You dont need foreign HRV-ERV PM me I'll tell you how.

Aaah, this has matured into quite a thread.

My problem with solar thermal, either hydronic or air is about low output. The good news is that for commercial systems I can get a price quote and they have a rated output in BTUs. When I compare these with an assumed lifetime for the equipment like 20 years, I get a cost per BTU that is comparable to or higher than space heat BTUs from an ASHP or DHW from a HPWH.

Gary Reysa has done a great service with his site and his careful measurements, and the best results match those of the commercial units. The entire premise of payback is then based on the idea that the units can be made for next to nothing DIY. I am all good with DIY, but building a large, complex homebrew system, hanging it on the outside of my house and leaving it there for decades seems like it would be a problem for me and most other folks at resale.

Pro Solar Thermal is too expensive, DIY Solar Thermal will never be mainstream.

I don’t think SAHs will become mainstream anytime soon either. Unfortunately, this can be truthfully said about many green building methods and products. If you think of resale value in terms of market demand and ROI, anything less than conventional construction by a licensed GC will have less than optimal resale value, which again includes many green building methods and products. Research the resale value of Passive Hause or Leed Gold Certified homes sometime if you really want to get depressed. Most people who do the green building thing don't plan to ever sell their homes. This can turn out to be a good or bad plan...

I think there is still a LOT of low-hanging fruit (<5 years simple payback) out there in terms of increasing the energy efficiency of existing US housing stock. And if we move to a 'energy scorecard' system at resale where you are expected to produce a year's utility bills, then high eff will have some value at sale (prob 5X annual savings). But that is an 'if'.

Passive House and LEED certs do seem poised to go the way of the dodo in the next 10 years, esp in the face of a major cheap PV rollout. They will be 'of a time', like earthships and 70s passive solar, but will at least have the advantage of being better engineered and comfortable than those others.

Agreed, an honest year’s worth of zero or net positive utility bills is still likely the best energy scorecard one could obtain for resale. PV is certainly poised to become a dominant natural resource in the coming years.

First off my goal was to keep it simple. Between passive solar and the solar air heater, the sun accounts for over ½ of my total heating. The other ½ is split between a small wood stove and a munchkin t-50 boiler (Propane).

As far as the dhw goes I have a 80 gallon indirect tank heated by an AET 40 sf flat panel solar collector. On sunny summer days, the solar tank maxes out at around 160 F This tank feeds into a 50 gallon indirect tank heated by a boiler loop. In the summer, I am about 95% solar. The Indirect tank feed by the boiler is set for 120 ° I have to use about 25 gallons of hot water per day so enough hot(er) water is transferred to the tank, or else the boiler fires ~ once per day to account for standby losses. All in all the system works great. Downstream of the tanks is a thermostatic mixing valve set to 120° so there is no scald potential. In the winter the solar just works as a preheat. Incoming groundwater is around 51° But the solar tank is usually between 70 and 90 in the winter.
Including the basement, 2” xps under the slab as well as an ICF foundation there is around 2100 sf of heated area. Walls are 2x6 OVE- California corners, zip sheathing taped with 1” of ISO on the outside also taped- then a ¾” rainscreen and 7/8 EWP barn siding. Wet spray cellulose.
Roof- ceiling are scissor trusses with a 6” energy heel with a vented space above. On the underside of the truss cord I used 1” of iso- and air sealed it as the ceiling air barrier- then a ¾” airspace then drywall. Cellulose was blown in to around R 50 So with the Iso you end up with ~ R 56 plus a radiant barrier facing a ¾” airspace.
We are nominally ~6300 HDD climate- This winter was unusually long and I have used~110 gallons of propane in the last 12 months + ~ 1 cord of wood. I figure I use ~ 23 million net BTU’s per year- for heat- hot water and the gas clothes dryer.

BD test on the house yield around 1.5 ach50 in winter mode. With the ERV inlet and outlet plugged, it is around 1.3 ach50 Completely sealing the woodstove gets the house down to 1.15 ach50

Interestingly one of the big determinants in the BD numbers tests is the sun Direct sun on my front door and windows warps them all a bit and increase air lleakage- House is consistently leakier on sunny days.
Not enough to realy matter though

I have no cooling system- but eventually I will get around to installing a minisplit. As it is, the house temp increases about 3° per day when it its hot out. Generally If I get 2 days per week where the temp is under 60 ie low dew points it stays comfortable as I can open windows and cool it off. More than 3 consecutive hot days with muggy nights(windows staying closed) and the house temp climes into the high 70’s which sucks. The house has only gone to 80° once in 5 years.