Workshop (aka shed) humidity

[OliT]

Hi

I've recently set up a bit of a workshop in my shed, but am concerned about the humidity, particularly over winter. What would you guys say is acceptable and how do you manage it? It's an old shed that we'll probably look to replace in the next couple of years so I'm loath to spend too much on it.

Any advice or ideas welcome!

 

[Beau]

Cut out all the air leaks you can and get a dehumidifier in there. If its an unheated space a desiccant type will work better like the Meaco. As for what humidity it will depend on what you are making. The wood for furniture destined for inside use will require a far lower humidity than making external windows and doors

 

[Phil Pascoe]

97% humidity here atm. Gaps around an up and over door but I have no problems with rust so long as I don't heat it.

 

[Ttrees]

I have the same approach as Phil, using airflow and cold to remedy any condensation.
The trick is to keep the tools with thermal mass as warm as the surrounding air, as if warmer air is introduced it will stick to the colder machinery and tools and due will form and cause rust.

This is grand until you wish to make things that go indoors.
Last year I was bringing in timber to glue up, and noticed some checking on the timbers, as I was trying to heat it up way too quickly on a mesh table with oil rad underneath and tent over the lot, and wasn't keeping the timber wet.
Sticking it all in the house isn't an option, as I want to keep the same MC in all the timbers.

I will be very careful now and slowly heat any furniture that might get made
for the house, by sticking it in the cold room for a long while like over a month anyways...
That will be another adventure I have yet to find out.
A few heads up hints on this might be helpful in this regard, for peasants like myself.
T'would be lovely to have a nice cozy workshop, but that ain't happening any time soon.

Cheers
Tom

 

[AJS2018]

What is the recommended humidity level? Mine is about 58/62 and I have no idea if this is good or bad.

 

[TheTiddles]

What is the recommended humidity level? Mine is about 58/62 and I have no idea if this is good or bad.

That’s just a number, it’s meaningless unless you specify the failure condition. For instance, if you have high relative humidity and you put a bit of cold metal in there, it’ll get wet, more wet if you have higher relative humidity and higher ambient temperature.

The best way to illustrate the importance of relative humidity is where’s the largest desert on earth? It’s the Antarctic... because at below zero C the air can’t hold any water, so relative humidity is 0 too and you have very little precipitation from it.

If you change the air temperature with the same quantity of water in it, the relative humidity changes too, air 100% saturated with water at 5c had a lot less water in it than air at higher temperature and lower %

Aidan

 

[artie]

because at below zero C the air can’t hold any water, so relative humidity is 0 too and you have very little precipitation from it.

Is that why we get wet parts on a freezing night?, the air kicks out all the moisture onto the windows and tablesaw.
I really must take time to learn about this as my workshop and even my old house have quite high humidity.

 

[thetyreman]

I found that sealing the gaps and making it more airtight decreased rust problems, (around the garage door) increasing airflow by opening the gaps increases the amount of moisture in the air, I get more problems in late summer with rust than any other time, I've even had rust on tools that are in a sealed in a tool chest this year...not sure why? stockport is a particularly dank, wet humid place to live, and why they built all the cotton mills here in the industrial revolution.

 

[TheTiddles]

Is that why we get wet parts on a freezing night?, the air kicks out all the moisture onto the windows and tablesaw.
I really must take time to learn about this as my workshop and even my old house have quite high humidity.

Yep!

 

[Ttrees]

45 to 55% RH is what is specified in a climate controlled luthiers workshop.
It is important if you have a constantly heated area around a colder workshop, then everytime you open the door you are letting the warm air that holds moisture out, leading to a dry condition.

Are you sure you were getting wet parts on your tablesaw at night?
I would have guessed this would have been happening with the morning air being significantly warmer than your machine.
I haven't seen real condensation like that since the big freeze 10 years ago.

Don't leave the door open on a warm morning after a cold night, and keep the cold in, if your in what resembles more of a "shed"

 

[jrm688]

The amount (mass) of water that any given volume of air can hold is dependant on among other things the temperature (proportional) and the pressure (inversely proportional). That is why cloths dryers use heat and air compressor tanks get condensation in them. Relative Humidity is a comparison of the current amount of water in air compared to the maximum amount of water the air could hold at saturation under the current conditions. That is why in the spring when warm damp outside air meets cold metal or a cold brew the local temp drops to the dew point (100% RH) and condensation occurs.
Likewise as the temp drops at night the amount of water the air can hold also drops. The temp at which the RH reaches 100% and condensation begins is known as the dew point.
In Canada in winter we take cold dry outside air and when we heat it in the house it gets even dryer. We run humidifiers and aim for 30-40% RH. In summer the air conditioning usually keeps the RH to 50% or less.
I find that if I try to spray water based varnish at less than 50% RH it dries too quick, doesn’t flow out and I get an orange peel like finish.
Hope this helps.