Having watched countless Heat Geek youtube vids and done some of the calculations myself for my own house, the SEAI fabric-first target for a Heat-Loss Indicator of 2.0 is the major problem with heat pump adoption in Ireland. I calculated that I could halve my CO2 emissions from home heating with no changes to existing structure and heating system with a flow temp on the higher side (like 47 degrees or so) which wouldn't be a world-beating SCOP (some are getting 4.5 or so) but easily around the 3.5 mark. In terms of building fabric, I'm talking a 1989-build detached 4-bed with a 2010 internal drylining upgrade (before we purchased), a 2012 uPVC window upgrade and attic insulation raised by 175mm by yours truly. I just can't justify the incredibly expensive external wall insulation that would reduce our side passage width to barely shoulder width and would be of dubious incremental benefit anyway. But the CO2 savings are there to be had, but the fabric-first grant system is killing the economics of it for me.