PAS 2030 & PAS 2035 / mywarmhome.co.uk
Better retrofit starts with a plan.
Understand the standards, the checks and the reasons behind them — before work begins.
01
Assess
Understand the home, its condition and the people living in it.
02
Plan
Consider how insulation, heating and ventilation work together.
03
Install
Follow a suitable design with competent workmanship.
04
Check
Test performance and explain how the finished home works.
THE TWO STANDARDS
PAS 2030 and PAS 2035: what do they mean?
PAS means Publicly Available Specification: a standard published by BSI. These two standards address different parts of improving existing homes.
01
PAS 2035: the process
Sets out a whole-dwelling approach to assessment, design, coordination and evaluation. It considers how measures interact, rather than treating each upgrade in isolation. Read BSI’s PAS 2035 specification →
02
PAS 2030: installation
Sets requirements for installing energy efficiency measures, including installation processes, competence and commissioning. It works alongside the retrofit design. Read BSI’s PAS 2030 specification →
A product certificate is not the same as a compliant retrofit project. A good product still needs to suit the building and be designed, installed and checked properly.
WHY THE INDUSTRY NEEDED CHANGE
Each Home Counts.
Published in December 2016, the independent review chaired by Peter Bonfield examined consumer advice, protection, standards and enforcement in home energy improvements. It called for a stronger quality framework, clearer consumer protection and a more joined-up approach.
PAS 2035 developed as part of the response to that review. The central lesson remains useful for homeowners: an energy upgrade should be judged by what it does to the whole home and the people living there.
WHY WE REFER TO PAS
A warmer home should work as a whole.
At mywarmhome.co.uk, we explain upgrades together because changing one part of a building can affect another. Insulation, airtightness, heating and ventilation all influence comfort and moisture. The whole-home principles behind PAS help explain why the checks matter.
PAS requirements are used by many government-backed retrofit schemes. They can also provide a useful framework for privately funded work, but they are not a blanket legal requirement for every home improvement. Building Regulations and any applicable scheme or contract requirements still need to be met.
Check which edition and requirements apply to your project. TrustMark’s PAS guidance and updates →
WHO DOES WHAT?
The assessor records. The team turns evidence into a plan.
01
Retrofit Assessor
Surveys the home and records construction, condition, occupancy, energy performance and existing ventilation. Measurements and photographs help identify problems before work is designed.
02
Retrofit Coordinator
Oversees the retrofit process and brings the assessment, design, installation and checks together. The assessor does not make every design decision alone.
03
Retrofit Designer
Develops the technical solution, including how measures meet at junctions and how ventilation will work after the changes.
04
Retrofit Installer
Carries out the specified work and provides the installation and commissioning evidence needed for handover.
These roles support accountability through the project. TrustMark’s whole-house retrofit guidance →
WHY ALL THE VENTILATION CHECKS?
Air needs a way in, a route through and a way out.
An assessor checking door gaps, vents and fans is looking at a connected system. Sealing draughts or adding insulation can change air movement; the ventilation strategy must suit the improved home.
01
Door undercuts
A closed internal door can interrupt airflow. An undercut or another suitable transfer route lets air move between rooms towards extraction. A new carpet can reduce an existing gap.
02
Trickle vents
Background ventilators provide a planned supply of outside air where the ventilation design needs it. Suitable wall vents may be an alternative; the required provision depends on the system.
03
Extraction
Kitchen and bathroom extraction removes moisture where it is produced. A fan making a noise does not prove adequate airflow: the installed system needs appropriate testing.
04
Controls & handover
Residents need to know which systems run continuously, how boost settings work and what needs cleaning. A system that is misunderstood or switched off may not perform as intended.
For example, England’s 2021 Approved Document F describes an internal air-transfer opening equivalent to a 10 mm undercut beneath a 760 mm wide door, measured above the finished floor. This is an example from that edition, not an instruction to cut every door. The applicable guidance, door type and fire-safety requirements must be checked. See the 2021 guidance →
The design must be system-specific: MVHR normally supplies air mechanically and does not use background trickle vents in the same way as extract-only systems. England’s Part F guidance is not UK-wide; other nations have their own requirements, and editions have transitional arrangements. Check the applicable Approved Document F →
A window on a night latch is not an equivalent substitute for background ventilation under England’s published replacement-window guidance. Read the official ventilation FAQs →
LESSONS FROM PAST FAILURES
Standards need good design, workmanship and enforcement.
The following cases show why checks matter. They do not establish that every insulation problem is caused by ventilation; water entry, unsuitable measures and poor detailing can also contribute.
01
Fishwick, Preston — 2013
National Energy Action reports that around 360 households received external wall insulation. Poor choices of measures and poor-quality work left many homes with severe damp and mould. Its later project repaired 45 homes between 2022 and 2024, but other households still needed help. Read NEA’s account and remediation work →
02
ECO4 & GBIS — 2025 findings
The National Audit Office identified widespread quality problems with wall-insulation installations and failures in the schemes’ quality assurance and consumer protection. Its October 2025 report shows that having standards on paper does not guarantee effective delivery. Read the NAO investigation →
The practical lesson: ask for evidence of the assessment, the design, the installation checks and the route for putting defects right. A logo or completed checklist cannot replace careful work on the building.
BEFORE WORK STARTS
Four questions worth asking.
01
What has been found?
Ask for the assessment findings, including existing damp, defects and ventilation shortcomings. Understand which repairs must happen before upgrades.
02
What will change?
Ask how the proposed measures affect moisture and airflow, and which ventilation upgrades form part of the design.
03
Who is responsible?
Know who coordinates the project, who designed it and who will deal with a defect or complaint.
04
What will I receive?
Ask for commissioning results, operating instructions, maintenance advice, relevant guarantees and a clear handover.
1
home — assessed as a whole
mywarmhome.co.uk VIEW
The details are part of the job.
A door gap, a working extractor or a well-positioned vent can look like a small detail. Together, these details help the finished home work as intended. Ask your retrofit team to explain the reason for each requirement and how it fits your home.
BEFORE YOU UPGRADE
Understand the plan before the work begins.
Explore our ventilation guide or contact mywarmhome.co.uk to discuss the questions to put to your retrofit team.
Sources checked November 2026. This guide explains the principles; the project team must establish the requirements and design appropriate to your property.