1. Why Over-Rafter Insulation (Aufsparrendämmung) Outperforms Traditional Methods
In standard between-rafter insulation (Zwischensparrendämmung), wooden rafters create repeated thermal bridges that account for up to 20% of continuous conductive heat loss.
By applying continuous rigid PIR or high-density wood-fiber insulation directly over the rafters, we create an unbroken thermal blanket across the entire roof surface. This delivers superior thermal values (U-value down to 0.12 W/m²K) without reducing internal attic living space.
GEG Statutory U-Value Benchmark
The German Building Energy Act (Gebäudeenergiegesetz - GEG) and European Energy Performance of Buildings Directive mandate a minimum roof U-value of 0.20 W/m²K for renovations. Zappydoqust standard assemblies achieve 0.14 W/m²K, qualifying property owners for national BAFA / KfW energy modernization grant programs.
2. Summer Heat Protection & Thermal Mass
High-performance roofing must defend against peak summer solar irradiance just as rigorously as sub-zero winter frost. We incorporate dense wood-fiber composite boards (phase shift > 11 hours) that delay heat penetration through the building envelope until late evening hours when natural cross-ventilation cools the structure.
3. Airtightness & Blower-Door Verification
Thermal insulation only functions at rated capacity if moisture-laden interior air is physically prevented from infiltrating the insulation core:
- Variable sd Membrane: Adapts its molecular permeability between summer (humidity open) and winter (vapor tight) to guarantee dry rafters year-round.
- Precision Masonry Connections: Air-sealing tapes and expanding primers bonded to all chimney junctions, gable walls, and ventilation pipes.
- Quality Audit: Verified by differential pressure Blower-Door testing (DIN EN 13829) with n50 value guaranteed below 1.0 h⁻¹.