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What would be your relative humidity level (RH) if you do not run the dehumidifier?

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[OP]
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Jun 27, 2015
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East York, ON

What would be your relative humidity level (RH) if you do not run the dehumidifier?

Many of you posted here their numbers for what then want the RH to be in their houses

What is your RH level on the main floor and in the basement if you do not run the DH?

This question refers to summer levels

Edit: as discussed below there is many variables that can influence the RH
I will be more specific: in a normal house, without any problems, for the basement level, are you supposed to run the AC anyway or not?
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Deal Expert
Oct 6, 2005
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If you do not run a humidifier or air conditioning (which dehumidifies) in the summer, the main floor should be roughly the same as the outdoor humidity level. Basically outdoor air will be circulating inside your house. In the winter, the humidity level is different because the furnace affects the humidity of the incoming air - it dries it out and causes the humidity to drop even lower than the outdoor levels.
Deal Fanatic
Dec 5, 2009
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Main floor Depends on outside humidity.

I haven't had the a/c on much at all this summer and the humidity in my house is higher than I would prefer. I do run a dehumidifier in the basement set at 50%.
[OP]
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Jun 27, 2015
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East York, ON
coolspot wrote: If you do not run a humidifier or air conditioning (which dehumidifies) in the summer, it should be roughly the same as the outdoor humidity level. Basically outdoor air will be circulating inside your house. In the winter, the humidity level is different because the furnace affects the humidity of the incoming air - it dries it out and causes the humidity to drop even lower than the outdoor levels.
That is not the case for the basement, the ground humidity gets into your basement also
Deal Expert
Oct 6, 2005
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CuriousC wrote: That is not the case for the basement, the ground humidity gets into your basement also
True, I was referring to the main floor.
[OP]
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Jun 27, 2015
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East York, ON
coolspot wrote: True, I was referring to the main floor.
Your statement regarding the main floor is not accurate either
The main floor humidity might be higher or lower than the outside humidity, it depends a lot of the degree of "permeability" of your walls, widows etc.

Actually the amount of air that gets through your doors, windows (even when they are closed) and walls can be calculated and that is taken into consideration when
your furnance and AC are sized. Besides that there is humidity that comes from the people who live in the house, from the kitchen and bathroom..so it is not entirely accurate to say that what is outside is also inside in terms of RH
Deal Expert
Oct 6, 2005
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CuriousC wrote: Your statement regarding the main floor is not accurate either
The main floor humidity might be higher or lower than the outside humidity, it depends a lot of the degree of "permeability" of your walls, widows etc.

Actually the amount of air that gets through your doors, windows (even when they are closed) and walls can be calculated and that is taken into consideration when
your furnance and AC are sized.
So why bother asking the question if you already know the answer? What's the point of this thread?
[OP]
Deal Addict
Jun 27, 2015
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East York, ON
coolspot wrote: So why bother asking the question if you already know the answer? What's the point of this thread?
?
How would I know the humidity level in your basement when the AC is not running ? -this was in the initial question
How would I know the humidity level on your main floor when the AC is not running ? -this was in the initial question

What was the point of this thread? To actually see how many people have elevated RH levels in their houses in the absence of a DH
Deal Addict
Aug 27, 2009
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GTHA
Because your basement is cooler, the exact same air on the main floor will have a higher RH in the basement. The RH in my basement is usually about 60%.

When the RH outside is relatively low I will just put my furnace fan on circ - uses about 60W - to get fresh air into the basement and lower the RH. Sure beats running a DH at peak hydro rates. My DH consumes 600W.
[OP]
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Jun 27, 2015
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East York, ON
RETD wrote: Because your basement is cooler, the exact same air on the main floor will have a higher RH in the basement. The RH in my basement is usually about 60%.

When the RH outside is relatively low I will just put my furnace fan on circ - uses about 60W - to get fresh air into the basement and lower the RH. Sure beats running a DH at peak hydro rates. My DH consumes 600W.
you mean fresh air from the main floor, I think that actually this will rebalance the RH difference between the two
From what I understand the AC does or the fan for this matter does not suck air from outside

I was thinking about this yesterday, what would be cheaper and better, to get a DH or to run the AC ....
Deal Addict
Aug 27, 2009
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CuriousC wrote: you mean fresh air from the main floor, I think that actually this will rebalance the RH difference between the two
From what I understand the AC does or the fan for this matter does not suck air from outside
Yes, just circulating the air will balance the RH. If it's not too hot outside and RH relatively low (40-45%) we'll open the windows allowing fresh air into the house which will eventually make its way to the basement via the furnace circ.

CuriousC wrote: I was thinking about this yesterday, what would be cheaper and better, to get a DH or to run the AC ....
My 2-ton a/c uses about 2kW vs 600W for the DH. The a/c expels both latent and sensible heat to the outside while the DH discharges latent heat inside your home/basement. If its cool-ish and humid you may not want to run the a/c as it'll get too cold inside - that's when I'll run the DH instead.

So far this year I've found that I've often had to run both concurrently to get the house comfortable (e.g. a/c doesn't run long enough to dehumidify sufficiently).
Deal Addict
Oct 20, 2011
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Mississauga
To answer a couple questions,

My thermostat tells me the indoor humidity level on the main floor as well as the temperature indoor and outdoor. The dehumidifier tells me the relative humidity in the basement so I'm able to know what the RH is on the main and basement independently. The RH will change everyday based on whether it rained that day the day before or about to rain or whether we have the windows open or closed or even whether we have the low speed fan going on the furnace. If I don't have the A/C on or the dehumidifier going it can get as high as 65% which is way to uncomfortable for our family. I've been in home where the RH is at 55-60% and we found it also uncomfortable.
[OP]
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Jun 27, 2015
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East York, ON
Would it be safe to say that in an old or new house you need to run the AC or the DH at least from time to time to keep the RH in control ?
I can understand why you might what to do that when it comes to keep the humidity out of your closets or any other things that you you have in your house but ..on the other side the human body should be able to adapt and cope with changing levels of humidity.. Most of the people that posted in the thread linked in my initial message seem to be focused on their personal level of comfort.
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Oct 20, 2011
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Mississauga
CuriousC wrote: Most of the people that posted in the thread linked in my initial message seem to be focused on their personal level of comfort.
To me life is all about being comfortable which is why I purchased an higher quality A/C system and dehumidifier. It wasn't for the sake of the house environment, it's was for personal comfort for my whole family which is my priority. I've also have the A/C set to 75 degrees and the dehumidifier set to 45% so it turns on/off to maintain that setting.


Your thread asked about RH % and as mentioned there are too many variable to gauge what it is on a daily bases. Our Dehumidifier runs everyday for a couple hours to maintain 45% and a/c hasn't run for a couple days but surely will tomorrow.
We like being comfortable even if it comes at a slight cost, we're worth it.
[OP]
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Jun 27, 2015
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East York, ON
MyDream1 wrote: To me life is all about being comfortable which is why I purchased an higher quality A/C system and dehumidifier. It wasn't for the sake of the house environment, it's was for personal comfort for my whole family which is my priority. I've also have the A/C set to 75 degrees and the dehumidifier set to 45% so it turns on/off to maintain that setting.


Your thread asked about RH % and as mentioned there are too many variable to gauge what it is on a daily bases. Our Dehumidifier runs everyday for a couple hours to maintain 45% and a/c hasn't run for a couple days but surely will tomorrow.
We like being comfortable even if it comes at a slight cost, we're worth it.
Then I should probably change my initial Q again to be more specific.
I am not clear on this: in a normal house, without any problems, for the basement level, are you supposed to run the AC anyway or not?
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Jun 13, 2010
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CuriousC wrote: Then I should probably change my initial Q again to be more specific.
I am not clear on this: in a normal house, without any problems, for the basement level, are you supposed to run the AC anyway or not?
I close the vents in the basement 90% so almost all of the AC goes to the rest of the house.
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Oct 20, 2011
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CuriousC wrote: Then I should probably change my initial Q again to be more specific.
I am not clear on this: in a normal house, without any problems, for the basement level, are you supposed to run the AC anyway or not?
The humidity level in a basement will be effected by the environment outdoors (humidity levels) as well as indoors. By outdoors I'm referring to the climate, by indoors I'm referring to whether the basement is finished and if so, what products were used and how well was it build. In other words, was a vapour barrier installed, is there a sub floor and if so which type, is there waterproofing in place on the exterior walls, what type and how much insulation was used, is there return air ducts in the basement and the list goes on.

Then there are sevearal other factors in place without even turning on the A/C or dehumidifier such as, how often are the windows open or closed, what type of cooking do you do, is the low speed fan on 24/7.

Each house will be different, depending on how many people live in the house, how well it was built, exterior climate during that specific day or time of year, how many plants are in the house and how often you water, how many windows in the home, etc.

EDIT;

I'm not sure the reason for your initial thread but if it were me, I would only be concerned about what my levels are by taking an exact measurement on each floor and then determine what steps if any need to be taken in order to control said levels based on my person comfort level and or possible damage to the home based on too high or too low levels.

I see it as being that easy.
[OP]
Deal Addict
Jun 27, 2015
2281 posts
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East York, ON
MyDream1 wrote: EDIT;

I'm not sure the reason for your initial thread but if it were me, I would only be concerned about what my levels are by taking an exact measurement on each floor and then determine what steps if any need to be taken in order to control said levels based on my person comfort level and or possible damage to the home based on too high or too low levels.

I see it as being that easy.
My problem was explained in another thread (wet smell in the basement) and I am trying to determine what is normal humidity for a basement in a 50-60 years old house
Since I just fixed what I believe it was one of the problems and I just learned that I should run the AC or the DH to bring the RH down below the 70% I am now doing this and I will not be able to find out if I actually fixed the problem because the DH will keep working
Since this is an old house the DH might just keep working to compensate what is normal humidity entering the walls of the basement but it might as well keep working continuously because I did not fix the problem

Since the problem that I fixed led to a wet wall (outside) it might take a while till that humidity evaporates via capillarity or by continuing to get into the basement. I like to believe that now little water gets to the wall from outside since the patio is now correctly sloped and sanded (joints filed with sand)

So unless I know what others experience in the absence of my problems there is no way to know now if I fixed the problem. I will have to wait
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Jan 16, 2015
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CuriousC wrote: My problem was explained in another thread (wet smell in the basement) and I am trying to determine what is normal humidity for a basement in a 50-60 years old house
Since I just fixed what I believe it was one of the problems and I just learned that I should run the AC or the DH to bring the RH down below the 70% I am now doing this and I will not be able to find out if I actually fixed the problem because the DH will keep working
Since this is an old house the DH might just keep working to compensate what is normal humidity entering the walls of the basement but it might as well keep working continuously because I did not fix the problem

Since the problem that I fixed led to a wet wall (outside) it might take a while till that humidity evaporates via capillarity or by continuing to get into the basement. I like to believe that now little water gets to the wall from outside since the patio is now correctly sloped and sanded (joints filed with sand)

So unless I know what others experience in the absence of my problems there is no way to know now if I fixed the problem. I will have to wait
OMG. Let's explain this again. The MOLD is in your walls, your drywall your wood, what ever is behind there as well as on the concrete. Mold loves concrete. There is no way to fix it accept rip it out. No matter how low your humidity is. Once it is all ripped out, you can wash the walls, floors and get it nice and clean and the smell will be gone. At that point you can 1) water proof from the outside 2) install weeping tiles. Then when you are sure it is nice a dry put in a new basement. Or just leave it like most basements are - unfinished. That way you can wash it down 1-2 a year and your DH will work better. No more mold.

If you want a quick fix : ignore it.
Deal Expert
Oct 6, 2005
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CuriousC wrote: I am not clear on this: in a normal house, without any problems, for the basement level, are you supposed to run the AC anyway or not?
I always run my AC for comfort, but I direct most of the output to the upper floors.

If you have humidity problems in the basement, you can just run a dehumidifier. My basement is around 55% without a dehumidifier, and 45% with a dehumidifier.

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