@Mark, since 4,800 includes
@Mark, since 4,800 includes basement and given your description (re: heavy S/SW shading, few windows on south), I bet the cooling load is 4 tons or less. Of course, without modeling I can’t know for sure.

Yes, I was referring to an air-to-air heat pump. Ground source is more efficient but additional costs are (usually) well beyond the efficiency bump, even with tax credit. I specify air-source heat pumps in all climate zones, especially in areas where there’s no natural gas. It’s just a matter of how much supplemental heat is required and which type. More on that in a minute.

Here’s an interesting factoid: the colder the climate, the more heating hours there are in the heat pump’s ‘sweet spot’ (i.e., outside temps above the balance point, typically in mid-20’s with today’s construction). Air source heat pumps are rapidly making inroads in northern tier states, Canada and even Alaska. For every BTU the heat pump produces, it will save roughly half to two-thirds in heating costs compared to propane. BTW, if you go with a heat pump, you should probably stick with 5 tons for the additional heating capacity it would provide.

I can’t help with distribution through floor trusses sight unseen, but I strongly recommend open web floor trusses, which can easily be designed with large duct chases (requires close coordination between truss and HVAC designers). Also, keep in mind that metal ducts can be built to any aspect ratio. I also recommend increasing the truss height to 18 or 20 inches (additional cost is relatively small). That way branch ducts can be routed through the truss webs as required. You shouldn’t need to forfeit ceiling height if you can add another stair riser.

Lastly, you have several options for forced air supplemental heat, thus saving the cost of installing radiant:
a) Least expensive would be electric strips in the air handler. Keep in mind that a conventional heat pump produces ~40% of nameplate capacity at 0F, at around half the cost of electric heat. The strips pick up the difference.
b) More expensive would be a small propane boiler to feed a hydronic fan coil on discharge side of air handler. Depending on relative cost of electricity vs propane, the additional first-cost may not be justified.
c) Tie wood stove to main duct system — the connection must be AFTER the air handler (requires a separate blower). In this case, you’d still want strip heat in the air handler so the wood stove remains optional. Unfortunately, I’m not familiar with how to adapt a wood burning insert to a duct system but I know it can be done. It may require purchasing a stove designed for that application. Perhaps someone else will comment on that.

Forgot to ask if I decide to install HVAC in main floor how is it best to accomplish that. Presently we have designs for 11-7/16 I Joists, 16″ O.C. and a slightly more expensive floor truss design. Certainly there are minimum depths to accommodate ducts which I assume are close to 24″ x 8″. Since we were trying to achieve a uniform basement ceiling height of 9 feet we did not want random soffits or dropdowns. Our builder indicated a solution would be to rough in a uniform soffit beneath the I Joists within the entire basement to contain ducts and infrastructure while maintaining the uniform ceiling height. Builder thought it might be accomplished without sacrificing a lot of ceiling height (estimated 8 inch lower ceiling with final around 8′-4″.
Mark

Thank you for the advice. You confirmed some of my suspicions. Yes, basement will be fully developed for livable space which places the home in the neighborhood of 4,800 SF total. The stairway to basement will be open so passive air flow should be no problem.

Since I am a novice and trying to learn quickly I am uncertain what you are referring to in the form of a heat pump. I am experienced in my last home with a ground water heat pump which performed great and I assume your reference to heat pump is an air to air system? Isn’t building this far north in Zone 7 a problem for heat pumps?

Five ton cooling load calculation was based on SF with lots of east facing glass; however, the southeast, south and southwest sides of home are sheltered by numerous 100 year old pines which really cuts down on the solar heat and south side of home has few windows.
Mark

BTW, if the basement is at least partly finished, you should consider a central return in the basement thus avoiding the cost and potential interference of ducted returns for the main level. The stairway door (if any), would need to be louvered to provide a return path from the main level, or you could provide a passive (non-ducted) chase between the floors. This offers the additional advantage of forced air mixing between main level and basement during cooling season, thus avoiding the ‘musty basement’ syndrome when RH is higher.

I’d take another look at propane fired radiant heat. A heat pump would cost far less to operate, not to mention the lower first cost. Since you already need central ducts for A/C, a heat pump would only add on the order of $400 to $800 to the cost.

Re: 5 ton cooling load… How big is the house? With today’s energy codes, the cooling load in your climate zone should be at least 1,000 ft2 per ton unless there’s an unusually large amount of glass. Even that can me mitigated with low SHGC glazing, shading, etc.

My understanding is that the
My understanding is that the heat pump will shut off at the designated minimum temperature, which would explain the rapid drop in the indoor temp. However, I haven’t had the opportunity to test or witness this. Depending on the climate zone and other circumstances, I advise clients as to the various supplemental heat options. For ductless, that usually means one or more baseboard or portable electric radiators.

I should have had a comma in
I should have had a comma in that sentence. I meant that when the outside air got to -15F, the room temperatures were at 65F and falling. Indicating that the HyperHeat models appeared to lose capacity very quickly when the ambient temps get below specified -13F. As Shawn mentioned above the capacity loss from +5F to -13F is about 25%. From -13F to -20F it seemed to lose all capacity to heat. The local rep could not give me a capacity at -20F only stating that the units are tested to -13F. The unit is installed on a long line technician spaces with a 300′ west exposure and an interior east wall. There is no supplemental heat in the Mitsubishi indoor indoors and they’re not available if I remember correctly. Plug-in space heaters were used where needed if the occupants where there (everyone was asked to work from home that day if possible). All-in-all, I’m impressed with the HyperHeat models as they did perform well down to below -10F making them a good fit to do all heating in most of the country.

That’s impressive, Lee.  Can

That’s impressive, Lee.  Can you tell us more about what you mean by “outside room temps”?  If by that you mean rooms on the perimeter of the house, what were the interior room temperatures?  And did you have any supplemental heat?

Oops, I dropped some bad
Oops, I dropped some bad grammar in that first post, anyway just to update. The Mitsubishi “Hyper heat” models performed as they were designed, holding space temperatures around 70F with ambient temperatures into -10F range. At -15F outside room temps were 65F and falling. At below -20F outside, temps bottomed out at 58F on both Wednesday and Thursday AM with the unit providing virtually no heat as far as I could tell.

We have to remember to vote with our dollars. Almost every time we choose the lowest cost option, we support the status quo, make a withdrawal from our worldwide bank account, and spend future dollars someone else will have to pay back. And the balance is due soon.

History and cognitive biases show us that humans make fairly bad choices all the time. So let’s remind each other to make purchasing decisions that are aligned with what we believe to be true. And if we are extra thoughtful, decisions with a longer term perspective.

This is why I have solar that costs me an extra $100 a year. This is why I pay $100 a year for carbon offsets for my cars. This is why I donate, tip well, and buy local. Do I end up paying more? Sure. But I believe it to be the right thing to do and that it has a positive impact, even an exponential impact beyond the accounting.

Thanks for everything each of you does to make a difference.

By the way, just finished the trip to Chicago where I got to see and hear about multiple Mitsubishi Hyper Heat models operating at -22*F to -25*F, in the shade. Wow.