I’m in construction 25 years.
Just heating/plumbing For a typical modern 3 bed semi
A Heatpump costs €4.3k zoned smart heating controls, €300, UFH downstairs, aluminium rads upstairs, €2,400, ensuite, main bathroom, downstairs WC, fully pumped plumbing system €2.5k
Labour €6k total

€15.5k ex-VAT
Old way = gas boiler, <€900, 120l copper tank €150, gravity fed plumbing €300, steel radiators upstairs/downstairs (€400), ensuite, main bathroom, downstairs WC €1,300
Labour €6k total

€9K
Insulation specs (roof/wall/attic) MVHR, Air tightness membrane, smoke alarm regs, PV,Car charging ports, increased U-Values for windows and doors etc all to be factored in yet.
Thats just a regular 3 bed-semi.
Don’t get me started on apartments with fire regs, dual aspect etc.
To say building regs haven’t had a significant impact on business costs is totally at odds with my own experience tbh.
Developers cleaned up during the celtic tiger. There’s no developers today making the margins they did 2000-2007.