Don't twist my words- there's a huge difference between bringing it inside the thermal & pressure boundary of the house vs. actively heating it.

jonr
In the Passive House article your refer to, Paul Eldercamp suggests that the basement essentially be eliminated in favor of a slab due to the cost of insulating and sealing it. I'm not (at this point) building to PH standards so I don't need the same levels of insulation, but he's right that a slab is less expensive than a basement and easier to insulate. The BC Passive House/Rainbow duplex shows a double floor assembly - with cellulose filled TJIs and a second layer of 2x6 joists filled with rock wool,and it includes three layers of plywood. I'm unclear why you're referencing this, but it is possibly a good way to thermally isolate the basement, especially if the joints are taped with Siga ($50./roll) However, you can probably thermally insulate the basement as I'm doing for equal or less cost than building a double floor. If you are suggesting this to Myrtleboone as a way to put her garage down there; this may work IF it is well sealed inlcuding all penatrations. But I'll go out on a limb and suggest that few contractors are going to follow this to the letter, meaning it either won't be insulated well enough or sealed well enough. And even a R60 floor is colder than a R2 floor over a conditioned space. And here in New England, there is no "free heat" to gain from the dirt; it's always colder than the basement should be.

"And here in New England, there is no "free heat" to gain from the dirt; it's always colder than the basement should be."

TESTIFY, brother Robert!

Any location in ME with the reported 8300 HDD local climate has deep subsoil temps in the low 40s F, which is not an acceptable margin for freeze protection on uninsulated basements, and has a small but real risk of frost heave damage to slabs in uninsulated foundations if there's a high-R floor to the conditioned space above. Design frost depths in those parts of ME are six feet or more, and when the slab drops below freezing during a week long cold snap the heat loss direction is from the ground up, and frost heave pressures from the ground as it freezes is in the direction of the heat loss- UP! To keep the direction of heat loss in the "correct" direction you'd have to partially heat the uninsulated basement anyway to prevent this.

But if you just insulate the foundation the heat loss will always be in the correct direction as long as the space above the basement is being heated, even if the basement drops during an extended cold snap, it will stay above freezing, as will the ground below the slab. No frost == no frost heave no damage (and no frozen pipes/drains in the basement to mess with.)

you'd have to partially heat the uninsulated basement anyway to prevent this.

As the success of unheated FPSFs shows, you can make use of only ground heat to prevent a foundation from freezing. No freezing, no concerns about direction. It would be interesting to confirm that the passive houses with basements are doing this.

Paul Eldercamp suggests that the basement essentially be eliminated

It's clear that he is suggesting that that is easier (and I agree), but if you decide to have a basement, he writes: "decouple it firmly".

"And here in New England, there is no "free heat" to gain from the dirt; it's always colder than the basement should be." TESTIFY, brother Robert!

Except that "free heat" isn't what I wrote.

Oh, you mean if you add insulation to protect the foundation from frost heaving you don't have to heat it? Golly, why didn't I think of that?