Is an Energy Audit Enough? Why Existing Buildings Need More Than an iSFP

Why an unrefurbished existing building needs more than an energy audit — and what neither energy consultants nor building surveyors can deliver on their own.

Around four in ten homes in Germany date from the 1950s, 1960s and 1970s. Many of these buildings are still largely in their original state: the electrical installation, water and heating pipes, and concrete components are often in serious need of repair. Windows and heating systems have usually been replaced once after 20 to 30 years, and the roof has been re-covered or re-sealed.

Is an individual refurbishment roadmap (iSFP) enough for buildings like these? The short answer: no. The iSFP answers a single question — what is possible in energy terms — and leaves the decisive one open: where is a euro sensibly invested in this building? Added to that is a second question that is rarely asked: who is actually giving the advice here — and with what mandate? Why both determine budget and sequence is what this article sets out in detail.

An example from a current enquiry: an owner is told that the access balconies of his apartment building require complete refurbishment — estimated cost: 300,000 euros. My initial assessment: partial renewal and repair are sufficient — for around a tenth of the sum. Whether that holds must be shown by the building survey. What is remarkable is the path to the recommendation: an assertion, a single quote, a recommendation to commission — and at no point did an independent planner assess necessity and scope or obtain a comparative quote. Many parties advise on a building: property managers, contractors, energy consultants — each from within their own mandate. The independent view of what the building actually needs only entered the picture here through the owner's enquiry.

What a refurbishment roadmap delivers — and where its mandate ends

The individual refurbishment roadmap is a good instrument. It assesses the energy performance of your building, calculates measure packages for insulation, windows and heating, arranges them into sensible steps and unlocks the BAFA subsidy — with an additional bonus if measures are implemented afterwards.

BAFA funds the consultation at 50 percent of the fee, capped at 650 euros for single- and two-family houses — and the underlying guideline expires on 31 December 2026. The iSFP bonus has also been tightened since 21 July 2026: the 5 percentage points now only apply from 30,000 euros of eligible investment and only to the amount above that threshold. Anyone planning a subsidised consultation should apply before the end of the year.

But that is where the energy consultant's mandate ends. The iSFP looks at the components that enter the energy balance — building envelope and system technology. That is not negligence; it is the definition of the tool. The limit lies not in the person but in the scope of the commission: a refurbishment roadmap is an energy concept, not a building concept.

What is not on the list

In existing buildings, the effort rarely lies in energy alone. What an energy-focused view systematically misses — and what decides costs and sequence in practice:

Damp cellars — usually not damage, but a concept error

The widespread misconception first: a damp cellar is not automatically a problem. Historically, that was precisely the cellar's job — together with the slightly raised ground floor, it kept the living floor dry; if anything got damp, it was the cellar. What has changed is the expectation: tenants today want dry storage there, and disputes between tenants and owners follow. The real damage pattern is a different one: over the years, unsuitable refurbishment concepts and materials were applied to walls that keep getting damp from outside or below — an unsuitable render on damp masonry will inevitably fall off again after a few years. A classic sight in existing buildings. It has little to do with the insulation question: it is the base of the walls that is damp, not the cellar ceiling — insulating the ceiling is usually possible without difficulty.

Roofs — pitched and flat roofs are two different subjects

On pitched roofs, the sarking membrane as a second water-bearing layer is often missing in older buildings. It is rarely considered whether clay tiles or concrete tiles are installed — in my experience concrete tiles are considerably less weather-sensitive: once the coating of a clay tile is defective, water penetrates and frost can burst the tile. And anyone planning a photovoltaic system first needs a look at the structural condition of the entire roof frame — what is needed are structural engineers with experience of existing buildings who can recalculate an old roof frame by the rules of its time; otherwise the PV system quickly turns into a complete refurbishment of the roof structure.

On flat roofs the first question is: has a test opening been made to establish the actual build-up? Even in the 1970s, insulation made of cork or similar materials may already lie beneath the bitumen membrane; whether a polystyrene layer was added decades later — possibly contaminated with the flame retardant HBCD — can only be established by opening the component. The refurbishment roadmap works non-destructively; component openings are not part of its scope.

Electrical installation — often closer to the limit than is visible

Two-wire installations and missing residual current devices, which are mandatory for bathrooms today. Outdated service connections with too little capacity for today's demands. Meter cabinets in stairwells — especially the old wooden ones — where utilities can refuse to replace the meter. None of this appears in an energy balance.

Water and heating pipes — the damage comes before the plan

With water pipes, the trigger is usually a pipe failure: pipes burst, the insurer pays — but only for repairing the affected area. Individual bathrooms end up with sections of new pipework while the majority remains in its original state. Add disputes between tenant and landlord over damaged belongings — the tenant's property is covered by their contents insurance, if they have one. And on the other side, building insurers not infrequently cancel older policies when a building has visibly not been maintained. What is consistently missing is a plan for bringing the building permanently up to today's standard. With heating and hot-water pipes, every refurbishment also starts with system questions no roadmap form asks: is hot water produced centrally or in individual flats? How does heat enter the building — oil, gas, electricity, in places still night storage heaters? Is there a contracting arrangement with a utility? Precisely these interdependencies make a detailed building survey and forward-looking investment planning indispensable.

Bathrooms and floor plans

Bathrooms and floor plans that no longer suit how people live decide lettability and value — they do not appear in an energy balance.

Hazardous materials — the cross-cutting issue

Hazardous materials affect almost every part of a building and change the cost and sequence of every measure that touches them. Since the amendment of the German Hazardous Substances Ordinance, buildings built before October 1993 are under a general suspicion of containing asbestos, with investigation duties before construction and refurbishment work. A refurbishment without a prior hazardous-materials survey is barely defensible today — yet many owners skip this step, knowingly or unknowingly.

Public safety obligations and operator responsibility

Railing heights and fall protection, first and second escape routes, to name just a few examples: the general safety situation of the property is checked neither by the energy efficiency expert nor by the refurbishment roadmap (more on operator responsibility in residential portfolios).

The sequence of trades

Anyone who insulates the facade first and replaces the windows afterwards pays for the interfaces twice — the sequence is itself a cost factor.

Behind each of these points stands the same question that no energy concept answers: what remaining service life does each component still have — and what does that add up to for the property as a whole? The remaining service life determines how urgent a measure is and where it belongs in the sequence. Technical condition, resulting costs and the overall economic view belong in one assessment — including a question that appears on no roadmap form: do you live in the building yourself, or is it let? The same measure pays off completely differently in the two cases.

And there is often an option that is rarely offered: temporary repair — a fix that keeps the building running and creates room to plan complete repair or modernisation properly instead of commissioning under pressure. Contractors frequently declare a component "beyond repair" — followed by a quote for complete renewal. In my experience a temporary repair is almost always possible; you just have to insist on it.

And the surveyor? He sees the other half

The obvious reaction: then I will additionally bring in a building surveyor. He assesses the structural condition — damp, cracks, roof, fabric — and names defects with their urgency. That too is a serious, clearly defined service.

But it mirrors the same problem: the surveyor documents what is. A concept for what it should become — which modernisation can be coupled with which repair, what that costs together and in which order it makes sense — is not part of his mandate. In the end, two reports lie on your table: an energy calculation and a condition description. The work of translating between the two papers remains with you.

Why the system pays for so little overall perspective

This is not about the competence of those involved but about the remuneration logic. The capped subsidy sets a price anchor around 1,300 euros gross — that is where the owner's share looks small, and competition pushes towards that point. From this, the consultant must deliver the on-site survey, the energy balance, the measure calculations, a 30-to-60-page report in the mandatory format and the explanatory meeting. Anyone doing that seriously works many hours for it — at this price, a standardised energy product inevitably emerges, not an overall view of your building. That is no reproach to the profession; it is the scope the subsidy model pays for.

The gap in between: thinking repair and modernisation together

This gap is exactly where I work. The frame is that of a construction project: a building survey across all trades, a viable concept, reliable costs, the right sequence. Repair (what the building needs anyway) and modernisation (what makes it better) are not calculated separately but coupled — because the money is won or lost at the interfaces: the scaffolding goes up once, the roof is opened once, the bathroom is done once.

A refurbishment roadmap tells you what is possible in energy terms. An architect tells you what makes sense for your building.

To be honest, this also needs saying: the classic architect's profile does not automatically cover this work either — design and construction supervision are its core; building diagnosis across all trades is a specialisation of its own. Mine comes from eleven years in the housing industry, where exactly what falls apart on a single building is brought together for entire portfolios — condition, costs and the question of which investment pays off when.

I do not replace the energy consultant — I put him in his place in the sequence. The subsidised energy consultation remains the right entry point; the formal iSFP is produced in cooperation with listed energy efficiency experts, while the building survey, the concept and the cost frame come from one source. And because I sell no construction work and take on no site supervision, the recommendation carries no self-interest: whoever earns from a measure should not be the one prioritising it.

Bottom line

A refurbishment roadmap is enough when the question is purely about energy. In unrefurbished existing buildings it almost never is — then the iSFP is an important building block, but the second document. The first is a view of the whole building: condition, remaining service lives, obligations, wishes, costs, sequence — and whether you live in it yourself or let it. Those who proceed in this order get not the maximum percentage out of the subsidy, but the maximum building.

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Related articles:

• What Does Energy Consulting Cost in Düsseldorf?
• Buyer Support vs. Building Surveyor
• iSFP 2026: Refurbishment Roadmap, BAFA Subsidy and Bonus

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