Why rush it? There will be a next winter.

As I've seen time and time again in my career, if you can't find the time and resources to do things right, you will have to find the time and resources to do it twice (or more).

I like Mr. Dovey's passive design. It is obviously the result of reasoning and experiment. The latter being the crucible in which ideas are tested.

From an engineering point of view, the amount of solar energy outside of summer is limited. As you have experienced with your solar panels. That implies that to use that energy effectively, energy capture should be combined with proper insulation to mitigate heat loss into the environment and enough inside mass to store the heat.

What I suggest is that you use this winter to measure how much energy you need to heat your home as-is. If you still have your solar panels, hang one on the south facing wall and measure the energy output. That can be translated back into solar energy input on that wall per unit of area. With these two figures you can see how much wall area you have to dedicate to solar collectors. It could be that the results point out that it would be wiser to work on heat loss mitigation first.

If you can tolerate a not completely passive design, using a fluid as a heat capture, transfer and storage medium could be very useful. Water is an excellent heat storage medium. Combined with radiant heating in the floor could make for a very comfortable home. You want to capture as much energy as possible during the day and release it during the night.

If there is too much sun, you can simply switch off the pump or divert the flow to produce hot water.

Our house has a similar design to this, plus 450cy of rocks for thermal mass and a sunroom. My HUGE caveat is that our part of the world (I’m about 4 hours north of you in Michigan) is really not sunny enough for reliable passive solar in the winter. Something like this design could work ok when it is sunny and the sun is at the right angle - a couple hours a week - but the rest of the time, if it’s not sealed off really well, it will pump cold air in.

The part of our system that works the best is the simple sunroom. We have exterior-grade patio doors between it and the living room. When it’s warm out there (generally 20+ degrees and sunny), we open the doors. Otherwise, the doors stay firmly shut all winter. And also most of the summer, when the sunroom is far too hot. I wouldn’t do a wall of south-facing windows without a good way to block the heat in the summer.

We blocked off all vents from the solar collector/rock room because the air blows all the time, and usually about 40-50 degrees in the winter. Yes, it’s warmer than the air outside but still much colder than inside.

Here’s the plan for the house: http://babel.hathitrust.org/cgi/pt?view=image;size=100;id=umn.31951p007429573;page=root;seq=156;num=146

Some details on the passive solar features: https://eatclosetohome.wordpress.com/2012/12/12/whats-not-working-yet/

I'm planning to add insulating Kume curtains to my windows this winter. I saw them in action at Living Energy Farm; with the curtain down the room was warm all night, and raising it only a little immediately cooled the room down. The idea is to trap a layer of still air in between the window the curtian, which acts as insulation. So you need a wide window sill for the curtian to fit snugly inside without leaking air.

I'd say, make sure to get good double glazed windows (or triple) and design window sills that will allow adding kume curtians if you need them.

The main downside of combining the curtians with passive solar is they have to be raised/lowered every day.