Here’s a graph of the Fanger box that I made. In his 1970 book “Thermal Comfort”, Ole Fanger included a number of tables to show when most people would be comfortable for various levels of clothing and activity. I’ve taken the two tables for “sitting still and programming, moving nothing but your eyes and fingers” for both cool-weather clothing (blue box) and warm-weather clothing (red box.) The green slice is the overlap; the combination of temperature and humidity at which Dr. Fanger says you’ll be comfortable no matter what:
The “Sandex” is an index that determines how awesome your weather is compared to the theoretically-perfect weather in San Diego, CA. X-axis: relative humidity. Y-axis: temperature. You can read more about professor Ole Fanger and his work to define “room temperature” in the previous blog post.
Note that, even though the Sandex is going to be calculated based on your distance from the Fanger box, I’m still comfortable calling it the “Sandex” because on Monday, the weather in San Diego is squarely within the box.
Next up is the challenge of calculating an actual value for the Sandex. Since the Sandex is to be used as an indicator of whether or not you should work outside, I want it to be a happy yes index, with fairly forgiving boundaries — “Oh, hell yes, it’s nice enough to work outside, sure!” — rather than a no index — “conditions are not perfectly optimal right now…”
So I’m thinking of these rules when calculating the Sandex itself. I’d welcome your input!
- If the temperature and relative humidity are inside the Fanger box, the Sandex is 100%. The message is “Yes, it’s 100% awesome enough to go outside. Just go.”
- If there is a high chance of rain, high wind, or the Air Quality Index is very low, there’s a deduction of 10 or 15 points from the Sandex. But if none of those conditions exist, it doesn’t “hurt” the Sandex at all
- Here’s where we get controversial. If it were up to my own preferences:
- Humidity lower than 30% is absolutely no deduction at all;
- Temperature lower than 68° is really not a problem until you get lower than 55° or so. And still, a cool, dry day is still pretty nice, relatively speaking;
- Temperature higher than the box is worse than lower, and it gets worse faster than lower. Eighty-four degrees? Yeesh. Ninety degrees? Ouch.
- High humidity is the worst thing for the Sandex score, and high temperature plus high humidity is the “ASS” zone.
In other words, the space below the Fanger box is still pretty comfortable, but the space to the right of it, and especially above and to the right, is TRIPLE EXPONENTIAL ASS.
Now, I have a pretty high Body Mass Index, so I’m tempted to tall the space above and to the right of the Fanger box the “fatty boomalatty zone.” And my survey sample of one triathelete (Will) seems to bear out that folks with very low BMI fear cold more than humidity. But Will also says he’s always been that way. And he lives in Colorado, where humidity isn’t an oppressive fact of life like it is here in PA.
Se right now, I’m planning on having the Sandex gem do the following for a given date (usually tomorrow; this will run daily):
- For the given date, get a set of conditions from the NOAA web service. Find the temperature and relative humidity, precipitation, wind, and air quality;
- Determine whether that combination is inside the Fanger box. If so, Sandex 100%! Send a tweet through @coworkout. END OF USE CASE.
- Okay, we’re outside the Fanger box. Determine how far above or below, and how far to the left or right we are.
- Set weighting based on assumptions: (down? not too bad. up? yuck. Right? YUCK). In other words, the penalty for being outside the Fanger box will be different for X and Y components of distance.
- Using the weights, apply a sigmoid Gompertz function so that the penalty will start off light, “blurring” the edges of the Fanger box, progressing steadily the farther away you get, and then slowing down as you get really far away. Because 90 degrees and humid is just as nasty as 95 degrees and humid.
- The penalty asymptotically approaches 100, because the lowest possible Sandex score is 0%.
- Subtract the penalty from 100, and that’s your Sandex score.
What do you think? Any improvements to suggest? Randy thinks that maybe everyone has their own Fanger constants, and of course he’s right, but I wonder if there are any generally-applicable trends that we could use. Is it generally true, do you thing, that folks with a very low BMI hate cold more than they hate humidity? What about old people? They sure seem to like, you know, Florida a lot. Your thoughts? What’s your very favorite point the graph?
My head just exploded.
The bottom edge of the Sandex seems really high considering that “room temperature” is generally considered about 68F… given that folks generally sit indoors with “warm weather” clothes on, I’m not sure how that temp could be considered outside the range of comfortable temperatures.
Might help to define “cold weather clothes” too… for folks who grew up in the Northeast or other cold regions, they may be fine in cold weather clothing (sans jacket) down to the low 50s.
Tom, I agree that the bottom edge of the Fanger box seems pretty warm. He calibrated his tables based on activity, and this is the table for “sitting still doing absolutely nothing for hours at a time.”
Given that this is meant to translate “room temperature” to outoor use, having the whole box set pretty “warm” seems appropriate.
Maybe we could handle this by having a relatively low penalty (almost zero) for your conditions being below the Fanger box, until they start to get seriously chilly — as you say, down to the low 50s.
We have nicknamed the blue area that “put on a damn sweater zone”, and the red area the “take off your damn jacket” zone. Maybe the area below the box altogether is the “put on a windbreaker and some fingerless gloves” zone
Hmm, maybe we could create a mechanical turk job to have people compare the relative awesomeness of two randomly-selected points in the temperature zone.
If we had folks also enter their geographical location and BMI, we could find out all sorts of interesting pseudo-scientific things.
I’m not sharing my BMI… that’s where I draw the line for the benefit of science:
should you differentiate between wind and breeze? even when it’s warm a breeze contributes a wind chill factor that can increase the comfort level. Then there’s under-shade vs. under-sun.