Proper storage humidity?
 

The snow is flying, so my 911 is in mothballs for the winter. The workshop where it is stored is heated and dehumidified. Obviously a damp environment is poor, but can it be too dry? What is an ideal humidity? What can be harmed if it is too dry?

not a problem

I asked this question over on DDK recently.....

DDK - Die Deutschen Klassiker :: View topic - Ruby Dry

Rgards, Mike.

I think it's possible to get too dry, even though the all the metal won't be affected, leather and rubber seals can be negatively affected. I used to live in Montreal and although it's a relatively humid place, at this time of the year when the furnace is going all the time, it's amazing how quickly things dry out. Does the garage door get opened frequently? Just wonder why you need a dehumidifier at this time of the year in a heated space? I have read somewhere that about 50% relative humidity is ideal for vehicle storage. Joyeux Noel

when you heat the air the relative humidity is less. BUT, it is the absolute humidity that drives the movement of water vapor, NOT the relative humidity.

warmer temperature will cause the molecules to move around faster tho

if he has leather, then any residual water in it will move out faster at lower partial pressure of water vapor (absolute humidity); if only the relative humidity changes then there is no change in diffusion rates of water vapor

a dehumidifier will reduce the absolute humidity IF it can still function at the already lower T and humidity

a dehumidifier is not needed at all if it is cold

rubber, vinyl, plastics, etc. will not be affected, as they contain nearly no water

Interesting remarks.

The reason I have a dehumidifier running now has to do with the fact that the workshop was newly constructed this past summer, and we had an unusually wet season, too. So, I'm trying to get the water out of the fresh concrete slab, the green lumber, the excess dampness from too much rain, etc.

My car came with vinyl, rather than leather, so it sounds as if I need not worry. As it gets colder the amount of water the dehumidifier pulls out is diminishing. I may shut it off fairly soon.

Google psychrometric cart

if you have green lumber & a new slab in with the car, you may want to measure RH - you can convert to abs. H

The whole relative/absolute question is a good one, since warm air can contain more moisture than cold, the absolute amount of water in the air can be much more in a heated environment. That explains why a ice cold glass on a hot day collects moisture on the outside due to the cooling of the adjacent air (and thus restricting the air's capacity to contain water). I was under the impression that rubber doesn't like it too dry for too long but I won't argue with ya buddy (RWebb). If that's the case, with a vinyl interior I guess you don't need to sweat it....it seems all good. Cheers

rubber has all sorts of issues - AFAIK, low water pressure is not one

but who knows, maybe there is some odd chemically bound OH that reacts...

for winter storage, it's no big deal

I insulated the walls and installed a baseboard heater in the garage this past summer; I planned to keep it turned down low thru the winter, just enough to take the chill off and prevent condensation. Am I thinking wrong?

Would it be better to keep the garage cold, and just use a dehumidifier

That goes against everything I have ever learned about gas saturation. Can you expound upon this statement?

sure - I even can, and have, taught courses on it.

but what do you need to know -- and which stmt.? BTW - not sure what you mean re gas saturation; it is a naming convention

This is a good question and I think you're good to go. I've read differing opinions on this, but much of it depends on the location, ventilation, and temperature. Is the garage door used often or will the temperature drop to freezing or below? Dehumidifiers do not work at freezing temperature or below so it's difficult to control humidity if the temperatures naturally drop to freezing. What is the normal absolute humidity in your area? If your garage is opened frequently or the seals around the door are not so good, you're attempting to dehumidify the neighborhood. Maintaining a low (but not freezing) temperature, and controlling humidity (from what I've read, about 50% RH) is ideal. If you're bringing other vehicles into the garage constantly loaded with slush or wet with rain, you may have a difficult time getting near that number on a constant basis, even with a dehumidifier. People see the pile of slush left in their heated garage disappear over night (as opposed to being completely intact in an unheated one)....but where did the slush go? It's in the air,in the garage....that's where. Cheers

There may be deluxe dehumidifiers that somehow defrost themselves, but my experience with several of these machines is that the cooling coils frost up at temperatures of 60F, or below. Of course, they stop working then.

60 F eh? Wow, kind of limits their practicality doesn't it?

Drisump, thanks for the input.

Didn't think about the dehumidifier not working in freezing temps.

I have a small 1 car garage attached to the house exclusively for the Porsche. The doors are sealed with extra insulating materials and will stay shut unless its a beautifull sunny day and the roads are dry. We get more rain than snow. Floor has thick plastic sheeting on top of the concrete with heavy canvas tarp on top of that, battery tender, marine stabil, car cover. I keep a 60w light bulb burning in a ceramic holder sitting on a 12" square tile on the floor in the front passenger area. It seems to keep the interior dry. I drive it thru out the winter when the roads are dry, never in snow, slush or rain. It rarely gets wet. The only time the door is opened would be to get the car out. I don't winterize it, it just sits and waits for its next workout.

Storage in humidity of 50% is recommended. Mold can form and grow in humidities of 70% and greater. Conversely, leathers in environments of 30% humidity and less can dry out the material.

Leather Preservation for leather tanned before 1890 (3/5's from the top of the document).