Waterproofing and solar energy: keys to a safe and durable photovoltaic installation on flat roofs
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The energy transition is driving a real revolution in the building sector. More and more companies, industries and building owners are opting for self-consumption by installing solar panels on flat roofs. However, this technological advance poses a crucial challenge: how to ensure the integrity of existing waterproofing when installing photovoltaic systems?
In this article, we share the main recommendations from the AIFIm Good Practice Guide, together with our experience at RENOLIT ALKORPLAN, to help you make informed and safe decisions in your solar roof projects.
The rise of solar roofs: an opportunity with challenges
The growth of photovoltaic self-consumption in Spain has been exponential. According to data from the Spanish Photovoltaic Union (UNEF), in 2022 more than 2,500 MW of new solar power was installed, representing a 108% increase over the previous year. The roofs of industrial, commercial and residential buildings have become key spaces for harnessing this clean energy source.
However, this boom has also highlighted a reality: many installations are carried out without taking into account the protection of existing waterproofing, which can lead to leaks, structural damage and high repair costs.
Why is it so important to protect waterproofing?
Waterproofing is a building's first line of defence against water. Although it represents a small percentage of the total cost of the work, its failure can account for up to 25% of building claims, according to data from the Musaat Foundation.
When solar panels are installed without respecting the integrity of the waterproofing membrane, there is a risk of:
- Uncontrolled perforations that compromise watertightness.
- Tears or punctures due to poorly distributed loads.
- Chemical incompatibilities between materials.
- Difficulties in roof maintenance.
For this reason, AIFIm and the main manufacturers in the sector, such as RENOLIT ALKORPLAN, insist on the need to follow rigorous technical criteria to preserve the durability and performance of the roof.
Key recommendations from the AIFIm Guide
The AIFIm guide, prepared by its Technical Commission, contains more than 90 pages of technical and practical content. Below is a summary of the most relevant points:
1️⃣ Preliminary assessment of the condition of the roof
Before installing a photovoltaic system, it is essential to:
- Check the age of the waterproofing. If it is more than one year old, tests must be carried out to verify its condition.
- Carry out on-site tests, such as tensile or wind resistance tests.
- Take samples for laboratory analysis (peel resistance, shear resistance, cold bending, etc.).
At RENOLIT ALKORPLAN, we apply this protocol in projects such as the installation of RENOLIT ALKORPLAN Solar on the STIHL roof, where the feasibility of the installation was validated after a thorough technical analysis.
2️⃣ Choosing the right fixing system
The guide distinguishes between several fixing systems:
- Mechanical systems: involve perforations that can damage the waterproofing.
- Ballasted systems: these require additional loads and can compromise the structure.
- Adhered or welded systems: such as RENOLIT ALKORPLAN Solar, which are thermally fixed to the membrane without perforating it.
Our recommendation: opt for systems that do not perforate the membrane, such as RENOLIT ALKORPLAN Solar PVC profiles with aluminium cores. They guarantee secure fastening and total watertightness.
3️⃣ Calculating wind action
One of the most common mistakes is underestimating wind suction. The AIFIm guide recommends:
- Performing a specific calculation for each area of the roof.
- Taking into account the height of the building, its location and exposure to wind.
- Ensuring that the fixing system can withstand dynamic loads.
At RENOLIT ALKORPLAN, we collaborate with specialist engineering firms to ensure that each installation complies with regulatory and safety requirements.
4️⃣ Material compatibility
Not all materials are compatible with each other. The guide recommends:
- Verifying the chemical compatibility between the membrane and the components of the solar system.
- Avoiding direct contact with materials that can degrade PVC or TPO.
- Use certified membranes and systems tested by the manufacturer.
5️⃣ Roof design and maintenance
A roof with a solar installation must remain accessible and functional. Therefore, it is essential to:
- Design walkways and maintenance areas.
- Ensure rainwater drainage.
- Plan regular inspections to detect possible problems.
Fire safety: a critical aspect
The guide devotes a specific section to fire safety. Some key recommendations:
- Use materials with appropriate fire reaction ratings.
- Avoid accumulations of dirt or vegetation under the panels.
- Ensure adequate ventilation of the photovoltaic system.
Common problems and how to prevent them
Among the most common problems in roofs with poorly executed solar installations, AIFIm identifies:
- Tears in the membrane due to point loads.
- Leaks due to unsealed perforations.
- Premature degradation due to material incompatibility.
- Lack of maintenance, preventing damage from being detected in time.
The best prevention is rigorous planning, the use of certified systems and professional installation.
Success stories: when technology and innovation come together
At RENOLIT ALKORPLAN, we have participated in numerous projects where solar systems have been installed while respecting the existing waterproofing. One of the most recent is STIHL, where:
- The waterproofed roof was assessed a year earlier.
- Technical tests were carried out to validate its condition.
- The RENOLIT ALKORPLAN Solar system was installed without perforations.
The result: a safe, efficient and 100% watertight installation.
