The mounting of photovoltaic (PV) panels on flat roofs has gained ground in recent years. Prior to installation, however, the roof should be examined and repaired, if needed, to ensure a long panel life.

Repairing a roof which already has a solar system in place will be much harder and costlier. If you want to mount it without replacing the roof system while also extending the lifespan of your roof, the best choice is a liquid membrane for flat roofs.

Liquid membranes are a type of roofing material in liquid form, which are easy to apply and offer flawless coverage. They can be applied with an airless sprayer or manually with a roller. They are particularly suitable for flat roofs because they form a fully watertight and seamless surface, which is crucial in preventing leaks and protecting the underlying structure.

When it comes to photovoltaic systems, liquid membranes are the perfect choice as they provide a reliable foundation for the panels. Since liquid membranes are applied directly to the roof surface, they createta flat and even surface that can bear the weight of the panels without any additional support structures.

Energy efficiency

Apart from these mechanical advantages, liquid membranes have other benefits in the context of energy efficiency. The reflective properties of white liquid membranes help to reduce the heat absorption on the roof, resulting in lower temperatures inside the building and lower costs of cooling. This also keeps down the temperature around the PV panels, which leads to better efficiency rates and, as a result, higher electricity yields. It is estimated that temperatures above 25 °C may reduce panel efficiency by up to 10-25% (0.2-0.5%/1 °C). Lower temperatures around the panels can increase the output of electricity. Moreover, liquid membranes are typically made of UV-resistant material which can help protect the underlying roofing material from the harmful effects of the sun. Liquid membranes therefore extend the lifespan of roofs.

Roof Expert AC at an outdoor temperature of 20 °C (at 11 a.m.):

Left: Bitumen roof: 52,8 °C, right: roof coated with Expert AC: 27.2 °C

ROOF EXPERT is a brand by KANSAI HELIOS that includes a range of liquid membranes for use on flat roofs, each of them bringing its own benefits. The water-based Roof Expert AC in white has excellent reflective properties and may also be applied as a coating.

Being water-based, it is the greener choice, but as a material it is less durable than the Roof Expert PU polyurethane system, which has a substantially longer lifespan when properly installed and is designed for walkable and heavy load-bearing roofs.

Roof Expert AC

What all liquid membranes have in common is elasticity and better tolerances to expanding and shrinking caused by temperature swings. When selecting a liquid membrane for use before installing a PV system, the specifics of the job should be considered. These include factors such as the existing type and state of the surface, walkable or non-walkable roof, the desired durability of the system etc.

Roof Expert PU510 and Roof Expert PU610

In addition to the practical benefits, the use of Roof Expert liquid membranes can also contribute to a more sustainable built environment. By creating long-lasting and watertight roof surfaces that can support the generation of renewable energy, liquid membranes help to reduce the carbon footprint of buildings, offer better power plant efficiency rates and promote an environmentally friendlier approach to building.

KANSAI HELIOS also offers other types of suitable materials for roof repair, such as Polyurea and a range of coatings for metal surfaces.

Table Roof Expert AC vs. Roof Expert PU