Potentially controversial housing opinion:

I am not at all convinced of the need to massively insulate homes as a means of combating climate change. Surely the objective should be to switch heat and power supplies to zero carbon options.

A few reasons:

1. The world is going to get (much) hotter. Is making homes even better at retaining heat the way to prepare for that?
2. What's the carbon cost of producing and fitting the insulation?
3. Does it actually work as a way of reducing energy use anyway?

I would add, perhaps controversially, that the well has been so deeply poisoned by lobbyists on this that it's pretty much impossible to make a proper judgement. I worry that it's a way of selling insulation not preventing climate change.

I've been gently ratioed with some insightful comments, so will temper my view to just say there is a big gap between a carefully built Passivhaus and the reality of the kind of job that will actually be done if we try to retrofit 25m UK homes on a budget.

I'd also say follow @Kate_de who is the best informed of all those patiently explaining why I'm wrong

I'd also add (just given the scale with which my mentions are pinging on this thread) that I don't disagree with bringing homes that are really poorly insulated up to a habitable standard. But that is a very different thing from a moonshot project to get every UK home to Band A.