Flat Roof Solar Panels for Harsh and Northern Climates
- Trygve Mongstad
- Apr 29
- 4 min read
Updated: May 30
Northern climates present a unique set of challenges for a flat roof solar installation. The risks are not well understood because these are relatively young markets and there are many inexperienced providers of solar solutions in these areas. Most solar panels and mounting systems have been developed with very different climatic conditions in mind, and the installations will experience:
High wind exposure
High snow accumulation
Low sun angles
All these factors can reduce performance and increase the risk of damage to the solar installation or even the building itself. Conventional flat roof PV systems – often tilted solar panels in ballasted mounting systems – are developed for more southern climates, and not designed with these conditions in mind.
Conventional flat roof solar panels covered in snow (Photos: Over Easy Solar and Frank Martin Fossland)
Vertical photovoltaics (VPV) is the future of flat roof solar in extreme weather regions. The VPV Unit is developed in Norway with the challenges of northern Europe’s climate in mind, and performs exceptionally well in wind-exposed, snowy environments where standard solutions often fall short.
Wind resistance on flat roofs: How the VPV unit reduces wind forces
A solar installation on a flat rooftop is particularly vulnerable to wind uplift - the vertical force that can lift conventional solar panels off the roof. To function safely in windy areas, traditional systems rely on heavy ballast or complicated mechanical fastenings, which add load and increase the risk of roof damage like insulation compression or membrane leakage.
The VPV unit has a fundamentally different approach. Because vertical panels generate no uplift, they typically don’t require ballast or roof penetrations - simplifying installation and preserving roof integrity. This has been validated through:
CFD simulations with Fraunhofer ISE
Wind tunnel testing at IFI Aachen
Field data from installations in wind zones of reference wind speed of up to 27 m/s
Take our installation in Tromsø, northern Norway - a highly exposed site by the sea. After multiple winters and storm events, the system remains stable and intact.
Vertical solar panels during a winter storm in Tromsø, Norway (Video: Over Easy Solar and Frank Martin Fossland)
The key lies in our aerodynamic design:
Low-profile panels (~25 cm) that reduce wind exposure
Arrays that distribute wind loads across the system
Close panel spacing that shields each module from wind
This makes the VPV Unit a reliable, ballast-free solution for most flat roofs - including those in coastal or open terrains.
Snow and solar panels: Better for flat roofs with vertical panels
Conventional solar systems on flat roofs are easily covered by snow - even a few centimeters of accumulation can halt energy production completely. And in extreme snow climates, the weight of the snow may damage the solar panels or the membrane and roof below.
Vertical solar panels work differently:
They remain partially or fully above snow, maintaining output
They benefit from albedo; sunlight reflected off snow that increases bifacial performance
The accumulation of snow is low and the vertical panels provide a passive melting function
For high snow loads that may damage roof and panels, vertical panels do not carry any snow loads or concentrate the load on the roofing membrane or insulation
We've seen this in action at several installations, as Sundvolden Hotel and Blussuvoll skole (Trondheim), where our vertical systems continued producing during winter while tilted systems remained covered.
A recent Master’s thesis from the University of Tromsø further supports these observations. In a comparative study of two solar PV systems at 69°N, the vertically mounted bifacial HJT system from Over Easy Solar achieved substantially higher specific yield than a conventional 10°-tilted monofacial system.
The decisive factor was the vertical system’s ability to remain free of snow coverage while also benefiting from reflected light (albedo), resulting in higher winter energy production, unlike the flat-mounted system which remained snow-covered and inactive for extended periods.
Frank Martin Fossland, Master Student at University of Tromsø
Read also: Vertical Solar Panels and Snow: Higher Energy Yields During Winter and Better for the Roof
Why vertical bifacial solar gives more energy in northern climates
Since vertical installation angle is not optimal for solar panels, many believe that vertical solar panels always underperform. But, bifacial solar panels that produce from both sides, give very good energy yield. In fact, in northern latitudes, we’ve seen that vertical bifacial panels can greatly exceed the performance of traditional systems – on the research installation mentioned in Tromsø we’ve seen 40-50% higher specific energy yield (kWh/kWp) for vertical solar than for a reference installation using a conventional 10° tilt east-west flat roof solar solution.
Key advantages include:
Better angle of incidence for the sunlight coming from low angles gives higher efficiency
East-west vertical orientation captures energy from almost all angles very well in northern areas
Higher value energy produced during morning/evening hours and early spring, aligning better with demand
Real-world results from Oslo, Trondheim, and Eastern Norway confirm that VPV delivers steady winter yields and stronger shoulder-season output compared to flat-mounted conventional panels.
Conclusion: A smart and safe solar solution for harsh climates
If you're planning solar for a flat roof in a northern or alpine region, conventional solutions may not be optimal. With minimal structural demands, no need for ballast in most cases, and real-world validation from across Norway and Europe, we see that vertical solar is a future-proof solution for buildings that face tough weather, wind, snow and northern conditions.
Interested in learning how the VPV Unit can work for your building?
Contact us today for a technical assessment or project consultation.
