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We have owned for 17 years a pavilion that we had built. Gradually, in recent years (I can not say how much because the phenomenon has developed slowly), we saw the presence of moisture in our home despite a VMC whose engine we changed recently (thinking that the problem came from there), condensation on the windows of the rooms with runoff along the windows in the morning, molds at the top of the walls, starting from the corners at the top to always extend in the corner. The worst is in our son's room: the wall facing the outside is very moldy in height at the corners but it extends over a good part of the surface of the wall in some places and the room smells musty despite aeration. I add that this room is adjacent to the bathroom but a priori no escape on that side. Molds at high angles are mostly in the rooms of the floor (semi-level house) but also in the living room but in this case I discovered that it was because I had backed the sofa against the wall giving on the outside (so condensation problem). I shifted the sofa off the wall, cleaned the wall, it's better. But for the floor, what can it come from? We have never done regular maintenance of the highest roof (against mosses and lichens) and it is precisely in this part of the house that the problem of humidity is very important. My husband went into the eaves to see if there was a leak, he saw nothing. Other information: we were labeled "promotelec" at the time / the insulation of the house. That's it, if you can help me identify the problem because it worries me a lot. Thank you in advance.

A description of the problems encountered, we can think that the house has become too tight, either for lack of renewal of the air, or because of the recent replacement of windows, but a house of 17 years was already equipped originally relatively airtight joinery.
If nothing has changed compared to the original configuration: insulation, windows, heating system... it is at the level of the VMC that there may be another problem, except the engine: fouling, rupture or duct debridement... or poor air clearance (eg in the attic).
The on-site diagnosis of a specialist (insulation / heating / ventilation) seems essential before going further.

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