EnerPHit: Passive House performance for existing homes.
We design deep retrofits to the EnerPHit standard using building physics analysis, PHPP modelling and engineering calculations — turning hard-to-treat existing buildings into warm, healthy, low-energy homes.
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 EnerPHit retrofit design?
EnerPHit is the Passive House Institute's standard for retrofitting existing buildings, where original constraints make full Passive House impractical. It delivers most of the comfort and energy benefit of Passive House on real, occupied homes.
We design the retrofit as one engineered system — fabric, airtightness, junctions and ventilation — and verify moisture safety and performance in PHPP and hygrothermal modelling before any work begins.
- Staged or single-step EnerPHit retrofit strategy
- Internal or external insulation build-ups, modelled for moisture safety
- Thermal-bridge and junction design at difficult details
- Airtightness strategy on an existing structure
- MVHR retrofit and ventilation design
- Verified energy demand and comfort in PHPP
An engineering-led EnerPHit design service
From survey to EnerPHit-ready design
We start from measured data — fabric, moisture, air leakage — often via a Home Health Diagnostics or Building Physics Assessment.
We model existing and proposed build-ups for energy and moisture safety, and set realistic EnerPHit targets.
We design a staged or single-step plan that fits how you live and how the building can be worked on.
We prepare the evidence and coordinate with the appointed independent certifier.
We support the works with details and verify the result against the modelled targets.
The engineering payoff
Warm surfaces and even temperatures in a building that never had them.
Build-ups modelled for condensation and drying before they are installed.
Deep, measured cuts in heating demand and running costs.
An engineered plan instead of a sequence of disconnected improvements.
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.
ExploreUltra-low-energy design to the Passive House standard, engineered from first principles.
ExploreAccurate Passive House Planning Package modelling, built and interpreted by a Certified Passive House Designer.
ExploreEvidence preparation and coordination with your independent Passive House Certifier, end to end.
ExploreEnerPHit Retrofit Design — FAQs
What is the difference between Passive House and EnerPHit?
Passive House is the standard for new buildings; EnerPHit is its counterpart for retrofitting existing buildings, with criteria adjusted for real-world constraints. We design to both.
Do you certify the EnerPHit project?
No. We are the engineering and design partner. Formal EnerPHit certification is carried out by an independent, accredited Passive House Certifier. We coordinate with them throughout and provide the modelling, design and evidence.
Can EnerPHit be done in stages?
Yes. EnerPHit supports a staged retrofit against a single overall plan. We design the plan so each stage is moisture-safe and moves you toward the target without locking in mistakes.
How do you avoid damp and mould?
Every build-up is checked with professional building physics modelling and engineering calculations for surface and interstitial condensation risk before it is specified — never assumed.
Retrofit it as one engineered system.
Plan your EnerPHit retrofit on building physics and PHPP — with a clear path to certification.