Workshop humidity???

[Larry Zarra]

I recently moved into a new build stand alone workshop. Thanks to all who provided input on design options for that project last year. I am finding that the humidity in the building is commonly in the 30's, as read off the smart thermostat. Does anyone have data or recommendations on optimum humidity for a dedicated woodturning shop? The decision I am aiming at is to install a humidifier, or just go with ambient conditions. I have noticed that a few blanks that I believe were dry are developing checks of endgrain. Location is northern New Jersey. This was not an issue in my last shop on the Texas gulf coast.

 

[Jerry Bennett]

Hi Larry, my friend. I wondered where you drifted off to! It will probably be an advantage to have a lower humidity than Texas. Most of the country is dryer than Texas so anytime we send anything out, the concern is always cracking from relocating to a dryer climate and a decrease in moisture content in the piece.
Jer

 

[Steve Tiedman]

Hi Larry. I don't have an precise answer for you (I'm not familiar with your climate), but like the old tv commercials said, "It's not nice to fool Mother Nature". Relative humidity inside your shop will be different from relative humidity outside your shop, unless your shop is wide open to the outside environment. Adding extra humidity in the shop in "dry winter" climates (like mine in MN) might be good for stuff inside the shop, but once your work leaves the shop, there could be issues. I'd exercise extreme caution adding too much moisture into the shop environment. Rather than a humidifier that may allow a gallon or more per day of water to be sent into the environment, grab a 9x13 cake pan from the kitchen, put a quart of water in it, and set it somewhere central in the shop. (Lots of surface in a pan vs. a bucket.) See how much water is left 24 hours later and watch that humidity gauge. Baby steps. (Something about 40% max inside humidity in winter conditions is sticking in my head.)

Also, humidity travels from wet to dry. Dry winter climates will have relatively dryer cold air outside, and your warmer, relatively wetter air from inside your shop wants to go outside. If you didn't build walls and ceilings with a vapor retarder on the inside face of the insulation (local codes are your guide to that) excessive humidity can condense to liquid inside wall cavities and air-permiable insulations (fiberous insulation and open-cell foams), causing real problems.

I know this doesn't answer your direct question, but I hope it sheds some light.

 

[DON FRANK]

I run a dehumidifier in the lathe room when I'm roughing out green wood blanks because the humidity goes way up. It's amazing how much water you can pull from a room.

 

[Kevin Jenness]

It depends in part on what conditions your work winds up in. Here in VT in-service moisture content of woodwork in my house can vary from 6-10% over the year. That correlates to about 30-50% relative humidity. I try to keep the shop between those extremes year-round with a heat pump in the summer and a couple pots of water on the woodstove in the winter. Simple turned pieces are fairly quick to adapt to humidity changes, but glued-up work, especially with any cross-grain construction, can have problems when the MC ranges more than +/- 2% as a rule of thumb.

One thing I have noticed is that it is easier to turn tearout-free when the wood has a higher moisture content. I find myself spraying water on the work before a final pass more often in the winter.

Thick turning blanks are rarely dry at the core. Best to store them in cooler, damper locations with low airflow and/or seal the endgrain and keep them near the floor in a heated shop.

 

[Doug Freeman]

I believe Jersey can get humid in the summer, so your shop humidity will vary. If the low humidity bothers you (dry skin, etc) it would be good to go with a humidifier.

 

[Kris DeVault]

Being in Alaska, the winters here are crazy dry and my shop will drop down to 15% or so if I let it while my home will be 30-50 depending. Lumber in my shop starts popping off at that point!

For me, 40% is my goal for the shop in the winter. In the summer I don't have to worry about it because its around that anyway. I ship most of my products and always worry about it being dry here and then going to Florida lets say... So far so good. I use 7-15 gallons of water a day out of two large humidifiers for 5 months out of the year.

 

[Roger Wiegand]

FWIW, here's what the humidity in my heated but not humidified shop looked like for the last year in MA. Ranged from 30% in winter to 60% in summer. The last few days went quite low because I cranked the heat up for a major finishing project. Normal daytime temp is ~64-65 in the shop in winter.

 

[Larry Zarra]

Hi Larry, my friend. I wondered where you drifted off to! It will probably be an advantage to have a lower humidity than Texas. Most of the country is dryer than Texas so anytime we send anything out, the concern is always cracking from relocating to a dryer climate and a decrease in moisture content in the piece.
Jer

Hi Jerry, We've been in north NJ a little over a year now, about 30 miles west of NYC and an hour drive to Philly. After nearly 1.5 years it's good to have my big lathe up and running again. I am finding that a few dry blanks I brought from Houston are developing end grain hairline cracks after being in a heated shop with low humidity. I'll either get a small humidifier for use in the winter, of maybe just let nature take it's course. Let me know if you plan to visit the area, my friend.

 

[Larry Zarra]

Hi Larry. I don't have an precise answer for you (I'm not familiar with your climate), but like the old tv commercials said, "It's not nice to fool Mother Nature". Relative humidity inside your shop will be different from relative humidity outside your shop, unless your shop is wide open to the outside environment. Adding extra humidity in the shop in "dry winter" climates (like mine in MN) might be good for stuff inside the shop, but once your work leaves the shop, there could be issues. I'd exercise extreme caution adding too much moisture into the shop environment. Rather than a humidifier that may allow a gallon or more per day of water to be sent into the environment, grab a 9x13 cake pan from the kitchen, put a quart of water in it, and set it somewhere central in the shop. (Lots of surface in a pan vs. a bucket.) See how much water is left 24 hours later and watch that humidity gauge. Baby steps. (Something about 40% max inside humidity in winter conditions is sticking in my head.)

Also, humidity travels from wet to dry. Dry winter climates will have relatively dryer cold air outside, and your warmer, relatively wetter air from inside your shop wants to go outside. If you didn't build walls and ceilings with a vapor retarder on the inside face of the insulation (local codes are your guide to that) excessive humidity can condense to liquid inside wall cavities and air-permiable insulations (fiberous insulation and open-cell foams), causing real problems.

I know this doesn't answer your direct question, but I hope it sheds some light.

Hi Steve, Thank you for your thoughtful reply. I will try your suggestion to monitor evaporation rate in the workshop. As a former research scientist, I appreciate experimenting and collecting data. Larry

 

[Larry Zarra]

I run a dehumidifier in the lathe room when I'm roughing out green wood blanks because the humidity goes way up. It's amazing how much water you can pull from a room.

Hey Don, Kind of the opposite of my problem. Maybe I should be roughing more green wood. Thanks, Larry

 

[Larry Zarra]

It depends in part on what conditions your work winds up in. Here in VT in-service moisture content of woodwork in my house can vary from 6-10% over the year. That correlates to about 30-50% relative humidity. I try to keep the shop between those extremes year-round with a heat pump in the summer and a couple pots of water on the woodstove in the winter. Simple turned pieces are fairly quick to adapt to humidity changes, but glued-up work, especially with any cross-grain construction, can have problems when the MC ranges more than +/- 2% as a rule of thumb.

One thing I have noticed is that it is easier to turn tearout-free when the wood has a higher moisture content. I find myself spraying water on the work before a final pass more often in the winter.

Thick turning blanks are rarely dry at the core. Best to store them in cooler, damper locations with low airflow and/or seal the endgrain and keep them near the floor in a heated shop.

Hi Kevin, I appreciate your local input on humidity ranges. I think that 30% humidity in the shop is too low. I will probably try to boost it to 40-50% after some experimentation. Spring to fall should not be a problem...it's just the combination of cold dry air and central heating that seems to be an issue. After a while I will certainly adapt to local conditions. Thank you, Larry

 

[Larry Zarra]

I believe Jersey can get humid in the summer, so your shop humidity will vary. If the low humidity bothers you (dry skin, etc) it would be good to go with a humidifier.

Hey Doug, I'm just trying to get a handle on dealing with the dry winter here in my new digs. Thanks for your comment, Larry

 

[hughie]

I recently moved into a new build stand alone workshop. Thanks to all who provided input on design options for that project last year. I am finding that the humidity in the building is commonly in the 30's, as read off the smart thermostat. Does anyone have data or recommendations on optimum humidity for a dedicated woodturning shop? The decision I am aiming at is to install a humidifier, or just go with ambient conditions. I have noticed that a few blanks that I believe were dry are developing checks of endgrain. Location is northern New Jersey. This was not an issue in my last shop on the Texas gulf coast.

I had similar problem with blanks from New Zealand got around the problem by installing a small container of water 1 Litre high on the rack near a skylight and kept it topped up. This I found to work very well and was extremely low tech, low cost solution.

 

[Larry Zarra]

Being in Alaska, the winters here are crazy dry and my shop will drop down to 15% or so if I let it while my home will be 30-50 depending. Lumber in my shop starts popping off at that point!

For me, 40% is my goal for the shop in the winter. In the summer I don't have to worry about it because its around that anyway. I ship most of my products and always worry about it being dry here and then going to Florida lets say... So far so good. I use 7-15 gallons of water a day out of two large humidifiers for 5 months out of the year.

Hi Kris, I appreciate the information. Consensus seems to be around 40% being ideal for inside winter time in a heated shop. I will try to get there and see if it makes a difference. Thank you, Larry

 

[Larry Zarra]

FWIW, here's what the humidity in my heated but not humidified shop looked like for the last year in MA. Ranged from 30% in winter to 60% in summer. The last few days went quite low because I cranked the heat up for a major finishing project. Normal daytime temp is ~64-65 in the shop in winter.
View attachment 71279

Hi Roger. I really appreciate you sending the year of data on shop humidity. I'll have to experiment with active vs. passive humidification, and see what works best. Thank you , Larry

 

[Larry Zarra]

I had similar problem with blanks from New Zealand got around the problem by installing a small container of water 1 Litre high on the rack near a skylight and kept it topped up. This I found to work very well and was extremely low tech, low cost solution.

Hi Hughie, This looks like a cool approach for passive humidification. I'll try this tomorrow. We're expecting a half foot of snow, so good time to be out in the shop. Thank you, Larry