How to weigh embodied against operational in zero emission buildings

In the past, studies that weighed the embodied carbon costs of envelope performance improvements (i.e. more insulation, triple glazed windows, sun shading) against operational carbon savings were based on assumptions of a certain degree of fossil fuel usage on-site, or off-site for all-electric buildings. But for projects where the owner is purchasing RECs to cover their full energy use, (so performance improvements would reduce the demand but not change emissions), is it still possible to make a carbon comparison? Would that study need to look at the carbon cost of building more PV/wind turbines vs less?

There’s a consideration that we can only clean the grid so fast, so any reduction in demand is leaving more renewables for others to buy, but not sure if that is quantifiable.

Also, can someone point me towards envelope performance carbon studies on any of those topics–insulation/glazing/shading? I have found Arup’s UK/EU facade EC study here: