As most will have gathered by now, my house plans are for off-grid with solar-only (or mostly) heating with a large thermal store in the north of Scotland. Calculations  say this won't work but that the shorfall is not as large as some might initially assume. More importantly, there's a lot of uncertainty in how the systems will perform overall so I want to take an iterative approach of doing an initial construction which I'm fairly confident will work survivably then tweak to make comfortable.
What it will likely not do at first is meet the requirements of provably being able to keep one apartment at 21 ° and the rest at 18 °C.
(But then I don't think I've ever lived anywhere that's met that requirement without silly-expensive amounts of heating. Even the house I lived in in Zambia for a year as a child probably cooled below 21 °C on at least a few nights a year in the dry season - it had no heating and the “house boy's” grandmother remembered once seeing frost.)
Originally my house designer was going to do the SAP rating for the house. He thought he could do it in a way that would meet the requirements. Unfortunately, the council now require somebody with some certificate or other to do the job so he's subbed it out. The new person has taken it all rather seriously and “escalated” questions up the certification chain. AIUI, she thinks there's a get-out clause if she can calculate that the PV and solar thermal will be sufficient for the job.
Maybe she or somebody up the chain to BRE can come up with a creative calculation which means I can get on with things. If not, though, any suggestions?