Understanding PAS 2035

Taking practical steps towards combating climate change (or simply improving your own energy system) can be tough. Entire retrofit projects have collapsed due to a single slip in the installation or evaluation process, and it can be hard to know how significant the changes will be.

Home dwellings account for almost 15% of all greenhouse gas emissions, and getting that number down to zero is going to be a daunting task. 

To guide the rework projects being done across the country, the UK government has guidelines for retrofitting dwellings and employing energy efficiency measures in domestic buildings.

The PAS 2035 retrofit project document serves as the core of the retrofit standards framework. Introduced alongside some recommendations from the Each Home Counts review, it delves into the process of providing high-quality energy retrofit measures in existing buildings.

This document covers not only these retrofit measures but also any related energy efficiency measures. This serves as a guideline for contractors to follow during the installation and monitoring of retrofit projects across the UK.

What is PAS 2035?

PAS 2035 is a key document for all energy efficiency and energy retrofit tasks, providing the clear guidelines needed to handle each retrofit project correctly. This includes a variety of information, from building assessment requirements to long-term monitoring methods.

The core reason behind the existence of PAS 2035 is to prevent a piecemeal retrofit process. A retrofit installer can’t simply adjust lighting units or monitor energy use before passing it on to another company – they need to aim to make a significant change. This is meant to speed up the slow progress towards a lower carbon emissions goal.

What does PAS 2035 do?

In terms of its actual contents, PAS 2035 is a specification for whole-dwelling assessment and retrofitting. 

It requires contractors and other related parties to take into account the requirements of the entire building, meaning that retrofit designs need to be more than just a single small change in part of the home.

PAS 2035 heavily revolves around assessing domestic homes for energy retrofit design options. This involves identifying areas of improvement and specifying the improvement measures, from monitoring and evaluation to the way that contractors demonstrate compliance.

What is PAS 2030?

PAS 2030 is the document that specifies energy efficiency installation measures. PAS 2035 and PAS 2030 are often used alongside one another since both relate to emissions and energy efficiency in slightly different ways.

Both domestic retrofit projects and business energy efficiency measures benefit from steps like the Energy Company Obligation scheme, but internal changes also have to be made. A retrofit advisor usually needs to do a risk assessment under both PAS 2035 and PAS 2030.

Simaxx for an Energy Retrofit

A complete energy refit, or any other long-term change, requires careful data management to get right. Both PAS 2030 and PAS 2035 require you to monitor and compare information cleanly, and that is something that Simaxx can do extremely well.

Simaxx can allow you to pool information in one place, format it into all kinds of reports, and handle raw data with a lot more clarity. 

No matter the specifics behind the retrofit, this can make a massive difference, especially to residential homes or smaller commercial buildings that may not have as much direct support.

Roles and responsibilities in PAS 2035

PAS 2035 (alongside PAS 2030) often requires a building manager or company to establish new roles. This includes:

  • The Retrofit Advisor – tasked with offering advice relating to the retrofit tasks.
  • The Retrofit Assessor – tasked with doing assessments on the property, from occupant appraisal or an investigation of the property’s heritage to an overall risk assessment. All the data gathered by them goes to the retrofit coordinator.
  • The Retrofit Coordinator – tasked with managing the entire project, especially during a transitional period. The retrofit coordinator is effectively the leader of a compliance team.
  • The Retrofit Designer – tasked with carrying out the design based on gathered data and plans. This usually means a building fabric-first approach, focused on materials and quality first and foremost.
  • The Retrofit Evaluator – tasked with monitoring the completed projects. This may sometimes be the same person as the retrofit assessor or retrofit coordinator.

These are not (usually) handled like actually hired positions. With the right qualifications, one person could fill all roles, from data gathering and air tightness testing to intermediate monitoring and building fabric-first plans.

How does PAS 2035 impact Landlords, Tenants, Contractors?

PAS 2035 forces contractors, tenants and landlords alike to think about the way they make energy efficiency improvements. Retrofit assessors and retrofit evaluator specialists need to perceive the retrofit work as part of an overall retrofit design, both from a technical standpoint and from the perspective of the tenants.


Landlords who own domestic buildings have to choose a retrofit assessor and retrofit installer that will follow PAS 2035 retrofit project guidelines. They also need to arrange for improvement opportunities that will impact the whole building, requiring more of a focus on whole house retrofit tasks.


Tenants also need to make sure that new projects meet with PAS 2035 standards, as do the retrofit assessor specialists or retrofit installers they work with. Domestic retrofit projects have to take a whole-house approach, and tenants need to be willing to let these projects happen.


Contractors are impacted by PAS 2035 the most. Their existing planning constraints and styles may need to be overhauled, especially when it comes to improvement option evaluation. 

A comprehensive review of a property requires the entire property to be considered, often alongside a significance estimate to judge the overall impact of the changes.

Retrofit Coordinator

Coordination and planning of a domestic retrofit need to be handled very differently under PAS 2035. A dedicated retrofit coordinator needs to approach the project as part of a larger whole.

Retrofit Assessor

Even the most basic retrofit risk assessment has to be conducted under these new requirements. This often means that risk assessments focus on more than just the individual project and that every in-depth assessment has to be performed to a high standard of accuracy.

Retrofit Installer

The end-to-end framework of PAS 2035 dictates how the installation should be carried out. While every project is different, following the best practice guidance included in the document makes both companies and individuals deliver quality retrofits that meet with PAS 2035 standards.

Retrofit Evaluator

Evaluating retrofit tasks under PAS 2035 also has to be approached in a similar way. A completed project may have to be checked for more than just installation quality but also overall effectiveness and any unintended consequences or flaws.

Retrofit Designer

A retrofit designer needs to work on complex projects, especially within any industrial strategy or as part of public-funded projects. Following a plan laid out by a retrofit coordinator may take some specific qualifications to get right.

How remote monitoring helps the PAS 2035 compliance process

Remote monitoring and evaluation make it easier to monitor specific details about a project’s overall compliance. 

Simaxx provides an effective way to monitor key measurements continuously, whether that is energy & temperature monitoring or the overall safety standards of a property.

Through Simaxx, the team assigned to handle a retrofit can make use of continuous monitor options, combining the platform with a range of sensors or automated systems to make data-gathering even easier. 

Not only does this provide more information to give to local authorities or inspectors, but it also provides more metrics to measure during and after the project.

Simaxx for a Retrofit Project

A retrofit requires a lot of data to be gathered, as well as constant monitoring and evaluation work to ensure that the entire project is progressing as intended. Simaxx is an invaluable platform for managing and transforming data into a variety of reports and analytics documents.

Careful handling of this data can be important for any retrofit, providing some clear points of comparison between the pre-and-post-retrofit compliance levels of the property. 

When working with historic buildings or other important spaces, it is vital to keep track of this information since PAS 2035 is focused on sweeping and noticeable changes instead of small tweaks.

Simaxx also provides a powerful space to manage long-term data monitoring, including information such as yearly fuel consumption. This data can be useful for a wide range of reasons, and being able to store or report on it effectively can be extremely important.

Simaxx for Energy Efficiency Measures

Simaxx can be a powerful tool for collecting and breaking down raw data. For example, more energy-efficient heating systems may use less energy, but Simaxx can also allow you to take into account extra details like yearly power/fuel consumption and overall heating potential.

Beyond that, you can use the Simaxx platform to highlight potential PAS 2030 or 2035 problems, such as poor air quality. Using specific sensors and measuring equipment can provide you with accurate air quality testing data, and Simaxx offers you a place to convert that raw data into something more practical.