[ecomodded]

The theory with a passive house is Pay now save later

With ingenuity or the right plan it can be done on the somewhat cheap. My brother in law built a straw bail house with a turf roof heated by a large Rocket stove built from stone and cement in the center of the house.
He lights the stove twice in 24 hrs and lets each fire be started and burn itself out which heats the massive rocket stoves stone work and releases it threw out the day.

I like the idea of expending all your resources at build time so when the build is completed you are not throwing your money down the toilet paying electric and fuel bills.

Instead your money is invested in the house.