Flat roof or tiled roof? What changes in performance
You do not choose your roof type – but it determines the study, the mounting, the cost and the final appearance. See what each one means in practice.
In short
- Flat roof: freedom in tilt and orientation, but spacing between rows is required.
- Tiled roof: use of the whole surface, but the tilt and orientation are fixed.
- Both work excellently when the study is done properly.
- What matters is not the roof type – it is the shading and the structural adequacy.
Flat roof: you choose the geometry
On a flat roof the panels are mounted on metal frames with adjustable tilt. At Greek latitudes we choose a southern orientation and a tilt of roughly 25-30 degrees, or a shallower tilt when we want a denser layout and less wind loading. This is the scenario with the greatest design freedom.
The price is the inter-row shading: each row casts a shadow on the next during the winter months, when the sun is low. That is why we leave a calculated distance between rows – resulting in fewer kWp per square metre than on a pitched roof. In addition, flat-roof mounts are secured with ballast or anchoring, and in every case a structural adequacy check and protection of the waterproofing are required.
An advantage that is often forgotten: ventilation. Panels on flat-roof frames are well ventilated underneath, run at a lower temperature and therefore at a slightly better efficiency in summer.
Tiled roof: the roof sets the rules
On a tiled roof the panels are mounted parallel to the roof plane, with special hooks that bear on the rafters and pass beneath the tiles. There is no inter-row shading, so you use almost the entire available surface – and the visual result is far more discreet, which matters on homes and in areas with architectural restrictions.
The constraint is that tilt and orientation are fixed. A south-facing pitch at 20-35 degrees is ideal. An east-west roof loses a little annual production, but gives a broader curve – production in the morning and the afternoon – which under Net Billing may suit a home consumption pattern better. A north-facing pitch is not used.
The critical detail on any pitched roof is the watertightness. The hooks have to be placed at the right points and the tiles refitted correctly. This is the job where you can tell whether the crew knows its trade.
Comparison at a glance
| Criterion | Flat roof | Tiled roof |
|---|---|---|
| Tilt & orientation | Freely chosen | Fixed by the roof |
| kWp per m2 | Lower (row spacing) | Higher (continuous coverage) |
| Panel ventilation | Very good | Limited |
| Appearance | Visible frames (usually not from the street) | Discreet, flush with the roof |
| Maintenance & access | Easy and safe | It requires safety equipment |
| A critical point in the study | Ballast, wind loading, structure | Watertightness, hook positions |
What we look at first in the survey
Whatever the roof type, two things determine the result more than anything else: the shading from neighbouring buildings, stairwells, chimneys, tanks, antennas and trees; and the structural adequacy of the site. A roof with ideal orientation but shading from the neighbouring building at 3pm can perform worse than a less correct roof with no obstructions.
In an energy study we run a shading analysis with real geometry and a month-by-month production simulation, so you know what you will see in your app rather than what a general rule of thumb says.
See the residential applications in residential solar and on business buildings in commercial solar.
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