It is possible to considerably improve the heat insulation of a building while still allowing turnover of fresh air. We don't specifically want to throw away the heat, we just want to change the air, and you can arrange to do that. The laws of thermodynamics forbid us from arranging to keep all the hotter molecules and lose the cool ones, but they allow us to insist on a roughly fair swap, hot air going out gets cooler, cold air coming in gets warmer.

This will be more expensive than just sealing everything up and hoping, but that's the sort of reason why you want somebody figuring out how to do it properly and only subsidising work that we know insulates homes without destroying ventilation so that they're horrible to live in. Modern homes here have much better heat insulation than when I was a kid, yet there isn't the damp problem I saw in cheaply retro-fitted rental places where I lived.