Attic Temperature Records for a House in SE Virginia

Dave has provided below a great record of attic temperatures for his house in southeastern VA, as well as some good observations about using attic heat and a thermal image of the attic ceiling.

This is part of the section on using solar heat from attics...

Thanks very much to Dave for providing this excellent material!

From Dave:

Here's some more information on the attic to help in understanding the temperature data:

The entire attic is floored with 3/4 ply. On the living space side of that ply is a 1-2" layer of the expanding spray foam + a layer of R38 batt insulation, then the drywall ceiling.
The peak of the attic for the main part of the house is 18'.
Total floor space in the attic is roughly 3400 sqft.
The ridge vent runs due east-west so a good portion of the roof faces south but the roof line is quite complex as there are several half-octagon bump outs that the roof has to extend to cover. In any case... it's a large volume of space.
There is roughly 70' of ridge vent with soffit vent around the entire house.
My sensor location is a little different from yours in that the sensor is mounted 6' off the attic floor but in the middle of the attic space (i.e. almost directly below where the ridge line is). My thinking on the sensor location was that if I'm going to pull hot air from the attic into the living space, I need to know what temperature the main volume of air is at and not have the sensor affected by how hot the shingles are.
The house is located in southeastern VA at latitude 37 degrees, 24 minutes.
When I looked at the graph for the year worth of data, what stands out is how that attic temps started to have a larger delta with ambient temp starting in May of this year. That corresponds to a upgrade in my logging hardware that has allowed me to add in a lot more sensors. I thought I got the sensor back close to where it was. A few feet apparently makes a big difference.

I asked Dave: Has the data convinced you that its worthwhile to use the attic heat?

As far as usable heat... no.

What I've found is that attic vents itself quite well. During the summer months when the outside temperature gets to 90 or so the temperature may get to 110 in the attic (this is at the 6' level where the sensor is), but even when it gets over 100 outside, the attic doesn't seem to heat up much more than 110-112.

During the winter the attic temp during the day seems to track right along with the outside temp + 5 degrees or so. In the winter evenings the attic temp will cool off but rarely does it ever drop below freezing even when it's in the 10's outside.