[Bldg-sim] cooling energy / solar loads

[Daniel Tuhus-Dubrow]

I'm looking at two south-facing multifamily residential buildings in
eQuest that are identical except for the wall construction.  The base
case walls are uninsulated 18" brick, while the proposed case walls
have an R-11 resistance layer of insulation in addition to the brick.
Windows are double low-e with around a 40% window-wall ratio.  The
building is located in Boston.

Cooling energy is higher for the proposed case (insulated walls), and
while investigating I found a strange result in the hourly reports.
The glass transmitted solar load in the insulated case consistently
peaks higher (and troughs lower) than in the uninsulated case.  I had
expected the solar loads to be the same in both cases (the solar gains
are indeed the same) since window properties are the same.

How come adding a resistance layer to the walls causes solar loads in
the space to change?
Okay, I just checked the number of response factors for the walls in
both cases.  The uninsulated case has 30, and the insulated case has
38.  I guess that's the difference, but I still don't feel like I have
a good understanding of it.  Thanks for any insights or explanations.

-Dan