PAS2035 is a retrofitting framework document developed and published by the British Standards Institution (BSI), principally in response to the recommendations made by the UK Government’s Each Home Counts (ECH) review. There are 27 million domestic buildings in the UK. However, the majority require significant energy efficiency improvements. Unfortunately, the UK has the ignominious label of having the worst insulated building stock in Europe. A staggering 37% of homes in the UK were built before 1946, resulting in graphics like the one below.

What is PAS2035?

Simply, PAS2035 is an overarching specification in the retrofit industry. It is specifically designed with a ‘whole-house’ or ‘whole building’ retrofit in mind. PAS 2035 is designed to ensure that retrofit work is carried out to a high standard, focusing on achieving energy savings, reducing carbon emissions, and improving the comfort and health of occupants. It also aims to protect consumers from poor quality workmanship and ensure that retrofit work is carried out safely and efficiently. The document sets out an extensive collection of targets in response to the Government’s recommendations:

• enhanced functionality, usability, and durability of buildings
• improved comfort, health, and well-being of building occupants and visitors
• improved energy efficiency, leading to reduced fuel use, fuel costs, and pollution (especially relating to the operational carbon of buildings and the subsequent emissions)
• reduce environmental impacts of buildings
• protection and enhancement of the architectural and cultural heritage as represented by the building stock
• avoidance of any unintended consequences related to any of the above
• minimisation of the “performance gap” that occurs when reductions in fuel use, fuel cost, and carbon dioxide emissions are not as large as intended or predicted (PAS2035 PDF, accessed at Retrofit Academy)

The specification promotes a holistic approach to retrofitting. The holistic approach is not limited to the building assembly; the building impacts the occupants and interfaces surrounding the assembly impact and. They are not independent of each other, therefore require the utmost consideration to complete retrofits holistically.

Scope of PAS2035

PAS 2035 outlines the key principles and requirements for the assessment and improvement of existing buildings, including the following stages:

1. Initial assessment of the building’s energy performance and identifying areas for improvement.
2. Develop a retrofit plan considering the building’s fabric, heating, ventilation, and lighting systems.
3. Implementing the retrofit plan, including the selection of materials and contractors.
4. Verifying the performance of the retrofit work through testing and monitoring.

As of the 30th of June 2021, full compliance with PAS2035 became mandatory for all companies installing Energy Efficiency Measures. The introduction of this measure was warmly received as it truly codified the standards retrofits should be held to. The specification introduced a set of roles crucial to the proper enforcement and execution of retrofits. Each role does not necessarily require a separate individual. However, whoever does carry out each role must have received the levels of training and certification listed in PAS2035.

• Retrofit Advisor
• Assessor
• Coordinator
• Designer
• Evaluator

The Retrofit Coordinator ensures that the holistic plans for a retrofit are cohesive and consequently implemented as originally designed. The Retrofit Assessor is a crucial cog as they provide the surveying of the building:

‘Domestic retrofit assessments are very wide-ranging and include factors such as the building’s construction, structure, and architectural features. The assessment will also consider the building’s current condition, including any structural defects, and issues such as leaks, condensation and mould build-up. Current installations such as heating and hot water, lighting, and ventilation will be documented. Any protected status, conservation restraints, or planning permission requirements will be investigated before work can begin.’ (Retrofit Academy)

Fabric first

Another facet of PAS2035 is the ‘fabric first’ approach to any retrofit. This usually relies on the method being technically sound and cost-effective, prioritising 5 stages of improvement. Firstly, bring the building fabric into good repair by dealing with defects that work against energy efficiencies, like water ingress and damp, structural defects like cracks, and poor pointing work. The poor pointing work and cracks can lead to the creation of cold bridges. Secondly, install simple measures that are low-cost and easy to install. This can include energy-efficient lighting, basic heating controls, and more effective control settings. Securing structural defects will also be enhanced by installing insulation and air-tightness measures, once again minimising thermal bridging. The final two measures concern themselves with energy efficiency and renewable energy sources; these are intrinsically linked to the role of insulation and the resulting operational carbon of the whole assembly.

PAS2035 is an integral part of the overarching Net Zero strategy of the UK. The building industry inevitably benefits from a specification that codifies the aims for retrofits; consequently, retrofits are executed to the same standard and make a positive impact on the carbon emissions of the industry. Given that approximately 40% of global CO2 emissions stem from the building industry, it is imperative to lower that figure. This accounts for both embodied and operational carbon emissions.

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