my garage sweats

Page 1 of 2  
what causes condensation to build up in my garage? I live in midwest & weather isn't extreme. The garage is not insulated or heated. I am tired of the rust on my tools. anyone know how to cure it?
Thanks Rob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
longshot wrote:

Most of the time, you drive you car in the rain, bring in a large warm car in to a cooler enclosed area and you get condensation. Leave the door open or provide some sort of ventilation.
--
Joseph Meehan

Dia duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Temperature differential and moist air. The garage is probably cooler than the outside air right now. You bring in the warm outside air, close the door and the moisture condenses. Leave the door open longer or heat the garage a bit.
Meantime, protect your tools with something like Top Cote, Boeshield, etc.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I don't park im my garage, i have too many tools in there. :o) it's pretty much ajuys ta shop & storage, besides, my car is a company truck. :o)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In the winter, the slab gets very cold. In spring the outside air gets warm (which holds more moisture), but the garage and especially the slab is still cooler (which holds less moisture). If the cool slab does not make it condense (like on a cold drink), the temperature drop at night can.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Or use an exhaust fan with a differential humidistat.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You need to ventilate or heat it. Even spot heating with a light bulb will help. You need to keep the temperature of your tools above dewpont. Greg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
longshot wrote:

It's a moving target. It is the temperature where the humidity hit's 100% If your tools are below that temperature, even if the air is warmer, the moisture will condense on the tools.
--
Joseph Meehan

Dia duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Longshot,
Be careful of ventilation. If the humidity ratio outside in grains of moisture per pound of air is higher than the humidity ratio inside the garage, you will not make things better. You would do yourself a favor to add some heat instead. Also, don't use a kerosene heater or some other UNVENTED fuel burnung heater, they add a lot of water vapor to the air. If you have a cabinet that you keep your tools in, you can add a heat lamp or a couple of light bulbs to warm the air inside the cabinet. If the tools hang on a wall, a couple of heat lamps aimed at the tools should help. Be careful not to get the lights too close to wood or other flamable materials as you could start a fire.
Stretch
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dew collects on grass when the grass temperature is less than the dewpoint temperature of the air near the grass (which increases with increasing humidity.)
Condensation appears on a tool in a garage when the tool temp is less than the dewpoint of the garage air near the tool.
If you stir a glass of water with an ice cube with a thermometer, it reads the dewpoint temp of the ambient air when condensation (dew) first appears on the outside of the glass.
Td = Ta/(1-Taln(R)/9621), approximately, with temperatures in absolute Rankine degrees and RH R in fractional form. For instance, 70 F (Ta = 70+460 = 530 R) air at 50% RH (R = 0.5) has Td = 530/(1-530ln(0.5)/9621) = 510.5 R, ie Td = 510.5-460 = 50.5 F.
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks, that cleared it right up! Greg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

R degrees = F degrees + 460.

R = RH/100.

In an amazing coincidence, F degrees = R degrees - 460... and "ln" is the natural log, the inverse of the "e-to-the-x" key on a Casio fx-260 solar scientific calculator ($8.76 at Wal-Mart.)

You are welcome. Now what's the dew point above with 60% RH?
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@ece.villanova.edu wrote:

You got me. 23?
--
Mortimer Schnerd, RN

snipped-for-privacy@carolina.rr.com.REMOVE
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
i think i should just replace my rusted tools. :o)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Nonono. The dew point temp goes UP with increasing RH.
You DO have a Casio fx-260 solar scientific calculator, no?

R degrees = F degrees + 460.

R = RH/100.

With RH = 60%, R = 0.6, so Td = 530/(1-530ln(0.6)/9621) = 515.5 R, ie Td = 515.5-460 = 55.5 F.
Nick
PS: The price of a standard basement Humidex is $1095, installed. Loren says they have a 1 year performance guarantee, ie you can get your money back after 1 year if you don't like it. And she says it works better in houses with AC. But moving air from near the basement floor upstairs would be more efficient than moving it outdoors and moving more outdoor humid air indoors, in a house with AC.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Nick,
The humidex is one of the dumbest ideas that I have seen in years. I went to their web site and found it is a basement exhaust fan. It sucks cool air conditioned air from the house, through the basement and then blows it outside. Now the house is under a negative pressure and outside air will come in to the house to replace the exhausted air.
If the humidity ratio of the outside air is lower than the humidity ratio of the basement air, there is no point in getting the house air involved, it would be better to blow basement air outside to be replaced with dry air from outside. You may as well run the AC with the windows open. Or run the heat in the winter with the windows open.
If the humidity ratio of the outside air is higher than the basement or crawlspace air, you are adding a lot of moisture to the house and adding load to the AC system, increasing electric bills in the process. You could start growing mold in the house. The Humidex just moves the problem from the basement to the house. Bad Idea.
Buy a dehumidifier instead. In humid climates the Humidex is a disaster about to happen. In dry climate areas, it is just a waste of money.
Stretch
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Dumber than a dehumidifier that uses lots of electrical energy?

It sucks up basement air from near the floor and exhausts it from the house when the basement air exceeds, say, 60% RH.

If the house is air-conditioned.

Yes.
Sure, if the house is being heated or air-conditioned.

Does the Humidex add more than 5 cents/pint to AC and heating bills? That depends on the weather. Moving basement air upstairs would use less energy in a house with AC. A dehumidifier would use more, since it adds to the AC load.
A little extra ventilation as needed isn't so bad in wintertime. Moving cold air in from a basement window seems better than moving warm air down from upstairs. It might come in through a concentric duct inside the exhaust duct. Moving basement air out through an air heater on a south wall and back to the basement after condensation (with an airflow high enough to avoid freezing) could use less energy than ventilation.
My newish Kenmore dehumidifier acts like a heat pump with a 1.6 COP, ie for every kWh of electricity consumed it condenses 2.047 pounds of water, which makes 0.6 kWh (2047 Btu) of sensible heat. Condensing a pound of vapor requires 1/2.047 = 0.4885 kWh worth 4.9 cents at 10 cents/kWh. If 1 kWh consumed offsets 1.6 kWh of electric resistance heat in winter, the net energy profit for removing a pound of water vapor with a dehumidifier is 0.6/2 = 0.3 kWh. If the house has a heat pump or gas or oil heat, the "profit" is likely a net loss.
NREL says the outdoor humidity ratio wo = 0.0025 pounds of water per pound of dry air on an average 30 F January day near Phila. Indoor air at 70 F and 60% RH has wi = 0.009476, so removing a pound of water by ventilation requires moving 1/(wi-wo) = 143 pounds of fresh air through the house. Warming it from 30 to 70 F requires 0.24x143(70-30) = 1376 Btu, ie 0.4 kWh. A 2470 cfm 90 W fan can move 143 pounds in 143/(2470x0.075) = 0.77 minutes, consuming 90x0.77/60 = 0.001 Wh. So winter ventilation uses less electricity than the dehumidifier, but there's no desirable heat pump effect.

Mold seems unlikely to me, if the AC works and the Humidex shuts off when the basement RH drops to 60%.

Maybe, in wintertime. But most houses don't need dehumidification then.

That's a concern, in a house without AC. I can picture the Humidex pumping humid outdoor air into a basement with a cold slab that keeps condensing water out of the air until the slab warms to the dewpoint, when condensation would stop, but that might take a long time and make a big pool of water which doesn't disappear until winter. IMO, these things could use better controls, at least, and more competition, in light of their price.
Nick
Herbach and Rademan (800) 848-8001 http://www.herbach.com sell a nice $4.95 Navy surplus humidistat, their item number TM89HVC5203, with a 20-80% range, a 3-6% differential, and a 7.5A 125V switch that can be wired to open or close on humidity rise...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
longshot wrote:

For any given amount of moisture in the air, dew will form at a specific temperature. The more moisture in the air, the higher the temperature where it will begin to form. It varies directly with the ambient humidity.
Look at the weather report for your area on any given day and see what the dewpoint is reported to be; it'll be different every day. Then keep your garage warmer than that number.
As a pilot, I've always been leery of flying to an airport where the temperature/dewpoint spread was two degrees or less; fog is almost always going to be a consideration. It doesn't take much for a forecast to be off a couple of degrees... just enough for the temp and the dewpoint to become one and the same. The result for me: poor visibility. For you: rusty tools.
--
Mortimer Schnerd, RN

snipped-for-privacy@carolina.rr.com.REMOVE
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The machining guys say that a fan to keep the air moving does the trick. I have not tried it yet.
RJ

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.