Humidity in Joshua Tree

(Reblogged from Nathen’s Miraculous Escape, from February 21, 2012.)

Reanna is from the Pacific northwest and I grew up in Joshua Tree, CA, where we are currently living. We have an ongoing conversation about humidity here because having grown up in a wet climate, she is vigilant for the ways that moisture in the air decomposes things. “If we don’t keep it warm in here, won’t condensation damage the books?” No, it won’t, and probably wouldn’t even if we had a constantly boiling pot of water. The only place I’ve ever seen mildew in Joshua Tree is in one of our bathrooms which, until very recently, had no windows and no fan. This was not aggressive mildew either, just noticeable every once in a while. “If the roof of the trailer has leaks, won’t there be tons of mold in the walls?” No, not likely, because even if rain was pouring right through the trailer, it would be completely dry again within hours.

I have never tracked humidity levels before, so while I knew that Joshua Tree was dry, I didn’t know what level of humidity qualified as dry. I also didn’t fully understand the different measurements of humidity that are floating around out there. The short version of that story is that there are three units of humidity: absolute, specific, and relative humidity. Absolute humidity is grams of water per kilogram of moist air and specific humidity is kilograms of dry air. Relative humidity is more complicated. If I understand correctly (if incompletely) it is the ratio between 1) the pressure that the water vapor in a given amount of air would exert on the insides of a container, should it somehow be trapped there without its accompanying dry air, and 2) the pressure below which water would start condensing out of the air. Relative humidity is the measure of humidity that you usually see in weather reports, partly because it takes into account temperature–at lower temperatures, air holds less water.

Here are some cities with different levels of relative humidity, to give a sense of where we are in Joshua Tree. I’ll also include precipitation. (Data is from Weather Underground unless otherwise noted.)

Seattle, WA, 2011: High 99%, Low 34%, Average 82%, Precipitation 12.92 inches

Honolulu, HI, 2011: High 96%, Low 18%, Average, 65.6% Precipitation 23.82 inches

Joshua Tree humidity, 2011: High = 83%, Low = 10%, Average = 30.7%, Precipitation 1.53 inches

Las Vegas, NV, 2011 (the driest city in the US): High 98%, Low 2%, Average 28.7%, Precipitation about 2.5 inches (precipitation according to climatestations.com)

Kolkata, India one of the most humid cities in the world, on July 15, 2011: High 94%, Low 64%, Average 84%, Precipitation 0.0 inches

And Kartoum, Sudan (Sahara desert), on January 4, 2011: High 43 %, Low 10%, Average 24%, Precipitation .51 inches

Nathen, Reanna, Quilt, Desert
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Some Thoughts on Sealing the Outside of my Trailer

(Reblogged from Nathen’s Miraculous Escape, from February 2, 2012.)

Reanna and I have just about finished re-sealing our 1962 Kenskill travel trailer. Everything that was screwed into the corrugated aluminum that covers the outside of the trailer had to be resealed: access hatches, tail lights, door, windows. It turns out that this is hard work and takes a long time. We did not anticipate this, mostly because the instructions for the process are very simple: 1) unscrew the window or vent or whatever, 2) remove the old putty tape, 3) apply new putty tape, and 4) screw the part back in. No problem!

Reanna vs. Butyl Putty

These instructions leave several questions unanswered, foremost of which is how much of the old putty tape needs to come off for the new putty tape to seal well? Old butyl putty is sometimes impossible to completely remove with a putty knife, short of scraping all of the paint off the aluminum. No one mentions solvents in removing this stuff, but that is the only way I can imagine getting it all. Even the non-butyl putty, which gets crumbly and easy to scrape off in its old age, hides in the tiny crevices created by staples and folds in the aluminum and takes almost forever to remove completely.

Another question is how important is it to leave the paint on the aluminum intact. I found that I could speed up the process of chipping and scraping the five or six layers of rubbery and/or rock hard sealants on the roof vents using my putty knife at a sharp angle and hitting it with a hammer. Uncovering a vent could take two hours to uncover, pre-hammer technique, and now takes only just over an hour. Unfortunately, it is an unsubtle technique which inevitably gauges the paint and the aluminum underneath. Is this a problem? Even if we are going to cover everything in sealant?

Also, is there any advantage to using non-butyl putty tape? Our extremely reticent local RV repair guy would say only that he used butyl for roofs and non-butyl for walls and that butyl was stickier. People who talk about it online mostly seemed to use butyl. We found the butyl to be much easier to work with and stopped buying the non-butyl after a couple of rolls. Half of the wall-mounted stuff like windows are sealed with butyl now. Will that be a problem?

I’d like to share the several techniques I invented during this job, but I have no idea what the results will be during the next rain, much less in a couple of years. There are only three things that I know I wish I had known beforehand:

1) Don’t go to the putty knife too quickly when removing the remnants of non-butyl putty. You can get a lot of it off by rubbing hard with a wet rag for a while. It is not easy to do for hours, but quicker than going after each speck of putty with the corner of a blade.

2) You will probably have to throw away almost all of the screws you pull out, so you will spend a lot of money on new ones. And while you are correct in your initial assessment that the trailer is put together almost entirely of #8×3/4″ and #10×1″ screws, you will need a large assortment of other sizes because of water damage. I now have 3/4″ screws in #8, #10, #12, and #14, 1″ screws in #10, #12, and #14, and 1 1/2″ screws in #10 and #12. And several of those kinds of screws meant another trip to the hardware store to get them.

3) Sealing up the trailer will take a lot longer than a week if you have anything else you like to do with your life. More like three weeks. (Actually, I’m not sure I would have been better off knowing that one…)

And finally, here is the only video we found, after considerable searching, of someone actually applying putty tape. (Thanks, Canned Ham Trailers!)