Heater core shutoff valve?

[VetteMed]

My recent A/C issues have gotten me wondering about hot water flow through the heater core, which in these cars occurs regardless of A/C setting, from what I can tell. It seems like having 200+ degree coolant in the heater box, when trying to deliver cold air just inches away, is counterproductive and likely to reduce ultimate cabin cooling capacity. I know there's the blend door, which closes fully when the Temp is set to "60", but I would assume there's still some heat being radiated through that door and perhaps through the plastic heater box housing into the underdash space and into the cabin.

Has anyone installed a valve to block off coolant flow into the heater core in the summer months? Or does someone have a reason why this would be a bad idea? Or am I just making something out of nothing?

Thanks
Andrew