Well, our plans are currently in planning and we are living in limbo, uncertain whether the months of work we have put into the design and the PHPP calculations will translate into the home of our dreams.
The UK planning system does not fit well with the Passivhaus approach, which involves much more upfront, detailed design work than a traditional build. Normally, an architect produces an outline design with just enough detail to satisfy the planners; the point being not to commit more resources than necessary until after planning permission has been given. In any Passivhaus project, but particularly in ours, which is much more challenging because we are new to Passivhaus in the UK and because it is a refurb, more work is needed to be sure we would meet the Passivhaus standard before the planning application can be submitted. If we had submitted our plans earlier, we would have locked in window sizes and other variables that have a significant bearing on the building's energy performance. We have found getting down to the key Passivhaus standard for heating of 15kWh/m2 per annum quite difficult, without throwing silly money at some exotic materials.
Similarly, although we are stuck with some thermal bridging - at the floor wall junction of the existing house - we have managed to eliminate most other potential bridges. If we had submitted our planning application earlier, we would almost certainly have inadvertently designed in thermal bridges into other junctions.
All this means that we have had no choice but to stick our necks out and spend a lot more before planning permission has been secured. The alternative would have been probable failure to achieve the Passivhaus standard and unnecessary design work and building costs later in the project.
As a newcomer to the construction sector, it strikes me that more detailed design work, early on, pays dividends. The build costs should be easier to tie down accurately before contracts are signed and the build starts and there should be much less risk of unexpected costs. Of course, being a refurb, there are still some unknowns which could throw a spanner into the builder's cost estimates. By the time we submitted our plans, we were only a week or two away from being ready to submit plans to building control.
Maybe, in these times of looming public expenditure cuts, it would make sense to combine the full planning application and building control application into a single approval process, with a much simpler initial approval in principle procedure for new builds and larger schemes or where a building is listed or in a conservation area. Whatever the solution, the planning system needs to give clients and architects enough certainty about a project early on to allow them to commit the resources necessary to do the more detailed design work required for a Passivhaus.