Passive House design, engineered from first principles.
We design ultra-low-energy, comfortable and healthy buildings to the Passive House standard — using building physics analysis, PHPP energy modelling and engineering calculations, not assumptions or product sales.
Retrofit IQ provides the engineering, modelling and design. The formal Passive House and EnerPHit certification is carried out by an independent, accredited Passive House Certifier. We coordinate with the appointed certifier on your behalf throughout the project.
What is Passive House design?
Passive House (Passivhaus) is the world's leading standard for low-energy buildings. It delivers consistent comfort, excellent indoor air quality and very low heating demand through a fabric-first, engineering-led approach — not bolt-on technology.
As your design partner, we develop the building fabric, airtightness strategy, thermal-bridge-free junctions and ventilation design, and verify the whole design in PHPP before it is built.
- Fabric and U-value strategy for walls, roofs and floors
- Thermal-bridge-free junction design
- Airtightness strategy and continuous air barrier
- High-performance windows and shading
- MVHR ventilation design
- Verified heating demand and comfort in PHPP
An engineering-led Passive House design service
From brief to certified design
We establish your goals, site constraints and target standard, then sense-check feasibility in PHPP.
We model the fabric, junctions, ventilation and energy balance — the engineering core of the design.
We develop fabric build-ups, details and specifications that hit the targets and stay buildable.
We prepare and submit the evidence and coordinate with the appointed independent certifier.
We support the build with details and answer site queries, then verify performance on completion.
The engineering payoff
A fabric-first design that needs little energy to stay warm.
Warm surfaces, no cold spots and stable temperatures year-round.
Continuous filtered fresh air through designed MVHR ventilation.
Performance verified in PHPP before a single brick is laid.
The engineering & design partner — not the certifier
Retrofit IQ provides the engineering, modelling and design, led by a Certified Passive House Designer. The formal certification is always awarded by an independent, accredited Passive House Certifier. We coordinate with them on your behalf — so you get rigorous engineering and a smooth certification, with one point of responsibility.
Part of one engineering-led workflow
Our services connect into a single, engineering-led journey — measured diagnosis, professional building physics modelling and engineering calculations, and a designed retrofit. They are not separate offers; they are stages of the same process.
Measured diagnosis of heat loss, damp, mould, air leakage and ventilation — the evidence base for everything that follows.
ExploreProfessional building physics modelling and engineering calculations to predict how your construction will perform before any work begins.
ExploreIndependent assessment of whether your building fabric is ready for an efficient, low-running-cost heat pump.
ExploreAccurate Passive House Planning Package modelling, built and interpreted by a Certified Passive House Designer.
ExploreThe Passive House retrofit standard — a staged, engineering-led path to a high-performance existing home.
ExploreEvidence preparation and coordination with your independent Passive House Certifier, end to end.
ExplorePassive House Design — FAQs
Do you certify the Passive House?
No. We are the engineering and design partner. The formal Passive House certification is carried out by an independent, accredited Passive House Certifier. We prepare the design and evidence and coordinate with the certifier throughout — so you have a single engineering point of contact.
Does it have to be a new build?
No. Passive House principles apply to new build, while existing homes follow the EnerPHit retrofit standard. We offer both — see our EnerPHit Retrofit Design service.
What software do you use?
We model in PHPP, the recognised Passive House energy-balance tool, alongside professional building physics modelling and engineering calculations. We focus on the engineering result, not product sales.
Who carries out the design?
Every design is led by George Sora, a Certified Passive House Designer, so your project is grounded in recognised Passive House principles and building physics from day one.
Design it to perform. Then certify it.
Start your Passive House project with an engineering-led design partner and a clear path to certification.