PHPP energy modelling, by a Certified Passive House Designer.
We build and interpret your project's PHPP model — the Passive House Planning Package — so design decisions are driven by accurate energy-balance calculations and building physics, not assumptions.
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 PHPP energy modelling?
PHPP (the Passive House Planning Package) is the validated energy-balance tool used to design and certify Passive House and EnerPHit projects. It calculates heating and cooling demand, primary energy, comfort and overheating from your real building geometry, fabric and climate data.
A PHPP model is only as good as the engineering behind it. We build, validate and interpret the model so it genuinely guides the design — and so it stands up to certifier scrutiny.
- What is the annual heating and cooling demand?
- Does the design meet Passive House or EnerPHit criteria?
- Where is the energy being lost, and what fixes it?
- Is there a summer overheating risk?
- How do different fabric or window options compare?
- What is the most cost-effective route to target?
Accurate, certifier-ready PHPP modelling
From geometry to a model you can trust
We take off areas, junctions, openings and climate data from your drawings and surveys.
We build the PHPP model with validated inputs for fabric, ventilation and thermal bridges.
We run the energy balance, test options and identify the most effective route to target.
We translate the numbers into clear, engineering-led design recommendations.
We hand certifier-ready outputs to the appointed independent certifier and answer queries.
The engineering payoff
Design choices driven by the energy balance, not by guesswork.
Test fabric, glazing and ventilation before committing money.
A robust model built to withstand independent certifier review.
Summer comfort checked, not discovered after handover.
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.
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.
ExplorePHPP Energy Modelling — FAQs
Is PHPP the same as SAP?
No. SAP is the UK compliance method; PHPP is a detailed engineering energy-balance tool used for Passive House and EnerPHit. PHPP is far more granular and is what certifiers rely on.
Do I need PHPP if I'm not certifying?
Many clients use PHPP purely as an engineering decision tool, even without seeking certification, because it predicts real performance and comfort accurately before construction.
Who builds the model?
Modelling is carried out by George Sora, a Certified Passive House Designer, so inputs and interpretation reflect recognised Passive House and building physics principles.
Can you model an existing PHPP file?
Yes. We can review, validate and develop an existing PHPP model, and coordinate it with the appointed independent certifier.
Model it accurately. Decide with confidence.
Get a PHPP model built and interpreted by a Certified Passive House Designer.