Airway between ground floor and first

[Moggaman]

Hi. 
I am building an airtight house with masonry. There will be hollowcore slab which will have membrane at the external wall for sealing . My question is relating to the air transfer between ground and first floor. My intention is to have a suspended ceiling off the hollowcore, 150mm hollowcore and a structural screed. 
Does the screed act as an airtight barrier between ground and first . I ask because I will have underfloor downstairs but havent decided if we are going with any heating upstairs ... so one floor may be 21 degree and the other 18?

thanks

 

[nod]

You will have a membrane and slip membrane under your But an expansion gap around the perimeter You can seal the skirting to the floor which should make a good air seal 

In not a plumber but separate  manifolds for up and down will allow you to have different temperatures 

We have UFH on the ground floor and never use the heating on the first floor as it tends to correspond with the large open hallway As the heat rises and has nowhere to go once up there 

[Mr Punter]

In a single dwelling you don't need airtightness between the floors, just between inside and outside.  Air will travel up the stairs.  Keeping the doors closed will help.