Smarty wrote:

I did not state nor have I assumed that my house is an idealized, perfectly
closed system with no flows in or out. There are, however, no longer
economical ways to further reach a 60X improvement to go from my present
"airtight" house to the Canadian 1 cfm "ideal" you refer to.

Have you sought professional help with a blower door test?

Why 1 CFM? How many min CFM do we need to keep a house RH 50% at 70 F with
an indoor humidity ratio wi = 0.00787 pounds of water per pound of dry air
when the outdoor humidity ratio wo = 0.0025 (Phila in January) and you and
your pint-a-day green plants naturally evaporate 1 gallon of water per day?

Hint1: 8lb/24h = 60CFMx0.075(wi-wo).

Hint2: ASHRAE suggests 15 cfm of fresh air per full-time occupant.

I have never disagreed with the physical fact that energy is required to
evaporate water.

You may well find that you did, if you re-examine your words carefully,
but it's nice to see you reagreeing with yourself :-)

... moisture evaporated into the air requires energy from someplace.

Sure. Aprilaire's advertising ignored that for years and claimed people
could save energy by turning the thermostat down, but they dropped that
claim after I pointed out that the thermostat savings were 10X less than
the heat required to evaporate the water, in a typical US house.

Perhaps in some home in the future where there is only 1 cfm of 'leak' it
will be, as you assert, possible to avoid a humidification method entirely,

It's perfectly doable today with more than 1 CFM.

but I, for one, will reserve judgment until much more is known about the
consequential issues of mold, oxygen deprivation, smells, radon effects, and
other poor air quality issues.

"Build it tight and ventilate it right" with a mechanical system, eg
a bathroom or kitchen exhaust fan with a humidistat that turns it on
when the indoor RH rises to 50% in wintertime. For extra credit, you
might figure out how to automatically decrease that 50% setpoint when
it's colder outdoors to avoid condensation on indoor window surfaces.

... a Honeywell humidistat using only a software algorithm might...
compare to the method used by several other manufacturers who add
an outdoor temperature sensor to allow their algorithms to adjust to
outside changes.

Clever Honeywell thermostats measure indoor air and wall temps and
temporarily raise the air temp to compensate for initially colder walls,
which can save energy by prolonging night setbacks, compared to air-temp-
only thermostats. Maybe clever Honeywell humidistats are mounted indoors
on exterior walls, so they can get an idea of the outdoor temp, which
would be colder with a larger air-wall temp difference, but how would
it know the wall or window insulation values? It might get calibration
help from an owner who pushes a button when there is condensation.

Nick