Well, there's your problem

See the little louvered vent above the second floor windows, right under the roof peak?
That's a gable vent.

Ian and Windy were over the last two days getting the ventilation set to right in advance of the insulation people coming on Monday. Part of the deal was to make sure that the gable end vents, visually obvious from the ground, were wide enough to ventilate correctly.
I got a text this morning, as I was on my way into work to call about the vents.
"It's blocked" he said, " the one in the old side of the house, away from the driveway. With drywall and insulation."
"Huh?"
"The opening. Is blocked. Also, the "opening" is low."

Ah. To open it completely would expose the gable vent to an area that is currently the master bedroom.

"Send a picture?"

Bonus: abandoned wasp nest.

The solution (of which there are no pictures) was to open as much as could be opened above the ceiling level, to at least get SOME airflow in that end of the house.
And other bonus: They left the clapboards on and just vinyl sided over it, so I know the house was white, and the trim looks burgundy*.

*Edit 10/17 - The more I look at it, it appears that the house was burgundy and then painted over white. I think that's siding, not trim.