Multi-purpose roof use places new demands on design, application and finish
Urban densification and our climate challenge require efficient(er) use of space. Also with regard to our roofs, which places new demands on design, application and finishing. "The flat roof is increasingly regarded as a 'fifth facade' and used multifunctionally," notes Atze Walsweer, Technical Manager at Derbigum. "And that is not surprising, because with more than 400 million square meters of flat roof surface, there is enormous potential here. By performing the roof as a (combined) sedum roof, solar roof, residential roof, parking roof or water retention roof, sustainability and livability come together in a unique way and the ground level remains available for other (useful) purposes."
Within Derbigum, multifunctional roofs are called "special roofs. Here a distinction is made between the color groups green, yellow, red and blue.
"Green roofs are roofs with vegetation, which can range from moss, sedum, grass and herbs (extensive) to shrubs and trees (intensive)," Walsweer says. "Sustainable (solar) energy is generated on yellow roofs, while red roofs provide space for recreation. From terraces to sports fields or swimming pools. Finally, blue roofs are designed to store and/or buffer as much water as possible, possibly in combination with vegetation."
Derbigum produces an extensive range of high-quality and KOMO-certified products that enable multi-purpose roof use within all color themes. "All our special roofs are insured in the 'titanium insured roof warranty', in which both product and application are covered."
The company provides high-quality bitumen roofing materials for flat roofs, with high durability and proven longevity of more than 40 years. "In addition to black bitumen, we are seeing a growing demand for white roofing," Walsweer says. "This is mainly because the sunlight-reflective properties of the white finish positively affect the efficiency of solar panels. In addition, the reflectivity and high emissivity (heat radiation) of white roofing reduce the heating of the underlying space."
The relationship between solar reflectance and emissivity is expressed as the Solar Reflectance Index (SRI), he says. "Here the higher the SRI value, the better the solar reflectance and the cooler the roof."
The range features two white roof coverings, with an SRI of 100 (Derbigum Aquatop) and 51 (Derbicolor White). "Both are excellent for mounting solar panels, with Derbigum Aquatop also having a maximum effect on indoor temperatures."
says Walsweer. "Those who choose Derbicolor White are also choosing a significant percentage of recycled bitumen."
A second trend that Derbigum is observing is the trend of green roofs where the roof is provided with vegetation. "The reasons for this trend are diverse," Walsweer said. "Examples include aesthetic considerations, CO2 reduction, enhancing biodiversity, increasing livability, absorbing and delaying rainwater runoff and/or lowering ambient temperature. In some cases, green roofs are also combined with water collection in crates. In this case, we speak of blue roofs or water retention roofs."
To avoid the risk of leaks, green roof structures require a roofing material and execution with a high level of security, he emphasizes. "After all, leaks are not easily detectable through the finish."
Derbigum supplies, for example, Derbigum SP WW; a root-resistant roofing material with a separate double inlay of glass fleece and polyester, high resistance to external forces and excellent walkability. But also Derbigum GC WW; a root-resistant roof covering with heavier inlays that is also suitable as waterproofing for parking roofs or underground seals. In short: so this works for all projects that are subjected to extreme loads. For smaller roofs, there is the Derbisedum; a crated pre-cultivated sedum finish that can be applied easily and quickly. The root resistant roof coverings will soon be added to the Derbigum NT range and produced from a significant proportion of recycled content.
To ensure the quality, durability and waterproofing of special roofs for a long time, risk mitigation is essential. "This starts at the design stage, with the selection of the right structural substrate, insulation of sufficient compressive strength and the right underlayment, vapor retarder and top layer. But also with preventing water stagnation, with the exception of blue roofs," Walsweer said.
"It is also important that all roofing materials go well together. Our Derbigum Specification Service helps with this. With this free online tool, architects, designers and consultants can easily create and download the Stabu specification for their flat roof. The software was developed in cooperation with Bouwconnect and guides users step by step to the desired roof type and the correct roof composition. Unique here is the product selection. For example, anyone choosing an intensive green roof with a two-layer C-EPS substrate can select only the top layer, vapor retarder, carpet pad and insulation that combine with it. The same is true for a substrate with Foamglas, XPS or other insulation materials, cleverly overcoming errors in the roof structure. At the end of the selection process, the specification text can be easily downloaded after which it is integrated into the overall specifications of the architect, designer or consultant."
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