2017
We wanted to understand what really happens when solar modules become part of a roof rather than sitting above it in the open air. Building-integrated photovoltaics can make a roof produce electricity without adding a separate layer of equipment, but the construction detail behind the panel matters. In this study, we followed ventilated and non-ventilated BIPV rooftop sections in the Netherlands for three years. We measured their electricity production as well as temperature, humidity and air movement, then examined the modules for signs of damage.
The difference between the two approaches became difficult to ignore. The ventilated roof sections continued to perform in much the same way as each other. The non-ventilated section, by contrast, lost a substantial part of its output during the monitoring period. It was hotter, had less moving air behind the modules and showed more damaged cells when we inspected it with electroluminescence imaging. Measurements under standard test conditions supported the same conclusion: modules exposed to the harshest non-ventilated situation supplied less peak power, especially higher up the roof.
It is tempting to treat the cavity behind a solar module as a small installation detail. Our results say otherwise. A roof can provide an elegant solar surface and still create conditions that gradually work against the technology. Heat, moisture and stagnant air affect both immediate yield and the long-term condition of the module. That means the decision about ventilation belongs alongside decisions about orientation, shading and the electrical system.
We also learned why long observation matters. Short tests can miss degradation that only becomes clear after several seasons of real weather. The installation we studied gave us a way to see the whole relationship: roof geometry, airflow, module temperature, visible cell damage and lost power are connected. Looking at one of those factors in isolation would have told only part of the story.
For designers, installers, manufacturers and building owners, the practical message is straightforward. Building integration should not deprive photovoltaic modules of the conditions they need to keep working well. Good BIPV design is not only about capturing sunlight on day one; it is about creating a roof assembly that can keep doing so for years. In our test case, a well-ventilated backside proved to be a basic requirement for durable electricity production.