Isolatie en energie
Rc-waarde
The R-value (Rc) expresses the thermal resistance of a construction in m²K/W. The higher the R-value (Rc), the better the construction insulates. For new builds and large-scale renovations, the Bouwbesluit (Dutch Building Decree) prescribes minimum values.
Hoofdgids · 16 min lezenDakkapel isolatie: complete uitlegIndicative requirements
| Building component | Indicative minimum R-value (Rc) |
|---|---|
| Facade | ≥ 4.7 m²K/W |
| Roof | ≥ 6.3 m²K/W |
| Floor | ≥ 3.7 m²K/W |
Veelgestelde vragen
Vragen over dit onderwerp
What is a good R-value (Rc) for a dormer?
For new builds and major renovations of a roof construction, the Environment and Planning Act (Besluit bouwwerken leefomgeving) dictates a minimum R-value (Rc) of 6.3 m²K/W. For existing buildings, the minimum is lower (often 3.5 m²K/W), but in practice, the new build value is used for a new dormer to prevent thermal bridges and condensation.What is the difference between R-value (Rc) and U-value?
The R-value (Rc) expresses the thermal resistance of a built-up construction (in m²K/W, higher is better) and is used for walls, roofs, and floors. The U-value expresses the thermal transmittance coefficient of a building component (in W/m²K, lower is better) and is mainly used for windows and window frames.How is the R-value (Rc) of a dormer calculated?
The R-value (Rc) is determined by dividing the thickness of each material layer by the thermal conductivity coefficient (lambda) of that material and adding all layers together, increased by the internal and external surface resistances. PIR insulation has a low lambda, making a high R-value (Rc) achievable with just a thin layer — relevant given the limited thickness of a dormer wall.