 

• Retrofit requires similar skills to conventional construction but with case-specific knowledge. The skills and principles used to install measures such as EWI are the same as those required for a newbuild property. The key differentiator is the application of those skills to specific scenarios; good practice for new build properties may not be good practice in a retrofit setting. 

• The method for completing measures varies on a property-by-property basis. Every property archetype and build-up is different and has unique features and elements to deal with when installing retrofit measures. This is further exacerbated when each individual installer may adopt a bespoke method to complete an install. 

• The skills shortage as discussed in the Skills and labour chapter highlights the need to make retrofit more accessible and lower the barrier to entry while also ensuring a high-quality job. It also highlights the lack of skilled labour which is required to complete retrofit at scale. 

• A major blocker to successful retrofits is the difficulty of knowing “what good looks like” without access to images or worked examples. This can mean that install instructions may be misinterpreted or incorrectly followed. 

• With installers not having clear and comprehensive instructions, what is actually done to a property to install a measure can vary greatly and is potentially unknown or undocumented. This can lead to a lack of understanding of changes if further works are subsequently carried out. 

• The lack of clarity in instructions, process, and methods to follow can result in issues that lead to worse performance post-retrofit, compared to before performing the retrofit. This has been exhibited with many cavity wall installations. UK Homeowners Facing Cavity Wall Insulation Failures – HomeOwners Alliance 

The future state of installation would advise in the creation of rule logic trees/documentation, that would enable an installer on site to step through critical decision points, through guided choices.

The principle is that an installer uses a series of questions, such as: what archetype is the property, what is the age of the building, does the building have a cavity; all of which would lead to a decision about how a measure should be installed for that specific property.

The following benefits could be realised by utilising such a method:  

• Reduction in skill requirement and installer experience – installer could use the guidance documentation to understand what the measures are and how to install them, eliminating the need for them to have experienced or observed the scenario previously. 

• Reduction in errors and poor quality – from having a visual guide of “what good looks like”, and instruction on how to complete a process, the opportunity for incorrect installation is greatly reduced leading to improved quality outputs. 

• Faster installation – the decision tree system enables questions, queries and delays to be resolved instantly, instead of requiring escalation, expediating project delivery. 

• Improved consistency of delivery – with a logic tree to follow for retrofit delivery, the likelihood of undocumented variation decreases, meaning outcomes are more consistent and repeatable. In the event of further work being needed, the specifics are identified and understood. 

• Scalability – a logic tree is scalable to cover the different variations or pathways as required. The logic tree can expand to cater for all the cases and eventualities posed by retrofit of buildings, to aid with achieving retrofit at scale. 

Questions

• Who should own rule logic trees; manufacturers, installers, or alliances?  

• Can a select amount of scenarios cover the majority of cases?  

Enabler

• Consortium based projects and open learning, and sharing across manufacturer and installation teams.  

Key insight

• Rule logic trees are often used in engineering to aid with quality control and root cause analysis. Translating them to this application shifts the outputs towards a precision engineered product. 

Guidelines

• As projects are delivered, documenting what works well on a case–by–case basis would help inform and create a logic tree.