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Ideal or Target Humidity level in garage

Started by gkhashem, July 12, 2019, 03:42:11 PM

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gkhashem

I have a garage that is heated for the winter, I put a dehumidifier in the garage for the summer.

What is a good level to try to keep it at. I have it set for about 45% now.

Any suggestions on what to keep it at?
1959 Oldsmobile 98 Holiday Sports Sedan
1960 Cadillac Coupe Deville (CLC Sr #72)
1964 Oldsmobile 98 Town Sedan (OCA 1st)
1970 GMC C1500
1977 Oldsmobile 98 Regency Coupe
1978 Cadillac Coupe Deville (CLC Sr Crown #959)*
1992 Oldsmobile 98 (OCA 1st)
1996 Oldsmobile 98
*CLC Past President's Preservation

Past Cadillacs
1959 Coupe Deville
1966 Coupe Deville (Sr #861)*
1991 Eldorado Biarritz (Sr #838)

BJM

45 to 50% is pretty good for summer.  In my opinion. 

Eric DeVirgilis CLC# 8621

Not necessary in warm weather IMHO. Just a couple fans to maintain air circulation.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

"Cadillac Kid" Greg Surfas 15364

George,
The target humidity would depend on the application. General health indicates that virus's "love anything less than 40% and fungus and mold love an atmosphere above 55%.
That said of you do not intend to air condition the garage and control the temperature, accurate humidity control can be a bit tricky. If your unit can actually maintain 45% you will be okay.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Jim Miller

I have also wondered about a dehumidifier. I have heat for winter, summers I just have a couple box fans circulating air. In summer and in the garage, I don't cover the cars and I leave the driver and passenger window open so the car doesn't get musty.
Jim Miller

1941 6219
1949 6237X
1970 CDV
2021 XT6
Past:
1991 SDV
1999 DeElegence
2006 DTS
2013 XTS
2016 SRX

gkhashem

I got it down to 45% today from about 55%. Plus my garage is well insulated. It takes about 3 days of really miserable weather to raise the temperature and humidity.

So I will shoot for 45%.
1959 Oldsmobile 98 Holiday Sports Sedan
1960 Cadillac Coupe Deville (CLC Sr #72)
1964 Oldsmobile 98 Town Sedan (OCA 1st)
1970 GMC C1500
1977 Oldsmobile 98 Regency Coupe
1978 Cadillac Coupe Deville (CLC Sr Crown #959)*
1992 Oldsmobile 98 (OCA 1st)
1996 Oldsmobile 98
*CLC Past President's Preservation

Past Cadillacs
1959 Coupe Deville
1966 Coupe Deville (Sr #861)*
1991 Eldorado Biarritz (Sr #838)

Jeff Wilk

45% is real good. Curious what kind of humidity/dew point levels you’re at outside?  Also how long does the unit run?  Mine goes nonstop and struggles to get down to 52% but our outside dew points have been in the 60-70%+ range now for weeks in Southern NJ. Then with the unit running this long the heat inside the garage spikes from the dehumidifiers exhaust blower.

Jeff W
"Impossible Only Describes The Degree Of Difficulty" 

Southern New Jersey

1959 Cadillac Fleetwood Sixty Special
1975 Eldorado Convertible (#12 made)
1933 Phaeton Chevrolet - "Baby Cadillac"
1933 Master Sedan Chevrolet - "Baby Cadillac"

SOLD
1976 Cadillac Mirage (factory authorized Pick-Up)
1958 Cadillac Sixty-Special
1958 Cadillac Sixty-Special
1958 Cadillac Sedan
1958 Cadillac Coupe Deville

Scot Minesinger

Agree 45% RH is awesome. 

Even better to go to ac, which I keep at 78'F because then you can still paint, reduce operational cost, and windshield does not fog up on hot humid summer days when you first set out to drive.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Is 45 a good number for leather?    I assume the plastics are more sensitive to heat and cold than humidity?

I could see a dehumidifier in a reasonably insulated garage getting pretty warm.   Even with insulation in the sun all day its going to get warm on its own and then you add that dehumidifier pumping in more heat.   I would think you would be better of with AC.    Only a slightly more expensive unit and not likely any more expensive to operate.   Just don't go with one of those 'portable' units unless maybe its a 'dual hose' one.   The dual hose ones don't seem to be very common for some reason which stinks because they are the only ones that have a decent chance of working.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

"Cadillac Kid" Greg Surfas 15364

Just to stick my nose and 50+ years of HVAC experience in here.  You cannot seriously talk about "humidity control" without having temperature control as an integral element.  45% RH at 60 degrees F is q quantum leap form 45% RH at 95 degrees F. IF you are talking about humidity control for preservation of leather, fabrics, rubber, plastic, Bakelight, etc. you need both temperature and humidity controlled.
The range of acceptable temperatures is 65-78 degrees F with a commensurate 45-55% RH.  Right now here ion Southern Texas the outdoor humidity is 44%. Great? Not. The dry bulb temperature is 96 degrees mak9ing for a 105 degree heat index and a very hot humid, mold producing environment.
It is a rather complex relationship and one that is not well understood by many.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

Scot Minesinger

George is in NH, so there are two months of summer and 85'F is a hot day (my family has lived there since 1983).  Agree a dehumidifier rejects work of compressor into garage will raise temperature, hopefully not too much.  Even a thru-wall/window ac unit (9,000 btuh) 115V-1 for $500 install in half an hour (half a day for thru wall) might go a long way for every 1,000 sq ft limited window well insulated garage to keep the environment more hospitable for classic cars - a total guess see second paragraph.  NH is humid in the summer, I designed a 2.0 ton central forced air unit for my parents 4,000 sq ft home and they were thrilled with performance.  Normally here in VA, that would be more like a 5.0 ton for that size home.  I only have 36 years of HVAC experience in Washington, DC area (very humid).

However, to really get the right size an HVAC calculation for cooling requirements must be executed based upon insulation, building materials, shade, orientation and the like.  We can't really recommend to well without visiting your garage.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

fishnjim

Best to maintain a constant temperature and humidity, all times, but that's museum quality.   If you take them out and drive them, they'll see something completely different anyway.   So where's the happy medium?   Has to be cost based.
If you're just storing vehicles, then all you really need to do is make sure the lowest daily interior temperature won't cause condensation.  ie, want to keep the wet bulb temperature(dew point) below the low temperature.   Say it gets down to 65F over night, then anything less than that in F wet bulb, ~60F, is good.   That RH will be much higher than (>>) 45%.   You convert to relative humidity from a psychrometric chart.   45% RH is quite "dry" so is more than OK so takes a little more energy to achieve.   The dehumidifier has to cool the air down to below that to condense out the water, so it's in effect cooling all the air it treats, but does so by taking a small stream to a lower level.   Depends how your unit is controlled and how tight the building is how efficient.   If it runs alot, you have too large outside air or water infiltration or to low RH setting.
The vehicle parts that absorb water, dry out, or are affected; like paper, wood, wovens, electrical, etc will not be much of an issue so long as they doesn't see liquid water(dew or condensation).   And that'll maintain the metal too.   You can take a piece of clean new sheet metal and leave out and monitor to see if it starts to rust.   If surface rusts, it's too humid.   The reverse is true, so if it's cold in there and a large amount of warm humid air comes in, like opening the door, it might condense on the colder surfaces/fog the windows.
If you're working in there, the humidity will affect your comfort, so adjust accordingly.   60F dew point is in the onset of "feel like" "heat index" corrections.  Feels humid/sticky if >70F dew point.   Where 68F and 45% RH might feel "cold".
That's why it's easier to control temp and humidity to the "ideal" thermostat setting of 72-75F and 50-60% RH and leave it.

Hope you have a way to drain the dehumidifer so water doesn't stay in the area.   Causes mold/mildew issues as the spores go with the water.   Some shut off if the reservoir fills, so need monitored daily or more in high humidity.


wrench

#12
I have to laugh, I went to refrigeration school about 40 years ago, and all that chart jive and scientific jargon. I know it is valid, relevant and applicable.

But, To air condition my garage, I just stuck one window unit I had laying around and crank it up and let it run and turn it off when the day or night time temps go down and keep the garage doors shut as much as possible and the temp and humidity as even as I can with manual control of a digital thermostat on the unit.

Takes about an ounce of brain power and 10 minutes a week of time to manage the complex relationship between the thermodynamic forces of nature and man.

I think the car generally benefits from the effort.

My goal of the exercise is not to control or overcontrol, but to create as steady a state of environment over the longest possible time period using the least amount of effort and brain power.

No, it’s not perfect, but it is simple and effective.

1951 Series 62 Sedan
1969 Eldorado
1970 Eldorado (Triple Black w/power roof)
1958 Apache 3/4 ton 4x4
2005 F250
2014 FLHP
2014 SRX

BJM

My experience is due to needing to control humidity in my basement where I have a model train layout. I have an expensive de humidifier that takes 5 gallons of water out of the air daily.   When I shut it off it spikes to 75% pretty quickly.

I too would consider installing a small efficient window unit in New Hamphire. Here in Iowa it’s tropical right now and for another 6 weeks or more.

BJM

Most modern window A/C units, which as everyone has noted is actually a dehumidifier as well, have great features - are easy to set and forget it and many even have remote control. 

Eric DeVirgilis CLC# 8621

All I know is that towels and freshly shampooed car interiors dry out very quickly on hot days regardless of how high the humidity is.

A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

INTMD8

In the summer I keep it at 70. Humidity is usually in the 50-55% range.

Could get it lower but would need to go much colder (or intentionally heat it then cool it?)

I don't know, seems fine to me :)

Tom Boehm

Question to the pros who chimed in on this topic-   Is there an accurate device available to monitor the humidity?  My workshop is insulated and sealed up. I have a large window unit A/C and a stand alone dehumidifier. Is the digital readout on the dehumidifier accurate? The only gauge I could find was a $5 plastic one made in china. The reading on that does not match that on the dehumidifier. I have a woodwoking shop and I use the dehumidifier in the summer in an attempt to keep the humidity constant year round. I set the dehumidifier between 35% and 45%.

"Cadillac Kid" Greg Surfas 15364

Tom,/-
There are many relatively inexpensive devices like the one I show below, Costs range around $50.00 for one not fabrique a Chin.
The one shown has an accuracy of +/- 6%.
For the most accuracy commercial HVAC control systems where greater accuracy is mandated have devices that actually measure the dewpoint temperature  and by combining it with the dry bulb temperature calculate the percentage Relative Humidity.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

bcroe

Those window units may be very inefficient and noisy.  Lately I
am using mini-split heat pumps which are far more energy
efficient and extremely quiet.  They can cool and heat, run off
my solar array for free. 

This one is for the car shop.  The roof is protection from ice that
slides off the roof in spring.  Bruce Roe