Photovoltaics - leave the roof as is or wait?

Hello everyone, I am planning a new facade next year (VHF, wood fiber, and Eternit) on a single-family house built in 1970, everything is arranged and planned. In the course of facade planning (scaffolding setup), I thought I would put the photovoltaic system on the roof. There are several options, the tiles are apparently still okay, according to the carpenter: 1. Photovoltaic on the 50-year-old tiles. 2. Re-roofing, new ventilation, no insulation - 30k additional cost. 3. Complete roof renovation with insulation. Option 1 would just barely be feasible cost-wise, for 2-3 I would have to wait a couple of years and set up scaffolding again. I am a bit concerned about thermal bridges. The attic is uninhabited, the ceiling (ground floor roof) additionally insulated with 16 cm concrete, 2 EPS, screed, and afterwards with 12 cm Gutex and OSB boards for walking on. I have now measured the temperature, it is about 3 degrees, humidity 70%. The joints between the OSB boards all look good. The energy consultant also warns about later thermal bridges at the facade-roof connection if the roof/exterior envelope is not continuously insulated. The question is therefore - photovoltaic on the roof or better wait, save up, renovate, and only then install photovoltaic?

Hello, the holders of the photovoltaic modules are attached, depending on the system, to the rafters or to the battens. Therefore, the question arises about the condition of the roof structure, not about the tiles. Regards Joerg Klöcker

Makes sense, thank you very much. The roof structure is okay as long as you remove 1-2 tiles. The attic floor is uninhabited. In the summer, I insulated the floor with 12 cm of wood fiber and put OSB on top for walking. I measured with a hygrometer; under the roof it is always 2-3 degrees and the humidity is at 70%. Is such insulation okay for the next 15-20 years or is it absolutely necessary to insulate the exterior shell=roof outside?

What kind of roof tiles do you have and what condition are they in? If you install a photovoltaic system on top now, the roof should also last 20-30 years.

And your attic is just an attic space, right? Then it is enough to properly insulate the top floor ceiling (=the floor of the attic). Insulating the sloping roof would be redundant since you have already insulated the intermediate ceiling. Depending on the exact construction, it may also be necessary to additionally insulate the spots where the roof structure rests.

The clay tiles are old but thicker than today's; so far, none have broken in 50 years (that's what I was told, I've only lived in the house for 1 year). The ventilation and the roofing felt after 50 years is of course a concern, but so far it is dry under the roof. If well executed, the modules also protect the tiles a bit, don't they?

has already written that it is sufficient to insulate the top floor ceiling. So now go ahead with the photovoltaic system. The framework conditions are becoming really good again (compensation, availability, prices). But get several quotes, the prices from solar installers vary quite widely (quickly 50% difference for very similar performance). If you decide later to insulate the storage after all, it might also be possible to do it from the inside. We did it with blown-in insulation material (paper flakes), which has worked perfectly for 15 years.