Another thing very interesting about that passive house was that even with all that insulation, they still suffer from thermal bridging especially wherever there is a join or a corner. Below are three thermal images from inside, first was top floor where the roof windows are, second was in the kitchen and third was an office. Around the window frames there is clear bridging, though the false colour makes it look worse than it is, it's just a 5 C drop. There is also bridging where the roof meets the walls, and where the walls meet the ground. Not all the windows were as bad by any means, some were virtually indistinguishable from the walls. Lars (the business owner) was telling me that is the difference between windows from 2005 versus windows today, he had replaced one side of the house with the latest windows. The newer windows have much better insulated frames and when installed they use much better expanding foams which don't bridge heat and cold as much. Not much has improved though for joining concrete floors to wooden walls, they always lose a lot of heat. He did also speak a fair bit about their proprietary technique for joining walls to roofs, he said they were way ahead back in the 1990s for not losing a ton of heat when they started the company, but as the EU clamps down on new home heat efficiency the average new house is now not too bad at that one thing (he had a long list of where they're bad on other things, particularly lack of ventilation leading to rampant mould infestations and failure to prevent summer overheat).