Humidity During Build

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BearLeeAlive
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Joined: Tue Aug 18, 2009 7:00 pm

Humidity During Build

Post by BearLeeAlive »

I have my 500sf woodshop/garage arranged so my with can park her car in there this winter when the weather is bad. I have tried to bribe her with a remote start to no avail. I will have lots of room to build my canoe with the machinery to the sides, but if I have to mill any big/long wood, the car would have to leave for a bit.

My concern is the humidity caused by the snow that will melt off the car and pool on the floor. Sure I will shovel or squeegee out what I can when I get the chance, but nonetheless the humidity will surely go up a lot at times. Last year we had two vehicles in the garage and the humidity was very noticeable.

I am concerned with the adverse affect this humidity will have. Is it something to be concerned about? Has anyone else dealt with this issue? I am willing to purchase a dehumidifier if that would be necessary, and be a good solution to this situation.

Any thoughts or ideas?
-JIM-
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Glen Smith
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Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

I would purchase a dehumidifier. It will also help prevent rust from forming on your tools.
If possible, install a direct drain hose so you don't have to empty the reservoir 2 or 3 times each day.

Enjoy your project.
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DSJ
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Location: Thessalon, On.

Post by DSJ »

You may want to check out an air exchager.
I found that a dehumidifier did not make a noticeable difference in my garage. Mine's 28x28 with two vehicles usually parked inside.
BearLeeAlive
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Post by BearLeeAlive »

Glen, I have heard that when working hard that the built-in tray have to be emptied a few times a day. I may start this way and move to pumping it into a bigger bucket next. The route I need to take to drain it would take a bit of work, but could be done if I really think it is worth it.

DSJ, I had not thought about using an air exchanger, I do have one sidewall that could be used if needed for that. I do think I will try the dehumidifier route first though, just because it will be way easier initially, and will only run when lots of snow is drug into the garage.
-JIM-
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Glen Smith
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Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

Additional comment: power off and cover the dehumidifier when doing any cutting, routing, sanding, etc...or the filter will quickly become blocked.
BearLeeAlive
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Post by BearLeeAlive »

Good thought, Glen. It need only run while the puddles on the floor evaporate.
-JIM-
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Redbird Bernie
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Location: Illinois, USA

Post by Redbird Bernie »

Hey BearLeeAlive, is your garage heated? Is it vented to the outside? If not, you might consider insulating and installing a heater.

As DSJ pointed out, a dehumidifier is not going to work well . The reason for this is that a dehumidifier works like an air conditioner whose air intake and exhaust are in the same space. Dehumidification only occurs when condensation forms on the cooling coil, which means that the coil has to be at a lower temperature then the ambient air. Also, since the air coming through the coil is going to be cold, it may cause the coil to freeze up. Even if it works, the process will be very inefficient. In addition, the amount of moisture that air contains is a function of temperature. In other words, air is more dense when cold and less dense when warm. The ideal solution is to heat your garage and see if the furnace dries the air sufficiently, and if not, add a dehumidifier. My guess is that if your garage is insulated properly you'll only need to heat.

Bernie
BearLeeAlive
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Post by BearLeeAlive »

Bernie, my garage is heated, and I just checked last night, and it is at 15ºC in there, and can be bumped when I am working. 3 out of 5 sides (excluding the floor) are adjoining my house, only the front and one side exposed to outside temps. This was all part of a reno over the last couple years, and the garage is very well sealed and insulated.

I have looked further into a heat recovery ventilator (HRV). A local firm has a nice Lifebreath one (LINK), but it will cost about $1k for the purchase of all the components.I could do the install myself. I think it is a bit overkill for what I need though. I am going to look further into other units. There are some as low as $400 out on the net, but most would require shipping too.

For that kind of money, if I was to bribe the wife with a remote start, and keep her car clean of snow, plus maybe a couple dinners out, I could also then have the entire space. This would not stop certain amounts of complaint though. Man, the things one does to make a marriage work. :smile
-JIM-
Peter Kotowych
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Joined: Sun May 09, 2004 8:10 pm
Location: Midland, Ontario

excess humidity

Post by Peter Kotowych »

Why not park your car outside?
Humidity problem solved and studies show
that vehicles will not rust as fast when
parked outside in the winter.
Pete[/b]
I love wood!
BearLeeAlive
Posts: 196
Joined: Tue Aug 18, 2009 7:00 pm

Re: excess humidity

Post by BearLeeAlive »

Peter Kotowych wrote:Why not park your car outside?
Humidity problem solved and studies show
that vehicles will not rust as fast when
parked outside in the winter.
Pete[/b]
I would love this solution, unfortunately it is not my car, and my wife has made quite a few concessions and only wants this one thing, a nice warm, snow free care. I am working on her, but even if I succeed it will cost me dearly, and that does not mean that I won't hear anything about it in the future either.

My SUV and pickup sit outside. The funny thing is, lately with all the cold and snow we have gotten over the last week, my wife prefers to drive my Honda Pilot, and leaves her car all cozy inside. :rolling eyes
-JIM-
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Redbird Bernie
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Location: Illinois, USA

Post by Redbird Bernie »

Before you spend any big bucks, have you measured the humidity inside and out of your garage? If so, how big is the differential? Does the inside measurement track the outside measurement during winter, summer?

I do not see how an HRV by itself is going to reduce humidity. The purpose of HRVs is to bring in make-up air, fresh air which may contain more or less moisture, in such a way as to minimize heat loss. They don't address moisture content in the air, for that you'll need a dehumidifier.

Why not try a bathroom exhaust fan instead of the expensive HRV. Unless your house is super tight, you should not need make-up air from outside. And, if you keep the air moving with an exhaust fan humidity will be minimized. Since your garage is well insulated and heated it is not unlike your bathroom, which you dehumidify by running an exhaust fan. Depending on the size of the exhaust fan you use, you may find that you only need to run it intermittently.

You do realize that you are fighting a loosing battle whatever solution you choose. Each time the garage door is opened you'll have almost 100% air exchange. So at best you'll only be reducing interior humidity a bit below exterior humidity depending on how often and how long the door is used.

Bernie
BearLeeAlive
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Post by BearLeeAlive »

Bernie, thanks so much for all your input and thoughts, it is greatly appreciated. I have plans to buy a hygrometer when out today, I am headed out to pick up sander to fair out some station moulds anyway. I will also be checking the humidity levels. I also have a chunk of cedar I will do moisture checks on. I really have no clue as to the humidity in the garage at its worst, but it is very sauna like in there then.

Here in Calgary, Alberta, the climate is very dry. Our house uses a humidifier for comfort and it also helps the wood floors and furniture from drying out too much.

A bath fan would remove humidity just as an HRV would, it is just that that is one huge volume of heated air to exchange, and to capture some of that heated air would save a few bucks over time too.. When the car dumps a load of snow, it continues to melt for some time, and evaporate even longer. A fairly constant air exchange would be needed.

The garage is 100% sealed from the house and outdoors (well, maybe 98% here).

When the overhead door opens, there is a huge exchange of air, but far from 100%. Most of the time you can barely see to back the car out due to the fog created.
-JIM-
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Redbird Bernie
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Location: Illinois, USA

Post by Redbird Bernie »

You are right, I wasn't thinking straight. Although the primary function of an HRV is make-up air, it will dehumidify by way of the warm air exhaust.

Is anyone else in your neighborhood experiencing this severe a "sauna" effect? It is incredible that you would have fog in the garage with the door open. Are you sure that you are not getting moisture from somewhere else? Check all of your venting.

It seems really odd that the snow melt from one car alone would bring the humidity up that high even if your wife parks the car with a full load of snow on it. I was just thinking about how humid a room gets when painting. A couple of gallons on the wall quickly brings the humidity to an uncomfortable level. But your garage is a big space and you probably don't get more than a couple of gallons of snow melt off the car. Still, it is a closed space with no ventilation and it is possible that you could have an air leak somewhere that you are not aware of.

Why not keep the cars out of the garage for a few days to see how much of a contribution you get from the snow melt. Doing so will help you determine if you have another contributing factor.

Good luck.

Bernie
AsaBlanchard
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Joined: Mon Mar 29, 2010 10:10 pm
Location: Lexington, KY

Post by AsaBlanchard »

Glen, Bear Mountain Boat Builders Forum, see attachment
BearLeeAlive, Jim, and all woodworkers could benefit from the Microsoft Excel Spreadsheet prepared by Terry Conners, Ph.D. at the University of Kentucky on Equilibrium Shrinkage of Wood. Please note the page tabs at the bottom of the spread sheet for different wood specie. These were prepared for my cabinet company based on the species we offered. I am sure western red cedar would be similar to pine or alder. The ideal moisture content for stable kiln dried wood is 6 – 8%. The relative humidity must be between 30-45% to maintain the wood moisture content 6-8%.
I have checked hundreds of wood cabinets in the winter time for moisture content. I would be shocked if the wood has a moisture content above 8% in a heated environment(for kiln dried lumber). Most of our problems occur when the moisture content approaches 5% and below. Keep in mind it takes 45 to 60 days for wood moisture content to stabilize when moved from one environment to another. Two gallons of melted snow does not have time to effect the wood unless the wood is laying in the water. I used a hygrometer to measure the humidity in my stand alone garage heated by a kerosene “salamander” to make sure it was warm enough for the varnish to cure. I opened the garage door frequently and bathed the canoe with water, leaving it puddled in the floor, to control dust. The humidity never rose above 50%. The water always evaporated within two-three hours.
I hope this gives a better insight to the relationship of relative humidity and wood moisture content for all the boat builders.
Asa Blanchard,
Prospector 17’1’’
Lexington, KY 40504
BearLeeAlive
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Joined: Tue Aug 18, 2009 7:00 pm

Post by BearLeeAlive »

It is so darn cold here right now, today's high was only -20ºC (-4ºF), and the car has only gone in and out a couple times in the last few days, and because it is cold, has not dragged in much snow stuck underneath. The RH in the garage is at a comfortable 40%.

The moisture content of the WRC can't be determined, as it is less than 6%, the lowest my meter measures to. My biggest concern is not the actual content, but the change and how that might affect the wood. More learning to do.

I will keep monitoring these two elements before making any kind of move.Once it warms up a bit, there will be way more moisture brought into the garage.

I just finished the moulds yesterday, and will be mounting them on the strongback today. Stripping will follow in short order.

Asa, I found a link to Terry Conners at the U of Kentucky, but could not find the spreadsheet. It is interesting the correlation between relative humidity and moisture content in wood. As can been seen by my concern, I expected the moisture content of the wood to increase more than it has with the higher humidity of the room, although temporary. I guess my biggest concern would be for glassing and varnishing. I would definitely get the conditions under control for that time period.
-JIM-
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