Hi everyone. Newbie here. We are in the process of preparing our house for sale.
All our "new" windows installed have blown and are all fogged up. We can't afford to replace them all and they are out of warranty.
Ok to my problem. We have 3 of the glass from pation doors installed as windows in a sunroom my husband built. The seal is shot on them too, but is much more obvious because of course, they get the sun every day and you can see water condensing and running in them.
Is there a way to get the water out? If we drilled a hole in the outside pane would the whole window shatter? Or would just the outside one shatter?
Sorry, the answer is no. Sure you could drill a hole and the liquid water could come out, but remember that the water got in there through even smaller holes. It will just get back in.
You may want to check about replacement glass. Not replacement windows, but just the glass. Most cities have a local source of replacement sealed windows. It may be cheaper than you think. It is a lot cheaper than new windows. If you are handy, you may be able to do the work yourself.
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Maybe, but as already mentioned, you might somehow drill a hole in the material at the edge between the two panes and vent that to the outdoors. Warm air rises and humid air rises, so that hole should eventually move the water vapor outdoors, assuming it's less humid outdoors and the ne exit hole is larger than the tiny leak entrance holes.
If the condensed water has etched the glass (a white frosting), you might take the panes apart and remove the frosting with a weak HF solution made from greenhouse "glass cleaning crystals."
"Maybe, but as already mentioned, you might somehow drill a hole in the
material at the edge between the two panes and vent that to the outdoors. Warm air rises and humid air rises, so that hole should eventually move
the water vapor outdoors, assuming it's less humid outdoors and the ne exit hole is larger than the tiny leak entrance holes.
If the condensed water has etched the glass (a white frosting), you might take the panes apart and remove the frosting with a weak HF solution made from greenhouse "glass cleaning crystals."
Nick "
More practical real world advice from the resident egg head.
Just for the record, the humidity inside vs outside is not the proper measure. Frankly I can't recall the proper name for it, but we should be talking about the moisture content. Humidity is a measure of the moisture content measured as a percentage of the total possible in the air at a given temperature. If you take air at 50% humidity and heat it, it will reduce the percentage say to 25% but the same total amount of water will still be there. If you cool that same 50% humidity air the humidity will increase up to 100% at witch it will become fog (or super saturated).
The meaning of all this is that to assure that they inside of the window remains fog free, you would need to maintain air circulation from the cool side of the glass (out side during winter, inside during summer with A/C on) and vented out to the other side. You would also need a good amount of circulation or you would likely get condensation when the temperature changed during the day or night, cooling the window.
If venting a window worked, then it would never fog up since it is the breaking of the seal, creating a vent, that causes the fogging to begin with.
Two holes are better. We might remove the window and drill two holes down from the top through the wood into the window cavity, then drill two more from outside to inside far enough to meet the vertical holes in the wood.
Absolute is, relative isn't, but we also need to account for bouyancy.
That's relative humidity. Absolute humidity is the water to air weight ratio. For example, w = 0.0133 pounds of water per pound of dry air on an average July day in Phila.
I disagree. We don't need circulation between two sides, IMO. We just need to assure that the temperature of the air in the window cavity is above the dew point of that air. This doesn't seem difficult... w = 0.0133 corresponds to Pa = 29.921/(1+0.62198/w) = 0.626 "Hg, with Td = 9621/(17.863-ln)Pa)-460 = 64.9 F. The average daily min temp in July is 67.2 F. With a 64.9 F cavity temp, indoor air might be 2x64.9-67.2 = 62.5, at night, when nobody's looking out the fogged window. This also requires drier indoor air to mysteriously stop leaking into the window cavity and reducing its dew point on that night. Nick
Note. The above quote was from snipped-for-privacy@optonline.net I had quoted it, I don't know how it ended up looking like I wrote it to start with.
I don't know about "bouyancy" (frankly I don't know what it means in this context :-) ) but I agree with the relative vs absolute issue.
I agree, but that is what most people mean when they refer to humidity.
No. You need the temperature of the air above the dew point AND the temperature of the glass surface facing the inside above the dew point as well.
However the end result of real life is, they don't fog up as long as they remain sealed and they do fog up when they loose their seal I don't think we are likely to find that increasing the leaks as a good solution to the problem caused by leaks to start with. I suppose under certain conditions it might work and it is cheap to do, if you do it yourself.
Or drill them all the way through to the inside, and plug them as needed inside in wintertime and outside in summertime to "put the vapor barrier on the warm side."
You might try that with triethylene glycol, but it would be a temporary fix, if the leak is still there.
Warm air rises and humid air rises... T = 70 F dry air weighs 0.075 lb/ft^3, and this decreases with temperature as (460+70)/(460+T.) The density also decreases with increasing moisture content, since the molecular weight of water vapor is about 18 vs 29 for air... 70 F air at saturation (w = 0.0158) weighs 0.073 lb/ft^3. A closed cavity with a hole near the top is a natural "cold trap" as well as a "dry trap." (By contrast, igloos are heat traps.)
In wintertime, any warm or moist air that leaks into a glass cavity from inside a house is likely to find its way out the top of the cavity via a larger hole by bouyancy as well as diffusion. In summertime, with AC in a house and cavity air cooler than outdoor air, warmer outdoor air is lighter than cavity air, so it's unlikely to enter a hole at the top of the cavity. Outdoor air with more absolute humidity is also lighter than cavity air, so it's unlikely to enter a hole at the top of the cavity.
Drilling more holes in the TOP of a leaky boat might help a little :-)
I really don't know and have not checked, but is it not likely that in the confined space of a window would diffusion not even out the moisture content before it would become a serious factor in air movement? I will take you figures for the weight of moist air vs dry air as you presented them.
Convection is usually more important. IIRC, Fick's law says 0.2RhoAdw/dx g/s of water vapor would move through area A cm^2 with a dw/dx absolute humidity gradient normal to A, where Rho is water vapor density in g/cm^3, but there's still a bouyant force from humidity if the average water vapor density in the cavity is less than the density in the air surrounding it, whether the density in the cavity is uniform or not.
There are times when holes in the cavity top won't help, eg when it's close to 100% RH indoors and outdoors at the same temp and one temp drops, which might cause temporary fogging, or when it's very humid outdoors for a long time in summertime with house AC and the window cavity leaks air out at the bottom which gets replaced with warm humid air from the top holes. That's when venting to the indoors would help. Nick
through area A cm^2 with a dw/dx absolute humidity gradient normal to A, where Rho is water vapor density in g/cm^3
Rho = 0.000018 g/cm^3 at 70 F, so I = 3.6x10^-6Adw/dx g/s. A 1mx2mx1cm glass cavity with a horizontal flow area A = 100 cm^2 and wu = 0.005 in the upper half and wl = 0.010 in the lower half and dw/dx = (wl-wu)/100 = 5x10^-5 might have an initial vapor flow I = 3.6x10^-6x100x5x10^-5 =
1.8x10^-8 g/s from bottom to top by diffusion alone. We might have something like this with an RC time constant, electrically-speaking:
Vl R Vu ---www--- | I---> | --- C/2 --- C/2 --- --- | | - -
The upper and lower window cavities each have 10K cm^3 of volume, and each contains about 12 grams of air. Initially the lower cavity contains about 0.12 grams of water vapor, and the upper contains 0.06 grams. Moving 0.01 grams of water from lower to upper makes this 0.11 and 0.07, with wl = 0.11/12 = 0.00917 and wu = 0.07/12 = 0.00583 and dw/dx = Vl-Vu = 3.33x10^-5, so C = IdT/dV = .01/(5x10^-5-3.33x10^-5) =
600. R = dV/I = 5x10^-5/1.8x10^-8 = 2778, so RC = 1.67 million seconds, or 463 hours, or 19.3 days. After 19.3 days, diffusion alone might reduce the initial 100% difference in absolute humidity to 100/e = 37%.
If air in a glass cavity starts with wg = 0.0079 (like 70 F air at 50% RH) and wa = 0.0025 on an average 30 F January day in Phila, and the R2 window with (70-30)/R2 = 20 Btu/h-ft^2 of heat flowing through it has an R0.2 outdoor air film and two R0.9 still air films, the water vapor might initially condense on the inside of the outdoor pane at 30+0.2x20 = 34 F, reducing the vapor pressure Pa to e^(17.863-9621/(460+34)) =
0.1993 "Hg, with wg = 0.62198/(29.921/Pa-1) = 0.0042 and dw/dx = (0.0042-0.0025)/5cm = 3.4x10^-4. This might diffuse to outdoors through a 0.08 cm^2x5cm (1/8"x2") hole at I = 0.2x1.8x10^-5x0.08x3.4x10^-4 =
9.8x10^-11 g/s, approximately. Removing 0.0079x12 = 0.095 g of water this way would take 0.095/I = 970 million seconds, ie 31 years :-)
But warm air rises. A cubic foot of cavity air at about 43 F and
100x0.0042/0.0058 = 72% RH weighs 0.0787 lb, vs outdoor air at 30 F and
100x0.0025/0.0035 = 72% RH and 0.0809 lb/ft^3, which is equivalent to a dT = 15 F temp diff. If cfm = 16.6Asqrt(HdT) and A = 8.5x10^-5 (for 1 of 2 1/8" holes) and h = 6' and dT = 15 F, 0.013 cfm might flow through the window cavity, replacing its 0.71 ft^3 of air every 0.71/0.013 = 54 minutes.
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