An example given in this thread was that current Passivhaus practices specify that embodied energy (one time energy cost that goes into the materials and the c

An example given in this thread was that current Passivhaus practices specify that embodied energy (one time energy cost that goes into the materials and the construction) be no larger than 50 years of operating energy costs. Stricter energy eficiency means reducing operating energy costs. Reducing operating energy automatically reduces the allowable embodied energy budget. This limits how much energy you can spend upfront to improve efficiency with current techniques. We need better techniques. Increasing the number of years doesn't help that much, as it can lead quickly to a higher energy TCO than a conventional house, so why bother. Remember it's the energy TCO (total cost of ownership over project lifetime) that captures the full environmental impact of the house, as every MJ of energy - regardless if embodied or operating - translates into a known quantity of GHG emmissions, particle pollution, and so on. In a pleasant surprise, spending energy later (in energy costs, rather than embodied) is better than spending it today for the environment! Energy produced in the future will surely emmit less GHG and pollution than today (better techniques!), and the GHG will dwell less time in the athmosphere, so less compounding effects on the total temperature rise that we'll have at the end of this century. If you care about the environment, you have to consider the energy TCO.