Solar or ventilation? Energy Saving Ordinance

Do you notice a significant saving in your heating energy?

For that, people here would have to have lived in the same house for a few years only without controlled residential ventilation. How should one notice that? The average homebuilder here moves from some cave into an energy saving ordinance-or-better-house with or without controlled residential ventilation. Yes, then they save heating energy, in any case. Take the controlled residential ventilation! It even has a benefit if its energy saving never pays off.