Prefabricated wooden houses insulation / heating

Hello forum,

I am currently looking for a holiday/weekend house.
With €25,000 it is really affordable and quite spacious and attractive. I wonder how the insulation is and what it looks like in winter? Are there any experiences here with such prefabricated wooden houses? For example, I have chosen the thickest wall thickness here, an idea would also be to insulate the whole thing myself with glass wool. But is such a house also habitable in winter and above all affordable?

Thanks & regards

The wall thickness is: 95 mm and is made of spruce wood. Is it possible to live energetically efficiently in such a house?