A green roof is often chosen for its water buffering and green appearance, but its insulating properties also play a role. While a green roof is not a replacement for traditional roof insulation, it does contribute to a more stable and comfortable indoor environment.
Additional protection against heat and cold
A green roof consists of several layers, including substrate and vegetation. Together, these layers form an extra shell on top of the existing roofing. In the summer, this helps to dampen solar heat. The roof heats up less quickly, keeping the underlying structure and the space underneath cooler.
In winter, a green roof acts as a slight insulator by reducing heat loss through the roof. The vegetation layer and substrate create additional stagnant air, which contributes to lower heat transfer. The effect is modest, but continuous.
Constant temperature
A major benefit of a green roof is reducing temperature fluctuations. Whereas a traditional roof gets hot quickly and then cools down again, a green roof provides more stability. This is not only pleasant for the indoor environment, but also beneficial for the life of the roofing material. Fewer extreme temperatures mean less stress on the roof.
No replacement for roof insulation
It is important to remain realistic about what a green roof can do for insulation. A green roof does not replace insulation boards or Rc values needed to meet building requirements. It does, however, provide a valuable addition to a well-insulated roof. Especially when combined with existing roof insulation, the effect becomes noticeable.
Additional insulation with an XPS insulated roof
When additional insulation is needed, a green roof can be combined with an insulation roof based on XPS sheets. This is an effective way to significantly increase the insulation value of the roof, while keeping the system technically reliable and affordable.
In this construction, the existing waterproofing layer is retained, usually bitumen. XPS insulation boards are installed on top of this layer, with the green roof system on top. This brings the insulation in contact with moisture. XPS is ideally suited for this: this material does not absorb water, does not mold and retains its insulating effect even in wet conditions.
XPS has a favorable lambda value, achieving an Rd value of approximately 3.85 for an insulation thickness of 100 millimeters when combined with a green roof. This insulates the roof from the outside and greening it at the same time. This is a sustainable long-term solution.
One concern with this roof structure is the height. Because of the extra insulation and the green roof, the total roof structure will be about 25 centimeters higher. This is always included in the design and quotation, so that it is clear in advance.
Conclusion
A green roof has an additional insulating effect and improves comfort in the home or building. Those who want additional insulation can combine it with an XPS insulation roof, which insulates and greenens the roof from the outside. This creates a future-proof roof solution that brings together comfort, sustainability and functionality.
