Hi Mirza,

In my experience, "shared walls" are not counted as "exterior surface
area" for any WWR calculations or similar.

In eQuest/DOE2 terminology: "Interior walls" model heat transfer (or
lack thereof, in the case of an adiabatic wall) between two spaces.
They will not interact directly with exterior conditions.

Surfaces separating building spaces from outside ambient conditions are
"exterior" surfaces.

There are no hard rules as to how you "should" model a shared wall, but
in eQuest you have at least a few options I think anyone would agree are
acceptable in most cases:

- Assuming heat transfer between the associated conditioned
spaces is negligible, but assuming the thermal mass of said wall is
important for accuracy, model an adiabatic wall (default approach coming
out of the wizards in eQuest).

- Assuming heat transfer between the associated conditioned
spaces is negligible, and the thermal lag caused by the mass is also
negligible for accuracy, simply delete any such walls and don't model
them at all.

- Assuming heat transfer is important for the model's accuracy,
model a normal interior partition and also expand your model to include
the adjacent building space and its envelope, internals and systems.

If somebody demolishes half of your building in the indeterminate
future, I think we'd all agree that would probably warrant an update to
the model and you'd treat the surfaces newly exposed to the exterior as
such.

NICK CATON, P.E.