Here's a presentation based on our work with Natural Resources Canada on The Path to Net Zero Energy housing. The study challenge was to look at incremental reductions in energy use and flag where the envelope improvements ended and the mechanical system design started. There was a lot of number crunching. A lot. (EnerGuide Ratings are like HERS ratings, but are based on a 0-100 scale for energy use, with a NZE house being 100 or more).
Slide #5 is the key: looking at the end use patterns and changing the proportions means that as the space heating load goes down, the water heating load drives more mechanical system choices.
Four case studies are included.