Well, it’s a cheap starting place. To properly figure out the entire scope of it would cost time and money. A thermometer is nothing but a jumping off spot. Does the house get hotter and hotter all day and stay hot well into the evening? Does it get REALLY hot just before the house warms up?
It’s a data point, nothing more.
One point (the red line) amongst all this. Which is what I will use when we get Brian’s thermal data to figure this all out. Two points are required.
You’re going to laugh when you find out that you wife has been switching it over to heat each night just to screw with you.
Might be too soon to prescribe a remedy… However, the attics I have gone into that incorporate a radiant barrier are genuinely 10 to 20 degrees cooler, which could make a big difference.
With this old house, it can only help! 
Stack effect.
During the day surfaces absorb and retain heat. At night, when there’s no more direct sunlight, those surfaces radiate stored heat, energy back into the rooms.
1: You need to stop any air from entering the home’s lower levels.
2: Close your blinds during the day.
Sorry Robert, but that is not the total or correct scenario. Just for your info;
During the day surfaces absorb and retain heat. At night, when there’s no more direct sunlight, those surfaces radiate stored heat, energy back into the rooms.
You are only looking at 1/3rd of the equation. There are three types of heat transfer, as you know. Do not mix up the source. Remember the direction of heat flow. Higher to lower.
It is the hottest time of the day, here in Tn. 99F
Indoor Air: 79F,
Wall temp 79.3F, 136 roof - 79 IDA = 57 Delta
Ceiling 82F, 136 roof - 43 Sky= 93 Delta At night it could go to -70Fsky,
Smoke laden sky: 43F a 163 Delta.
Outdoor roof: 136F.
Outdoor wind speed: 3MPH
At the moment the sun goes down, which direction, by which means, and at what rate will the heat transfer?
You’re discussing radiated heat back into the house. Don’t forget the other two heat transfers. All three rates, conduction, convection, radiation, equal total energy movement.
As for the heat transfer, hot migrates to cold at a rate relative to the energy differential. What is the indoor air temperature we keep in the summer? Now, go outside this evening with your thermal camera and measure the atmospheric temperature. It is well below the indoor air set point. Even with all that Canadian smoke dumping in down here!
1: You need to stop any air from entering the home’s lower levels.
Leaks at the lower levels (crawlspace) can be cooler than the outdoor air.
Leaks at the upper levels, stop leakage at the lower levels.
So, if just addressing lower level leaks, do you really stop the leaks?
Answer: no, they find another opening and convect at a higher rate and pressure.
2: Close your blinds during the day.
Blinds and curtains stop radiated heat, as you state, but it’s like a blast furnace at the top of the window treatment.
We stopped radiated energy, but converted it to convected energy.
I have been trying to find a past IR scan to show this, but nothing yet.
Remember, energy can not be created (except nuclear) or destroyed (Law of conservation of energy), only transformed. So when we change the mode of transfer, the energy is all still there, but in a different form. All three must equal 100%
How heat passes through the roof into the living space of the house is very complicated compared to how we perceive it to be.
Just curious if you ever had the time to research this further and what your results were?
Much appreciated, and informative, as always, David.
Question, 79 IDA = 57 Delta refers to?
No, I did not make the time. Unfortunately, the small window I had carved out for the experiment the weather did not cooperate.
