Re: Zoned Heating Control

["rb_ziggy" <rb.lists@xxxxxxxxxxxx>]

Bit of a gap - been away since your post!

I wouldn't worry about the underlay. All these 'engineered' wooden
floors work this way.  The planks are glued/locked together and the
whole floor 'floats' loose on the screed.  This is what allows it to
expand and contract without self destructing.  As long as the whole
floor is subject to the same conditions (and it will be with UF) then
there are no problems with differential expansion (i.e caused by damp
one side and dry the other).

I think the underlay does two things, it reduces noise (as stated
before) and it can (if you use the thick stuff) give a bit more
insulation to the slab.  You don't need the latter in a under-slab
insulated house so just go for the 2-3mm underlay.

It doesn't need any additional calculations / pipe as such. (Adding
more pipe running at a lower temperature is actually a waste of money
as it's the temperature gradient that is the determining factor.)