Ideal basement humidity %

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packet
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Ideal basement humidity %

Post by packet » Wed Jun 21, 2017 4:27 pm

Is there such a number?
What ranges would there be for percent humidity to call it bad, OK, good, or ideal?
At what point do you need a dehumidifier upgrade or addition?

All the same question really... :/

Basement is finished-ish... as in it's rough, being used for storage and a workshop of sorts (thus there are tools and the like with metal bits), but it's not living space.

Thank you for your time.

:beerCheers,
packet
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ByThePond
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Re: Ideal basement humidity %

Post by ByThePond » Wed Jun 21, 2017 4:44 pm

Because I have wine stored in barrels and bottles in my basement, I keep the humidity at 50%, as a compromise between a lower number for general purposes, and a somewhat higher number to prevent excess evaporation. The humidity would be quite high otherwise.
I think the recommendation is something like 40% for a general space, and about 60% for wine cellaring. Tools and electronics might like it dryer, though. YMMV.

Found this:
Mold and mildew flourish when the relative humidity level is above 80%; therefore all basements—finished or unfinished—should be kept at or below 50% relative humidity. In order to maintain that humidity level, May suggests using a dehumidifier and measure the humidity level often.Jan 15, 2013
6 Tips for Healthy Below-Grade Spaces - Basement Health Association

user5027
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Re: Ideal basement humidity %

Post by user5027 » Wed Jun 21, 2017 5:27 pm

Less than 60%, except 70% in the cigar humidor.

KT785
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Re: Ideal basement humidity %

Post by KT785 » Wed Jun 21, 2017 6:00 pm

After some work completed last summer, ours fluctuates between 50-55% this time of year and runs lower during the winter.

Last year, we had a new HVAC system installed and as part of that work, I had an air return installed in the main room of my finished basement (there were four air supplies in the basement, but no return). Since the air return and new system were installed--including a variable speed blower and communicating thermostat that is supposed to help with humidity control--the basement has stayed in the 50-55% range on its own. Previously, I used a dehumidifier from spring to fall but now I only have to use it in the "bridge" period when we're not consistently running the central air or the furnace.

For point of reference, our basement is mostly finished though we do keep wine (and my supply of good German beer :beer) in the unfinished, mechanical room area which tends to stay a little cooler than the rest of the basement.

Spirit Rider
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Re: Ideal basement humidity %

Post by Spirit Rider » Wed Jun 21, 2017 7:24 pm

If you are storing clothes, paper, metal in the basement, you will want to keep humidity more like 40% - 45%. The clothes and paper tend to get musty when the humidity gets above 50%. Also, some exposed metal can be prone to rusting/pitting above 50%.

Yooper
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Re: Ideal basement humidity %

Post by Yooper » Thu Jun 22, 2017 7:12 am

Point of reference. The past 7 years anytime the humidity gets above 52 I turn on the dehumidifier until it drops below 50 and then turn it off - usually once in the morning and once at night. Essentially spring through fall. Never had a musty smell. We store papers/books/clothes/etc., basically everything that's not upstairs. Having said that, it's an open basement without any separate rooms. If there were separate rooms you'd have to account for airflow into those rooms to keep their humidity under control as well.

On a personal note, I think airflow is almost as important as humidity level. Upstairs during the spring/summer/fall the humidity is always above 50%, usually WELL above, and yet there's never a problem. I think it's because the air is constantly being "stirred up" due to household activity. Again, just my uneducated guess.

beardsworth
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Re: Ideal basement humidity %

Post by beardsworth » Thu Jun 22, 2017 7:37 am

OP, not quite sure why you chose to post a question about basement humidity on a forum that's mainly about personal finance. But if you just do a regular Google search for your own thread title phrase "ideal basement humidity," in quotes, you'll find all sorts of results from home care websites.

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packet
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Re: Ideal basement humidity %

Post by packet » Thu Jun 22, 2017 9:05 am

beardsworth wrote:OP, not quite sure why you chose to post a question about basement humidity on a forum that's mainly about personal finance...
Because I'm trying to gauge how big of a unit I need to purchase... :)

I have a dehumidifier currently, but it's struggling to keep the percentage at ~55/60% and is running constantly. Either I up that percentage, get a bigger unit, or add a similar unit... which is why I posted in the consumer issues forum.

Besides, Boogleheads are way more knowledgeable than Google-U !

Thank you all for your replies. Definately sounds like I need to spend a few dollars to get this under control.

:beerCheers,
packet
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Spirit Rider
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Re: Ideal basement humidity %

Post by Spirit Rider » Thu Jun 22, 2017 9:39 am

Personally, I consider Bogleheads to be one of the best sources of information on just about any consumer issue and any issue for that matter.

Bogleheads seem to engage in the same discipline that lead them here for personal finance and investing. They investigate, determine and trade off quality and cost to determine there own personal value. I may not always agree with other points of view, but this is a high volume site that brings a great wealth of knowledge on any area. On any given day your might find; doctors, lawyers, mechanics, HVAC contractors, people in the building trades, economists, teachers, professors, and maybe even a rocket scientist. All willing to share their diverse knowledge, skills and experiences.

mancich
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Re: Ideal basement humidity %

Post by mancich » Thu Jun 22, 2017 9:49 am

Spirit Rider wrote:Personally, I consider Bogleheads to be one of the best sources of information on just about any consumer issue and any issue for that matter.

Bogleheads seem to engage in the same discipline that lead them here for personal finance and investing. They investigate, determine and trade off quality and cost to determine there own personal value. I may not always agree with other points of view, but this is a high volume site that brings a great wealth of knowledge on any area. On any given day your might find; doctors, lawyers, mechanics, HVAC contractors, people in the building trades, economists, teachers, professors, and maybe even a rocket scientist. All willing to share their diverse knowledge, skills and experiences.
+1000 Overall a very smart group of people!

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hand
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Re: Ideal basement humidity %

Post by hand » Thu Jun 22, 2017 11:13 am

See Chapter 2, Lesson 3 "Humidity" from the EPA:
https://www.epa.gov/mold/mold-course-chapter-2

"Indoor relative humidity (RH) should be kept below 60 percent -- ideally between 30 percent and 50 percent, if possible."

I target for just under 50% for my finished basement.

Note that basement humidity problems can typically be addressed in multiple ways:
1) Mechanical dehumidification (bigger dehumidifier)
2) Better Air sealing of basement (rim joists) to limit hot moist outside air entering basement
3) Insulation of basement walls to prevent / reduce condensation on the walls

If you will be in the house for a while, insulation & air sealing (at least for the rim joists) is likely to both have a financial payback and improve comfort / humidity.

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