I wonder if anyone can advise me on some questions that I cannot find
mentioned anywhere on the web for an simple wet UFH project.

I have just laid a 7-loop underfloor heating pipe system in my (very well
insulated) small 3 floored 3 bed family Victorian house.

I intend to use a combi-condensing boiler, and run the boiler flow heating
pipe first to two directly in-line conventional radiators. Then return that
flow to the input manifold for the 4 underfloor heating loops for the
wooden upper floors. (FYI – I have used old thin aluminium offset printing plates as spreader plates wrapped around the pipes!)

The upper floors' return manifold will then go to the input manifold of the
concrete ground floor 3 heating loops. This ground floor return
manifold will then return to back to the boiler!

I figure the radiators will initially lower the water temperature down for
the wooden floor input manifold. Then this lowered return water will go
into the concrete floor input manifold, which will then return to the
boiler at a very cool temperature. Thus making a very efficient condensing
system! (If not very tepid)

To save costs (and as an experiment!) am intending to construct the two sets of
manifolds with 22mm push-fit copper tee pipes (with 15mm reducers) and locate it under the ground floor staircase in cupboard, about 4m from the boiler using 22mm insulated copper pipes.

I will balance each loop with gate valves (or any ideas?) on the
return manifolds, using temporary temperature gauges clamped onto each return pipe to get even return temps. I will put stopcocks on the input valves for isolation purposes.

I intend to only use the in-built boiler pump to circulate the heating, and
use the in-built boiler water temperature thermostat and timer to
control the room heating temperature.

I can will make allowances to retro- fit TRVs in each room if the room on the upper floor loops only If heating is uneven. But I intend to have the heating on in all rooms constantly from November to April

Q.1. Do I need to put in any Automatic Airbleed Valves on the upper storey
loops, (If so where should the AAV be positioned -Just before the return pipe goes vertically down to the manifold to catch the air?)Or does the UFH water have enough pressure force the bubbles down to the ground floor manifold AAVs.

Q.2. Do I put AAV’s on BOTH the inlet AND return manifolds, or just returns?

Q3. Is this idea workable? If so can anyone recommend a decent boiler with a tough enough pump!?