Flat roof PV panels vs. Pitched Roofs

Solar Panel Installations: Flat roof PV panels vs. Pitched Roofs

Choosing between a flat roof with solar panels and a pitched roof for installations hinges on the project's unique needs and circumstances. Both roofing types offer distinct advantages and face their own set of challenges when it comes to accommodating solar panels. Sometimes there is no option other than a flat roof with solar panels, other times customers have the option of different roofs - This article delves into the benefits and considerations of installing solar panels on flat roofs versus pitched roofs.

The Advantages of Solar Panels on a flat roof

Flexibility in Panel Placement

Flat roof PV panels present a prime opportunity for solar panel installations due to their flexibility in panel orientation and positioning. Unlike their pitched counterparts, flat roofs do not limit solar panels to a specific direction, allowing for optimal placement to maximise sun exposure. This adaptability is particularly beneficial in the northern hemisphere, where south-facing installations yield the best results.

Flat roof solar vs Pitched Roof solar - if there's a choice like in this photo, most opt for a pitched roof installation.

Optimal Angle Adjustment

For maximum energy production, solar panels ideally sit at a 30-35 degree angle. Flat roof solar panels can facilitate the adjustment of this tilt angle (because of the mounting materials used), enabling an optimal setup for energy capture. This ensures that solar panels can efficiently harness solar energy, despite the flat roofing surface. However, a 30 degree angle on a flat roof casts a large shadow behind it, meaning that the next row of panels needs to be set back to ensure shading doesn’t impact upon its production. This can reduce the system size possible for solar on a flat roof considerably. This is why most flat roof installations are of a significantly lower angle of 5-10 degrees, to reduce the shading behind it. Another reason could be planning constraints, because the solar panels on a flat roof are not permitted to protrude above the highest point of the property.

Considerations and Challenges

However, installing solar panels on a flat roof comes with its additional considerations. If the panels need to be weighed down to the roof rather than fixed, a structural engineer would need to be involved to ensure the system weight can be handled by the roof. You can fix the system to the roof, but it is worth considering that drilling a flat roof has a higher chance of leaks, due to the potential of standing water, this is why a lot of systems are weighed down via a low ballast method. The additional consideration of the age of the roof and the felt also needs to be thought through, if the felt is 15 - 20 years old, it will need to be renewed during the solar P.V. systems life and thus would need to be removed and re-installed.

The need for different mounting materials to achieve the desired panel angle can increase installation costs also. Moreover, flat roofs tend to accumulate debris and dust, potentially obstructing panel efficiency and necessitating regular maintenance.

Furthermore, depending on the building's height planning permission could be required and thus, securing planning permission for flat roof solar installations may introduce additional procedural steps.

The advantages to Pitched Roof Solar Installations

Natural Alignment with the Sun

Pitched roofs are the most common type of roof for solar installations. If the pitch and direction of the roof align well with the sun's path (south, southeast and southwest facing in the northern hemisphere), it could provide an ideal situation for maximising solar energy production in your home. Pitched roofs also tend to have angles of between 20-60 degrees, and with optimum generation angles of between 30 to 40 degrees, this really helps maximise the generation of the system on your roof.

Considerations and Limitations

The major limitation of pitched roofs lies in their fixed orientation. If the existing roof structure does not favourably align with the sun's path, options to optimise solar capture are limited. However, there is normally a roof in most properties that is suitable, and the generation from pitched roofs is superior to that of flat roof installations that are only installed to an angle of 5-10 degrees.

Conclusion: Balancing Factors for Optimal Solar Installation

In the end, the decision between a flat roof solar installation and a pitched roof and a pitched roof depends on a few factors. These include the roof's orientation, design specifics, planning regulations, and the property owner's preferences. While pitched roofs currently dominate the solar market due to their prevalence and alignment advantages, flat roofs offer some flexibility and optimisation opportunities for solar panel installation.