I agree with @Flickersy and @DrinkFeckArseBrick
Also - follow the money. Look at the house builders in the FTSE, what their profits are, what they pay their CEOs. Then look at the planning laws around insulation, solar panels, heat pumps, electric vehicle charging points, cycling infrastructure etc. Then look at donations to the Tory party. There are your answers.
My proposals would be similar to others -
Ban 2nd homes and Air BnB. No one needs more than one house to live in.
Redevelop brownfield. It’s expensive. So what, the developers can afford it. They’ll still make a profit, just a little less profit.
Look at zoning. Some areas can be redeveloped as residential/ mixed.
Make the green designs compulsory. There is a housing estate in South Wales that is a power station - generates all its own power from ground pumps and solar. Look it up on the Fully Charged YouTube channel. It can be done easily for new build (one of the advantages of new build in fact).
And enforce the law! The ones that allow planning as long as there is social housing, and the ones saying local authorities can take over derelict properties and bring them back into use.
If you want to get really radical about it, you could solve the foreign ownership problem, or the problem of differential wealth that blights some areas, by charging an out-of-area premium, like Jersey does - eg it costs 50% more, there are two prices. It wouldn’t do away with the problem totally (the very rich can afford it) but it would help in some places for young people to buy a first home (thinking St Ives, Snowdonia, etc).
There, fixed it. Now what? 🤣