New Build in Siegen — Planning Your KfW Efficiency House
Why the KfW 40 standard pays off, what it costs, and how to plan optimally in the Siegen region.
New Build Standards 2026: What Applies?
Since 2023, Efficiency House 55 is the legal minimum standard for new builds (GModG, formerly GEG). That means: every new house may only use 55% of the primary energy demand of a reference building. But those seeking subsidies need to aim higher.
💡 Important: KfW subsidies for new builds are only available for the 'Climate-Friendly Residential Building' standard (KFW) — which requires at least Efficiency House 40 with sustainability requirements.
What Is an Efficiency House 40?
Efficiency House 40 uses only 40% of the reference building's primary energy demand. Several requirements must be met:
Building Envelope
High-quality insulation of all components: exterior wall U ≤ 0.18 W/(m²K), roof U ≤ 0.14, floor slab U ≤ 0.20, windows Uw ≤ 0.90.
Heating
Renewable energy required: heat pump, pellets, or district heating. No more fossil heating in new builds.
Ventilation
Mechanical ventilation with heat recovery (≥ 80%) is standard for EH 40.
Airtightness
Blower door test with n50 ≤ 1.0 h⁻¹. Every air leak costs energy and can lead to building damage.
How Much More Does EH 40 Cost?
Compared to the legal minimum standard (EH 55), an EH 40 typically costs 5–10% more in construction costs. For a 150 m² single-family home:
EH 55 (Minimum Standard)
- Construction~320.000 €
- KfW subsidy—
- Heating/year~1.200 €
EH 40 (Climate-Friendly)
- Construction~340.000 €
- KfW loan (297/298)up to €150,000
- Heating/year~700 €
* Construction costs excluding land and development. Heating costs with air-water heat pump, electricity price €0.30/kWh.
Subsidies for New Builds 2026
KfW 297/298 — Climate-Friendly New Build
Subsidized loan up to €150,000 per residential unit. Requirements: EH 40, renewable heating, no fossil fuel, lifecycle CO₂ calculation.
KfW 300 — Climate-Friendly + QNG
Loan up to €150,000 with even better interest rates. Additionally: Quality Seal for Sustainable Buildings (QNG). Requires QNG auditor and sustainability certification.
Specifics of Building in Siegen
The Siegen-Wittgenstein region has some specifics that should be considered in new build planning:
Climate Zone and Heat Load
Siegen is in climate zone 12 (design temperature −12°C). This means higher heat load than e.g. the Rhineland. The heating system must be sized accordingly.
Hillside and Topography
Many plots in Siegerland are hillside locations. This affects orientation (south-facing ideal for solar gains), earthworks, and drainage.
Solar Yield
Approx. 900–950 kWh/kWp per year in Siegen. Less than southern Germany (1,000–1,100), but sufficient for economical PV use. Plan PV from the start!
Regional Construction Costs
Construction costs in Siegerland are 5–10% below the average of metropolitan areas. An advantage that puts the extra cost for EH 40 in perspective.
Why an Energy Consultant Helps with New Builds
For KfW subsidies, an energy efficiency expert is mandatory. But even without subsidies, the support pays off — because planning errors cost many times more later.
- ✓Energy planning and GEG/GModG compliance documentation
- ✓KfW application and confirmation
- ✓Construction monitoring: insulation, airtightness, thermal bridge check
- ✓Organize and supervise blower door test
- ✓Optimally size PV system and storage
- ✓Coordinate QNG certification (if desired)
Planning a New Build in Siegen?
We support your new build from energy planning to completion — including KfW application and construction monitoring.
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