Fuzzy mold on stained/sealed window wood
Moisture is condensing on the windows at the bottoms of the panes. Windows are Andersen thermal double pane double hung, wood inside with vinyl? factory cladding on exterior. Location is Long Island NY on south shore near the water.
I had stained and then sealed the wood window frames. Used Minwax stain and their Polycrylic sealer.
I *thought* mold/mildew would not grow on the acrylic sealer.
It does not FEEL like there is high humidity level in the house. I guess I will have to buy a hygrometer to know for sure.
Any recommendations on a good unit that costs less than hiring a testing company?
I know I have to clean the woood windows with bleach or borax. What can I do to inhibit mildew on stained/sealed wood window frames? Anything to add to clear sealer?
Replies
....anyone?.....anyone? Bueller....?
What can I do to inhibit mildew on stained/sealed wood window frames? Anything to add to the clear sealer?
I have heard that putting anti-freeze on the wood will stop the mold.
My doctor told me this but do some checking for yourself.
hmmmmmm...... I do not think I'd like the green or orange patina that antifreeze would leave on the wood.
A doctor said this? (Quack Quack).
Your doctor told you to put anti-freeze on your wood to prevent mold?
I've had Andersens. I've only had moisture problems when the humidity in the house was too high. They publish a chart of what outside air temperature will produce condensation for given interior humidity levels.
You may want to try Woodlife, which is a wood preservative. Check the can because it may not be permitted for interior use because of toxicity.
Have you contacted Andersen themselves?
Have you contacted Andersen themselves?
No; I figured it is a moisture problem and the stain/sealer issue. I do not get mold on any other stained wood surface.
Condensation on windows is kind of a funny animal.
Basically, if the window surface temperature is below the dew point temperature of the air in your home, then you will have condensation on the window. That pretty much describes it and explains it.
But, the problem is that you can have two windows in the same room and while one condensates, the other does not. This may be related to the location of the window, the type or style of window, even warm air convection currents in the room. There are potentially a number of reasons why a particular window surface may have condensation, and another may not.
Relative humidity is not necessarily a good indicator of whether or not a window will have condensation....and I know many folks will disagree with that comment...nonetheless, it is true. Relative humidity is, well, relative.
Relative humidity is a comparison of actual vapor density versus saturation vapor density at a particular temperature.
Essentially, dew point equals 100% relative humidity or the point where the air - at a particular temperature - is no longer able to hold any more moisture. If the air has reached vapor saturation (100% relative humidity), then the air will release moisture...in this case on the interior glass surface of a window. If the surface temperature happens to be below freezing, then that moisture becomes frost or even ice.
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In order to stop condensation from forming on the surface of a window, you either have to lower the dew point temperature of the air in your home to a level below the dew point temperature of the window surface, or you have to warm up the window surface to a temperature above the dew point temperature of your home, or a combination of both.
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As I said earlier, lowering the relative humidity of the air in your home may have absolutely no effect on controlling window condensation…because<!----> <!---->there are two ways to lower relative humidity – increase air temperature or decrease moisture content. If you increase the air temperature you will lower the relative humidity but you will not affect the dew point...and even though you might have a relatively low relative humidity reading, you may still have window condensation. You have lowered the RH level, but you have not removed the excess water vapor from the air.
The amount of moisture in the air is measured in grams per cubic meter, which is kind of nice for metric folks but not so nice for us non-metric folks; but the metric version is much easier on the calculator than the English version (grains per pound of air? shudders!). However, in the interest of making this stuff easier to understand for all of us non-metric types, I am going to use Fahrenheit rather than Celsius temperatures in some quick calculations.
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Okay – consider your home at 65 degrees F and with a relative humidity reading of 40%. At this temperature and RH, there are 6.25 grams of water in a cubic meter of air in your home - which then equates to a dew point temperature of 38 degrees F. So at 38 degrees the air will be at 100% relative humidity or at saturation vapor density.
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Now, imagine your neighbor keeps her house at 75 degrees, but she also has 6.25 grams of water per cubic meter in her air. The relative humidity in her home is 29% - versus your 40%, but, and here’s the kicker, the dew point temperature in her home is still 38 degrees...no different than yours
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The relative humidity in her home is much lower than is the relative humidity in yours, but if the surface temperature of the windows in her home is 35 degrees she will have condensation on those windows, because that temp is below the dew point of those windows…yet if the surface temperature of your windows is 40 degrees – only five degrees warmer – you will not have condensation on your windows because the temperature of your window surface is above the dew point.
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Edited 12/2/2005 8:17 am ET by Oberon
continued...(I can be long-winded)
So, while her handy humidity gauge reads (correctly) only 29% RH – she has a condensation problem.
While your handy humidity gauge reads (correctly) 40% RH – you don’t have a condensation problem…SWEET…well, for you anyway, not her.
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If your home hygrometer measures the relative humidity in your home at 60% while the temperature of your home is 70 degrees, you will have a dew point temperature of about 51 degrees – meaning that if the temperature of the window surface is below 51 degrees then you will have condensation - so now we talk a little more specifically about windows.
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The interior surface temperature of a single lite of glass, when the temperature outside is 0 degrees F and the inside air temperature is 70 degrees, will be about 16 degrees.
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Add a storm window on the outside and the surface temperature of the inside lite jumps up to about 43 degrees – a huge improvement.
But these are center-of-glass readings and not the temperature readings at the edge of the window where condensation usually forms. A typical clear glass dual pane window is going to have center-of-glass temperature reading pretty much the same as a single pane with a storm – however, if that dual pane has a LowE coating and an argon gas infill then the center-of-glass temperature will be about 57 degrees – a 14 degree improvement over a clear glass dual pane or a single pane with storm window – but again, and more importantly, there will be a comparable edge of glass improvement as well, particularly if the IGU (Insulating Glass Unit) was manufactured using a warm edge spacer system. Also, the dual pane is going to have desiccant between the glass layers. Desiccant absorbs moisture keeping the inside of the dual pane system very dry.
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So what does a window temperature of 57 degrees mean? Well, as I mentioned earlier a home kept at 70 degrees with a 60% relative humidity has a dew point temperature of 51 degrees so it is unlikely that there will be condensation problem on those particular windows despite the rather high relative humidity in the home.
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But what happens to the dew point if you keep your home at 70 degrees and you have a 65% relative humidity? Well, for one thing the dew point has jumped up to 57 degrees which we have already noted is the same as the window temperature. For another thing, anyone with 65% relative humidity in a home at 70 degrees has way too much moisture in their air and they are in serious need of some sort of ventilation system – or at least several good exhaust fans!
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Somewhere back in this post I mentioned that lowering the relative humidity in your home may not help control condensation…that is still true…IF the relative humidity is lowered because of an increase in temperature. But, lowering the relative humidity by removing water is a different story because in that case you will also be lowering the dew point as you lower the relative humidity and that WILL help to control condensation on your windows.
This guy is good. This was clear yet detailed.
most mold isn't "white fuzzies", usually darker in color
Bread mold is pale green. Mold on wet lumber is often light green.
A lot of detailed information. I appreciate the time you spent on it.
I still have the issue of needing to discourage mold from returning (besides reducing the humidity levels).
There is mildewcide additives for paint.... are there any for stain &/or sealers?
You used to be able to buy the real good stuff with Mercury in it. What happened to the good old days?