I don't have a wayback machine, but if my memory serves me, the definition of wofati has evolved somewhat over time. Insulation of the sheltered mass, as one would with a Hait inspired umbrella (PAHS) home, seems to have become minimized or abandoned altogether, now emphasizing the R-value of the dry dirt itself.
Imho, without sufficiently thermally isolating the sheltered mass from the air and surrounding soil, and R-5 of
wood duff is nowhere near close enough (Hait recommended at least R-20), you are limited to whatever the average soil temperature for the area is at depth. Without that thermal break, any heat you add, through whatever means, passive or active
solar, or fuel or electric fired furnace or boiler, will quickly dissipate into the vast heat sink that is the surrounding soil.
That may not be bad, if the that soil temperature is the temperature you want in the house, but even temps in the low sixties can wear on you, day in and day out, without at least some direct sun or spot heating. If you get it too far off, you may find yourself insulating the living space to keep the walls and floors from sucking out your supplemental heat.
Hait's PAHS homes were designed and built in Montana, with only slightly warmer temperature averages than Ottawa. A PAHS home built utilizing
Oehler's building techniques and natural materials (except the moisture barrier, though a clay barrier could be use, but it can be a lot more problematic) ought to work fine (even into the Arctic with some more insulation, including underneath, to isolate from permafrost, and you may need to
boost passive
solar heat gain in Summer by using thermal solar panels and/or trombe walls). The tricky part is coming up with the right balance of insulation, mass and solar gain to give a comfortable, year-round, living space without the need for heating or air-conditioning.
If you are in doubt, but still driven to give it a try, maybe building a small outbuilding (or folly, which may be a more appropriate, if antiquated, term) will give you an opportunity to prove its merits in your area.