Renovate room by room, diffusion barrier and vapor barrier?

[jeppezon]

Hello,
We live in a brick townhouse built in the 60s.
We want to do one room at a time, so it will take a long time before everything is finished.
I would also like to install an FTX later on, today we have mechanical exhaust ventilation.
However, my question is whether we should install a diffusion barrier and vapor barrier in connection with the renovations when doing one room at a time before installing an FTX, or if it will result in problems I cannot foresee right now.

What happens if we install a diffusion barrier + vapor barrier in, for example, the bedroom and leave it like that for a year before the FTX is put in place? I understand that the air quality will generally be poor in the room.

 

[klaskarlsson]

Hello,
We live in a brick townhouse built in the 60s.
We want to do one room at a time, so it will take a long time before everything is finished.
I would also like to install an FTX system later on, today we have mechanical exhaust.
However, my question is whether during the renovations we should install a vapor barrier and a vapor diffusion barrier when doing one room at a time before installing an FTX, or if this will result in problems I cannot see right now.

What happens if we install a vapor diffusion barrier + vapor barrier in, say, the bedroom and leave it like that for a year before the FTX is put in place? I understand that there will generally be poor air quality in the room.

Generally, the ventilation shouldn't go through the insulation, so from that perspective, it shouldn't make a difference. If there's so much airflow today through the insulation, then there's quite a significant problem, and you definitely risk drawing too much moisture into the structure, which can lead to mold.

Then I would personally recommend a vapor retarder instead of a vapor barrier in such an old house that you are also doing part by part. But there are different schools of thought on that.