For a ne whole adding both wouldn’t increase the cost to the buyer - they are already willing to pay X for the house. It would increase the cost to the builder,

For a ne whole adding both wouldn’t increase the cost to the buyer - they are already willing to pay X for the house. It would increase the cost to the builder, who would then have less money to pay the land owner for the land, who had received a massive planning gain when the 50k field was given to build 100 houses and increased in value to 3m. I dont see the problem, PV and heat pumps should be mandated.