Things are all over the place without much common ground. When I question it, the typical response is "we have never seen something like this, so were not quite sure how to approach it"...

Here is a run down of the home:
Climate zone 6, approx 6900 HDD, design temp -14.
Homes is a 1600 sqft ranch style with full basement. Daylit rooms.
2" XPS r10 underslab, Superior wall r15 basement walls with additional r-19 batts. Main floor walls are r40, 100% thermally broken double stud walls with ZIP sheathing for exterior air barrier and air tight drywall for interior air barrier. Home will be blower door tested with a goal of <.1 air changes @ 50 pac. There is about 9% glass on the south face, triple pane u .20 with SHGC of .44. No glass on east or west. About 8% on the north with u of .19.
Roof is vented truss, r60.

Heat loads have been right around 19k BTU including the basement. Cooling around 13k. Other load calcs have been in the low 20ks. HVAC guys have been everywhere from low 20s to 45k! Lots of research will show super insulated homes using hvac as simply as a single mini split heat pump. However I think we want to go with a traditional furnace/hp or ac setup, 2 stage, 2 ton.

Does anyone on here have any experience, thoughts or suggestions on something like this?

as a rater I have worked with several hvac companies
and provide several companies to contact.
in my experience it is the rater who provides the homeowner
with like minded trades people.

I would go back to the rater and find out who they have sucessfully worked with in the past.

in my area the utility company has an energy efficient
'design one' guide. maybe yours would also.
has utility provider worked hvac compaines
that have sucessfully installed low tonnage high
efficiency units on other efficient homes they were involved with?
this may be the battle.

could the builder provide companies that he has sucessfully
worked with on efficient homes?

heat pump association?

the 'answer' to your situation for too many
hvac companies, is to oversize with vs/2stage that runs
most of time in low speed.
higher cost to the homeowner..but when temps are severe
the unit has extra capicity is there a reason for oversizing?

best of luck

Any winter shortfall in heating is easily handled with staged backup heat strips when using an electric fan coil, although I understand your desire for proper sizing. However, cooling must be sized right from the outset in order to get proper run times for humidity removal.

Has an HRV or ERV been added to this equation?

SR

ER- that is the problem. The utilities companies have not seen something like this in this area, and do not really know how to approach it. Same with hvac guys. I have contacted many good ones, and have a couple on board with figuring it out, but I also do not want to be the guinea pig either.

While I would like to get a HP, there is also a $5k rebate if I use gas as my primary heating source on this type of a house.

we are in different locations, erv rather
than hrv.
we put a 12x12 filter back grill located
under porch or patio. ducted to return air
with barometric damper.
only operates at fixed rate when house
calls for fresh air. air is cleaned
measured and dehumidified before it
enters living space.

with access to natural gas, I'd look at
two stage high efficiency gas heat with
mid seer (15 to 17) seer a/c.

have you tried posting at hvac-talk.com?
they have aop section and lots of like minded
hvac people there. some may be in your area.

just a thought.

best of luck

Two years ago I was going through the same thing for our new house (superinsulated, Zone 6, 7500 HDD). I did my calculations with a simple spreadsheet. That way I knew what the "behind the scenes" calculations were and could make the model as detailed as I had to, without making guesses as to what a package was doing. I used the model to tweak some aspects of the outer shell, such as window selection.

A new well would be needed for the house anyway, so a GSHP made a lot of sense; no extra drilling just for the heat pump would be needed if the depth expected for just house water was enough for a heat pump if the load was small enough.

At the time I was looking for an installer, three heat calcs were done by others, and all gave numbers within a few thousand BTU/hr of about 55,000. Since my own calculations at the time showed about half that, I asked for details of the calcs the others did. I was given detail for just one set, so I could do side-by-side comparison of the numbers.

What I found was that two key assumptions had been made as to air leakage. An assumed (but nonexistent) fireplace and a much higher hourly air leakage rate accounted for about 80% of the difference between my total load and that done by the other. Selection of numbers from the bottom of drop-down menus for such things as wall R value were off considerably also, accounting for the rest of the difference.

After making final design changes, I got my total load down to about 22,000 BTU/hr. The house has a footprint of about 2,000 sqft and is on two levels, the lower of which is half walkout (the house is on a hill). This was comfortably below the capacity of the selcted mfg's tables for a two-ton unit, so I specified that. The three other sets of calcs called for a five-ton unit, although their calcs for the final design might have been low enough that their recommendations could have been for a four-ton unit with reliance on electric strips for the peak of the load. I didn't ask for a recalculation, as I had no confidence in their ability to get it right for such a house.

While this winter has not been severe, with very few nights down around zero, the two-ton unit has been keeping the house at setpoint quite easily, in just first stage, and not running all the time either. My choice of size was spot on. Last summer, the occasional use of cooling mode kept the house cool easily, also in just first stage. The energy model I built showed that the two-ton unit would be twice what was needed in the worst conditions.

To rely on your own heat load calculations, you must be very sure of your numbers, especially those with significant impact on the bottom line. Leave out nothing; a lot of small numbers add up and may be quite important for a small system. However, if you are confident of your numbers and can't compare line by line with calculations done by others, you have to go with your own. For the house you described, it does sound like the two-ton size is correct, and you can go with it. Just make sure the ground connection is properly sized.

client: what?

contractor: and you know on the 4th of july or new years eve when you have 40 people over, the unit will be able to
keep up. it has the capacity.

client: so this is still $$AABBCC price?

contractor: oh no..its $2,000 more.
and if we increase from legal minimum of 13 seer
add another $800

client: so what about the load calc? the duct
sizing & design?

contractor: don't need them..this is what we have
been doing for xxx years.
if you want 2 tons..I'll put it in, but won't warranty
it. let that company that did those calcs warranty it.

client: ok ok...what about zoning the unit?

contractor: we can do that. one unit for living kitchen den,and another for bedrooms. that way if one unit goes
out, you still have a warm/cool place to go.

contractor @ heat pump association: yeah made another
customer double size of system..and sold some high efficiency equipment..
and not one system..but two!
hey anyone know how to stage
heat strips or install a programable t-stat??
and what the heck is a fresh air intake??

I've heard it before. as always there are
two sides to every story.

education only helps if you pay attention.

OP why not contact the rep of the mfg of the system you
want to use? I've had clients that worked with
trane, goodman, lennox. the co rep did calcs
and recommended a local company to install.

best of luck

I have narrowed it down to a single company who seems to be getting it, and actually enjoying it. Our numbers are now meshing now that they understand the design and the effects the design has on the equipment.

over the years I've realized that the rule of
thumb companies make business for the problem
solvers.

hopefully you will share the process with
everyone.

best of luck.

Now on the heating side - are you just using electric strips when it gets really cold? Obviously a 2 ton rated HP won't produce that at zero degrees. I'm not suggesting you go bigger but you will be in backup often - or at least at design temp. I wasn't sure if you were doing a Carrier greenspeed but even that can't get near rated output at -14. Sounds like Carrier is recommending going oversize in colder climates (makes sense).

Nice for heat, what about cooling load?

Cooling loads are actually tougher since solar gain can easily become a large factor with a lot of south windows.

It sounds like you need someone who is more experienced than 'running code' on a laptop.
It might be time for an actual licensed ASHRAE pro (a real engineer) to take a look.

I have never used 'canned' software for load calcs, but have my own software that I know and trust, and can alter as needed.

I have even used actual heating data from energy bills to compute loses against the weather that occurred at the time to determine measured building losses.

The measurement has been performed, all you have to do is back out the loss numbers.