Sense Check on Drylining and Insulation Quote for New Build

Hi all, hoping those of you more knowledgeable than I can help me with something.

We're getting quotes in for drylining and insulation on our new build (two storey, Hollowcore slab between floors, 1 sloped ceiling area). I've got a couple of quotes and they're all a little different….wanted to sense check whether everything on it is actually needed or whether any of it is optional or overkill

Here's what we've been quoted for:

Ceilings

• Metal Frame ceiling system under the Hollowcore slab — 120m²
• 12.5mm plasterboard on all flat ceilings upstairs, ground floor and flat roof area — 231m²

Roof/Ceiling Insulation

• 400mm fibreglass insulation in the attic upstairs — 82m²
• 150mm Volcalis Alpha 34 on sloped ceilings upstairs and vaulted area — 82m²
• 62mm insulated plasterboard slab on sloped ceilings and external timber stud wall in vaulted area

Wall Insulation

• Pumped cavity wall insulation for entire outer walls

Underfloor Insulation

• 50mm insulation under the upstairs floor — 107m²
• 150mm insulation under the ground floor — 158m²
• 25mm perimeter strip and 1000 gauge plastic membrane

Airtightness

• Full airtightness membrane across all upstairs ceilings, vaulted area and flat roof
• Airtightness tape around all windows and doors — 125 linear metres

Window/Door Reveals

• 13mm edging bead and plasterboard to all reveals — 102 linear metres

I suppose what I'm wondering is, do you actually need 50mm insulation under an upstairs floor on a two storey build with Hollowcore, is this standard or unnecessary?

Is the ground floor insulation at €39/m² a fair rate?

Is a full airtightness membrane required or is tape alone sufficient? Anything on this list optional or overkill for a standard two storey new build in 2026?