Humidity in the shop

[Bugle]

My workshop is an unfinished basement with a concrete slab floor and cinder block walls. Three of the walls are partially below grade. I have a small window A/C unit and I recently purchased a dehumidifier. My next step is to seal the cinder block.

What is the ideal humidity percentage? It is currently at 60% and falling due to the dehumidifier.

Any other suggestions?

Thanks

 

[Joe Scharle]

One of my storage rooms is exactly what you describe. Sealing the block will be a huge improvement and look for unsealed areas between the wall and floor. Caulk everything!
I keep a fan running 24/7 as well.

 

[robliles]

My shop is exactly what you describe for your shop. Mine is about 25" X 25" x 9" (best thing I did when building my house was digging the basement out an extra foot!) I run a dehumidifier 24/7 and try to keep the humidity level around 45 to 50%. I empty 3-4 gals of water a day this time of year. At 80 degrees, which is about the temp it stays this time of year, that will keep lumber stored in the shop at between 8 and 9.5%, which for me is ideal. I have never thought about sealing the walls since I never have that much down time in the shop and the logistics of doing that almost scare me. I think it would be an excellent idea, however. I would love to have an AC in my shop but the dust, etc. concern me. Is that a problem for you? Good luck.

Rob Liles

 

[Bugle]

... I would love to have an AC in my shop but the dust, etc. concern me. Is that a problem for you? Good luck.

Rob Liles

Dust is a minor problem. The AC has a washable filter, so it's pretty easy to keep clean.

 

[scsmith42]

Preston, I keep my inventory room between 40% - 45%. I think that you'll be fine with anything less than 50%, but the closer that you get to 40%, the closer that your lumber will be to a modern home's environment.

 

[petebucy4638]

My workshop is an unfinished basement with a concrete slab floor and cinder block walls. Three of the walls are partially below grade. I have a small window A/C unit and I recently purchased a dehumidifier. My next step is to seal the cinder block.

What is the ideal humidity percentage? It is currently at 60% and falling due to the dehumidifier.

Any other suggestions?

Thanks

I suggest keeping the humidity in the room at less than 50%, if possible. If you paint the masonry walls with Dry-Loc(tm) and seal the concrete floor with a good floor paint you should be able to get below 45% easily with a decent wall A/C and a dehumidifier.

Most houses have an average humidity that is between 30% and 60%. When it comes to woodworking a little dryer is better than wetter.

 

[stave]

My shop has two walls backed by earth. The walls are sealed with Drilock(?) and the floor is sealed with a floor paint. My books are in a enclosed cabinet and although not moldy definitely smell from the humidity. I have noticed that with air circulation the humidity goes down and I have less problems but let me be gone for a few days and the effects show. I think for me keeping air moving would solve alot of the problems. I mounted a bathroom vent fan from the ceiling and this helps greatly.

Stave

 

[ehpoole]

Insofar as humidity is concerned:

>60% = Favorable for mold and mildew growth and uncomfortably humid for occupants.
50-60% = Borderline between comfortable and uncomfortable.
40-50% = Ideal range for comfort, roughly equivalent to the interior of an air conditioned home during summer. This range is unfavorable for most mold and mildew.
<40% = This range becomes increasingly uncomfortable for occupants as the drier the air the more the sinuses are dried out (leading to possible nose bleeds if humidity is extremely low). Much below 30% and the risks of end checking and mid-board splits increases due to internal stresses from shrinkage (especially if quickly dried to these levels).

Because I overheat (the downside of pain medication) very easily -- even in a 71F shop -- I keep my shop at between 40-45%RH. If I were less prone to overheating I would probably aim for 45-50%RH. If minimizing energy consumption were my priority then I would likely aim for for 50-55%RH. A benefit of maintaining your shop and wood supply within this range is the minimal movement incurred when moving shop-built furniture and accessories indoors to an air-conditioned home.

When shopping for a dehumidifier look for a model with a digital hygrometer as this type is most easily and accurately set to maintain a reliable humidity range. However, do not trust the readout to be accurate, many models may read plus-or-minus 5-10% -- so verify with a trusted hygrometer and adjust upward or downward as necessary.

From an energy efficiency perspective, it is recommended to invest in the larger (at least 50-pint/day) dehumidifiers as the smallest models (typically 25-30 pints/day), while cheapest up front, are considerably less efficient at removing moisture from the air and will also run considerably longer. When I was shopping last, a 25-pint model had an efficiency of 1.0, a 50-pint an efficiency of 1.3 and a 70-pint an efficiency of 1.4 -- that is a 30-40% efficiency improvement with the larger models. I opted for the 50-pint for my 520 sq.ft. shop and it does a very good job at maintaining a stable humidity without running all that much. I estimate it costs a maximum of $0.55/day (or about $16/month) --measured -- during the hottest and wettest months of the year, tapering to almost nothing in the dry winter months.

Thanks to the dehumidifier I have a much more comfortable shop and wood movement is kept to a minimum -- a real benefit for someone who needs 10-20 times more shop time to complete a task compared to most of you. It is pretty much the norm that my milling and essembly will take place many days (or weeks) apart, so minimizing wood movement is a necessity!