Smart Rooftop transformation is close at hand

Did you hear about Rotterdam rooftop walk? Few years ago, more than 200.000 visitors experienced "second city layer" by exploring numerous potentials of rooftops. Why was this event such a success? Because more and more, we realize that perspective of a rooftop as a sole shelter and protection from outside elements is no longer valid. Nowadays, the rooftop is so much more! It can be a terrace, a garden, community gathering place, recreational place, greenhouse, art installation, bar or restaurant with breathtaking view. It can be graveled, but it can also be lushy green, offering aesthetic pleasure and climate comfort for inhabitants.

And even more, it can be used for energy generation, accommodating solar panels or even small wind turbines, it can be used for rainwater collection and stormwater management. These solutions can significantly contribute to the economic aspect of investing into the rooftop transformation. Let’s take a closer look on a case of solar-green combination. Extensive green roofs allow for the integration of solar arrays, which together are often called Bio-solar green roofs or Solar-Green Roofs.

Solar Green Roofs - questions and answers

There is a lot of buzz about the solar -green roofs. What are the figures and numbers behind this combination, what does the recent research data show and at last, but not least: how complex is such project itself?

Wang et al. (2023) claims that the combination of photovoltaic technology and green spaces in urban environments provide multiple benefits and optimized land usage. The principal research findings are twofold: firstly, the integration of solar and green can yield mutually beneficial outcomes; and secondly, the cooling effect of greening on photovoltaic systems primarily hinges on the distance between the two components and the surrounding microclimate. It was found out that evaporation from plants decreases the temperature of PV panels and consequently enhances energy output. His research indicates that installing a green roof on a conventional solar array can potentially increase the energy output of the system by 23.88 kWh and reduce greenhouse gas emissions by 0.019 t e‑CO_2.

Interesting study, published in 2022, by Fleck et al., offers in depth insight into real life observations and comparison of performance of the two subjects – bio-solar green roof (BSGR) and Conventional Solar Roof (CSR):

• Average BSGR output 4,5% higher than CRS output across all seasons

• Average BSGR output (kWh) was 4,14%, 4,16% and 5,21% higher than CSR for spring, summer and autumn.

• BSGR produced 14,16 MWh more than conventional solar, valued at $4526,22 AUD.

• BSGR reduced 11,55 t e-CO₂ more than CSR. Up to 1,56 t CO₂ was removed by plant biomass.

• BSGR produced 23,88 kWh and reduced 0,019 t e-CO₂ emissions per m² of panel coverage more than CSR.
  
  

Complexity of the Solar Green Roof project

Numerous other studies show that solar green roofs provide greater energy output than conventional solar arrays due to the constant plant evapotranspiration process which creates a cooler rooftop microclimate, reducing solar panel temperatures and increasing performance. Solar green roofs can also regulate rooftop temperatures through reduced latent heat and lower solar reflectance than conventional concrete roofs (Fleck, 2022).

When it comes to urban land use conflict, are green roofs in competition with the use of photovoltaic (PV) systems on roofs? Not at all. In fact, the combination of photovoltaics and roof greenery has considerable advantages over a homogeneous surface using only PV:

• In comparison with an unprotected roof sealing, the addition of greenery increases the life span of the installation and delays the need for the first major repairs by several years.

• The evaporative properties of plants also create a cooling effect, which subsequently leads to a higher level of efficiency in the PV module.

• At the same time, the yields generated by the PV installation contribute to the economic viability of green roofs which, in turn, can be counted as a climate protection measure (Homel de Mendonca, 2022).
  
  

Specifiers, designers, architects and investors can visit one-stop shop, where they can learn and discuss with Knauf Insulation technical sales team about the new Solar Base System. Solar Base System includes Solar Base ballasted substructure which secures fast, efficient and safe installation of PV modules. For the ballast, you can choose between Urbanscape Green Roll, Urbanscape Green roof system, green roof substrate or gravel.

Are you still in doubt how shall a solar green system look and function like? Contact us: urbanscape@knaufinsulation.com. Our specialists will advise you with layout proposal plan, together with safety measures (Knauf Insulation Safety Systems), you can discuss about the location and building height, panel orientation and angle, outlets, potential roof windows and HVAC device locations. You will learn about assembly and installation phases, step by step. The result is a tailor-made advice which will suit your building, your expectations and requirements in best possible way.

Key takeaways

Fire Resistence A1

• Solar Base System ballast – Green roll RMW is fire resistant Euroclass A1 → by keeping potential fire of PV on the GR surface and preventing its further exposure

• Comparison of RMW to PIR (Polyurethan) which is declared as excellent in fire resistance: Fire tests show that PIRs integrity in case of fire was compromised as EPS layer below was ignited. In case of RMW the fire didn't penetrate to EPS. EPS was melted in a limited area due to conductive heat transfer, but the EPS didn't ignite. See below PIR (on the left) and RMW (on the right) fire behavior comparison (Jomaas and Kristensen, 2018).