ᐅ How important is a "traditional" roof in the era of photovoltaic systems?

Hello everyone,

Our construction project is currently being reviewed by the architect, but I would be very interested in the forum members’ opinions regarding the upper part of the house.

The house (bungalow) faces almost directly south and will have a roof pitch of about 20 degrees. The total roof area is approximately 14 x 14 meters (46 x 46 feet) with a gable roof, and there is no shading from neighboring buildings or similar. Given the affordable solar panels and energy storage options, a full coverage with solar panels makes sense (heat pump, electric car, home office).

Now the question is, how up-to-date is a traditional roof covering with clay tiles beneath the solar panels?
What options would there be if one plans to build an insulated roof with photovoltaics in 2025, prioritizing the most economical solution?

• Traditional roofing first, then adding the solar mounting system?
• Sandwich panels or even roofing felt like in the USA, with solar panels mounted on top?
• Integrated/in-roof solar modules like SunRoof (probably the most expensive solution)?

I hope the question isn’t too dismissive, but despite all my online research, there is little information on this topic, and the differences between countries regarding roofing are immense.

Well, beaver-tail tiles under photovoltaic modules are really just pearls before swine.

If you want to cover everything properly, you can also use standard roof tiles.

I have about 500 sqm (5400 sq ft) of roof area across various buildings, all covered with engobed beaver-tail tiles. I do have photovoltaic modules, but they are installed on a less-than-ideal area that is hardly visible. I also placed the modules somewhat hidden on an outbuilding for aesthetic reasons.

My roof faces south, but I still wouldn’t spoil the roofs with photovoltaic modules. The efficiency of the modules keeps improving, so less surface area is needed. You can also install modules on a pole in the garden or use them as a garden fence. There are countless options. It’s no longer necessary to have them on the roof.

So, you have to decide: either a nice appearance or photovoltaic modules. I don’t think in-roof modules are practical.

There are also metal alternatives that look like tiles. They are less expensive and less complex to install. Most of those will be hidden anyway under the modules.

tempusfugit schrieb:

The house (bungalow) is almost 100% south-facing

The house is oriented in all four cardinal directions

tempusfugit schrieb:

will have a roof pitch of about 20 degrees. Total roof area is approximately 14x14 meters (46x46 feet) with a gable roof

So, roof faces south and north? Or east and west?

tempusfugit schrieb:

Now the question is how modern a traditional roof covering with beaver tail tiles under the panels is?

Any normal roofing is still modern. You just won’t see the look if you cover both roof sides (do you want to cover both sides fully?) with photovoltaic panels. Roofing costs money—depending on the type of tiles and roof structure, it can vary (beaver tail tiles are generally more expensive).

tempusfugit schrieb:

What options would there be if you want to install an insulated roof with photovoltaics in 2025, prioritizing the most cost-effective solution?

• Classic roofing first, then the solar mounting system?

That’s the answer.

Buchsbaum066 schrieb:

I also have a south-facing roof but would not spoil the roof with photovoltaics.

So, you have a roof that is 100% south-facing—a single-pitch roof. That should be flat enough so it is barely visible from below and ideally suited for photovoltaics.

Buchsbaum066 schrieb:

You can also install modules in the garden on poles or as a garden fence. There are countless possibilities.

… to waste money. The only reasonable (economical) solution at the moment is the classic photovoltaic system on the roof, on the garage, or similar.

If you install a matte black roof today and put frameless full-black modules on it, these become almost invisible. That would be my choice if the roof’s exterior appearance is that important to me. But since I mostly spend time inside my house or in the garden looking out over the fields, I don’t really care. I am more pragmatic. The only thing I would avoid is red tiles combined with black photovoltaic modules or similar.

nordanney schrieb:

The house is oriented in all four cardinal directions.

My bad – that was a bit too informal.
Gable roof with about 7 x 14 m (23 x 46 ft) south side and 7 x 14 m (23 x 46 ft) north side.

I should also add that the exterior appearance is fairly unimportant to us and we think similarly: you’re either inside the house or in the garden overlooking the lake. Black is the preferred color anyway (and if it were up to my partner, the facade would be black as well).

I’m still a bit hesitant about the sandwich panels. I had them once in a house I lived in while in the USA and found them quite comfortable (the panels were about 10 cm (4 inches) thick). But in Germany, they seem to be mostly used for commercial buildings. The typical concerns about noise from rain and heat in summer should be less relevant with solar panels on the roof, right? Ventilation still remains an issue.

tempusfugit schrieb:

I’m still a bit hesitant about sandwich panels. I once lived in a house in the USA with them and found it quite comfortable (the panels were about 10cm (5 inches) thick). However, in Germany, they seem to be used mainly in commercial buildings. The common concerns about noise during rain and heat in summer should be less significant with solar panels installed, right?

Sandwich panels are occasionally used here as well. However, the internet—and also this forum and the green building forum—are full of issues with this type of roofing. Mainly loud popping noises caused by the panels expanding and contracting. There’s also no real cost advantage. And aesthetically, the house needs to suit this look.
Rain and heat aren’t really a problem. Regarding the site, photovoltaics certainly help protect the roof as the sun doesn’t hit it directly.

tempusfugit schrieb:

One remaining issue is ventilation.

What do you mean by that?

I would also choose a traditional roofing material and make sure the modules or roof width are designed so that nearly the entire roof is covered.

We have various options around here and were lucky that it looks decent. In my opinion, this includes completely black modules (which were even cheaper for us) as well as at least symmetrical placement. One neighbor positioned theirs slightly far to the left and quite high, another one has red tiles/black-checked modules and left out an antenna area, etc.

I understand that this doesn’t have to be a major issue, but if the costs are similar, the house should look good from the outside as well. Otherwise, the color of the car or the paint on the walls wouldn’t matter either.

So, I would at least spend some thought on that. A house that’s really nice inside rarely has a careless exterior, even though I’m afraid some will tell me otherwise.

Standard, affordable flat tiles and fully covered photovoltaic panels on both sides will probably appeal to you as well, I think.

With a sandwich roof, I would be concerned about sound, which was even a problem for us despite living in a village. The above-rafter insulation works really well against temperature but poorly against sound, so we could even hear the neighbor’s trash bin lid or loud wind noise. Ultimately, we solved it, but we probably should have included a sound-insulating intermediate layer.