You're still relying too much on theory and not enough on observation.
It was my intention to be very simplistic in addressing the concerns of opening the doors when smoking or grilling. To me, it seems that there are many people who are so overly fearful of peaking into the cooking chamber.
The reality is that most newbies don't just peek. They open the door and start messing around doing something which is almost always unnecessary. For instance beginners tend to mop and/or spritz way too much. Most experienced pitmasters don't peek at all. When they open the cook chamber door it's with the specific intent to do something important; and more often than not combine several important things.
Sure, you can open the door a crack for 10 seconds without doing much harm, but to what end? Cooking well requires self-discipline and attention to detail. Learning not to peek is one of the hardest and most important lessons in learning to smoke.
One simple fact you and I can both agree on is the plain fact that one cubic foot of air, if completely escaped, can only carry away 0.018 BTUs per degree F. In other words, it only takes 0.5 watts of power to heat up air from 0 F to 100F.
OK. But we can also both agree that it takes significantly more than an 0.5W heating element to heat a pit to 100F on a 0F day. So, although your figures are accurate they are misleading in that they lack context.
Furthermore, something we have not addressed is the effect that fresh, dry, cool air will have on the fire itself.
That would be a function of the thermal quality of the smoker.
"Thermal quality" should be written as "thermal qualities." There are a lot of things which go into the best methods to keep temperatures as steady as possible.
My 4.5 cubic feet smoker can go from 40F to 200F in 40 minutes using only a 400w halogen bulb.
And that relates to a raising a charcoal fired, 8 cu ft, offset smoker with 1.2mm mild steel walls, from 150F to 250, with 66F ambient temp how?
As I understand, the Guru uses a very low power low volume blower to fan the fire.
It's a typical pancake fan as you'd see in a computer. They come in several sizes, each appropriate for different size pits. In any case, they're all relatively low power, low flow -- at least as compared to a show-biz Ritter.
But, context, context, context. There's a limit to how much you can stoke a fire in a 'q, imposed by the dangers of several different types "run away" fires. The right size guru for a given pit, will not only meet but exceed that limit. "Slight excess capacity" is another way of saying "barely big enough."
Yes, humidity control is important also. However, if you let one cubic foot of 212F air out, you are only losing 0.6 oz of water
Why 1 cu ft? Why 212F? This hypothetical data seem to mean something important, but are in fact quite misleading because they are so incomplete. There's also a fundamental inaccuracy. One doesn't "let one cubic foot of 212F air out." When the doors are open, hot moist air mixes with cool dry air.
If the outside relative humidity was 10%; the outside temperature 70F the pit's relative humidity 85%; the pit temperature 225F (typical rib or shoulder cook temp); the pit facing N; the wind running SSW at a steady 7mph; and the door were opened by 2 sq ft for 2 minutes, what would the pit's relative humidity be when the doors were closed? How low would the temperature drop? How long would it take for the temp to return to 225F? How long for the humidity to return to 85%? What if the pit were tuned and humidified using two loaf pans filled with water as ballasts?
I'm sure you see what I mean.
0.6 oz might not seem like much, but just as the difference between a cool, dry, air-conditioned home and the humid outdoor environment of DC in August matters to your significant other, so pit conditions matter to a brisket. Something else they share in common is that if conditions are not to their liking they'll get even.
There are limits to what environmental conditions you can ignore and still come up with useful deductions. "Science" requires that you deal with the all of the important parameters; also requires some investigation into what is and what is not important; but mostly requires you to accept reality before hypothesizing and to recognize that any hypothesis which doesn't accord with observation is not "scientific," but chopped liver.
First comes the observation. Then comes the explanation. Not the other way around.
The reality is that opening the door a few times in the first part of a 3:2:1 rib cook long enough to spritz the racks of ribs will result in drier ribs than if they'd been left alone. If your pit isn't tuned, sadly, you'll do less harm by opening the door to turn the ribs as needed (might as well spritz then), than to leave the ribs alone. Compromise isn't necessarily disaster. But a tight, tuned pit is better.