Whole passivhaus religion based on the idea that building is so well insulated that it doesn't need any heating power. All heat is coming from domestic machines, peoples and so on. In "real" passivhaus, you don't need any heat pumps or expensive heating system, because consumption is so small, that direct electricity will do the job.
Bull sausage...my house has been build with year 2002 regulations (10cm EPS on floor, 20cm rock wool walls, and 40cm rock wool roof, 3 glass windows) and has GSHP + UFH.
New houses have pretty much double insulation and passive houses even more. Still even passive houses in Southern Finland canīt beat my consumption even they have 15-20% less heating degree days
We had several passiv house projects in 2008-2009 and they promise measurements after a year, but guess what? Nothing ever showed up.
Answer is: No you donīt. Increasing insulation makes your house hot at summer, it doesn't warm your DHW, risk of bad ventilation (=sick house) increases and so on. In climate of UK->
Sam, I'm glad that your energy consumption is so low. It's a great example of what can be done without needing to implement PassivHaus. However, some of what you say is wrong.
Insulation does not make your house hot in the summer. Bad design makes houses hot in the summer, be they well insulated or not. A badly designed house, with too much solar gain and little thermal mass will overheat. That is why the PassivHaus design tool not only looks at the heat requirement, but it also estimates overheating risk. If a designer chooses to ignore it then it is their fault.
The problem with post-build consumption measurements is that the usage of the house can have more impact than the insulation saves you. The post build measurements vary wildly from one house PassivHaus to another, but for a given usage pattern a PassivHaus will always consume less energy than a house built to (UK) building regulations.
Finally, I agree that poorly maintained ventilation could possibly cause problems. But a poorly maintained house in most respects will cause problems, be it PassivHaus with MVHR or not. Houses that have had their trickle vents blocked will also suffer humidity and mould problems. MVHR can help, and reduce energy loss, but it must be maintained.
