Assuming the worst-case scenario that the units don't comply with most of the HHS requirements:Healthy homes is relatively simple or else there are exemptions if it’s impractical to meet them?
How can an a/c unit, a few fans and some insulation take 12 months to do?
Pensioner flats wouldn't have a large lounge/kitchen/dining area (assuming it's one space) so $1500 per AC unit.
$500 per unit for supply and install of rangehood.
$300 per unit for bathroom ventilation.
$1500 per unit for ceiling insulation.
$1500 per unit for underfloor insulation.
So say $6000 per unit to upgrade to the healthy homes standards (and they should be able to get a much better "bulk deal" over 50 units).
50 units in total so $300K to upgrade all of them. There's no way it's uneconomic to upgrade them compared to demolishing and rebuilding them (50 units @ 60m² per unit @ $3,000 per unit equals $9,000,000).
Consider this, at $3,000 per meter, they're demolishing 50 units and supplying one new 100m² unit for the same price of upgrading them.
The units may have reached their economic "use by date" but the trust is only using the healthy homes requirements as a feeble excuse in my opinion.