Why isn't a vaporizer affecting the humidity in my room

[moriah]

@raindog

Stick to topics you know something about. I’m done with this thread.

While this is getting away from the OP, since an argument from authority has been asserted, it needs to be addressed:

When you’ve stood outside in all sorts of weather every day for two years swinging a sling psychrometer like I have, then maybe I’ll consider you an expert in Relative Humidity.

As an HVAC tech, I’ll trust what you have to say about furnaces, but from my experience dealing with HVAC techs for residential and commercial properties that I’ve managed is that they usually don’t give a damn about relative humidity. When I ask them about installing humidifiers or dehumidifiers, they do a song and a dance about how it’s not really necessary or too much trouble.

And they’re all too quick in commercial properties to draw in huge amounts of outside air in the spring and fall for temperature control. E.g., 74ºF inside, so, draw in the 68ºF outside air for cooling instead of using the air conditioning. Problem with that is that when it’s foggy out or there’s a huge downpour it draws in stultifying 100% RH air into the building. So, I have to get them to stop doing that.

So, sorry, I regard HVAC techs as people who only have a passing familiarity with RH unless they are the type that have actually installed and successfully maintained central humidifiers and dehumidifiers.

[raindog]

@moriah

While this is getting away from the OP, since an argument from authority has been asserted, it needs to be addressed:

When you’ve stood outside in all sorts of weather every day for two years swinging a sling psychrometer like I have, then maybe I’ll consider you an expert in Relative Humidity.

As an HVAC tech, I’ll trust what you have to say about furnaces, but from my experience dealing with HVAC techs for residential and commercial properties that I’ve managed is that they usually don’t give a damn about relative humidity. When I ask them about installing humidifiers or dehumidifiers, they do a song and a dance about how it’s not really necessary or too much trouble.

And they’re all too quick in commercial properties to draw in huge amounts of outside air in the spring and fall for temperature control. E.g., 74ºF inside, so, draw in the 68ºF outside air for cooling instead of using the air conditioning. Problem with that is that when it’s foggy out or there’s a huge downpour it draws in stultifying 100% RH air into the building. So, I have to get them to stop doing that.

So, sorry, I regard HVAC techs as people who only have a passing familiarity with RH unless they are the type that have actually installed and successfully maintained central humidifiers and dehumidifiers.

You need to stop while you’re behind. I’m not a service tech, I’m a state licensed contractor, with over 20 years experience, and even this post has factual errors.

Unless you have more air changes than the virtually all economizers and blower produce, you can’t cool a commercial space with 68° air.

Not only that, the enthalpy controls on an economizer won’t initiate the economizer in high humidity conditions. (and wouldn’t initiate economizer with 68° air either)

I don’t think you understand how economizers work. It is almost always an automatic process in the RTU that looks at temp and humidity and brings in outside air for “free cooling” and initiates an exhaust to neutralize the building. If you have people doing that manually day to day (?!?!), I have to wonder just what kind of HVAC system you have.

So I don’t know what in the world you were doing “every day for 2 years” (?!?!), outside with a sling psychrometer (?!?!), or what kind of HVAC people you’ve dealt with, but to someone who knows this kind of stuff, it’s clear you don’t really know this stuff. (and using “sling psychrometer”, or providing a link (?) doesn’t impress)

You might be a gifted property manager. And…that experience may have given you a false sense of expertise (and allowed you to say sling psychrometer), but when you say things like "It is not. At least, not according to the OP’s hygrometer, which could possibly be not working correctly. If it is working correctly, then the humidifier is having a neglible to no effect " which is a take-to-the-bank-she-doesn’t-know-she’s-talking-about comment, it indicates you’re not qualified to answer the question.

You’ve learned a little HVAC in your job managing properties. Great.

And…I’m done talking to you about this.

[snailboy]

Just to throw this out there, raindog’s explanation seems pretty logical to me. If the relative humidity of the cool air at the windows hits 100%, condensation is going to start occurring and that air cannot become any more humid. I’d also expect diffusion of the water vapor to occur such that the absolute humidity stays roughly the same throughout the room. (Blinds and/or curtains would probably slow it down some though.) Obviously if this is true and there’s a significant temperature difference from the windows to other parts of the room, then the warmer parts will not be able to have nearly 100% relative humidity since the absolute humidity can’t surpass that of the saturation point at the window and a given absolute humidity equates to a lower relative humidity at higher temperatures.

So anyone who disagrees with him, can you explain why this reasoning would be invalid?

[DSeid]

There is no debate that the condensation on the windows decreases the absolute humidity in the room and thus the RH of the warmer air away from the windows. As has been pointed out earlier by several posters, that is essentially the process of a dehumidifier. Dehumidifiers only do so much.

Analogously, no, diffusion of water vapor does not mean that absolute humidity stays roughly the same throughout the room. I can have a dehumidifier going condensing water into its container in a high humidity environment and it will decrease the humidity some but only a little. Practically speaking, our op has put a gallon of water in the air; it seems unlikely there is nearly a gallon on the windows and pooled on the sills.

So where else is it going? Air infiltration has to also be evoked. A room is not a tightly sealed container and in many homes the air leakage and exchange with the outside is highly significant.

raindog, I think, has blinders on that are the result of his profession. Indeed the customer should be told (given the windows that are there) that no more humidity is advised once the windows are sweating. That is not because the room cannot be made any more humid but because the condensation that results from that humidity level and above will cause problems (mildew, mold, etc.). So his answer is that that is top humidity level. But the question was not whether or not higher humidity was a good idea or advised – it was why is the humidity not higher given the amount of water put into the volume of air? His response is not a complete answer for that question even though it is the correct response for an HVAC expert to give to a customer requesting more humidity at a given temperature in a given structure.

Once again, changing the structure, would allow the same amount of water placed into the room to increase the humidity to a greater degree. Those changes include decreasing air infiltration and having the interior surface of windows (and walls whose other side are exterior) be less cold. And again, the simple solution of a shrink wrap plastic during winter will work to some degree, avoiding the window sweating that is his sign to say no more humidity is allowed, and decreasing the air infiltration (likely experienced as some drafts near the windows) that are likely also contributory to what the op describes.

[moriah]

@snailboy

Just to throw this out there, raindog’s explanation seems pretty logical to me. If the relative humidity of the cool air at the windows hits 100%, condensation is going to start occurring and that air cannot become any more humid. I’d also expect diffusion of the water vapor to occur such that the absolute humidity stays roughly the same throughout the room. (Blinds and/or curtains would probably slow it down some though.) Obviously if this is true and there’s a significant temperature difference from the windows to other parts of the room, then the warmer parts will not be able to have nearly 100% relative humidity since the absolute humidity can’t surpass that of the saturation point at the window and a given absolute humidity equates to a lower relative humidity at higher temperatures.

So anyone who disagrees with him, can you explain why this reasoning would be invalid?

Post #26.

[Chronos]

You can’t even define relative humidity for a room with varying temperature, since relative humidity depends on temperature. Which temperature do you use for the calculation, the temperature in the middle of the room, or the temperature of the windows?

And on the topic of air exchange, there’s probably a heck of a lot more air exchange between the room and the rest of the building than there is with the outside. Yeah, exterior walls are often a bit leaky, but there generally isn’t even any effort at all to seal interior doors, and they tend to get opened wide pretty often too.

[drachillix]

@Wesley_Clark

I do notice the window will develop condensation. But the hygrometer still says the humidity is a constant 25-35% or so.

So what is happening?

Think of this window as basically, a naturally occuring dehumidifier due to the temperature differential.

[ethelbert]

I have a similar situation to the OP, the only difference is that there is no condensation anywhere in the room. My vaporizer runs constantly and the hygrometer shows 36%. The hygrometer on the vaporizer shows 40%. I am confident that both hygrometers are reasonably accurate. I only run the humidifier to keep my guitar from drying out and it manages to do this.
I moved this summer from a house with hot water baseboard heat to a condo with forced air (one town over in Northern NJ, so the same climate). I was able to affect the humidity much more (and faster) in the house, despite dealing with a much larger room. I attribute this to the fact that the forced air system is collecting my humidified air, drying it out and sending it back again (the air in the house was only heated, not recirculated).
I do not think my room is “saturated” in the sense that raindog uses, and I might be able to raise the RH in the room a bit by adding another humidifier, but it is not worth the trouble. I think if you have forced air and desparately want higher humidity your only option is to add water at the furnace (Aprilaire, or some such) and even then you might not get the result you wanted (although your water bill will jump).
This is only a WAG on my part. I am not an expert on anything and I know far less than I think I do.

[raindog]

@DSeid

…snipped…

Once again, changing the structure, would allow the same amount of water placed into the room to increase the humidity to a greater degree. Those changes include decreasing air infiltration and having the interior surface of windows (and walls whose other side are exterior) be less cold. And again, the simple solution of a shrink wrap plastic during winter will work to some degree, avoiding the window sweating that is his sign to say no more humidity is allowed, and decreasing the air infiltration (likely experienced as some drafts near the windows) that are likely also contributory to what the op describes.

This is an example of what I’m talking about. There is a fundamental difference between knowing a little about something *(and learning along the way from the from the thread itself!)*and having a comprehensive understanding.

An HVAC professional--------likely blinded by his profession-------- would want to know the location of the OPs home, and the outdoor temperature and humidity for the days in question.

He might also tell the OP that shrink wrapping the windows is a bad idea and might stop the windows from sweating, but run the very real risk of fostering mold growth in the walls------a pretty nasty health hazard.

But take that with a grain of salt.

[raindog]

@DSeid

Expert opinion tends to be taken with a huge grain of salt by most here. The physicians don’t get away just saying because I said so, neither do the physicists. Maybe in an “Ask The …” thread but not otherwise.

Your expert status gives you access to the knowledge and resources to prove what you say and to explain it clearly … perhaps … or it does not. If it does not then your opinion aint worth much. Sorry.

Surely you don’t expect us to believe that.

There are several members who have established over several years and hundreds (if not thousands) of posts a given expertise in an area. The notion that their expert opinions are “taken with a grain of salt” is a silly comment. Someone posting a question in GQ (as opposed to GD) is looking for a *factual *answer, from someone who has some specific knowledge in that area.

And long time members look to QtM (et al) for medical answers, or Bricker **(et al) **for legal answers because of their expertise. (As well as posters knowledgeable about military matters, middle eastern matters, IT, automotive, and dozens of other topics) Far from taken with a grain of salt, other posters readily direct them to those members who are known to be experts. It happens all the time.

Perhaps you’re confusing GQ with GD. In GD-------a forum that by nature rarely has a factual answer and relies on debate----a person’s experience means little, (although often makes them a more formidable debater on topics they know well) but in GQ an OP wants a factual answer to a specific question and wants an accurate answer from someone who knows what they’re talking about.

In fact, there has been more than a few comments recently, including a thread asking for more vetting of answers from GQ because the quality of answers. (was it mangetout?) Has there not been a host of complaints recently about the poor quality of answers recently in GQ?

And so you would seriously say that in GQ, “expert opinion tends to be taken with a huge grain of salt by most here”?

[DSeid]

Chronus, a reasonable point.

raindog, work on your reading comprehension. “Blinders on” is not “blinded” – it means overly focused on a narow aspect. That happens to “experts” all the time. They hear the question they have the answer to. Not what was asked.

QtM (and other physicians, such as myself) are sometime “looked to” not to give answers from authority, but because we can answer with access to information (including cites as appropriate) and with the background knowledge to make the point. An answer is rarely accepted just because one of us says so from our perch of authority. An expert who has to claim something is true “because I said so” rather than by cites and by logical explanation is usually scoffed at. Or mocked. Answers based on “because I, the expert, said so” are part of the poorer quality answers, not what is desired, any more than IMHO answers or joke ones as initial responses are. This board is not a place that experts can expect to be kowtowed to and one who gets offended at being questioned will be rerspected by few. Puzzle smiley all you like at that.

Again, your blinders are making you answer a question that has not been asked. You are answering what would the HVAC expert recommend should be the humidity level for that room given the fact that there is window condensation. The op did not ask that. They asked why the humidity level is not increasing. Where is that water going?

[FrankJBN]

I haven’t read all 50 posts but I do have 2 comments:

Hygrometers are notoriously inaccurate and really should be calibrated. (See any cigar discussion site for verification)

25% RH is low, rather a bit low for indoor humidity. (Easily confirmed via search). My house is normally around 40% RH.

As OP’s indoor RH while running a humidification device is lower than normal without supplentary humidification, I think it very likely, most likely that the RH readings are inaccurate.

[raindog]

@FrankJBN

I haven’t read all 50 posts but I do have 2 comments:

Hygrometers are notoriously inaccurate and really should be calibrated. (See any cigar discussion site for verification)

25% RH is low, rather a bit low for indoor humidity. (Easily confirmed via search). My house is normally around 40% RH.

As OP’s indoor RH while running a humidification device is lower than normal without supplentary humidification, I think it very likely, most likely that the RH readings are inaccurate.

“25% RH is low, rather a bit low for indoor humidity. (Easily confirmed via search).” * :rolleyes:

I’m warming to mangetout’s ideas…

[DSeid]

Medical recommendation (from WebMD)

Aim for humidity no lower than 30% and no higher than 50%

A more academic source.

Studies indicate that RH about 40% is better for the eyes and upper airways than levels below 30%.

Lower absolute humidity also fosters the survival of various viruses, including influenza virus.

25% is low.

[snailboy]

@DSeid

There is no debate that the condensation on the windows decreases the absolute humidity in the room and thus the RH of the warmer air away from the windows. As has been pointed out earlier by several posters, that is essentially the process of a dehumidifier. Dehumidifiers only do so much.

Analogously, no, diffusion of water vapor does not mean that absolute humidity stays roughly the same throughout the room. I can have a dehumidifier going condensing water into its container in a high humidity environment and it will decrease the humidity some but only a little. Practically speaking, our op has put a gallon of water in the air; it seems unlikely there is nearly a gallon on the windows and pooled on the sills.

Okay, so regardless of whether or not all of the water is condensing at the window pane, what would prevent it from doing so if you eliminated everything else? There has been no explanation for how the absolute humidity in the room could be higher than saturation at the window, even if all the walls, doors, and the ceiling were perfectly sealed and insulated and you used an electric heater in the room alongside a humidifier. There are only two possible answers - the air near the window is supersaturated or diffusion isn’t occurring as I’d expect it to - and I’d like to know which and why, not just that it could.

[DSeid]

Enough window surface that is cold enough with enough convection of air to and from it? Nothing theoretically stopping it from dehumdifying very effectively.

Maximum humidity at the widow pane is much lower than maximum humidity in the middle of the room (say at 68 degrees F = 20 degrees C). What is absolute humidity at RH of say 30% with a temperature of 68 degrees? What would be the dew point at that level? We can use this table. 5.2 g/cubic M and a dew point of 1 degree C, about 34 degree F, likely above the temperature on a cold window pane.

[moriah]

@snailboy

Okay, so regardless of whether or not all of the water is condensing at the window pane, what would prevent it from doing so if you eliminated everything else?

Dynamic systems.

Sure, water is condensing on the windows. And at the same time, water on the window is evaporating into a warm and dry room.

As the water is condensing, we often think of the action as one way, from vapor to liquid. But in fact, as soon as water condenses, some of it starts evaporating.

So, there are two actions happening simultaneously: condensation and evaporation. If the condensation is happening faster than evaporation, then the water starts dripping down and off the window and starts pooling in a puddle below it. If evaporation is happening faster than condensation, then the window stays dry (and this happens in all houses on mildly cool days – there definitely is condensation happening on the cooler windows, but evaporation off the window is happening faster making them appear mostly dry).

Then there is an effect that happens when the two opposing actions reach a balance, when there is as much water condensing as there is evaporating. When these two rates reach a steady state, it is called dynamic equilibrium. (Which I referred to in post #26.)

Anyone who isn’t aware of dynamic equilibrium as it pertains to chemical and physical reactions isn’t in any condition to comment intelligently on what is happening with regard to localized effects such as a humidifier on one side of a room and a plate of glass at dew point on the other and how they might interact with each other.

The OP said they put a gallon of water vapor in the air. So… where is it? According to the hygrometer, the air doesn’t have more relative humidity in it (and even a poorly calibrated hygrometer can still show whether RH got higher or lower even if it’s not registering the right amplitude). Is it on the window? Unlikely that there’s a whole gallon of water droplets on the window. Did it puddle off the windows? Unlikely, cause the OP probably would have mentioned the gallon puddle in the room. So, where did the gallon of water go?

The whole condensation on the window issue is a red herring. There is no gallon of water there.

The most likely culprit is exchange of inside and outside air. Most houses have drafts. And they’re usually more significant than people think. Sure, the OP’s house could be very airtight, but considering the OP has windows that are so poorly insulated that they sweat, that’s unlikely too.

[DSeid]

moriah, the funny thing is that raindog’s initial response was pretty good:

Humidity is being transferred to the outside environments at a rate that is as great as your vaporizer can produce/ replace it.

Just leave outside as outside the room. To the rest of the house, via draft through the windows, leaks in the walls, whatever. If only he hadn’t gone off on trying to claim that the air in the middle of the room at 68 F with a RH of 25% was “fully saturated.”

Again the window is functioning exactly as a (somewhat inefficient) dehumidifier and his claim that that dehumidifier can only condense water out of a room that is fully saturated, that 25% RH is fully saturated, is silly … especially coming from an “expert.”

Nothing like unwarranted condescension about condensation, eh?

[snailboy]

@moriah

Dynamic systems.

Sure, water is condensing on the windows. And at the same time, water on the window is evaporating into a warm and dry room.

As the water is condensing, we often think of the action as one way, from vapor to liquid. But in fact, as soon as water condenses, some of it starts evaporating.

So, there are two actions happening simultaneously: condensation and evaporation. If the condensation is happening faster than evaporation, then the water starts dripping down and off the window and starts pooling in a puddle below it. If evaporation is happening faster than condensation, then the window stays dry (and this happens in all houses on mildly cool days – there definitely is condensation happening on the cooler windows, but evaporation off the window is happening faster making them appear mostly dry).

Then there is an effect that happens when the two opposing actions reach a balance, when there is as much water condensing as there is evaporating. When these two rates reach a steady state, it is called dynamic equilibrium. (Which I referred to in post #26.)

Anyone who isn’t aware of dynamic equilibrium as it pertains to chemical and physical reactions isn’t in any condition to comment intelligently on what is happening with regard to localized effects such as a humidifier on one side of a room and a plate of glass at dew point on the other and how they might interact with each other.

I’m well aware of what dynamic equilibrium is having taken chemistry in college. The system is not going to reach dynamic equilibrium while the humidity is above saturation.

The OP said they put a gallon of water vapor in the air. So… where is it? According to the hygrometer, the air doesn’t have more relative humidity in it (and even a poorly calibrated hygrometer can still show whether RH got higher or lower even if it’s not registering the right amplitude). Is it on the window? Unlikely that there’s a whole gallon of water droplets on the window. Did it puddle off the windows? Unlikely, cause the OP probably would have mentioned the gallon puddle in the room. So, where did the gallon of water go?

The whole condensation on the window issue is a red herring. There is no gallon of water there.

The most likely culprit is exchange of inside and outside air. Most houses have drafts. And they’re usually more significant than people think. Sure, the OP’s house could be very airtight, but considering the OP has windows that are so poorly insulated that they sweat, that’s unlikely too.

I don’t think anyone said that all of the humidity is going to the window pane. I imagine the original poster is running central heat and most of it is getting blown under the door to the rest of the house. For that matter, we really don’t know there isn’t a puddle below the window. If his bedroom is arranged like mine, he has a dresser in front of one window, a nightstand in front of the other, and possibly soggy carpet underneath. I doubt it though.

What was said though is that the humidity can’t climb above saturation at the window, at least not without blocking the air from getting to the window, and that still seems like the most logical explanation so far.

[DSeid]

@snailboy

… humidity can’t climb above saturation at the window, at least not without blocking the air from getting to the window …

Why do you think that?

Assume a closed system: Humidity cannot climb above 100% RH at the window (dew point at the window) without some some condensation (dehumidification) occurring at that location. For that portion of air that has gotten to that location (small portion of the room) over that particular period of time. Resulting in some rate of dehumidification.

IF the rate of that condensation/dehumidification exceeds (or at least equals) the rate of new moisture entering the air (both from the moisture being put into the drier warmer, 25% RH, air in the center of the room and from the condensate evaporating back in at it drips away from the coldest areas) THEN the absolute humidity of the room will decrease or at least stay the same.

IF, however, the rate of condensation/dehumidification at the window pane is less than the rate or humidification THEN the absolute humidity of the room and the RH in the warmer drier center of the room increases.

I think that you are assuming that the only alternative to “blocking the air” must be complete air mixing at all times and a capacity for the window to condense any theoretically large amount of humidity at any rate. In reality you have only a fairly small portion of the air in the room coming into contact with the pane even over the whole night, let alone at one time, while in the meanwhile more moisture is being put in elsewhere.