There are three PAS2035 Retrofit Risk Pathways, graded A, B, and C. Buildings graded as risk pathway C will require an air tightness test.

The PAS2035 framework was introduced by the government in 2019 as a way to standardise the process of retrofit and make sure that publicly-funded projects are carried out properly. 

Risk pathways are determined by a number of factors, including a building’s age, size and the complexity of the work planned. An independent Retrofit Coordinator oversees each retrofit project and determines the risk pathway they should take at the outset. Each pathway is described below but the general principle is that as projects become more complex, involving multiple units or complicated installations, the more in-depth the onsite assessment needs to be. 

PAS2035 Risk Pathway A

This is the lowest risk path, representing simple measures required for standard properties. For instance, installing loft insulation in a property built after 2012 is a good example of a Pathway A project.

A standard whole dwelling retrofit assessment can be carried out for Pathway A projects by a competent assessor. 

PAS2035 Risk Pathway B

This pathway is required for high-risk, multiple, or complex measures installed in several properties.

The Retrofit Coordinator needs to find more experienced Retrofit Assessors for Pathway B projects because additional information is required to complete the final assessment. Fuel use metrics must be included in each SAP calculation. A thorough ventilation assessment should also be carried out to identify any danger areas. These are generally where condensation is likely to collect and black mould could develop. 

PAS2035 Risk Pathway C

Pathway C is followed for large-scale projects with multiple high-risk measures planned. They could be in conservation areas, for instance, or need special planning approval. An example Pathway C project would be any work carried out in a high-rise block of apartments. This also includes any big building with a complex layout. 

Are air tests required for Pathway C projects?


Retrofit Assessment requirements at this stage are even more advanced than at pathway B. In addition to the advanced SAP calculations and ventilation tests, an air tightness test is also needed. It is rare to find an individual or company that can offer comprehensive retrofit assessments to pathway C, so additional time and resources are often required at the assessment stage. 

What additional factors need to be considered for high-risk pathways?

The more complex projects in atypical buildings will often require thermal imaging surveys to be carried out. Sometimes a cavity inspection using a borescope is also necessary in order to gather sufficient detail to inform the retrofit design process.

Commissioning a Retrofit Assessor who can undertake all additional elements will produce significant cost and time savings for complex projects, yet finding these people is difficult. There is a national shortage of fully qualified assessors who both have working knowledge of PAS 2035 and a background in assessing high-risk pathway projects.

Building Energy Experts Retrofit Assessors

From a Retrofit Assessment perspective, we are primarily concerned with carrying out the most appropriate set of tests in relation to the project’s risk pathway. If an assessment isn’t properly carried out, the knock-on effect on the Designer, Installer, and Coordinator is huge. We pride ourselves in avoiding these issues and are responding to the nationwide scarcity of decent assessors by:

What next?

We’re bridging the retrofit assessment skills gap for a growing number of councils and housing associations across the UK. We are trusted, competent, and reliable, so contact us today with your project requirements.

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