Do you happen to have a schematic sketch of your system? What temperatures does your system operate at?
What brand of DHW tank to you have? I have been looking for something similar, but am having a hard time finding anything. We are building a new house this summer and I want to ensure it is ready for a future solar system. I want to also incorporate a wood boiler at some point.
Why did you use a hydraulic separator? For high-efficiency, gas-fired boilers, the burner will modulate to meet demand, so the water flow should vary as well to maintain a constant delta-T. I know some manufactures do require near constant flow, which would then require a hydraulic separator, but I try to avoid those boilers. My concern is that the hydraulic separator will mix the primary loop, causing a higher return water temperature and therefore reducing your combustion efficiency. Remember with condensing boilers, once the return water temperature gets above the flue-gas dew point (typically 130°F - 140°F), the boiler will not condense, resulting in a max efficiency of ~82%.
In-Floor Radiant vs Radiators:
We are doing in-floor radiant. In my opinion, the largest drawback of these systems is poor response to solar heat gains and occupancy. The low mass/temp panel radiator addresses these issues well.
On the flip side, radiators are less effective at making the occupants feel comfortable. Low-temperature radiators don't really radiate, they mostly convect. A lot of wasted heat is trapped at the ceiling, not the occupant level.
High-temperature radiators (including stoves and fireplaces) have the issue of radiant asymmetry. One feels hot on one side and cold on the other side, which results in poor thermal comfort. This effect is worsened with cold, poorly-insulated walls. For whatever reason, this effect ins't an issue when the asymmetry is vertical. Humans have evolved to deal with this (hot sun above and cool ground below; cold night sky and warm ground).
The old adage "Warm feet, cool heads..." describes the physiology of human thermal comfort very well.
I'll post my design at some point to give you a fair chance to criticize my design.
That's funny you mention a John Siegenthaler presentation. I really enjoyed his wood boiler presentation.