Generating energy on the roof

Creating energy-efficient buildings is at the forefront of the construction agenda today. The emphasis is not only on implementing sustainable architecture practices aimed at reducing the amount of energy that buildings need to operate, but also exploring the generation of energy on the buildings themselves. Solar or photovoltaic (PV) installations have been gaining popularity in the last few decades as a renewable energy source to power commercial and industrial buildings, but also offices and homes.

Flat roofs provide an ideal support for PV installations: they provide easier access than pitched roofs for the installation and eventual maintenance of the PV system and solar panels can be tilted to the most convenient angle to capture the optimum amount of solar energy and maximize results.

There are three main types of photovoltaic systems that can be used on flat or low slope roofs:

  • Penetrating system: solar panels are installed on a mounting system that penetrates the roofing membrane. Detailing becomes therefore critical to ensure the water tightness of the roofing system.
  • Non-penetrating system: solar panels are mounted on a rack support system that is installed on top of the membrane without anchoring, sometimes held in place using ballast.
  • Laminates: photovoltaic strips are adhered over the roofing membrane.

Choosing the right roofing system

A flat solar roof system typically consists of a load-bearing structure (or roof deck), followed by a vapor barrier membrane, an insulation layer and finally a waterproofing membrane over which the solar system is mounted.

No matter the chosen type of solar installation, the total roof system must be considered during the design stage to achieve a durable rooftop photovoltaic system. If one layer fails, the whole system will fail. If the roof needs to be repaired, the PV installation would need to be removed and re-mounted again afterwards, generating substantial financial and environmental costs. Choosing the right components is therefore critical to avoid damage and ensure a high performance, robust and long-term solution.

Rooftop PV investments are typically based on a financial projection of minimum 20-25 years, so the service life of the roofing system must at least match this period to maximize returns. Besides fulfilling its insulating and waterproofing function, the roofing system needs to withstand the increased foot traffic that will take place during installation and maintenance, in addition to the permanent weight of the mounting racks and solar panels themselves.

EPDM for solar roofs

EPDM roofing membranes are compatible with all types of PV installations. They are resilient and offer excellent resistance to ozone, UV radiation and heat ageing, which translates into an outstanding service life of over 50 years. Installation is flame-free and straightforward and requires virtually no maintenance.

Firestone’s RubberGard EPDM 1.5 mm thick roofing membrane, fully adhered over a cover board, is ideal for industrial and commercial flat solar roofs, both for new build and renovation projects. RubberGard EPDM has a proven durable performance under different types of PV systems. Adding a cover board under the membrane makes the whole roofing system more robust.