Dealing with moisture in the shop air.

[petersb]

Well, up here in the great northwest, we get our fair share of rain. Today was one of those wet days that reminds me that more, not less, are heading our way. I just hope that it will delay a little bit longer.

Seeing the gray day makes me think of all of the moisture in the air in the shop. I have been dealing with surface rust on tools for the past few years and finally this summer I did some shop upgrades that will help but not eliminate the moist air that comes in from the outside. My shop was built somewhere around 60 years ago (I think) and it has a lot of gaps that let the outside air come in. I have done as much as I can, without tearing the building down and rebuilding it, to seal it up.

So my question is this....

What else can I do to help keep the moisture down in the shop and help the fight against surface rust???

Its not heated or insulated. It's exposed framing.

Is there a product that absorbs moisure in the air?

Should I keep a small raidiator heater on low with a small fan?

What have you done?

Any suggestions, thoughts, or ideas would be greatly appreciated.

Thanks a bunch!

Brett

[Vic]

Brett, heating the air wont help reduce moisture, as warm air can hold more moisture than cold. That's partially why an improperly vented attic can actually rain in the cold season.

[Beechwood Chip]

You can run a dehumidifier. I'd rig it up to drain into a sump or outside, or into a shop sink, because emptying the catch basins on those things is a pain.

[Renzo]

We recently moved to a new home and the humidity in the basement is about 65-68% so I got a dehumidifer. Works really well. You can find them at Home Depot etc.

[jHop]

Keep a few of those dessicated sillica gel baggies in the areas where you store the tools. They won't cut down completely on the rust, but they will absorb some of the moisture.

It's the concept of taking a few shavings off a tenon to get it to fit, mind. It's not a blanket solution.

If you have any biscuit tubes, there should be some silica bags inside you can use - once the biscuits are gone, anyway.

I like the idea of the humidifier... you can rig some of them up with a simple garden hose to snake through the shop and drain outside. Or you can go "civilized" with pvc tubing. It's not under pressure, so pretty much any type of pvc should work. Keep the dehumidifier in center, it will pull from everywhere. (Or keep it near enough to your wood storage, to help stabilize.)

Just be aware that the humidifier might run around the clock for the first few weeks. And sealing the cracks with spray foam or silicon, then insulating and adding moisture barriers will help. If you try just drawing moisture into the humidifier without sealing the building, you're just creating a vacuum other moisture will fill.

[Chester]

That is a tough one. The really tough part is that your building is so porous. A dehumidifier, although expensive to run, will do the job. But if you keep receiving new moist air from the outside, you could overtax the DH's capacity or have some very big electric bills (or both). Have you really done everything possible to seal-up the envelope?

[Chester]

Another possibility is a fan of some sort. We use a circulating fan in our basement to keep the air moving. This seems to keep our DH from running as much and reduces the occorrences of mold in the corners.

[petersb]

Thanks everyone for your ideas.

I think that I will start out with the silica to help absorb some of the moisture. As I thought about the subject more, I remember reading somewhere about using a certain type/brand cat litter. The main ingredient was silica. Now I need to start looking at the kitty litter selection at the store!

Like I said, the building is not air tight, but what I have done to it sealed up about 75%-80% of the gaps compared to what it was. It's not perfect, but it is as perfect as it is going to be this season. I could try the foam in the crack idea, and I may. I just need to think about how I go about it. I could make it look really ugly the way the gaps are now. You would have to see what it looks like to see what I mean.

I like the idea of the dehumidifier, but I think the vacuum created it would definately bring in more of the moist outside air. I may be another option to try out if the silia doesn't work as well as I hope it will.

My idea about the heater was to keep the tool surface temperature greater than the outside air to keep condensation down.

Well, with what I have already done so far this summer, I should be out in the shop a lot more than I have been in the past. I will hopefully be able to spot rust before it grows to be big. I have started treating my tool surfaces with T9 this year and I have been out there building more too, so I should be able to keep on top of it.

Thanks a bunch, you guys are cool!

Brett

[Vic]

Thanks everyone for your ideas.

I think that I will start out with the silica to help absorb some of the moisture. As I thought about the subject more, I remember reading somewhere about using a certain type/brand cat litter. The main ingredient was silica. Now I need to start looking at the kitty litter selection at the store!

Like I said, the building is not air tight, but what I have done to it sealed up about 75%-80% of the gaps compared to what it was. It's not perfect, but it is as perfect as it is going to be this season. I could try the foam in the crack idea, and I may. I just need to think about how I go about it. I could make it look really ugly the way the gaps are now. You would have to see what it looks like to see what I mean.

I like the idea of the dehumidifier, but I think the vacuum created it would definately bring in more of the moist outside air. I may be another option to try out if the silia doesn't work as well as I hope it will.

My idea about the heater was to keep the tool surface temperature greater than the outside air to keep condensation down.

Well, with what I have already done so far this summer, I should be out in the shop a lot more than I have been in the past. I will hopefully be able to spot rust before it grows to be big. I have started treating my tool surfaces with T9 this year and I have been out there building more too, so I should be able to keep on top of it.

Thanks a bunch, you guys are cool!

Brett

Brett, just use a bread knife to flush up any excess of the spray foam. Be sure to use low expanding around doors and windows. Air sealing will help tremendously and is the first defense against heatloss, even before insulation.

[petersb]

Brett, just use a bread knife to flush up any excess of the spray foam. Be sure to use low expanding around doors and windows. Air sealing will help tremendously and is the first defense against heatloss, even before insulation.

Thanks Vic!

Here are a couple of pictures to show what I have for gaps. some are as much as 1".

The shop was built right on the dirt. The lower portion of the walls were rotted off and and it was in pretty poor shape. I spent a lot of evenings working on propping the walls and getting a footing underneath it. Now it rests on a concrete footing with treated seal plate and the lower half of the walls rebuilt. That was where the most air would come in. And it was right by the wet soil too. I could feel a breeze in the shop when the wind would blow outside.

I am thinking that it should fair a lot better this winter and maybe next summer I can pull everything out again and seal the rest up and paint the inside white, to reflect some more light and freshen things up in there.

Thanks and take care Buddy,

Brett

[Vic]

Thanks Vic!

Here are a couple of pictures to show what I have for gaps. some are as much as 1".

The shop was built right on the dirt. The lower portion of the walls were rotted off and and it was in pretty poor shape. I spent a lot of evenings working on propping the walls and getting a footing underneath it. Now it rests on a concrete footing with treated seal plate and the lower half of the walls rebuilt. That was where the most air would come in. And it was right by the wet soil too. I could feel a breeze in the shop when the wind would blow outside.

I am thinking that it should fair a lot better this winter and maybe next summer I can pull everything out again and seal the rest up and paint the inside white, to reflect some more light and freshen things up in there.

Thanks and take care Buddy,

Brett

Wow...looks like my first place. I had to use some cross arms from power poles to raise up the entire structure. I had a monolithic pad poured. I had to replace some wood rot and some termite damage. Sprayed for the termites, too.

The biggest thing is air sealing. Get an incense stick and put a box fan in your man door and seal it up with some plastic so only the air will go through the fan housing. That is a poor man's blower door. Have the fan blowing into the shop and use the incense stick to find all the leaks..seal with either expanding foam for larger holes or elastomeric caulk for smaller holes. Get them all, if you can. Moisture travels with heat. So if you can stop the air, you can do a pretty good job of stopping the moisture migration. If you want to really combat the moisture you need a moisture barrier, which can be plastic. A heavy coat of rated paint will help, but is not really considered a moisture barrier. If you want more info, pm me and we can have conversation about it.

[PaulMarcel]

Wow...looks like my first place. I had to use some cross arms from power poles to raise up the entire structure. I had a monolithic pad poured. I had to replace some wood rot and some termite damage. Sprayed for the termites, too.

The biggest thing is air sealing. Get an incense stick and put a box fan in your man door and seal it up with some plastic so only the air will go through the fan housing. That is a poor man's blower door. Have the fan blowing into the shop and use the incense stick to find all the leaks..seal with either expanding foam for larger holes or elastomeric caulk for smaller holes. Get them all, if you can. Moisture travels with heat. So if you can stop the air, you can do a pretty good job of stopping the moisture migration. If you want to really combat the moisture you need a moisture barrier, which can be plastic. A heavy coat of rated paint will help, but is not really considered a moisture barrier. If you want more info, pm me and we can have conversation about it.

Hmm, i want to try that to my house, actually. Not to veer off tangent too much, would that work on a 2-story house or would I need a considerably larger fan? On a house, would you have to cover the A/C vents or should that system, when off, have no leak?

[Vic]

Hmm, i want to try that to my house, actually. Not to veer off tangent too much, would that work on a 2-story house or would I need a considerably larger fan? On a house, would you have to cover the A/C vents or should that system, when off, have no leak?

Paul. You're in a two story house with all HVAC on the interior space, right? Theoretically, there should be no leakage to the outside with your ductwork. As far as this with a huge house, probably hard to get the cfm you'll need with a regular box fan. These are what we use at work. http://www.energyconservatory.com/products/products1.htm?gclid=COX88v6C96MCFQEMbAodfwG83g You can appoximate one of these for testing leakage with one or two furnace squirrel cage fans. But, I would check your local utility to see if they provide this service. We do it for free. If you depressurize a house, be sure to turn off all gas appliances, seal any chimneys (real bad messes, don't ask). Maybe, I should write up some basic energy stuff for the shop forum. But, really, most leaks can be felt by the back of your hand on a day that it's colder out than in, which I know doesn't help you guys in AZ. Anyway, you know how to get hold of me, Paul. Just call if you want to up the energy efficiency of your house, or shop.

[PaulMarcel]

Oh definitely I've picked your brain before about this. I just didn't think of doing a pressure test like that somewhat "DIY". I'll call my energy provider and see. The shop thing we've talked about and you gave me loads of ideas; now, on to execution. Spelunking in my attic with foam bottles was all your doing, but I definitely found some surprising gaping holes.

[b33tl3]

How big is the shop?

I would look at some closed cell foam like Tiger Foam it's a little expensive but if you plan to stay in the shop it might be worth it. You will not need a thick layer because you are more worried about sealing the gaps instead of getting a high R value. A cheaper option would be to line the wall with a house wrap just staple it inside over the studs and siding then tape all the joints.

Either of these should help seal the gaps then you could easily run a dehumidifier. I have one on my basement shop and one it gets the humidity down it doesn't run very much. I keep the fan on the high setting and empty the bucket every few weeks.

You can also buy Damp-rid some dollar stores carry it too. We used it in an old basement for a while and it worked well.

[jHop]

If you are going to insulate the walls, there are a variety of options. you can do closed-cell foam insulation (Styrofoam or similar products), open cell foam (think spray on, but "professional" applications, not the small can variety), denim (yes, recycled blue jeans), traditional fiberglass (backed or unbacked) and concrete foam. The latter is probably the most expensive, but arguably the coolest (pun intended) to install. Remember the moisture barrier goes between the interior wall and the insulation, in most applications.

As for the canned stuff, I've seen a product by the name of "Great Stuff" that has multiple formulations. They do have a product for sealing around the doors and windows that will remain semi-flexible (so the window or door does not pop out of the casement) but is rigid enough to block the wind. However, I believe the cans state that it's not to be used for gaps greater than one inch. Be careful which can you pick up, so that you can make sure it's the proper application. That gap on the ceiling joint should be filled with wood, not foam. I'd also extend the roof line to let the rain drip farther from the foundation you just had installed.

as for the pressure test: can you do a room-by-room test with the plastic and box fan, instead of the whole house at one time? I need to do a lot of work on my current abode, and I know there are leaks. Since I can only do a little bit at a time, I'd rather check the individual rooms than the whole house, which I know will fail.

[petersb]

How big is the shop?

I would look at some closed cell foam like Tiger Foam it's a little expensive but if you plan to stay in the shop it might be worth it. You will not need a thick layer because you are more worried about sealing the gaps instead of getting a high R value. A cheaper option would be to line the wall with a house wrap just staple it inside over the studs and siding then tape all the joints.

Either of these should help seal the gaps then you could easily run a dehumidifier. I have one on my basement shop and one it gets the humidity down it doesn't run very much. I keep the fan on the high setting and empty the bucket every few weeks.

You can also buy Damp-rid some dollar stores carry it too. We used it in an old basement for a while and it worked well.

My shop is a little over 500 sq ft.

I will try the damp-rid/silica route this winter and see how that goes.

I had thought about the house wrap at one point too. I may just end up blocking in some wood, over the gaps, to keep most of the air out. Its already waaaay better than it was.

[DannyBoy]

During this past summer I've been running a DH and fan constantly. I empty the DH twice a day and I suppose I could hook it up to the sump, but I water the plants instead....going green. In my shop (the basement) I've found that the most important thing is to keep air circulating because stagnant moist air is no good for iron or wood. I would like to purchase an indoor thermohygrometer similar to the one in the link below. Anyone have experience with them?

http://www.emovendo.net/magnet/indoor-thermohygrometer-thermometer-humidity-meter-with-clock-digital-htc-1.html

[Beechwood Chip]

Speaking of going green, does anyone have plants in their shop? I had a pothos that went for several years without being watered - I assume it was just absorbing moisture from the air. In Philly, there's a lot of water in the air. Plants also clean the air by breathing it in and out (better their leaves than my lungs). Pothos don't need much light, and do really well under flourescents.

Of course, they'd die if you took a break from woodworking and left the lights off. Maybe that's a good thing, "I have to get some shop time or my plants will die!"

It's just a thought that popped into my head. Anyone have experience with house-plants in the shop?

[markhochstein]

FYI, I run a dehumidifier in my shop 24/7. It's set for 35% RH and it does a good job of keeping it there. I've got a Kill-A-Watt meter on it and at 10.8 cents per kilowatt/hour it costs me $10/month to run it. I also run a propane blue-flame heater in my shop in the winter and it's normally about 50 degrees in there. Propane heaters give off water which loves to collect on cold metal. The dehumidifier does a great job then too. I'd say that you can't go wrong getting one. Get the biggest capacity one you can. Mine was about $200 from Sears. The discharge line runs into my sink. It may not solve the problem now, but will certainly help and you'll want it running in your shop after it's sealed up anyway. I build my shop 3 years ago so it's pretty tight, but it's got a big garage door on one side that is not as tight.

[Vic]

I cannot state this emphatically enough. If you use a not vented gas/propane unit in an unventilated space, you are risking your life. I know I'll get hate mail for this, but I'd rather put it out there than know one of you has died and I didn't. If you want to heat with a gas appliance, vent it and use a CO detector.

[markhochstein]

I cannot state this emphatically enough. If you use a not vented gas/propane unit in an unventilated space, you are risking your life. I know I'll get hate mail for this, but I'd rather put it out there than know one of you has died and I didn't. If you want to heat with a gas appliance, vent it and use a CO detector.

Vic, Thanks for your cautionary words. I too am very cautious about CO in my shop. I only installed this heater (I also have mini-split ductless heat pump unit installed in my shop but that's way more expensive to use) after having a lengthy conversation with my HVAC guy about the merits and pitfalls. The blue-flame unit was his idea.

My Blue Flame heater is an unvented unit. I have two CO detectors (one Kidde, one First Alert) in my shop on opposite walls and at different heights and the heater has an O2 depletion sensor built-in. My shop is not "ventilated" during the winter if I can help it. In the last two years I have seen a measurable reading on my CO sensors only once: one read 32 and the other 35. That was last winter during a severe cold snap after I had been gone for two weeks with the heater running on it's minimum setting which keeps the shop at about 50-55 degrees. Nobody had been in the shop so it had been sealed up for 13 days. I opened two windows in my shop for about five minutes and the CO level was back down to below the measuring threshold of the detectors - which is 30. My shop is 25' x 30' with 10' ceilings so that's 7500 cu/ft of air. I think that the air that leaks around the garage door is enough to act as a vent

I would recommend CO vigilance to anyone installing any type of "burning" heat in their shop, but in my case I feel very comfortable using the unit I have in my size shop without consequence.

[Vic]

The ductless heatpumps do have their limitations for cold. As I stated earlier, my house was able to stay at 65 with the heatpump when the outdoor temps got into the single digits. But, at that point the compressor would have been running full on and the COP (coefficient of performance, which is how many watts of energy in for how many equivalent btus/watts of heat out) would have been down to almost 1. You would need a back up for any heatpump at this point. The really efficient models being sold in the Scandavian countries can still pull heat out of the air down to 17 degrees F below zero.

Plus, sizing of the heatpump has a lot to do with its efficiency. The ductless heatpumps great efficiencies are derived from a variable feed compressor. When they reach the temperatures they are set to keep, the compressor ramps down and maintains that temp, pulling very few amps. On my house, I have 2.5 ton compressor (30,000 btus) with three interior units throughout the house - two 9,000 and one 15,000 btus units. Our back up is our original direct vent gas furnace. If a space has too much air leakage, a persons best bet for staying warm would be a radiant unit.

When trying to build a shop that is easily heated or retrofit a shop to become easily heated, my recommendations for the order of expenditures would be going after the "low hanging fruit" first. Air sealing would be number one. Spray foam and caulk is cheap. Next would be the insulation, first in the attic to at least R38. I have R50 blow in cellulose in mine. Then comes the walls to at least R21 for 6 inch walls and R11 for 4 inch walls. I have about R25 from blown in polyurethane foam (closed cell). The next would be R30 in the crawlspace, if you have one. If you are on a slab that has already been poured, I would dig a perimeter around the slab and install at least one layer (two is better) of rigid blue board, which is approximately R6 per inch. Concrete loses heat to the side of the slab faster than down. If building new, I would put a layer of the blue board between the ground and the concrete to help de-couple it from thermal bridging.

After you have the envelope tight and insulated, then you'll be able to appropriately size your heating system.

Enjoy your shops!!

[don reilly]

I cover all my equiptment with move blankets that I bought from Harbor Freight and took them to the local laundry mat and washed them once to make them softer. it seems to work for me But I also dont live in a state with a lot of humidity as you do.