Humidity Warning

Originally Posted by AZLiberty

Again, possibly if you live way up north. Cold winter air in many places contains more moisture than hot dry summer air.

Now that it is winter/fall, the humidity is up to the mid 20s here.

If you're getting that humidity from the weather report, it doesn't tell the whole story. Virtually every place that experiences seasonal changes that could be described as "substantially colder in the winter" have lower absolute humidity outside, but the weather report only indicates relative humidity.

Take Kentucky for example. We're not "way up north" in the sense that I think you mean it, but our winter air is dry compared to our summer air in terms of moisture content. The outdoor conditions may be 30 degrees and 90% RH, but that 90% RH at 30 degrees turns into about 20% RH when you warm it up to 75 degrees.

[cmd612]

Originally Posted by Todd Yates

If you're getting that humidity from the weather report, it doesn't tell the whole story. Virtually every place that experiences seasonal changes that could be described as "substantially colder in the winter" have lower absolute humidity outside, but the weather report only indicates relative humidity.

Take Kentucky for example. We're not "way up north" in the sense that I think you mean it, but our winter air is dry compared to our summer air in terms of moisture content. The outdoor conditions may be 30 degrees and 90% RH, but that 90% RH at 30 degrees turns into about 20% RH when you warm it up to 75 degrees.

This is why dew point is so much more useful than RH as an indicator of comfort.

We have a local radio host who on summer days loves to say things like "the temperature is going up, but at least the humidity is dropping, so that should make things more comfortable!" Uh, no, it won't, since the only reason the RH is dropping is because the temperature is going up.

ASHRAE 55 indicates dew point control, but the ASHRAE Comfort Zone is still defined by dry bulb temperature and relative humidity. Dew point control is used only to achieve that goal, not to define comfort. Making the leap to using dew point in everyday thought about comfort is a tough one. IMO dry bulb temperature are RH are still the best two measures to easily and generally define comfort.

[cmd612]

Originally Posted by Todd Yates

Making the leap to using dew point in everyday thought about comfort is a tough one.

I don't find it tough, but I seem to be in the minority. Maybe it's because I live in a warm and humid climate, but if the dew point is 70F or higher, I know it's not going to feel good outside (or inside either, unless the AC and dehumidifier are both going). When the dew point gets down to the 50s, it feels a heck of a lot better.

[Guitars+gems]

Originally Posted by Todd Yates

If you're getting that humidity from the weather report, it doesn't tell the whole story. Virtually every place that experiences seasonal changes that could be described as "substantially colder in the winter" have lower absolute humidity outside, but the weather report only indicates relative humidity.

Take Kentucky for example. We're not "way up north" in the sense that I think you mean it, but our winter air is dry compared to our summer air in terms of moisture content. The outdoor conditions may be 30 degrees and 90% RH, but that 90% RH at 30 degrees turns into about 20% RH when you warm it up to 75 degrees.

Ok, I think I get this. The absolute humidity is the actual amount of water in a certain volume of air, and the relative humidity is a percentage of how much water that volume of air could potentially hold based on the temperature of the air. Is that right? I think the energy from indoor heat causes the air molecules to move faster so the air expands and makes more room for water, if it is available. But without deliberately adding water, the amount of water doesn't change. So say the 50 deg temp in the house has an RH of 60%. Then you warm the air to 70 deg. The number of water molecules is still the same, though the RH is now a smaller % of what the AH could be based on the elevated temp?
I had been thinking that the heat in the house was drying the air as in burning off the water. But when I stop and think about it, there is no place for the water to go. (Duh). So then, if the heated air is expanded, and the walls of the indoor space are the limiting factor of how far it can go, then I see why the in-case humidifiers are a perfectly viable solution to keeping the guitar humidified. And even without the humidifier, wouldn't the air inside the case have a higher RH because it hasn't been heated as much as the air outside it?

Denise, absolute humidity is express weight of water per unit of air, such as "pound of moisture per pound of dry air". Relative humidity is in percent since it is dynamically linked with the dry bulb temperature. Basically, it seems like you've got that part well enough.

On the air inside the case, you would be right in the very short term, but given just a few hours, the air inside the case will be exactly the same temperature as the room and therefore the same relative humidity if there is no moisture source in the case. Actually, since cases aren't air tight, the air in the case gets exchanged over time, which is one of the reasons you have to keep adding moisture to the in-case humidifier. Being a small space with a slow rate of exchange, you only need a little moisture in the case to raise the relative humidity.

[Guitars+gems]

Thank you, Todd. I guess all I really need to know is that I do live in a very dry place, the mountains, and the best thing would be to store the guitars in their cases with their Oasis humidifiers. The Martin is out all day, everyday, but I'll case it overnight and not worry about it. Besides, the top is torrefied, so I think it'll be fine.

[CASD57]

We have run 58-65% here all through the summer....PNW Idaho...
Lucky us

[Earl49]

As a pilot and a mechanical engineer, dew point only serves one real purpose for me: an indicator of when the weather is likely dropping down to instrument conditions. A temperature / dew point spread less than 3 degrees is a recipe for IFR weather, especially in the evenings when the outdoor temp is likely to be dropping.

Indoor RH in your home is the thing to watch, which the "weather guessers" on TV do not and cannot provide.

[AZLiberty]

Originally Posted by Todd Yates

Take Kentucky for example. We're not "way up north" in the sense that I think you mean it, but our winter air is dry compared to our summer air in terms of moisture content. The outdoor conditions may be 30 degrees and 90% RH, but that 90% RH at 30 degrees turns into about 20% RH when you warm it up to 75 degrees.

I'm still running my A/C to cool things off. Mid 90's all week, though at night I can open the windows finally.

Most of the west coast, (CA/OR/WA) the humid/rainy season is Winter not Summer. Northern Calif is bone dry in summer and the winter rains start in late October (if you are lucky) and last through Feb.

Arizona also winter, though we do get one month of humid weather in August that promptly gets turned into single digit humidity after the A/C gets done with it.

East coast and Mississippi flood plain have humid summers and dry winters.

[mirwa]

Nothing too new, but may be of interest to others.

http://mirwa.com.au/HTS_Fix_Humidity.html

Steve

[wdean]

Up here in Western Canada it can get to -25 deg F in the winter. The RH in our house can be easily less than 20%. So for most of us we are paranoid about guitar humidification for our more prized guits in the winter

[Nyghthawk]

I live about 90 miles north of Houston. Most of the year our humidity is in the "need scuba gear to breathe this stuff" range. Nothing dries out much. Even in the winter, with natural gas central heat, the 1968 model house (read open floor plan and poor window and door seals) keeps the humidity in the house high enough not to worry.

I remember being shocked the first time we visited my brother-in-law in Denver. He has a humidity gage in his kitchen area. It read 17%! No wonder I was sucking down water like there was no tomorrow!

[BrunoBlack]

I have a relative who lives near Denver and owns a Martin DCPA5 with HPL back and sides. The solid spruce top cracked after a few years of doing fine. It is a pretty dry region and it can play rough if your not careful.

[Jambi]

Has this problem made anyone consider Carbon Fiber? It seems like a pain to be constantly monitoring humidity...

or conversely, does Carbon Fiber really sound that bad that it's not even an option? The few I've heard have an eerily haunting tone that I personally find appealing, that combined with the durability makes CF mighty alluring.

The price on the other hand...