You’re Not Dry Until You’re Hot And Dry

Well, here we are: in the (statistically, on average) coldest week of the year here. And reality is keeping up pretty well with statistics. The high temp today was about 10F/-12C, and the low tonight is predicted to be around
-8F/-22C. Housemate has been ridiculously supportive of the minimal-heat concept. Since January 1 we’ve pretty much had the furnace switched on only from 5pm to 10pm, and set at 60-64F/16-18C.

It wasn’t quite as cold last night as it will be tonight, but it was cold enough for me to wake up about 4am and go looking for a hat (foolishly, I’d left them all downstairs.) We may leave the heat on a bit longer tonight.

Housemate, and many others, have expressed a concern that keeping the house cool will increase risk of respiratory infections during winter. I theorize that it’s just the opposite (barring extreme life-sapping cold): that keeping the house hot causes the humidity to go way down, drying out your mucus membranes and making you susceptible to infection.

Here’s a Q&A article from a Minneapolis newspaper. The writer first complains that his house gets unhealthfully dry in winter, so he bought a humidifier. But then he got ice on his windows and, presumably, a lot of moisture condensing on other cool surfaces (not to mention and increased electric bill). Woefully, he states he cannot afford new, better-insulated windows, which the newspaper had previously suggested for preventing condensation, and asks if there is any other solution.

The newspaper’s expert responds, “You have discovered one of the conundrums of living in climates as cold as ours. Research indicates that for health and comfort, a relative indoor humidity of 40 to 60 percent is desirable. But keeping the air that moist over the course of a winter is more than most Minnesota homes can handle.” He goes on to advise that the dryness problem can be ameliorated by “slow the infiltration of cold, dry air by caulking and sealing windows, doors and other leaking areas.”

“More than most Minnesota homes can handle”?? This is peculiar. You can easily keep your home this humidified, if you really want to. What you won’t be able to handle, though, is the mess it makes of your house if you simultaneously insist on keeping the indoors at tropical temperatures.

In fact, this whole answer is just phony. The winter air in Minnesota is cold, but in terms of relative humidity, it is not dry. In fact relative humidity is about 70% all winter long in Minneapolis. It’s 59% right at this moment. Going outside in this air will not dry you out, and letting it into your house will not do so either. What does dry you out is excessively heating this air, which causes it to be capable of containing much more moisture, which causes it to suck moisture from you. Air that is 50% humidity at 32F/0C will become just 16% humid at 68F/20C, and 12% at 76F/24C.

So, I argue the writer’s problem is probably not that he had too little moisture without the humidifier and too much with it, but that that his house was too hot at both times. Chasing a severely unnatural goal of a hot house in a frigid climate has left the writer with more problems (the “solutions” to which will create only yet more problems.) Nowhere in the expert’s “solution” does he suggest the logical first step of turning the thermostat down a bit. Because, I gather, that is a step backward into historical wisdom, rather forward into the glorious technological future.


2 Responses to “You’re Not Dry Until You’re Hot And Dry”

  1. On Humidity: Hard Data « Cold House Journal Says:

    […] I’ve discussed before how heat is the real cause of the air “being dry” in winter.  But bet you didn’t know that the data logger has also been recording Relative Humidity all along, did you?  I haven’t been showing it, to avoid data overload.  But reviewing the data confirms what I already believed:  keeping the house cool keeps the air moist.  No need for fancy (or even simple) appliances that use even more energy to add extra moisture trying to make up for the dryness resulting from the burning of excessive energy in the first place! […]

  2. p Says:

    the first person on the internets to explain why our house is so dry when the air outside is cold and humid. our powerful wood stove should be bringing in humid air from outside yet the humidity inside is well below the outside. we have a very powerful humidifier running along with a big wood stove and this is the result
    out temp: 33 out hum: 91 in temp:81 in hum:36
    now i understand raising the heat has caused it to steal moisture from every object in out house including me and the hygrometer. btw i built a very powerful humidifier with ultrasonic fogger, uv lights and a water filtration system using an arduino uno and a DHT 22.

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