Joist void between ground and 1st floor, need to ventilate?

[tanneja]

I was having a discussion with a friend regarding airtightness and MVHR.  It was mainly in the guise of retrofit if one were to do a full or near full strip out of a property.  After all the mistakes I feel I made this first time around, we discussed how we would ideally establish the airtight layer around the shell of the house and then build within that.  We were also talking about soundproofing meaures too so to reduce sound transmission between rooms. 

 

A point raised which left us unsure was how to manage the ground floor to1st floor joist area.  In a traditional build this area might get ventilation through the walls of the building or gappy flooring.  In a airtight and soundproofed build, it feels like this cavity could end up being sealed off from the rooms.  Can anyone explain to a layman like me if this represents an issue for the house health?  My hope would be that moisture can still move through the timber floor boards and so while there might not be much air flow, that the chance of a condensation issue is minimal to zero?

[ProDave]

In a well insulated air tight house, there is no risk of condensation because that needs a cold surface to condense onto, and there will be no cold surfaces.

 

Trust me, in a well insulated air tight house with mvhr, condensation is simply something that does not happen.