Condensation (warning - long!)
#1
Member
Thread Starter
Condensation (warning - long!)
This past weekend, I received four different emails (not from this site though) concerning condensation and windows (I also received one concerning LowE, but that is a different story~). Anyway, it seems like this time of year a great many people become very concerned, and rightly so, about moisture on their windows in the form of condensation or even ice.
After reading the emails I wrote this rather long and involved reply, which I hope makes a certain amount of sense, and I decided to post it on the site in the hopes that someone might find it of some value…it is really long, so if you happen to feel the need to read, then here goes!
………………………………………………………………………………………
The reason why there is condensation on the interior of your windows has a really simple explanation – the surface temperature of the window is below the dew point temperature of the air in your home…that’s it.
The reason that the window surface temperature is below the dew point temperature can potentially become somewhat more complex, but I am going to offer a few thoughts and even throw in a few numbers that I hope might help your situation.
In the summer, when you pull something cold and refreshing out of the refrigerator, and the air is warm and humid, that cold and refreshing beverage container suddenly and quite magically becomes instantly wet – just as soon as it is exposed to the air. What has happened is that the temperature of the container fresh from the refrigerator is below the dew point temperature of the air – which has caused condensation on the outside of that container.
What happens to your windows in the fall and winter is that the surface of the glass is below the dew point temperature of the air in your home – which is causing condensation on the surface of that glass.
Dew point is defined as saturation vapor density...or put in simpler terms, when the air reaches 100% relative humidity and can hold no more moisture.
Relative humidity is, well, relative.
Relative humidity is a comparison of the actual vapor density versus the saturation vapor density at a particular temperature. Basically, dew point is 100% relative humidity or the point where the air - at that 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...be it on the outside of that cold beverage container in the summer time, or be it on the interior glass surface of your windows in the winter time, it makes no difference. If the surface temperature happens to be below freezing, then that moisture becomes frost or even ice.
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.
Lowering the relative humidity of the air in your home MAY have absolutely no effect on controlling window condensation…and I bet that that statement is a bit of a surprise to some folks…it is true however.
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 change the dew point - which is based on the amount of water vapor in the air and is not based on the temperature of the air.
The amount of moisture in the air is measured in grams per cubic meter, which is kind of nice for our metric folks but not so nice for our non-metric folks; but the metric version is much easier on the calculator than the English version. 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 the calculations.
Okay – consider your home at 65 degrees F and with a relative humidity reading of 40%. There are 6.25 grams of water in a cubic meter of air in your home in that particular scenario - 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.
Now, if your neighbor keeps her house at 75 degrees, but she also has 6.25 grams of water per cubic meter in her air, then 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.
While the relative humidity in her home is much lower than is the relative humidity in yours; if the surface temperature of the windows in her home is 35 degrees she will have condensation on 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.
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.
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.
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.
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 – something that is often claimed (correctly) by folks who advocate refurbishing windows rather than replacing (something that I am not going into here – I am NOT advocating either replacement or restoration in this post. It is long enough and detailed enough already without opening that particular can-of-worms!)…
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.
The advantage? If it gets cold enough outside, the temperature in the airspace between the lites can get very low. By keeping that space dry, it helps to keep the dew point temperature very low as well; something not always possible when using a single pane and storm window.
Although a single pane with a good and tight storm window can help the interior lite to avoid condensation (when compared with a single lite and no storm), the storm window itself will frost up when the temperature is low enough – at a temperature usually well above the temperature that will cause the dual pane to ice up. It is unavoidable given the right circumstances
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 relatively high relative humidity in the home.
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!
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.
Okay, there is much more to cover in this area, but I am going to stop now because this thing is long, even for me, and I am hoping that some folks have made it this far and have questions or comments - because that is the fun part of a post like this one!
Have a great day all!
After reading the emails I wrote this rather long and involved reply, which I hope makes a certain amount of sense, and I decided to post it on the site in the hopes that someone might find it of some value…it is really long, so if you happen to feel the need to read, then here goes!
………………………………………………………………………………………
The reason why there is condensation on the interior of your windows has a really simple explanation – the surface temperature of the window is below the dew point temperature of the air in your home…that’s it.
The reason that the window surface temperature is below the dew point temperature can potentially become somewhat more complex, but I am going to offer a few thoughts and even throw in a few numbers that I hope might help your situation.
In the summer, when you pull something cold and refreshing out of the refrigerator, and the air is warm and humid, that cold and refreshing beverage container suddenly and quite magically becomes instantly wet – just as soon as it is exposed to the air. What has happened is that the temperature of the container fresh from the refrigerator is below the dew point temperature of the air – which has caused condensation on the outside of that container.
What happens to your windows in the fall and winter is that the surface of the glass is below the dew point temperature of the air in your home – which is causing condensation on the surface of that glass.
Dew point is defined as saturation vapor density...or put in simpler terms, when the air reaches 100% relative humidity and can hold no more moisture.
Relative humidity is, well, relative.
Relative humidity is a comparison of the actual vapor density versus the saturation vapor density at a particular temperature. Basically, dew point is 100% relative humidity or the point where the air - at that 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...be it on the outside of that cold beverage container in the summer time, or be it on the interior glass surface of your windows in the winter time, it makes no difference. If the surface temperature happens to be below freezing, then that moisture becomes frost or even ice.
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.
Lowering the relative humidity of the air in your home MAY have absolutely no effect on controlling window condensation…and I bet that that statement is a bit of a surprise to some folks…it is true however.
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 change the dew point - which is based on the amount of water vapor in the air and is not based on the temperature of the air.
The amount of moisture in the air is measured in grams per cubic meter, which is kind of nice for our metric folks but not so nice for our non-metric folks; but the metric version is much easier on the calculator than the English version. 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 the calculations.
Okay – consider your home at 65 degrees F and with a relative humidity reading of 40%. There are 6.25 grams of water in a cubic meter of air in your home in that particular scenario - 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.
Now, if your neighbor keeps her house at 75 degrees, but she also has 6.25 grams of water per cubic meter in her air, then 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.
While the relative humidity in her home is much lower than is the relative humidity in yours; if the surface temperature of the windows in her home is 35 degrees she will have condensation on 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.
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.
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.
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.
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 – something that is often claimed (correctly) by folks who advocate refurbishing windows rather than replacing (something that I am not going into here – I am NOT advocating either replacement or restoration in this post. It is long enough and detailed enough already without opening that particular can-of-worms!)…
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.
The advantage? If it gets cold enough outside, the temperature in the airspace between the lites can get very low. By keeping that space dry, it helps to keep the dew point temperature very low as well; something not always possible when using a single pane and storm window.
Although a single pane with a good and tight storm window can help the interior lite to avoid condensation (when compared with a single lite and no storm), the storm window itself will frost up when the temperature is low enough – at a temperature usually well above the temperature that will cause the dual pane to ice up. It is unavoidable given the right circumstances
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 relatively high relative humidity in the home.
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!
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.
Okay, there is much more to cover in this area, but I am going to stop now because this thing is long, even for me, and I am hoping that some folks have made it this far and have questions or comments - because that is the fun part of a post like this one!
Have a great day all!
#2
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Thank you very much. Window condensation has always baffled me. Your post has increased my understanding though I'll have to read it several more times to really get it.
For what it's worth, the onset of cold weather has shown that I have a thus far slight condensation problem on the windows in my bedroom. (The previous owner replaced all windows in the house a few years ago and these are the only ones with condensation. The bedroom is colder than the rest of the house by two degrees celsius. It's an addition and I suspect it was not insulated properly.)
I seem to have eliminated the condensation on half of the window panes by putting clear plastic film on them, on the inside. The design of the frames prevented me from shrink-wrapping the whole unit, so I simply put the double-sided tape around each pane, attached the plastic and let loose with a hair dryer. There is now an air space of about a quarter-inch between the plastic and the window glass.
Not surprisingly, the windows with plastic on the inside are also much warmer to the touch than those without plastic.
For what it's worth, the onset of cold weather has shown that I have a thus far slight condensation problem on the windows in my bedroom. (The previous owner replaced all windows in the house a few years ago and these are the only ones with condensation. The bedroom is colder than the rest of the house by two degrees celsius. It's an addition and I suspect it was not insulated properly.)
I seem to have eliminated the condensation on half of the window panes by putting clear plastic film on them, on the inside. The design of the frames prevented me from shrink-wrapping the whole unit, so I simply put the double-sided tape around each pane, attached the plastic and let loose with a hair dryer. There is now an air space of about a quarter-inch between the plastic and the window glass.
Not surprisingly, the windows with plastic on the inside are also much warmer to the touch than those without plastic.
#3
Oberon,
Good explanation.
Thanks.
There is one thing that could be clarified:
There is a statement that is qualified by saying "MAY".
Moisture will condense on a cold window no matter how much there is is true.
It's when the moisture level is high there comes a problem with water running off windows in quantities that will damage a house.
The higher the humidity, the bigger the puddle under your windows.
Humidity levels in a house should be controlled within a range.
This does not pertain to windows specifically but humidity will always try to balance between areas of high and low.
When the humidity difference between inside and outside is great, there is a greater risk of frost forming on the inside surface of the outside walls.
Homes that allow the humidity level to go too high and do not have a good vapor barrier could suffer structural damage.
Good windows and humidity control go hand in hand.
Thanks again for the explanation.
Good explanation.
Thanks.
There is one thing that could be clarified:
Lowering the relative humidity of the air in your home MAY have absolutely no effect on controlling window condensation…and I bet that that statement is a bit of a surprise to some folks…it is true however.
Moisture will condense on a cold window no matter how much there is is true.
It's when the moisture level is high there comes a problem with water running off windows in quantities that will damage a house.
The higher the humidity, the bigger the puddle under your windows.
Humidity levels in a house should be controlled within a range.
This does not pertain to windows specifically but humidity will always try to balance between areas of high and low.
When the humidity difference between inside and outside is great, there is a greater risk of frost forming on the inside surface of the outside walls.
Homes that allow the humidity level to go too high and do not have a good vapor barrier could suffer structural damage.
Good windows and humidity control go hand in hand.
Thanks again for the explanation.
#4
Member
Thread Starter
condensation
Absolutely Greg...My point of saying "may have no effect" is that if the humidity level is changed by changing the temperature then there is no effect...but if it is changed by changing the level of moisture in the air, then there is certainly an effect.
The actual original question concerned why would one person have condensation with a relative humidity level of 40% while a relative did not have condensation with a level over 50%? So, taken in that context my explanation was based on the fact that there is much more to condensation control than simply changing the relative humidity level.
That statement was intended to "startle" a bit, but it was also intended to lead directly into the next paragraph which then discusses specifically changing relative humidity by changing temperature...
Thanks for the reply! I was hoping to start a bit of a discussion with this thing.
And thanks Canadianguy as well.
The actual original question concerned why would one person have condensation with a relative humidity level of 40% while a relative did not have condensation with a level over 50%? So, taken in that context my explanation was based on the fact that there is much more to condensation control than simply changing the relative humidity level.
That statement was intended to "startle" a bit, but it was also intended to lead directly into the next paragraph which then discusses specifically changing relative humidity by changing temperature...
Thanks for the reply! I was hoping to start a bit of a discussion with this thing.
And thanks Canadianguy as well.
#5
Join Date: Feb 1998
Location: The Shake and Bake State USA
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Window Condensation and or Excessive Moisture
Another factor needs to be considered. The condition may be caused by an unvented and/or improperly vented gas (natural or propane) appliance.
Appliance service techs in the natural gas industry should always be alert for the condition whenever a customer calls in for service on any gas appliance or to report about the condensation or moisture problems they are having.
The condition can often be tracted back to an appliance (often a heater) not venting or not venting properly, especially during cold winter months when heating is used.
Burning any fuel consumes large quanities of oxygen. The chemical changes that take place during the burning process of a fuel also produces large quanities of moisture, as one of it's byproducts. Therefore, condensation will form on windows as well as on ceilings and walls, etc.
Noticing such, the tech is than required to determine it's cause. May be the heating is done using an unvented appliance, such as an oven, stove top burners or an unvented applaince such as a fireplace.
However, if none of the above is in use or was recently in use prior to arrival, suspect the heating appliance and check it out. An improperly venting gas (natural or propane) heated is likely to be found to be the cause.
Even a properly burning heating appliance, meaning the flames are all blue and the unit is operating correctly but not venting correctly or non venting at all, will cause condensation to form on all inside house surfaces. Just more so on windows because of the huge temperature differences between indoors and outdoors.
Properly burning gas appliances will always produce moisture as well as small quanities of carbon monoxides. Low quanities of CO is acceptable and always present in our environment with or without fuel burning. A natural part of air in todays environment, indoors as well as outdoors.
However, what is important is the ambient amount of CO contained within the living environment. As a CO tester myself (past few years now gone by now) I have encountered the above many times.
Excessive moisture and or condensation on windows, etc. Most of the times harmless but certainly not always. My recommendation if such is the case, suspect the heating appliance as the cause, if all other options cannot be determined to be the cause.
One diy method is to not use the heater at all for a day and note what happens. Still condensation on the windows? Chances are some other condition exists. No condensation. Suspect the heating appliance and call for professional help!
Regards & Good Luck. Sharp Advice. Web Site Host, Forums Monitor, Gas Appliances Topic Moderator & Multiple Forums Moderator. Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.
Personal Safety Reminder:
Buckle Up & Drive Safely.
"The Life You Save, May Be Your Own."
Appliance service techs in the natural gas industry should always be alert for the condition whenever a customer calls in for service on any gas appliance or to report about the condensation or moisture problems they are having.
The condition can often be tracted back to an appliance (often a heater) not venting or not venting properly, especially during cold winter months when heating is used.
Burning any fuel consumes large quanities of oxygen. The chemical changes that take place during the burning process of a fuel also produces large quanities of moisture, as one of it's byproducts. Therefore, condensation will form on windows as well as on ceilings and walls, etc.
Noticing such, the tech is than required to determine it's cause. May be the heating is done using an unvented appliance, such as an oven, stove top burners or an unvented applaince such as a fireplace.
However, if none of the above is in use or was recently in use prior to arrival, suspect the heating appliance and check it out. An improperly venting gas (natural or propane) heated is likely to be found to be the cause.
Even a properly burning heating appliance, meaning the flames are all blue and the unit is operating correctly but not venting correctly or non venting at all, will cause condensation to form on all inside house surfaces. Just more so on windows because of the huge temperature differences between indoors and outdoors.
Properly burning gas appliances will always produce moisture as well as small quanities of carbon monoxides. Low quanities of CO is acceptable and always present in our environment with or without fuel burning. A natural part of air in todays environment, indoors as well as outdoors.
However, what is important is the ambient amount of CO contained within the living environment. As a CO tester myself (past few years now gone by now) I have encountered the above many times.
Excessive moisture and or condensation on windows, etc. Most of the times harmless but certainly not always. My recommendation if such is the case, suspect the heating appliance as the cause, if all other options cannot be determined to be the cause.
One diy method is to not use the heater at all for a day and note what happens. Still condensation on the windows? Chances are some other condition exists. No condensation. Suspect the heating appliance and call for professional help!
Regards & Good Luck. Sharp Advice. Web Site Host, Forums Monitor, Gas Appliances Topic Moderator & Multiple Forums Moderator. Energy Conservation Consultant & Natural Gas Appliance Diagnostics Technician.
Personal Safety Reminder:
Buckle Up & Drive Safely.
"The Life You Save, May Be Your Own."
#6
Member
Thread Starter
condensation
Very good point...although I didn't get into it specifically, if there is excess moisture in the home it is always a very good idea to find out WHY it is there. And a poorly vented or poorly opertaing gas appliance is about as high up on the priority list as is possible to be.
This is exactly the sort of discussion I was fishing for!
This is exactly the sort of discussion I was fishing for!
#7
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Fishing??? Someone Mention "FISHING?" Great!!! Let's Go NOW!
Hello: Oberon
Yes. I agree. A very good topic and discussion thus far. More info should be forth coming or so one should suspect or hope does come. This is the way we each learn more from each other and exactly what the entire web site is all about.....
Not exactly my kind of "FISHING." However, worthy anyway.
My kind of "FISHING" is from the stern of a fishing vessel in the footage range of 40 to 60 or more feet. But fishing in that context is off topic and not allowed, so we will drop the fishing subject....
Web Site Host, Moderator Hiring Agent & Forums Monitor.
Personal Reminder:
Buckle Up & Drive Safely.
"The Life You Save, May Be Your Own."
Yes. I agree. A very good topic and discussion thus far. More info should be forth coming or so one should suspect or hope does come. This is the way we each learn more from each other and exactly what the entire web site is all about.....
This is exactly the sort of discussion I was fishing for!
My kind of "FISHING" is from the stern of a fishing vessel in the footage range of 40 to 60 or more feet. But fishing in that context is off topic and not allowed, so we will drop the fishing subject....
Web Site Host, Moderator Hiring Agent & Forums Monitor.
Personal Reminder:
Buckle Up & Drive Safely.
"The Life You Save, May Be Your Own."
#8
We should rename this thread "Humidity chat".
If moisture levels were expressed as grains of moisture/pound of air, the subject might be a bit easier to understand.
That is, a grain as a measure of weight is 2/1000ths of an ounce.
(Didn't remember this from refrigeration school....... looked it up. I actually flunked that class. )
Don't get to discuss humidity theory too often.
I consider myself more of a student on the subject than an authority.
I have two "humidity customers" that keep me on my toes.
A museum that is built within a 100 year old courthouse.
They have a building envelope that has an air circulation chamber against the entire inside of the exterior wall where the humidity levels are maintained year round to be compatible with 100 year old construction.
The inside of the building is isolated by vapor barrier from the exterior shell with an attempt to maintain a constant 45% rh and 21 deg C (70 degF).
What makes this one interesting is their limited budget, as with all museums, and equipment that wasn't designed for tight control.
The other customer is a small casino where improper humidity levels cause card shufflers to malfunction and computer circuits to fry.
This one is interesting because of the amount of air change, they have a very high humidifying capacity.
There are five Neptronic brand humidifiers.
Combined they have a heater capacity of 150 kw creating 450 lbs/hr of steam!
You have to keep in mind this casino has only 200 slots and around 10 gaming tables.
Having outside temps with a range of +35 deg C ( 95 deg F) to -35 deg C (-31 deg F) and a humidity % range of 10 to 90 percent makes for some fairly demanding conditions in which to control humidity.
Anyway, just a bit of geeky gab about commercial humidifiers.
That is, a grain as a measure of weight is 2/1000ths of an ounce.
(Didn't remember this from refrigeration school....... looked it up. I actually flunked that class. )
Don't get to discuss humidity theory too often.
I consider myself more of a student on the subject than an authority.
I have two "humidity customers" that keep me on my toes.
A museum that is built within a 100 year old courthouse.
They have a building envelope that has an air circulation chamber against the entire inside of the exterior wall where the humidity levels are maintained year round to be compatible with 100 year old construction.
The inside of the building is isolated by vapor barrier from the exterior shell with an attempt to maintain a constant 45% rh and 21 deg C (70 degF).
What makes this one interesting is their limited budget, as with all museums, and equipment that wasn't designed for tight control.
The other customer is a small casino where improper humidity levels cause card shufflers to malfunction and computer circuits to fry.
This one is interesting because of the amount of air change, they have a very high humidifying capacity.
There are five Neptronic brand humidifiers.
Combined they have a heater capacity of 150 kw creating 450 lbs/hr of steam!
You have to keep in mind this casino has only 200 slots and around 10 gaming tables.
Having outside temps with a range of +35 deg C ( 95 deg F) to -35 deg C (-31 deg F) and a humidity % range of 10 to 90 percent makes for some fairly demanding conditions in which to control humidity.
Anyway, just a bit of geeky gab about commercial humidifiers.
#9
Member
Thread Starter
condensation
If moisture levels were expressed as grains of moisture/pound of air, the subject might be a bit easier to understand.
That is, a grain as a measure of weight is 2/1000ths of an ounce.
And thus my comment that working with moisture as grams per cubic meter is way easier on the calculator!!!
Greg, I am far from an expert on home or building humidity issues; while I can discuss at some depth possible problems related to moisture, sound, energy - within the framework of windows - when it comes to whole house issues I definitely recommend HVAC professionals to folks if they happen to have a larger problem...and your post and Sharp Advice's post further amplify that point!
That is, a grain as a measure of weight is 2/1000ths of an ounce.
And thus my comment that working with moisture as grams per cubic meter is way easier on the calculator!!!
Greg, I am far from an expert on home or building humidity issues; while I can discuss at some depth possible problems related to moisture, sound, energy - within the framework of windows - when it comes to whole house issues I definitely recommend HVAC professionals to folks if they happen to have a larger problem...and your post and Sharp Advice's post further amplify that point!
#10
I agree with you that metric measurement is a much easier system to use.
I'm really caught in the middle on this though.
Our country uses the metric system and the hvac trade in our country generally only uses degrees Celcius when discussing temperature with customers.
Other than residential thermostats though, the equipment and specifications we generally have available deal with US measurements.
This is mostly because many manufacturers of this equipment are based there.
I'm really caught in the middle on this though.
Our country uses the metric system and the hvac trade in our country generally only uses degrees Celcius when discussing temperature with customers.
Other than residential thermostats though, the equipment and specifications we generally have available deal with US measurements.
This is mostly because many manufacturers of this equipment are based there.
#11
Condensation
Good subject here!
Since the onslaught of winter, or colder weather is here, hopefully this forum will help people like ME-lol. I have read the post and still have a ? We have a furnace in our house that has a humidifier attached to it. I have noticed condensation on our windows,notably about half an inch up the window,not a big deal but still a pain. I have turned the humidifier off on the furnace and that still hasn't cured the problem?? We keep the house at around 69f when home. Should I be running a DE-Humifier to take the humid air out??? HELP ME-AHHHHHHHHH Or am I just worring over something not that big of a deal???
Thanks for any help folks.
Since the onslaught of winter, or colder weather is here, hopefully this forum will help people like ME-lol. I have read the post and still have a ? We have a furnace in our house that has a humidifier attached to it. I have noticed condensation on our windows,notably about half an inch up the window,not a big deal but still a pain. I have turned the humidifier off on the furnace and that still hasn't cured the problem?? We keep the house at around 69f when home. Should I be running a DE-Humifier to take the humid air out??? HELP ME-AHHHHHHHHH Or am I just worring over something not that big of a deal???
Thanks for any help folks.
#12
Member
Thread Starter
humidity
If you have wood windows, then even a little moisture could potentially damage them - or at least cause some staining. The ideal is no condensation at all, obviously.
If your window glass is cold enough, then there is potentially very little you can do to stop condensation from forming on your windows...you simply cannot remove enough moisture from the air in your home to bring the dew point low enough...and because of comfort and whole house performance considerations, you may not want your humidity that low to begin with....so in this case, you may need to raise the temperature of the glass to a level above the dew point.
Alternatively, the glass may be reasonably warm, in which case you may have to lower the level of water vapor in the air in your home. But unless you know how much water vapor is in your air, which you can do if you know the temperature and the relative humidity, you really won't be able to determine how much is too much.
There are several "fixes" for clearing your glass and preventing condensation...
By allowing the warm room air to circulate over your glazing you may be able to raise the temperature of the glass above the dew point. Keeping shade or curtains open may help the air to warm the glass. Removing inside screens from casement windows often is enough to make the difference between condensation and no condensation.
Even using a small fan to blow air across the window surface could help. In worst case scenarios, using a small portable heater to blow air over the glass may help.
It is difficult to suggest what can help in your situation without knowing what type of window you have and what the level of water vapor is in your home...
Good luck.
If your window glass is cold enough, then there is potentially very little you can do to stop condensation from forming on your windows...you simply cannot remove enough moisture from the air in your home to bring the dew point low enough...and because of comfort and whole house performance considerations, you may not want your humidity that low to begin with....so in this case, you may need to raise the temperature of the glass to a level above the dew point.
Alternatively, the glass may be reasonably warm, in which case you may have to lower the level of water vapor in the air in your home. But unless you know how much water vapor is in your air, which you can do if you know the temperature and the relative humidity, you really won't be able to determine how much is too much.
There are several "fixes" for clearing your glass and preventing condensation...
By allowing the warm room air to circulate over your glazing you may be able to raise the temperature of the glass above the dew point. Keeping shade or curtains open may help the air to warm the glass. Removing inside screens from casement windows often is enough to make the difference between condensation and no condensation.
Even using a small fan to blow air across the window surface could help. In worst case scenarios, using a small portable heater to blow air over the glass may help.
It is difficult to suggest what can help in your situation without knowing what type of window you have and what the level of water vapor is in your home...
Good luck.
#13
ryyback,
To sumarize what's been said, within a range, the humidity level in your home is too high for the insulating value of your windows.
In cold climates a maximum of around 30% RH at room temp is at the high end of what is good for your structure.
Below that you need to match the window quality to the humidity level you wish to maintain.
If you didn't want to replace all your windows you will then need to lower the humidity level in your house.
Reducing the moisture producing activities is one way. (Take out food and group showers. )
Even something as simple as making sure you keep a lid on a boiling pot will help.
Keeping your vented exhaust fans running longer is the simplest way.
We have timers on our bathroom fans and when cold will allow the fans to run for at least twenty minutes after a shower.
A dehumidifier will work but as the humidity level gets lower they become less efficient and take a long time to remove moisture.
To sumarize what's been said, within a range, the humidity level in your home is too high for the insulating value of your windows.
In cold climates a maximum of around 30% RH at room temp is at the high end of what is good for your structure.
Below that you need to match the window quality to the humidity level you wish to maintain.
If you didn't want to replace all your windows you will then need to lower the humidity level in your house.
Reducing the moisture producing activities is one way. (Take out food and group showers. )
Even something as simple as making sure you keep a lid on a boiling pot will help.
Keeping your vented exhaust fans running longer is the simplest way.
We have timers on our bathroom fans and when cold will allow the fans to run for at least twenty minutes after a shower.
A dehumidifier will work but as the humidity level gets lower they become less efficient and take a long time to remove moisture.
#14
Condensation
Hey guys,
Thanks for the help I like the idea of group showers : I have all new windows in the house (last year). The windows were better this morning and I think I found the problem. As you's stated, mosture content was the problem. My son had a cold (he's 3) and we had a vaporizer on, so I think that was the problem.
Thanks again, it's good to see a good site like this one.
Rick
Thanks for the help I like the idea of group showers : I have all new windows in the house (last year). The windows were better this morning and I think I found the problem. As you's stated, mosture content was the problem. My son had a cold (he's 3) and we had a vaporizer on, so I think that was the problem.
Thanks again, it's good to see a good site like this one.
Rick
#15
Rick,
Thanks for the compliment.
I forgot to make my stock comment that it is a good idea that anyone interested in humidity levels in the home should purchase a digital humidity temperature guage.
They are quite inexpensive, readily available and go a long way to knowing what is happening in the home as far as levels are concerned.
Click image:
Thanks for the compliment.
I forgot to make my stock comment that it is a good idea that anyone interested in humidity levels in the home should purchase a digital humidity temperature guage.
They are quite inexpensive, readily available and go a long way to knowing what is happening in the home as far as levels are concerned.
Click image:
#16
Condensation
Hi Greg,
I'm off to Canadian Tire later on just after a little lol. You're right, anyone interested in humidity levels or there home for that matter, should have digital humidity temperature guage.
Rick
I'm off to Canadian Tire later on just after a little lol. You're right, anyone interested in humidity levels or there home for that matter, should have digital humidity temperature guage.
Rick
#17
Member
Nice explanation.
We had a cold snap last week (15 F. overnights) and after a complete trim and windows paint job, I still hadn't sanded my storm windows to fit. After significant frost the first night, I rehung what storms I could, even though they would not fit against the frames completely. Even with the bottoms hanging open over an inch on some windows, I had little or no frost or condensation on those windows, while the windows without storm windows were fully frosted. No question where my heat is going.
We had a cold snap last week (15 F. overnights) and after a complete trim and windows paint job, I still hadn't sanded my storm windows to fit. After significant frost the first night, I rehung what storms I could, even though they would not fit against the frames completely. Even with the bottoms hanging open over an inch on some windows, I had little or no frost or condensation on those windows, while the windows without storm windows were fully frosted. No question where my heat is going.
#18
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Would it be fair to simplify by saying that warm air can hold more moisture than cold air, and that when the warm air gets cooled (like by bumping into a cold window) it gives up some of it's moisture in the form of condensation?