Evaluation of house in timber frame construction, built in 2005

It is about the assessment of a used property from 2005 built with a timber frame construction. My main concern is whether the wall structure was qualitatively acceptable by the standards at that time or rather to be considered cheap:

Wall structure from outside to inside:

Cement plaster 8.5 mm Polystyrene rigid foam 040 60 mm Chipboard V 100 13 mm Glass wool 040 160.00 mm Polyethylene foil 0.20 mm Chipboard V 100 13.00 mm Gypsum plasterboard 12.50 mm

U-value of the wall: 0.20

Values according to the energy certificate at that time:

Primary energy demand: 92.74 kwh / m2 a Transmission heat loss: 0.40 W / (m2k) Heating energy demand: 65.49 kwh/m2a

I also wonder how cables can be laid afterwards if apparently no installation level is present?

What kind of strange wall structure is this? A prefabricated house? From a building physics perspective, this is risky; the structure generally becomes more vapor-tight from the inside to the outside when I look at the sequence of materials. Moisture accumulation over time including possible damage from decay/mold infestation in the cavity spaces is to be expected. In a renovation, the outer chipboard should be completely removed and replaced with a diffusion-open wood fiberboard and a ventilated facade. Then the rest of the wall structure can remain if it has not yet been damaged (mold growth). By the way, the ventilated facade can also be plastered if it’s about the appearance.

If you want to buy the house:, I recommend either inspecting the entire property very carefully with an expert or refraining from the purchase altogether.

O.k. does this moisture accumulation necessarily have to occur? From inside to outside, there is the vapor barrier, right? It is a Fischer prefabricated house in timber frame construction, Fischer from Bodenwöhr.

The wall structure works as long as the vapor barrier functions flawlessly and without gaps. Experience shows that there are always defects that occur during processing, assembly, etc.: damages, unsealed joints. Through these defects, warm, humid indoor air can penetrate and condense at the latest on the inside of the EPS insulation.

The sd value of the insulation is 4, making it a serious vapor barrier. If moisture condenses there, it remains there. According to the U-value calculator, temperatures there can already be around 0°C; frost damage is therefore also possible.

If the cement plaster cracks, which it will because it is too hard for the EPS insulation, rainwater can penetrate the cracks. The EPS insulation can become damp but dries only very slowly because it has no capillary conductivity.

In short: the construction is not physically mature or fault-tolerant. It works fine as long as it works fine.

I would not give a purchase recommendation, except with the option of renovation as described, if the rest of the construction is okay.