My advice would be to focus much more on the wider urban design principles of new development from an energy perspective. There is an awful lot that planners can do to influence energy efficiency, overheating, etc. through tackling these issues (orientation, massing, layout and landscaping) rather than trying to spend lots of effort on the ‘behind the front door’ issues which are being dealt with through building regulations, increasingly outside of planning’s influence.
Good local design guidance on what constitutes bad development and good development in these respects will help to strengthen your hand from a DM perspective. I also think we should be putting the onus on to the developer to show that the chosen development design solution maximises energy efficiency and limits overheating, compared to other possible solutions, (layout, orientation, etc.) This could be done relatively simply with some basic thermal modelling.
As an side, something to be aware of, is that although the Zero Carbon homes policy and Allowable Solutions scheme has fallen by the wayside, the UK (whilst still a member of the EU) is required to implement the EU Energy Performance of Buildings Directive which required almost zero energy buildings from 2021. The way in which this would be enacted in the UK is of course unclear at this point but the development industry should be aware of this, particularly when looking at sites they are looking to develop in many years time. In some cases it may make sense to invest early in low carbon infrastructure to reduce the cost of carbon compliance later down the line. However, personally, I am becoming a little weary and a touch cynical as to what this might look like in the UK given the number of times the goalposts have shifted on this issue over the last 7 years or so!
