October 20, 2024
Difference Between Solar Panels and Solar Roofs: Where Sandwich Roofing Fits
When homeowners ask about the difference between solar panels and solar roofs, they usually expect a comparison of modules: which produces more, which looks better. The difference that really matters lies elsewhere. Solar panels are added to a roof that already exists; a solar roof is the roof. With the first, you have two systems living side by side — the roof that protects the house and the installation that generates electricity. With the second, you have one system doing both jobs.
In Ibiza, that distinction has very practical consequences, because many of the problems we see on roofs with solar have nothing to do with the panels and everything to do with what happens underneath them. This article explains both options, how a sandwich roof with integrated solar works — the solution we specialise in — and how to decide which one suits your home.
What solar panels on an existing roof are
This is the familiar option. Photovoltaic modules are fixed to a metal frame, which is in turn anchored to the existing roof: clay tiles, a flat roof, metal sheeting or fibre-cement. The roof stays exactly as it was; it simply now carries extra weight and fixings.
Done well, it works and it is very flexible. It suits almost any roof type, lets you choose the tilt and orientation of the panels and, if a module fails, it can be replaced without touching anything else. Its weak points sit at the boundary between the two systems:
- The fixings. Every anchor that penetrates the roof is a potential water entry point if it is not sealed correctly, and seals age over time.
- The roof does not improve. If it had poor insulation or waterproofing near the end of its life, it stays that way — only now with panels on top.
- Repairs get harder. If a leak appears beneath the array, the panels have to come off before anyone can reach it.
- Responsibility is split. Often the company fitting the panels is not responsible for the roof, and whoever built the roof is not responsible for the holes drilled into it later.
None of this rules out panels on an existing roof. It simply means they belong on a sound roof, fitted by someone who knows how to detail the fixings.
What a solar roof is
“Solar roof” is a broad term for any roof in which photovoltaic generation is part of the roof covering itself rather than an add-on. Within that family there are very different solutions:
- Solar tiles or membranes. Roofing elements with built-in cells, designed to blend in. The range is narrower and whether they fit depends heavily on the roof type and the architecture of the house.
- Bespoke building-integrated PV. Photovoltaic glass in pergolas, skylights or canopies. Striking, but a project in its own right.
- Sandwich roofing with integrated solar. A new sandwich-panel roof designed from the outset to carry the solar modules. It is the most technical option, and the one that best solves insulation, watertightness and generation together.
So the difference between solar panels and solar roofs is less about photovoltaic technology and more about approach: with a solar roof, the roof is designed around the energy system, and the energy system is designed around the roof.
How a solar sandwich roof works
A sandwich panel is a roofing element made of a rigid insulating core between two metal skins. That build-up gives the system its two defining qualities: highly effective thermal insulation in a slim profile, and excellent stability, with a continuous outer surface that acts as the waterproof layer.
On this roof, the solar modules are fixed to the profile of the panel itself, without piercing the layer that keeps the building watertight. It sounds like a small detail, but it is exactly where leaks tend to appear when the solar is installed by someone who had nothing to do with the roof. Here the roof and the installation are designed together, so the fixing is part of the system from the drawing board.
The result is a roof that does three jobs at once:
- Thermal insulation. Less heat under the roof in summer and fewer losses in winter, which cuts the home’s heating and cooling demand before a single kWh is produced.
- Waterproofing. A continuous surface, without the weak spots of an old roof that has been patched many times.
- Solar generation. Electricity for self-consumption, with any surplus credited on your bill under Spain’s Royal Decree 244/2019.
And a single company responsible for the whole assembly, which in practice is what gives owners the most peace of mind.
Comparison: panels on an existing roof vs a solar sandwich roof
| Aspect | Solar panels on an existing roof | Solar sandwich roof |
|---|---|---|
| What it is | An installation added to an existing roof | A new roof with the solar built in |
| Insulation | Whatever the roof already had | Built into the sandwich panel |
| Waterproofing | The existing one, plus fixings that pass through it | Continuous surface; modules fixed without piercing the watertight layer |
| Roof condition | Must be sound with years of life left | Renewed as part of the project |
| Responsibility | Often two parties: roofer and solar installer | One party for roof and energy |
| Best suited to | Recent roofs or roofs in good condition | Roofs due for refurbishment, lightweight roofs, outbuildings, carports, garages |
When to choose each option
Panels on the existing roof
This is the logical choice when the roof is in good condition, has many years ahead of it and is reasonably insulated. It also makes sense for a traditional clay tile roof you want to keep for architectural reasons, or for a usable flat roof terrace where the array sits on a frame without disturbing the finish. In these cases, what matters is that the fixings respect the waterproofing and the frame is designed for island conditions.
A solar sandwich roof
This makes sense when the roof was already due for work: recurring damp, exhausted waterproofing, poor insulation, or fibre-cement sheets that need encapsulating or replacing. Instead of repairing the roof and then drilling into it to mount panels, everything is solved in a single job. It is particularly well suited to lightweight pitched roofs, garages, carports, outbuildings and annexes, and to homes looking for both thermal comfort and self-consumption.
Signs your roof needs more than panels
Before deciding, take a critical look at the roof. In our experience, these are the signs that putting panels on top would only postpone a problem:
- Damp patches or flaking paint on the ceilings directly below the roof, especially after the autumn rains.
- An upper floor that becomes hard to live in during summer because of the heat coming through the roof.
- Patch repairs that keep recurring in the same spots every few years.
- Corroded sheets, open joints or rusty fixings, common on lightweight roofs near the sea.
- Old fibre-cement sheets, which must be encapsulated or replaced before any other work.
If you recognise two or more, the sensible approach is to treat the roof and the energy system as a single project.
If you are torn between the two, the useful question is not “which panel is better?” but “how many years does my roof have left?”. If the answer is “not many”, a solar sandwich roof is usually the more sensible decision over the medium term.
What stays the same, whichever you choose
Three things depend on the house, not the system:
- Sizing. System size is calculated from real annual consumption and the usable roof area, not from a standard figure. We explain this in our guide to solar panel installation costs for an Ibiza villa.
- Island conditions. Near the sea, frames and fixings must be stainless steel or anodised aluminium, and dust and salt deposits mean panels need regular cleaning.
- Paperwork. Prior notification or a licence depending on municipality and system size, plus legalisation and self-consumption registration. We summarise it in our guide to solar PV regulation and permits in the Balearic Islands.
If you are at the early stage and want the bigger picture, our practical guide to installing solar panels in Ibiza walks through the whole process, and our thermal insulation guide for Ibiza explains why the roof is the surface that weighs most on a home’s comfort.
How IBOSSIM approaches it
Our sandwich roofing service with integrated solar is built on a strategic alliance between IBOSSIM and Baleares Renovables: we take responsibility for the roof, they bring the photovoltaic engineering, and together we design, install and maintain the complete system. Before proposing anything we assess the pitch, orientation and structural integrity of the roof, because those are what decide which solution makes sense.
Where the roof needs it, we prepare it for stability and upgrade it with thermal insulation, waterproofing or fibre-cement encapsulation before integrating the generation. We also handle all the paperwork with the relevant authorities. You can see the full service on our sandwich roofing solar solutions page.
Frequently asked questions
What is the difference between solar panels and solar roofs?
Solar panels are installed on a roof that already exists and live alongside it as a separate system. A solar roof is a roof in which photovoltaic generation is part of the roof covering itself. In the sandwich version, that roof also provides thermal insulation and waterproofing, so a single system protects the house and produces electricity.
Can solar panels be fitted to a sandwich panel roof?
Yes, and it is one of the cleanest solutions. The module is fixed to the profile of the sandwich panel without piercing the watertight layer, which is exactly where leaks tend to start when the solar is installed by someone unconnected to the roof. The key is that roof and solar are designed together.
What is a solar sandwich roof?
It is a sandwich-panel roof — an insulating core between two metal skins — designed from the start to integrate photovoltaic modules. It combines insulation, waterproofing and power generation in one system, with a single party responsible for all of it.
Can any roof become a solar sandwich roof?
Most roofs can be adapted, but pitch, orientation and the condition of the structure all affect the outcome. That is why we always start with a technical assessment of the roof, which tells us whether it is better renewed as a solar sandwich roof or fitted with panels as it is.