(text post is fine :) )

I would say that we haven’t. However, we have a lot of old housing that needs improving.
As someone who’s been spending too much time on building work at the moment, the current regulations and requirements for insulation are not that light. ([Approved Document L(gov.uk/…/conservation-of-fuel-and-power-approved-…), if you’re interested)

The specifications are written in W/(M2-K), or watts of heat lost per meter squared, per degree delta from one side to the other.

New dwellings have to hit:

• External walls: 0.13wmk
• Roofs: 0.11 wmk (that’s about 330mm of glass fibre insulation, or 160mm of PIR board)
• External floors: 0.13

Or to put this in perspective: A 30 M2 roof on a new house, on a 0 degree day, with an internal temperature of 20 degrees should only be losing 66W of heat per hour.

An older building retrofitted with 100mm of insulation (effective wmk of 0.4) would lose 240W

An uninsulated roof (2.5wmk) would lose 1500W.

The ECO plans are trying to fix this in older properties, and they’re honestly pretty well thought out (they target the lowest hanging fruit, to get the best effect for the money spent). But things take time, and ensuring the work is done to a good standard costs a lot of money.