RetroFIT IQ — Building Performance Diagnostics
Retrofit IQ Building Physics Assessment

Most contractors recommend insulation. Retrofit IQ predicts how your building is expected to perform.

An engineering-led building physics assessment that uses advanced building physics modelling to calculate heat loss, moisture risk, thermal bridges and insulation options — predicting your building's performance before you invest in retrofit works.

George Sora
Certified Passive House Designer
Carried out using professional building physics modelling and engineering calculations — not by assumptions or product recommendations.
Book a Building Physics Assessment See a Sample Report

Most contractors recommend products. Retrofit IQ first models and predicts how your building will perform before any work begins.

This is our biggest differentiator. After a standard investigation or diagnostic survey, you can commission a Building Physics Assessment for an advanced engineering analysis — so your retrofit decision is based on measured data and building physics, not assumption.

Standard assessment vs advanced building physics assessment

One additional engineering stage sets us apart: Predict.

Our standard process runs Investigate → Diagnose → Design → Remedy → Verify. The advanced Building Physics Assessment adds a Predict stage between Diagnose and Design, where we model and predict how the proposed construction is expected to perform before any work begins.

Standard assessment
Step 1
Investigate
Step 2
Diagnose
Step 3
Design
Step 4
Remedy
Step 5
Verify
Advanced Building Physics Assessment
Step 1
Investigate
Step 2
Diagnose
Step 3 · Premium
Predict
Step 4
Design
Step 5
Remedy
Step 6
Verify
What it is

What is a Building Physics Assessment?

A Building Physics Assessment is a specialist engineering analysis of how a building element — a roof, wall or floor — performs in real conditions. Using advanced building physics modelling, we assess how your construction behaves before and after retrofit, so the design is based on evidence rather than assumption.

It is the difference between an engineering-led retrofit and a standard insulation quote — and it is how we de-risk your investment before any construction begins. The methodology is grounded in recognised building physics and Passive House principles.

It answers questions like
  • How much heat is being lost through this wall, roof or floor?
  • Which insulation build-up is most suitable for this construction?
  • Is there a risk of condensation forming inside the construction?
  • Will the internal surface temperature improve enough to stop mould?
  • How will the upgrade perform through a cold UK winter?
  • Could the upgrade increase the risk of summer overheating?
  • Is the proposed solution safe from a moisture perspective?
What we predict

Engineering predictions, before a single board goes up

Using professional building physics modelling and engineering calculations, we predict how your existing and proposed construction will behave across the year — so the recommendation is engineering-led from the start.

Winter heat loss
Summer overheating
Thermal bridge performance
Surface condensation risk
Interstitial condensation risk
Internal surface temperatures
Moisture behaviour over time
U-value improvements
Energy demand before and after retrofit
Retrofit performance before construction starts
Engineering decision support

We don't just inspect a building or recommend products

This is one of the biggest differences between Retrofit IQ and a standard survey. We use professional building physics modelling and engineering calculations to support real engineering decisions before any work begins — so you invest with confidence rather than hope.

The Retrofit IQ principle

Engineering decisions based on calculations, not assumptions.

Decisions we help you make
  • Which insulation thickness gives the best performance
  • Whether a proposed wall or roof build-up is safe
  • Interstitial condensation risk
  • Thermal bridge assessment
  • Moisture movement through the construction
  • Internal surface temperature prediction
  • Summer overheating risk
  • U-value optimisation
  • Build-up comparison before installation
  • Predicting performance before spending money on retrofit works
Predict before you build.

Engineering decisions based on calculations, not assumptions.

Don't spend thousands on insulation before knowing how your proposed construction is expected to perform. We calculate it first.

Engineering interpretation, not just software

Carried out by a Certified Passive House Designer

Every Retrofit IQ Building Physics Assessment is carried out and personally interpreted by George Sora, Certified Passive House Designer, using professional building physics modelling and engineering calculations — not assumptions or product recommendations. Every recommendation is based on engineering analysis, measured data and recognised building physics and Passive House principles, rather than generic insulation specifications.

Sample report

Inside a Retrofit IQ Building Physics Report

These are genuine outputs from one of our completed engineering models. Each page of the report turns building physics into a clear, evidence-based picture of how a construction is expected to perform.

Construction Build-Up & U-value Calculation — Retrofit IQ Building Physics Report
Report page 01

Construction Build-Up & U-value Calculation

What you're looking at

The complete wall build-up is modelled layer by layer — from internal plaster through to the external rainscreen — alongside the calculated U-value, total thickness, internal surface temperature and heat-storage capacity.

Why it matters

The U-value (here 0.176 W/m²K) is the headline measure of how much heat the fabric loses. Modelling it first means the insulation specification is proven by calculation before any money is spent — not assumed from a rule of thumb.

Temperature Profile Analysis — Retrofit IQ Building Physics Report
Report page 02

Temperature Profile Analysis

What you're looking at

A steady-state temperature gradient through every layer of the construction under cold UK winter conditions, showing exactly where the temperature drops across the build-up.

Why it matters

It confirms the insulation is doing the work and that internal surfaces stay warm enough to avoid the cold spots where condensation and mould take hold.

Moisture & Relative Humidity Profile — Retrofit IQ Building Physics Report
Report page 03

Moisture & Relative Humidity Profile

What you're looking at

The relative-humidity distribution through the wall, layer by layer, including the ventilated cavity that allows the construction to dry outward.

Why it matters

Trapped moisture inside a wall leads to decay, mould and insulation that quietly stops working. This proves the build-up manages moisture safely across the seasons.

Interstitial Condensation Risk (Glaser Analysis) — Retrofit IQ Building Physics Report
Report page 04

Interstitial Condensation Risk (Glaser Analysis)

What you're looking at

A vapour-pressure diagram comparing the actual vapour pressure against the saturation pressure through the construction — the recognised method for checking hidden, in-wall condensation.

Why it matters

If the two curves meet, condensation is forming inside the wall. Confirming a clear safety margin means the chosen build-up will not silently rot from the inside out.

Summer Overheating & Thermal Buffering — Retrofit IQ Building Physics Report
Report page 05

Summer Overheating & Thermal Buffering

What you're looking at

The dynamic summer analysis showing phase shift (here 9.5 hours) and amplitude damping — how long peak outdoor heat takes to reach the inside, and how far that temperature swing is reduced.

Why it matters

Retrofit is not only a winter problem. This predicts whether the upgrade keeps rooms comfortable in summer, rather than introducing an overheating risk.

Example outputs from a completed Retrofit IQ engineering model. Each assessment is modelled to your property and measured data.

What you receive

The Retrofit IQ Building Physics Report

You receive a clear, professional PDF report with graphical outputs — the engineering evidence behind your retrofit decision, interpreted by a Certified Passive House Designer and written so a homeowner can understand it.

Professional PDF report with U-value, temperature and moisture graphs, and a recommended build-up.
Existing construction assessment
Proposed construction assessment
Existing and proposed U-value calculations
Heat-loss calculations
Temperature profile through the construction
Moisture profile through the construction
Condensation risk analysis (surface and interstitial)
Surface temperature analysis
Comparison between retrofit options
Recommended insulation build-up
Practical retrofit recommendations
Visual graphs and technical outputs
Standard investigation vs engineering assessment

The same investigation — plus advanced engineering modelling

Standard Investigation Report
  • Site inspection
  • Visual assessment
  • Thermal imaging where appropriate
  • Moisture readings
  • Air leakage observations
  • Ventilation observations
  • Practical written findings
  • Recommended remedial actions
  • Budget upgrade options
Advanced engineering assessment
Retrofit IQ Building Physics Assessment

Everything in the standard report, plus:

  • Advanced building physics modelling
  • Existing and proposed U-values
  • Heat-flow and heat-loss calculations
  • Condensation risk modelling (surface + interstitial)
  • Moisture movement and drying-potential analysis
  • Summer overheating and winter performance prediction
  • Thermal bridge and surface-temperature assessment
  • Energy demand before and after retrofit
  • Comparison of multiple construction build-ups
  • Engineering interpretation by a Certified Passive House Designer
Assumption vs engineering

Standard contractor vs Retrofit IQ

A traditional contractor generally recommends products based on experience. Retrofit IQ investigates, measures, calculates, models and predicts building performance before making a single recommendation.

Standard contractor
Retrofit IQ Building Physics Assessment
Recommends an insulation product based on experience and habit
Investigates and measures the actual construction first
Insulation thickness is a guess or a rule of thumb
Thickness is sized from calculated U-values and heat-loss figures
No condensation or moisture check
Models interstitial condensation, moisture movement and drying potential
Thermal bridges and cold spots overlooked
Thermal bridges and internal surface temperatures analysed
No idea how it behaves in summer
Predicts summer overheating and winter performance
One option, take it or leave it
Multiple build-ups compared so you decide on evidence
You find out if it worked after you have paid
You know how it should perform before any work begins
Decisions based on assumption
Decisions based on engineering, measured data and Passive House principles
For homeowners, architects & contractors

Why choose Building Physics before carrying out retrofit works?

A Building Physics Assessment pays for itself by getting the design right before any money is spent on site.

Avoid expensive design mistakes

Catch problems on paper before work starts on site — not after you've paid for them.

Compare build-ups before installation

Test different wall, roof and floor options side by side and choose on evidence.

Reduce condensation & mould risk

Check moisture movement and surface temperatures before committing to a build-up.

Optimise insulation, don't overspend

Size insulation thickness from calculations rather than guesswork or rules of thumb.

Better comfort & energy performance

Engineer warmer, healthier, lower-energy rooms using building physics calculations.

Decisions based on calculations

Make engineering decisions based on calculations, not assumptions.

Connected services

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.

Home Health Diagnostics

Measured diagnosis of heat loss, damp, mould, air leakage and ventilation — the evidence base for everything that follows.

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Heat Pump Readiness

Independent assessment of whether your building fabric is ready for an efficient, low-running-cost heat pump.

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Passive House Design

Ultra-low-energy design to the Passive House standard, engineered from first principles.

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PHPP Energy Modelling

Accurate Passive House Planning Package modelling, built and interpreted by a Certified Passive House Designer.

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EnerPHit Retrofit Design

The Passive House retrofit standard — a staged, engineering-led path to a high-performance existing home.

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Passive House Certification Support

Evidence preparation and coordination with your independent Passive House Certifier, end to end.

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Frequently asked questions

Building Physics Assessment — FAQs

Is the Building Physics Assessment a separate service?

It is a specialist engineering assessment that follows a standard investigation. After we complete a diagnostic survey, you may choose to commission a Retrofit IQ Building Physics Assessment if you would like an advanced engineering analysis before investing in retrofit works. A standard survey identifies the problems; this assessment predicts how your building is expected to perform after the proposed upgrade, before any work begins.

What does 'advanced building physics modelling' actually involve?

We build a digital model of your existing and proposed construction using professional building physics modelling software, then use it to calculate U-values and heat loss, analyse thermal bridges, predict surface and interstitial condensation risk and moisture movement, and evaluate both winter heat loss and summer overheating. We can also compare several construction build-ups side by side and estimate energy demand before and after retrofit — so the recommendation is grounded in engineering rather than a generic insulation specification.

Who carries out the assessment?

Every Retrofit IQ Building Physics Assessment is carried out and personally interpreted by George Sora, a Certified Passive House Designer — not by a general builder. You are not simply receiving software-generated outputs; you receive professional engineering interpretation based on recognised building physics and Passive House principles, your measured site data and the specifics of your property.

Why model the building before installing insulation?

Because the wrong insulation build-up can move the dew point into the construction and cause hidden interstitial condensation, decay and mould. Modelling the existing and proposed build-ups first lets us compare options, check moisture safety and surface temperatures, and recommend a solution that performs — rather than guessing a thickness and hoping.

Do you guarantee exact energy savings?

No. We present predicted performance based on building physics modelling and your measured data — not guaranteed savings. Real-world results depend on workmanship, occupancy and how the home is used. The value is in making an evidence-based engineering decision and avoiding moisture risk before you spend on construction.

Which of my walls, roofs or floors can be modelled?

Any building element where a retrofit decision matters — solid or cavity walls, internal or external wall insulation, lofts and warm/cold roofs, and suspended or solid floors. We model the elements relevant to your project and compare the upgrade options that make sense for your building.

How do I commission an assessment?

Tell us at booking, or request it after your standard investigation once we know which elements need modelling. It follows on naturally from our existing services — Home Health Diagnostics, Thermal Imaging, Blower Door Testing, Insulation & Retrofit and more.

Predict the performance first. Then build it correctly.

Book a Building Physics Assessment and make an evidence-based, engineering-led retrofit decision before you spend on construction.

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