Vapor barrier and natural ventilation

[maah]

How important is it to have a 100% tight vapor barrier in a house with natural ventilation?

My house, which has been extended and rebuilt in stages, lacks a proper vapor barrier in some places or is punctured by various screws. However, I cannot see any tendency for problems anywhere.
We have a chimney that is used during the cold half of the year and several fresh air vents as well as a moisture-controlled bathroom fan.

My question is, is a tight vapor barrier less important in a house with natural ventilation than it is in a house with mechanical ventilation?

 

[klaskarlsson]

How important is it to have a 100% tight vapor barrier in a house with natural ventilation?

My house, which has been extended and remodeled over time, lacks a proper vapor barrier in some places, or it's punctured by various screws. However, I can't see any tendency of problems anywhere.
We have a chimney that is used during the cold months and several fresh air vents as well as a humidity-controlled bathroom fan.

My question is, is a tight vapor barrier less important in a house with natural ventilation than it is in a house with mechanical ventilation?

It is probably impossible to give a definitive answer. But exhaust and creating a negative pressure inside the house should be better than the opposite, "pushing in" air from that perspective.
Whether that has any actual effect or not is probably impossible to say - it should be set so that all the air that enters should exit through the ventilation, so there shouldn't be a positive pressure in the house, ideally.

 

[maah]

That sounds quite reasonable.
So you could say that as long as there is negative pressure in the house, the risk of moisture problems due to deficiencies in the vapor barrier is reduced?

Sometimes it feels like there's a bit of hysteria about the vapor barrier, for example taping the staples where you fasten the plastic.
But I'm not familiar with new construction, maybe you have to do that to get a tight house?

 

[klaskarlsson]

That sounds quite reasonable.
So one can say that as long as you have negative pressure in the house, the risk of moisture problems due to defects in the vapor barrier is reduced?

Sometimes it feels like there's a bit of hysteria about the vapor barrier, such as taping the staples where you fasten the plastic.
But I have no knowledge of new production, perhaps you need to do that to get a tight house?

New production has significant requirements for both insulation value and ventilation as well as heating, so you approach the limits more.
In an old house, it is difficult/expensive to achieve, then you probably have to take down all the interior walls and ceilings and install a new vapor barrier (and tape, etc.) and then build a 45mm installation layer so you don't puncture it, etc.

I think a vapor retarder is a good compromise in older houses that aren't completely airtight.