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HVAC-what is the minimum or ideal humidity % you would look for?

3,483 Views | 20 Replies | Last: 1 yr ago by The Fife
fishnvet
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AG
Sorry if this has already been discussed, but all the good HVAC discussions has me wondering what kind of % humidity a system should be striving for. What is an ideal or at least a minimum? Would the standard be different in the central Texas area vs. the coastal bend? If the humidity % is too high then what kind of humidifier would be recommended? I have seen quotes for a 1000 sq. ft house for $5000 for a humidifier set up which seems way beyond atrocious, but I have also seen references for a $200-300 system in posts here. Does anyone have a link for a simple one that could be installed-seems pretty straightforward.
Personal situation:
2200 sq. ft older house between Austin and San Marcos-runs avg humidity 50% for last month which seems fine.
850 sq. ft foamed small newer house in the coastal bend-runs 59% avg humidity for last month-seems very comfortable but if needed I would try to drive the humidity down further.
Thanks for any info.
fishnvet
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AG
Also, I mean DE-humdifier. Can't believe I typed humidifier........
rancher1953
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50-60 % is prefect. Too little and it drys skin out, too much and your are uncomfortable. 50-60 range is perfect sweet spot.
vmiaptetr
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AG
I have a whole home dehumidifier. I keep my house set at 40%.

From the EPA:




EDIT: We have a variable AC that handles the majority of the humidity load. The dehumidifier doesn't kick on very often. To Rancher1953's point, we did experience some chapped lips when we first started setting our RH to 40%. That being said, we increased our water intake (which was below the daily recommended amount, and I believe skin is one of the last things that is allotted water in your body) and that fixed the problem.
Jason_Roofer
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It's tough to accomplish less than 45% without some outside influence like dry air masses due to physics in the air handler. Either way, I like mine between 45-55%. More humid than that feel damp, and less humid than that dries me out.

But keep in mind the drier it is, the higher temp you can feel comfortable at. We usually keep our system at 80 during the day and it's comfortable.


Right now, I'm the evenings, it's 100 degrees at 8pm but it's 18% humidity and while it is hot, it's not bad. That's opposed to Houston when it was 80 degrees and 90% humidity.
Houston-Austin-Dallas-San Antonio - Infinity Roofing - https://linqapp.com/jason_duke --- JasonDuke@InfinityRoofer.com --- https://infinityrooferjason.blogspot.com/
tgivaughn
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AG
If your HVAC system is properly designed in central Texas, you should have no RH% concerns, as should be 50% or less. Rather than a dehumidifier, variable stage or sometimes dual stage HVAC system might be elected to better serve.

Dehumidifiers have been discussed many times on The Money Pit radio talk show and their website may store some of these talks.

We inherited a few allergies and the shots really don't help. We like any RH below 45% and dust mites need anything above 50% to survive. That said, one of us is medically recovering, so a 80F thermostat rules for their comfort. So a lower RH ... aids in comfort for all.
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Absolute
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AG
For your coastal home I would get something like this, but maybe a smaller one.

Amazon Basics Dehumidifier - For Areas Up to 4,000 Square Feet, 50-Pint, Energy Star Certified https://a.co/d/fjaqzHI

We have one like this and it is helpful.

Have friend with a house on SPI and they run 4 or 5 of these.

Personally, I wouldn't invest in a Built in unit at 5k.
fishnvet
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AG
I agree, Absolute, that price was way out of line, and I bet I could get one installed for much less. But for the one you mentioned, does it suck a lot of power? The house is only 850 sq. foot and foamed, so I might even get away with the 35 pint model. Does the drain hose also work OK? Since I am not always there, I was thinking about putting it in the (conditioned) attic space and draining the line out the AC drain line-would be very convenient and with no insulation above the ceiling any moisture pulled from the attic I would think would also help with the living space. I wouldn't always be there to empty the water collection reservoir.
CapCity12thMan
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AG
Four our house - 3300 sq ft, 2 -story:

warm season - stays in the 40-48% humidity range. Once it gets into the 50% range, I bump the thermo down a degree.

cold season - 40-44% range, but when if gets to low/mid-30s it gets dry in here. Skin feels it. I think at one point this winter I saw 24%.

As of this posting our house is 74 deg and 42% humidity
BenTheGoodAg
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AG
Warm season - highs of 40% indoors

Cold season - typically 20% indoors, but I've seen as low as 14% on our thermostat.

We have the opposite problems here and many people will even install whole-home humidifiers.

Some of my kids knuckles will get so dry they start to crack and bleed, and I think a lot of people deal with that.
Jabin
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Don't those small humidifier pump heat back into your house, which makes your AC work harder and offsets any comfort gained via lower humidity?
Absolute
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AG
Haven't check the power draw. It runs all the time and pulls a lot of moisture out. Old one died earlier this summer after several years and I could tell a difference without it.
Garrelli 5000
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AG
Guitars want 45-50% relative humidity to prevent damage from long term humidity or arid exposure. I would target that year round.

Edit: that's just ideal. Ymmv pending cost and what you consider comfortable.
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tgivaughn
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AG
Good information post and assume this would also be ideal for furniture, as the Int.designers always preached.
Ten words or less ... a goal unattainable
XXXVII
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I'm renting a place that regularly sees 60% humidity inside which seems high based on this discussion, but I'm not sure if the tool I'm measuring with is accurate. I am just using one of those little Accurite humidity/temperatures sensors I got off amazon.

What's the best humidity sensor to use?
El_duderino
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The $15 or so acu-rite one is spot on from my experience
XXXVII
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But don't you need to calibrate it? What's the best way to do that? Put it outside and match the humidity and temperature to what a weather app says?
El_duderino
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Oh I just compare mine to my thermostat and it's identical almost 100% of the time. There's the calibration instructions it comes with you can use
XXXVII
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El_duderino said:

Oh I just compare mine to my thermostat and it's identical almost 100% of the time. There's the calibration instructions it comes with you can use


I lost those instructions. Is it only possible to get accurate if you know the temperature and humidity of where you're measuring?
Absolute
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AG
Herein lies a potential problem with this discussion. Even the thermostat can be wrong. Mine was way off because they didn't seal at the wall and it was mixing attic and interior readings. Cheap devices may be off, way off. How much are you willing to spend?

Personally, I use humidity as amother General guideline. I don't live and die by the number I see. I know mine runs a little high, I have a Dehumidifier to help. Beyond that, I don't get too specific.

Had a client recently that was all upset at her builder because one bedroom was 1 percent (yes ONE PERCENT) higher on the cheapo Amazon humidity sensor she had purchased. Thought the whole hvac system needed to be replaced. I did not even try to explain all the potential error factors that were present in her data and theories.
The Fife
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Charleston, SC, 54% RH at 75 degrees while it's hot and raining outside. Life's good!
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