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Old 01-15-2010, 03:01 PM   #16
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humidity question


Doesn't require running A/C all year long.
In the winter. Some outside fresh air will keep the humidity down.

Sometime. You might want to cut the drywall, and see if its penetrating the drywall.

Are you sure its drywall. And not gypsum board.

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Old 01-15-2010, 03:30 PM   #17
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humidity question


Good point pyper. You could get the humidity down to almost 0% and you would still get mold and mildew in the shower. We run tests on the mold when we find large amounts on buildings at our base, and have never found a dangerous mold. Only mildew and other harmless molds that only affect those who are allergic. The only time I have seen a test that found a dangerous mold was after a severe storm which blew the roof off. It sat that way for months. I mean we should be aware of it but trying to get the humidity down below 55% in the summer will require a humidistat and possibly reheat.
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Old 01-15-2010, 03:48 PM   #18
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I mean we should be aware of it but trying to get the humidity down below 55% in the summer will require a humidistat and possibly reheat.
A correct sized A/C. And correctly setting the air flow for the homes latent load. Will keep the humidity below 55% most of the time. With the exception on low load conditions while its raining.

Sealing of the home will also help to reduce the indoor humidity level. Its an often over looked cure.

A large amount of a homes infiltration can come form the basement. Sealing the the receps and switches, and holes for wiring and plumbing pipes can also reduce the amount of humidity a house gets from its basement.

Along with sealing around floor or ceiling registers and grilles.

Sealing of crawlspaces and laying down a good thick vapor barrier also helps.

Its easy to come up with excuses not to get the humidity lower.

All of the above mentioned procedures also help to lower heating and cooling cost. So its not like there is no return on investment for the average home owner. And they are ALL easy DIY things.

Saying its too hard to get humidity below 55% in the summer. Is like saying its too hard to drive the speed limit( and that is hard).
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Old 01-16-2010, 07:41 AM   #19
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Originally Posted by beenthere View Post
Doesn't require running A/C all year long.
In the winter. Some outside fresh air will keep the humidity down.

Sometime. You might want to cut the drywall, and see if its penetrating the drywall.

Are you sure its drywall. And not gypsum board.
You live in Pennsylvania. I used to live there (central and western). It's really dry in Pennsylvania.

We get an average of an inch of rain a week here in western South Carolina. There's a porch on our house that runs the whole width of the building. It's 8 feet deep and 32 feet wide, and it's elevated three feet above grade. It's on the east side, and exposed to the sun from sunrise till past noon every day. It grows mold on the ceiling!

There's just that much moisture where I live. When it's 100% R/H every night in the summer 60% indoors is very dry in comparison.

Now that we've put in a wood stove I think the house will be dryer in the winter. Both because the warmer temperatures will lower the R/H and also because the stove burns indoor air, which is replaced by dryer outdoor air. On a typical winter day the R/H outside is around 70%, but when you raise the temperature of the air the R/H drops.

Oh, and yes, the bathroom is drywall. I remember when they put it in. Just plain old drywall everywhere. I've learned a lot since then.
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Old 01-16-2010, 09:56 AM   #20
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We're not as high of a humidity as SC. But 70% during the summer isn't unusual. And often, we'll be high 60's low 70's when its only 74 outside. A/C's don't always run much then. But we manage to keep the humidity down in the house.

You get a properly sized good 2 stage A/C. And you'll be able to have less then 50% RH in your house.
You'll end up having to raise the thermostat set temp cause you'll be freezing from the low humidity.

In winter, we just let a little fresh air in, and we have low humidity.
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Old 01-17-2010, 08:39 PM   #21
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Originally Posted by beenthere View Post
We're not as high of a humidity as SC. But 70% during the summer isn't unusual.
So your highest humidity is about the same as my lowest...

Quote:


And often, we'll be high 60's low 70's when its only 74 outside. A/C's don't always run much then. But we manage to keep the humidity down in the house.

You get a properly sized good 2 stage A/C. And you'll be able to have less then 50% RH in your house.
You'll end up having to raise the thermostat set temp cause you'll be freezing from the low humidity.
I understand 2-stage AC is more efficient than the generic heat-pump that we have. How long is the payback period for replacing it? Maybe it's true that it's possible to really dry out a house with the "right" type of AC, but I've never experienced one. Out of all the buildings I've been in in the summer in this state, none of them have had low RH. Lower than outdoors, but not low in absolute terms.


Quote:
In winter, we just let a little fresh air in, and we have low humidity.
In winter we still have high humidity outdoors. According to an online calculator, if it's 50F outdoors and I exchange 100% of the indoor air for outdoor air, and then heat it up to 65F, I still don't have low humidity.
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Old 01-17-2010, 08:49 PM   #22
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Originally Posted by pyper View Post

In winter we still have high humidity outdoors. According to an online calculator, if it's 50F outdoors and I exchange 100% of the indoor air for outdoor air, and then heat it up to 65F, I still don't have low humidity.
Maybe the online calculator is wrong.
Unless you don't heat the air to 70.

At 50F outdoor temp and 90%RH. If you bring that air in and heat it to 65F, its RH will be 52%. Thats from Carrier's Psychrometric Chart.

If your outdoor humidity at 50 is 80%, then bringing it in and heating it to 65 will make its RH 46.6%.

So what temp do you normally maintain in your house.
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Old 01-17-2010, 08:56 PM   #23
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I understand 2-stage AC is more efficient than the generic heat-pump that we have. How long is the payback period for replacing it? Maybe it's true that it's possible to really dry out a house with the "right" type of AC, but I've never experienced one. Out of all the buildings I've been in in the summer in this state, none of them have had low RH. Lower than outdoors, but not low in absolute terms.
2 stage is generally for comfort, and not savings.

But. Depending on how efficient your current unit. You might be able to save a lot on the efficiency alone.

Lots of customers end up setting their thermostat 1 or 2 degrees higher with the 2 stage. then what they could with the old single stage, and feel much more comfortable. And save a good amount on their electric bill.

High humidity in a house in the summer is generally caused by one or both of 2 things.

A. Over sized A/C.
B. Too much fresh air infiltration.

So how leaky is your house?
Is your A/C over sized?


Next. Why is it that other areas that have the same humidity and temps as you. They have no problem getting the RH in house down below 50%?
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Old 01-17-2010, 08:59 PM   #24
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So your highest humidity is about the same as my lowest...
We have our areas that have high 80's and low 90's in humidity. Not many areas. And they can get the humidity to 50 in those areas also.
We also don't have the high temps like you. So out A/Cs run less. But we still remove the moisture by controlling air flow. And sizing the A/C right.

See a fair amount of times listed when SC has the same humidity levels as we do.
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Old 01-17-2010, 09:15 PM   #25
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humidity question


We don't have a whole house AC. I have (2) 14k units built in the wall & a 12k I put in a window
Lucky if we run an AC 14 days a year - 4-6 hours a day
I never really check the house humidity level except in the winter
With burning wood to help heat the house I run 2 humidifiers to get it between 40-50%

In the summer I check the basement & try to keep it under 70%
I would have to run (3) dehumidfiers non-stop to get to below 60% most of the time
House has been here close to 60 years without a problem
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Old 01-17-2010, 09:21 PM   #26
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Then in the winter time. Circulate some of that basement air up to your first floor.
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Old 01-17-2010, 09:27 PM   #27
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Well the basement has dropped down to 55%
If it were higher I'd do it (Late Spring thru early Fall it is)
But I'd rather not pull the warm air into the basement - only 55-60 down there
Once I insulate down there I'll see how it goes
Its been very dry this year....1st time I have had both humidifiers going

One thought was to feed the fireplace hearth heater with air from downstairs
Time to do that would have been before I redid the hearth
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Old 01-17-2010, 09:30 PM   #28
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That can be your 5th project for this summer.
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Old 01-18-2010, 06:46 AM   #29
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Originally Posted by beenthere View Post

At 50F outdoor temp and 90%RH. If you bring that air in and heat it to 65F, its RH will be 52%. Thats from Carrier's Psychrometric Chart.
52% isn't exceptionally low -- and this would require an exchange of 100% of the air! If I only exchanged a quarter of the air, then what, my humidity would temporarily go from 60% to 58%?

With the heat pump we normally set the thermostat on 65, which is why I used that temp in the calculations -- but the bedrooms don't get as warm. With the wood stove (new) the temperatures vary a lot more. We're still getting used to living with it.


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Next. Why is it that other areas that have the same humidity and temps as you. They have no problem getting the RH in house down below 50%?
Like I said, I've been in a lot of houses down here, and none of them are dry in the summer. It just doesn't happen.



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Originally Posted by beenthere View Post
We have our areas that have high 80's and low 90's in humidity. Not many areas. And they can get the humidity to 50 in those areas also.
We also don't have the high temps like you. So out A/Cs run less. But we still remove the moisture by controlling air flow. And sizing the A/C right.

See a fair amount of times listed when SC has the same humidity levels as we do.
Come spend a summer here and see. Having lived both places, I can assure you that it's not the same. Yes, you occasionally have a warm, moist day. Even a few in a row. There's a big difference from that and high humidity 12 months of the year. A couple years ago we had a severe drought. It didn't rain for 60 days in the middle of summer. We had above normal temperatures too. So two months of 90+ degree temperatures. My grass kept growing, living off the humidity. Not as much, obviously, but it never turned brown.

Regarding how tight my house is, I have an interesting story. About 10 years ago I went to a presentation in a nearby state, and a government agency was telling multi-family housing developers how they were going to be required to make their buildings more energy efficient, and part of that was going to be requiring installing vapor barriers and sealing them up tight. A few years after that I went to another presentation and the same guy said that maybe they had made a mistake, because they started to have serious mold issues in apartments after making the new requirements.

Tighter houses aren't always better.

But anyway, I don't especially want lower humidity in the house. The initial point of my comment was that after having 60% RH inside my house every day for 10 years (how long we've lived here) there is no mold problem. There is occasional mold in the shower, but as I said, that gets condensation every day. Whatever the potential downsides of 60% humidity, it's great for musical instruments. Reeds like moisture.
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Old 01-18-2010, 07:15 AM   #30
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Like I said, I've been in a lot of houses down here, and none of them are dry in the summer. It just doesn't happen.

Sizing issues.

Come spend a summer here and see.

Got a guess house? LOL

Regarding how tight my house is, I have an interesting story. About 10 years ago I went to a presentation in a nearby state, and a government agency was telling multi-family housing developers how they were going to be required to make their buildings more energy efficient, and part of that was going to be requiring installing vapor barriers and sealing them up tight. A few years after that I went to another presentation and the same guy said that maybe they had made a mistake, because they started to have serious mold issues in apartments after making the new requirements.

Your area is behind the times then. that happened in the rest of the country in the late 70's and early 80's, and also becoame nown as sick house syndrome.

Tighter houses aren't always better.

Need ventilation. Generally a min of 1 air exchange every 5 hours.

But anyway, I don't especially want lower humidity in the house. The initial point of my comment was that after having 60% RH inside my house every day for 10 years (how long we've lived here) there is no mold problem. There is occasional mold in the shower, but as I said, that gets condensation every day. Whatever the potential downsides of 60% humidity, it's great for musical instruments. Reeds like moisture.
You get a proper sized 2 stage system. And you be able to set your stat higher and save money. And you might just feel better in a few days.

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