I've got a project. It's a 70's modular prefab plop on top of rectangular foundation - - - simple box.

So far I'm cleaning out the house and doing minor finishing ( preparing and painting 2 cm thick plywood floors to make rooms easier to keep clean )

I'm still concerned about the details of increasing the envelope performance.

I want to meet the German passivhaus performance standards and have minimum R-40 walls and R-60 roof.

I also want to design and build proper solar utility additions on the south and north ends of the house.

I'm in need of feedback and advise from the "pro's" ( and you are a "pro" )
What may I do that will increase the thermal performance a factor of ten which will not destroy the existing construction?

I'll be stripping the siding and roofing to expose the 2 cm sheathing and excavating the foundation to the footing and out around 1.5 m. I know a complete vapor barrier is needed and I'm concerned about mold and rot.

The wall cavities are currently insulated with 9 cm fiberglass

I've been thinking a lot about the possibility of having a positive pressure ventilation in the basement and a negative in house, balanced so the negative pressure in the house is great enough to keep vapor from entering the wall cavities.

Also thinking of a rigid 1" mineral wool "buffer" zone between the sheathing and vapor barrier that would allow "breathing" if the whole house is ventilated in a positive pressure.

Yup - - - I bit off a CHUNK ! ! ! and I really want and intend to do it right.

Hopefully by this time next year there will be accomplishments to talk about.

I should take this message and post it in a "green retrofit" tribe.

so - - - any good knowlegable advise out there?