Renovation Roadmap (iSFP): Process, Costs and Funding Bonus in 2026
The individual renovation roadmap (iSFP) is regarded as the most important planning document for energy modernisation in 2026. This guide explains what an iSFP achieves, how the process with the energy consultant works and which costs arise. Plus: the 5% funding bonus, a sensible order of measures and a case study for a prefab house built in 1982.
The individual renovation roadmap (individueller Sanierungsfahrplan) – iSFP for short – is in 2026 the central planning document for anyone who wants to bring an ageing house up to scratch energetically. It sets out step by step which measures make sense in which sequence, what costs to expect and how much saving they bring. And it pays off: anyone renovating according to the iSFP receives a 5 percent additional funding bonus for individual measures under the BEG EM. This guide clarifies what the iSFP achieves, what the process with the energy consultant looks like, what it costs, how high the BAFA subsidy is and in which sequence the measures should come – and works it all through on a prefab house from 1982. All figures are guide values for 2026. Beforehand, you can use our calculator to calculate prefab house costs and realistically estimate your budget.
What the individual renovation roadmap (iSFP) stands for
Short answer: The individual renovation roadmap is a standardised consulting document that a certified energy consultant prepares for your specific building. It documents the current condition, describes all sensible renovation measures including costs, saving and sequence, and bundles them clearly into a timeline. The iSFP is uniformly structured nationwide, is funded by 50 percent via the BAFA and at the same time serves as proof for the additional 5 percent funding bonus on later individual measures.
Unlike a simple cost estimate, the iSFP considers your house as an overall system: it ensures that you don't first renew the heating and then insulate – a sequence that leads to an oversized and more expensive system. Instead, a coherent plan emerges that you can implement in stages over up to 15 years. The iSFP is presented in two variants: as "renovation in one go" and as "renovation in steps" – so you can see at a glance which route suits your budget.
iSFP or BzA — don't confuse the two
The iSFP is a strategic consultation for the entire renovation path. Separate from this is the "confirmation for the application" (BzA), which the energy-efficiency expert issues separately for each funded individual measure. The two interlock: the iSFP provides the strategy and the 5 percent bonus, the BzA unlocks the specific funding. For the bonus, the respective measure must be implemented within the validity of the iSFP.
Process with the energy consultant: to the iSFP in five steps
Short answer: The route to the iSFP proceeds in 2026 in five stages: first you choose a BAFA-listed energy-efficiency expert and commission them. Then comes the on-site appointment with a survey of the envelope, heating and consumption. Next the consultant evaluates the data and works out the measure packages. After that you receive the finished iSFP in the uniform format including an explanatory discussion. Finally, you implement the measures in the recommended sequence – each one with a 5 percent bonus. The whole process usually takes four to eight weeks.
- 1. Find an energy consultant: only certified energy-efficiency experts from the federal list may prepare a fundable iSFP.
- 2. On-site appointment: the consultant records the building envelope, windows, roof, heating and hot water and reviews your consumption data.
- 3. Analysis and calculation: from the data, specific measure packages with costs, saving potential and CO2 impact are derived.
- 4. Handover of the iSFP: you receive the standardised document including an explanatory discussion — presented clearly with traffic-light logic.
- 5. Implementation in stages: you work through the measures by budget and priority, each with the additional 5 percent bonus.
Important: commission the energy consultant before you award any measure – only an expert from the federal list of energy-efficiency experts is eligible for funding. Ideally, the consultant accompanies you throughout the entire renovation, issues the required confirmations for each funding and takes over the construction supervision. This construction supervision is also eligible for funding. How individual renovation budgets in a prefab house are divided up is explained in the modernisation guide; the typical components and work steps of a prefab house renovation are described in detail by the corresponding guide. Anyone wanting to deepen the fundamentals will find them in the prefab house overview.
Costs and BAFA subsidy: what to expect with the iSFP
Short answer: An iSFP for a one- or two-family house is, as a guide value in 2026, between €1,300 and €2,000. The BAFA subsidises the energy consultation with 50 percent of the fundable costs, capped at €1,300 for one- and two-family houses. In practice, after deducting the subsidy, often only €200 to €700 remain as your own contribution. The subsidy flows directly to the energy consultant, so your invoice amount is reduced from the outset – you don't have to pay in advance.
Costs and subsidy for the iSFP 2026 (guide values)
| Item | One-/two-family house | Apartment building (from 3 units) |
|---|---|---|
| Consulting costs gross | €1,300–2,000 | €1,700–2,600 |
| BAFA funding rate | 50% | 50% |
| Maximum subsidy | €1,300 | €1,700 |
| Own contribution (guide value) | €200–700 | €300–900 |
| Payout | directly to the consultant | directly to the consultant |
| Validity of the plan | 15 years | 15 years |
Don't view the consulting costs as a mere expense, but as an investment: the iSFP prevents costly wrong sequences and unlocks the 5 percent bonus – which, with larger measures, quickly adds up to several thousand euros. A complete overview of all funding routes is given by the article on funding programmes.
Energy consultation and renovation bundled from a single source
Firms from our network combine iSFP preparation, funding processing and renovation at a fixed price. We connect you with suitable providers who put your renovation roadmap directly into practice — including application to BAFA and KfW.
The 5% iSFP bonus under the BEG EM: how the additional funding works
Short answer: Anyone who carries out an individual measure on the building envelope or system technology on the basis of an iSFP receives in 2026 an additional funding bonus of 5 percentage points – on top of the regular basic funding of the BEG EM. Thereby, 15 percent for insulation becomes 20 percent, and 15 percent for windows likewise becomes 20 percent. The bonus applies to the measures the iSFP has recommended and is limited to an annual maximum amount of the fundable costs. For the heating replacement itself, the iSFP bonus does not apply – other bonuses come into play there.
Funding with and without the iSFP bonus compared (BEG EM 2026, guide values)
| Measure | Basic funding | With iSFP bonus |
|---|---|---|
| External wall insulation (ETICS) | 15% | 20% |
| Roof insulation | 15% | 20% |
| Basement ceiling insulation | 15% | 20% |
| Windows with U_w ≤ 0.95 | 15% | 20% |
| Ventilation system with heat recovery | 15% | 20% |
| Heating optimisation | 15% | 20% |
| Heating replacement (heat pump) | 30% + bonuses | no iSFP bonus |
A calculation example: for a facade insulation costing €40,000, you receive €6,000 subsidy with basic funding (15 percent), but €8,000 with the iSFP bonus (20 percent) – €2,000 more, from the bonus alone. Across several measures, the consulting investment has thereby often already paid for itself at the first big step. As a general rule, it still applies: the funding application must be submitted before the contract is awarded.
The sensible sequence of measures: envelope first, then heating
Short answer: The sequence that is smartest both energetically and economically is in 2026: first the building envelope, then the system technology. Anyone who first insulates roof, facade and windows and only afterwards installs the heat pump manages with a smaller, cheaper system – both in acquisition and in operation. After the envelope comes a ventilation system with heat recovery to prevent mould, then the heating and finally photovoltaics with storage. Exactly this logic is depicted by the iSFP and justified for your building.
- 1. Insulation of the roof or top-floor ceiling — here the saving per euro is greatest and often a GEG obligation.
- 2. Insulation of the external wall (ETICS) — considerably reduces heat losses and thermal bridges.
- 3. Replace windows — ideally in parallel with the facade insulation to share scaffolding and connection costs.
- 4. Insulate the basement ceiling or foundation slab — noticeably more warmth underfoot on the ground floor.
- 5. Ventilation system with heat recovery — needed after the envelope insulation to prevent mould damage.
- 6. Heating replacement to a heat pump — now correctly sized for the insulated existing building and therefore cheaper.
- 7. Photovoltaics with storage — as a supplement to the heat pump for low operating costs.
If the heating replacement cannot be postponed due to a defect or a GEG obligation, at least factor the later insulation into your calculation and size the heat pump for the future, insulated heat demand. Which GEG obligations apply here is explained in the GEG guide 2026.
A case study: prefab house from 1982 with 130 m²
Short answer: A typical timber-frame prefab house from 1982 with 130 square metres consumes in 2026 around 230 kWh/m² per year – heating costs of about €3,800. Here the iSFP proposes four stages over eight years: roof and facade insulation, window replacement, ventilation with heat recovery and finally a heat pump with photovoltaics. The total costs amount to around €118,000 gross; after BEG funding and the iSFP bonus, about €72,000 remain as the own contribution. The final energy demand drops to around 70 kWh/m², the heating costs to a good €1,200 per year.
Staged plan for a prefab house built in 1982 with 130 m² (guide values 2026)
| Stage | Measure | Costs gross | Funding incl. iSFP bonus |
|---|---|---|---|
| Year 1 | Roof and facade insulation | €48,000 | 20% = €9,600 |
| Year 2 | Windows triple glazing | €16,000 | 20% = €3,200 |
| Year 4 | Ventilation with heat recovery | €12,000 | 20% = €2,400 |
| Year 6 | Air-to-water heat pump | €26,000 | up to 55% = €14,300 |
| Year 8 | Photovoltaics 8 kWp + storage | €16,000 | regional/EEG |
| Total | Full renovation in stages | ≈ €118,000 | ≈ €46,000 subsidy |
Why the stages come in exactly this order
The insulation is deliberately at the start: it pushes the heat demand down so far that the heat pump in stage four can be significantly smaller and cheaper. If the heat pump came first, it would have to be sized for the high demand of the unrenovated house – more expensive both to buy and in electricity consumption. It is exactly this chain of cause and effect that makes the iSFP so valuable: it justifies the sequence not with gut feeling, but with the figures of your specific house.
Once all stages are complete, the house in the example reaches a standard close to the efficiency house – at a fraction of the cost of a new build. Whether this route actually pays off for your building or whether a new build would be cheaper is examined by the comparison buying an old building or building new. Anyone who would rather build new will find initial pointers in the show home and in the house-building process.
Create a renovation roadmap and have it implemented immediately
Request quotes free of charge and without obligation from providers who offer iSFP, funding processing and renovation from a single source. This way you secure the 5 percent bonus and know from the start what your renovation costs.
What does your dream house really cost?
Request suitable quotes from vetted manufacturers for free and compare the prices per square metre for your construction project.
Compare house prices nowImportant questions briefly explained
The most common price questions around Renovation Roadmap (iSFP) – answered concisely by the Prefabricated House editorial team (as of 2026).
