Sandwich panel roofs are common for cold-storage warehouses, factories and other buildings that require insulation. The panels consist of a thick layer of insulating foam, which is sandwiched between two metal sheets (hence the name). The solar panels can be installed in one of two ways. The first is to attach the panels with self-tapping screws from the top. The screws come with rubber seals to prevent water leakage after they are fixed to the roof. This method is tried and tested in thousands of installations in Europe and North America, and can withstand very high wind loads.

Alternatively, the solar panels can be attached to the panels with industrial-strength adhesive tape. This mounting method does not require any roof penetration, thereby further reducing the risk of leakages. The minimal metal structure also helps reduce the weight of the installation, thereby making it ideally suited to roofs with limited weight-carrying capacity.

Sheet metal roofs are common for ambient warehouses, factories, sheds and other utility buildings. Made from galvanized steel or aluminum, the sheets are typically attached to a steel structure underneath with self-penetrating screws. Because the weight-carrying capacity of single sheet roofs is typically very limited, the solar installation needs to be designed to minimize the weight and wind forces acting on the panels.

The best way to achieve this is to attach the panels to short rails, which in turn are connected to the roof by self-tapping screws . The screws come with rubber seals to prevent water ingress after they are fixed to the roof. This method is tried and tested in thousands of installations around the world, and can withstand very high wind loads.

Concrete roofs are are a common feature of schools, universities, hospitals, labor accommodation and other public buildings. Given the strong concrete structure, weight is hardly ever an issue for the solar installation. However, shading from obstacles (air-conditioners, elevator shafts, satellite dishes, etc.) can be a concern.The easiest way to install a solar system on a concrete roof is by using ballasted structures. These have the big advantage of not needing any roof penetration, and can therefore be installed with little preparation. The structures can be optimized for maximum yield (e.g. facing straight south, at an angle of 20-25°) or for maximum energy density (typically facing east-west at a tilt angle of around 10°).

The Enerwhere team has carried out more than a dozen installations using ballasted systems and we believe that this is one of the easiest and most cost-effective ways to put solar on your roof.