On Tuesday, January 7, 2014 11:38:04 AM UTC-5, Ed Pawlowski wrote:
On 1/7/2014 8:30 AM, wrote:







Yes, but they won't freeze if the air temperature is 33 degrees and the



wind chill is 20. See the difference?







Yes I do. But continuing to use cases where the temp is above

freezing doesn't show that the lower the reported windchill, the

more likely pipes in a drafty crawlspace or an unheated cabin

are to freeze when the temps are well below freezing. Again the

qustion posed wasn't about 35F. It was about a day with 0F actual,

-10F windchill.



My point is, wind chill does not cause the pipes to freeze. Wind may

make them freeze sooner but the overall affect is the same.

Now try thinking this through one step further. You agree that windchill
can make pipes freeze sooner. So, it's very usual for the temp to drop
below freezing overnight and then rise above freezing again in the
morning. Let's say is 35F at 6PM and it's going to drop to a low of
20F overnight, before rising above freezing by 9AM. With a windchill
of 0F, the pipes in that drafty crawspace may have enough time to freeze,
while with no windchill they may not freeze. QED, windchill matters.
On a night with a lower reported windchill number, the pipes are more
likely to freeze. That is all that I, as well as the numerous references
I've supplied are saying.

And I'd take it even further. Without regard to time, some areas of
a drafty crawlspace might NEVER make it to below freezing, depending on
the windchill. The house is supply some warmth. With a high windchill
number you have wind. That wind might be necessary to produce a steadystate
temperature below freezing where the pipes are. Without it, the pipes
might never make it below freezing even if it stays 20F outside forever.
Now, you're gonna say "But it's the wind..." Sure it's the wind, but
the wind is reflected in the windchill. If I tell you the windchill is
0F, the outside temp is 20F, you can even calculate the actual windspeed.
It's a proxy for windspeed. Ergo, when asked which number matters,
the outside temp of 10F or the windchill number of 0F in determining
if pipes will freeze, clearly the windchill number does matter. That
was the question, was it not?









If your

example was correct, a 35 degree temperature with a 20 degree wind chill

factor would freeze the pipes. PIPES HAVE NO FEELING