Building Performance Quality Assurance
Independent quality assurance throughout design and construction — so the critical performance details are installed correctly and the finished building performs exactly as intended.
Most performance is lost on site, not on the drawing
The single biggest gap in UK construction is the difference between designed performance and as-built performance. A building can be beautifully detailed on paper and still fail to deliver — because the insulation was installed with gaps, the air barrier was punctured, a vapour layer was lapped the wrong way, or a window was sealed poorly.
These are not exotic failures. They are everyday, invisible mistakes that get covered up by plasterboard and render, and then quietly cost the homeowner in cold rooms, high bills, draughts, condensation and mould for the next thirty years. By the time the symptoms appear, the cause is buried.
Building Performance Quality Assurance closes that gap. We verify the critical building-physics details at the moments they can still be checked and corrected — turning a hopeful design into a building that measurably performs.
- Gaps in insulation can cut real thermal performance by a third or more.
- A punctured air barrier means draughts, heat loss and a failed airtightness test.
- A vapour layer on the wrong side traps moisture and rots the construction from within.
- Cold junctions create the surfaces where condensation and black mould form.
- Poorly sealed windows cause draughts, cold reveals and persistent condensation.
- Defects found after completion cost many times more to put right — if they can be reached at all.
Investigate → Design → Verify
Our three service categories form one connected engineering journey. Each stage builds on measured evidence from the last.
Why verification is as important as good design
You can investigate a building thoroughly and engineer a brilliant solution, but if it is not built correctly, none of that effort reaches the finished home. Verification is the third pillar that protects the investment made in the first two. It is the difference between a building that should perform and a building that is proven to perform.
Why quality assurance matters, from a building physics perspective
Building performance is governed by physics, not by good intentions. Three continuous, interacting layers determine how a building behaves — and each one fails at the gaps. Quality assurance exists to protect those layers where they are most vulnerable: at junctions, penetrations and interfaces.
Insulation only works when it is continuous. A 5% gap in an insulation layer can increase heat loss far out of proportion to its area, because heat takes the path of least resistance. Verifying continuity protects the U-values the design relied on.
Uncontrolled air leakage carries both heat and moisture. A single unsealed service penetration can undo a whole wall's airtightness, drive draughts and deposit moisture inside the construction. The air barrier must be continuous and tested — not assumed.
Where warm, humid internal air meets a cold surface, it condenses. Get the vapour control layer, insulation position or surface temperatures wrong and the dew point lands inside the wall — causing hidden interstitial condensation, decay and mould. Verification keeps the dew point where physics says it is safe.
These layers are designed at the engineering stage, but they are made or broken on site. A thermal bridge that was modelled out can be built back in by a careless detail; a tested air barrier can be punctured by a later trade. Quality assurance is simply the discipline of checking, at the right moments, that the physics the design depended on actually exists in the finished building.
Everything we review, inspect and verify
Our quality assurance runs from the drawing board to the final report. It is one complete service, delivered across three stages of your project.
Design-stage review & strategy
We review architectural and construction drawings for building-performance risks before work starts — checking insulation continuity, junction detailing, the air barrier line and buildability, so problems are designed out rather than discovered on site.
We set a clear, project-wide performance strategy — fabric targets, airtightness target, thermal-bridge approach and ventilation — so every trade is working to the same measurable goal.
We check that specified materials are compatible and fit for purpose — vapour resistances, insulation types, tapes and membranes — to avoid interstitial condensation risk and premature failure.
We brief the build team on the critical details and why they matter, turning a drawing into something a site can actually deliver. Clear guidance up front prevents costly rework later.
We define a continuous air barrier line through every junction, service penetration and interface — the single biggest determinant of measured airtightness and comfort.
On-site verification & inspection
We inspect insulation as it goes in — checking for gaps, compression, cold bridging and continuity. Even small gaps dramatically reduce real-world thermal performance.
We verify the vapour control and air-barrier layers are continuous, correctly lapped and sealed, and installed on the right side of the construction — protecting the fabric from hidden moisture.
We check that openings are installed in the correct plane, insulated and sealed to the air barrier — a common source of draughts, cold reveals and condensation when done poorly.
We verify that the thermal-bridge-free details from the design are actually built — insulation continuity at junctions, around openings and at the building's most vulnerable cold spots.
Scheduled inspections at the key build stages, with clear photographic records and actions, so issues are caught while they are still cheap and easy to correct.
Testing, verification & documentation
An airtightness test while the air barrier is still accessible — so any leaks can be found and sealed before they are buried behind plasterboard and finishes.
A completion airtightness test that measures the building's actual performance against the target and provides certified evidence for Building Regulations or certification.
Calibrated thermal imaging of the completed building to confirm insulation continuity and reveal any remaining cold spots, missing insulation or air leakage.
Confirmation that the completed fabric performs as designed, so a heat pump can be sized correctly and run efficiently at low flow temperatures.
A complete, organised record of inspections, photos, test results and evidence — invaluable for warranties, certification, sale and future works.
A clear final report confirming what was inspected, what was verified, the measured results and any recommendations — proof the building performs as intended.
We make good contractors look great
Quality assurance is not about policing the build. It is about giving the site team clear, practical guidance on the details that matter, catching issues early when they are cheap to fix, and producing documented proof that the work was done correctly.
The result is fewer callbacks, fewer disputes, a stronger reputation and a finished building the contractor can stand behind. The best builders welcome it.
Where quality assurance connects
Quality assurance verifies what diagnostics measured and engineering designed. Explore the services it draws on most closely.
Quality Assurance — FAQs
Is Quality Assurance the same as Building Control?
No. Building Control checks compliance with the Building Regulations at a high level. Building Performance Quality Assurance is a far more detailed, physics-led inspection of the specific details that determine real-world energy performance, airtightness, moisture safety and comfort — the things that are rarely checked but almost always cause problems.
When should you appoint a Quality Assurance partner?
As early as possible — ideally at design stage, so the critical details are reviewed before they are drawn into the contract. The earlier we are involved, the more we can prevent rather than just detect. We can also join mid-project for on-site verification and testing.
Do you replace the contractor or main builder?
No. We work alongside your contractor as an independent quality partner. Good contractors welcome the support — clear details, fewer callbacks and documented proof that they built it correctly. We guide rather than police.
What happens if something is built incorrectly?
We catch it while it is still easy and cheap to fix — usually before it is covered up. We explain the issue, the performance consequence and the practical correction, then re-check that it has been resolved.
Is this only for Passive House projects?
No. Any project that cares about comfort, energy bills, durability or avoiding damp and mould benefits from verification — from a single-room retrofit to a full new build. The principles are the same: verify the details that matter.
Who carries out the assessment?
Inspections and verification are led by George Sora, a Certified Passive House Designer, so the focus is always on the building-physics details that genuinely affect performance.
Build it once. Build it right.
Bring in independent quality assurance and prove your building performs exactly as designed.