You are a lover of all types of green design, especially solar power and green roofs. Right there you’d expect the clash to begin. Surely one would inevitably get in the way of the other. I mean, we have but one roof over our heads! Yet, what eventually becomes inevitable, is you discovering that there is no clash between solar and green roof technology. They are not only compatible, they are already being used together on sites around the globe.

Standing alone, green roofs have many benefits. They limit rainwater runoff, improve water quality, conserve energy, reduce the urban heat-island effect, actually extend the life of roofing materials underneath, and more. Still, the idea of plopping down a solar array on a green roof sounds a bit amusing.

Yet owners and designers of these “hybrid” systems purport that green roofs actually improve solar system efficiency. The green roof cools ambient temperatures around the solar panels, allowing the solar panels to stay cooler and function better. So there are two essential reasons why a green roof / solar panel relationship is a good idea:

1. Improved solar panel efficiency, as already mentioned, and
2. Green roofs conserve energy, especially in heating and cooling, thus reducing the workload for the solar system.

A green roof/solar electric roof system can take a number of forms. Because most green roofs are on flat or gently-pitched roofs, solar panels are typically mounted on supports to achieve optimal angle in relation to the sun. In these cases the panels are quite literally placed “in the garden,” with the solar panels returning the favor by providing partial shade for plant life during the day. One such installation in Germany even managed to avoid penetration of the preexisting roof altogether.

In a more residential sense, where a solar array can take up the majority of the southerly facing roof, the green roof could be placed on the north-facing slope or, if possible, dispersed throughout the solar array. So far most of the concepts I’ve come across focus on commercial space (check out Tom Cahill’s Green Solar Canopy for an example), probably because of the steeper pitches of traditional home design. Yet the concept is not difficult, it is a simple combination of two well vetted applications. I’m willing to bet you’ll find future home designs maximizing this fusional concept.