The proposed design combines several aspects discussed, and the sketch illustrates the winter day time situation.

Sun light enters beneath the eaves, striking the solar slab in the lower floor and the inertia timbers of the upper floors.  The structural mass members of the house start storing heat. The heated air raises upward and enters the roof cavity, which is heavily insulated to avoid heat loss.

This air flow creates a natural ventilating pressure which draws the cooler air into solar slab via the ducts and cavities created to channel this flow. If overheating becomes a risk a fan will be used to push the air through the thermal mass which would be at 58F and cool the air before it enters the rooms.

As the sun sets automatic insulated binds descend to reduce heat loss. Some evenings the fireplace will be used adding heat to the air and surrounding walls.  At the outside temperatures drop the heat loss is compensated for by the release of heat from the thermal structures. Should the temperatures drop below 58F a fan will push air through the now warmer thermal mass. Finally if just before dawn the room temperature is below human comfort levels, the heat pump can be used to take the chill off until the sun recommences the heating cycle.

We hope that the system will use the heat pump rarely, but we must design for the worst case scenario and it is perceivable that some morning a snow storm or heavy overcast conditions means that there's no sun light and then we must fall back to log fires and the heat pump as back-up.