Humidity Settings vs. Temperature / Humidity Tables

By Tim Carter
©1993-2010 Tim Carter

Summary: If humidity in your home is low, and you are getting zapped, you likely have air leaks. Plug them, or get a humidifier. Avoiding condensation within a tight home is not easy, however. You must adjust the humidity down as the outside temperature falls to avoid indoor "rain" on your windows and elsewhere you may not see. Use this relative humidity chart to keep comfortable as the temperature changes.

The following indoor relative humidity settings should provide you with a good comfort level. Almost all humidifiers come equipped with a humidistat. This device works just like your thermostat. You set the humidistat to a desired humidity level. When the humidity reaches that point, the humidifier stops working.

Suggested Indoor Humidity Settings

Outside Temperature	-10 F	0 F	10 F	20 F	30 F
Recommended Indoor Relative Humidity	20%	25%	30%	35%	35%

The following table gives you an idea of just how "dry" outside air is when it is brought indoors and then heated to room temperature. If you have low humidity in your home, you have air leaks. The dry outside air is mixing with your humid air and lowering the overall humidity. Plug your air leaks and you may not need a humidifier.

Indoor vs. Outdoor Humidity Comparison Tables

Outside Temperature	Outside Relative Humidity	Indoor Humidity when air is heated to 72 degrees F
-10 degrees F	40%	1%
	60%	2%
	80%	2%
0 degrees F	40%	2%
	60%	2%
	80%	5%
10 degrees F	40%	4%
	60%	5%
	80%	7%
20 degrees F	40%	6%
	60%	8%
	80%	11%
30 degrees F	40%	8%
	60%	13%
	80%	17%

Comments:

Jason
05 Jan 2008, 06:39

What settings should I set my attic fan humidistat and thermostat too? The fan came with the house and seems to run constantly. I've read your columns on powered attic fans and am somewhat confused if I even need one. I get ample sum on the roof during the day and keep the house temperature at 68 (winter) and 75 (summer). I'm currently running a Heat Pump system with oil heat back-up. I know the previous owner had a small mold build up in the attic before he removed the trees that shaded the entire roof. It was all irraticated with replacement wood and insullation as the final steps in the process.

Thank you for your attention--Jason

AsktheBuilder
05 Jan 2008, 10:21

Jason,
Humidity = 40%
Temperature = 115F

bill howell
14 Feb 2008, 23:55

I'm wondering if there's a way to save on propane heating costs by increasing or decreasing the humidity inside my house. For example, if I increase the percentage of humidity, will it then require setting the thermostat higher to still feel comfortable or will the increase in humidity store more heat such that I can set my thermostat lower and feel just as warm.

AsktheBuilder
15 Feb 2008, 17:24

Bill,
You want to save money on your heating bill? Simple. Turn the thermostat down to 60 F and wear long underwear, a hooded sweatshirt and whatever else you need to stay warm. Raising the humidity too much will cause huge issues.

Michael
28 Feb 2008, 07:40

I have HUGE condensation problems in my home which is just under 4 years old. I have no attic fan and only ridge vents in the roof. We even get moisture on the windows during spring, fall and even summer sometimes. I keep he humidstat at 10-20% during the winter and that does not make a difference. Any advice?

AsktheBuilder
02 Mar 2008, 15:30

Michael,
Yes, read ALL of my columns in the Condensation category.

Nancy
03 Mar 2008, 08:12

We just moved into a new home in the Northeast 6 months ago. We have oil heat. The builder forgot to install a humidifier, we have noticed significant cracking and separating in the kitchen cabinets and wood trim throughout the house. The house has a guarantee and the builder is now installing the humidifier . He is telling us "that this should solve the problems".

My question to you is what, if any, are the long term effects of this mistake?

AsktheBuilder
08 Mar 2008, 10:33

Nancy,
There should be no long-term effects so long as the builder replaces ALL of the damaged wood.

Don Pines
12 Jun 2008, 09:33

I just purchased a house with my wife and it seems the humidity is too high. We are having a problem trying to get it under control and discern where the cause is. Now that it is June, I have a dehumidifier in the basement(very moist down there) as the carpeted floors in the above level always seem damp. The shingles on the roof are curling as I am guessing they are getting to hot because the attic is so big, but is this causing humidity down below? I have a Holmes humidity gauge that always shows the house above 60% and as high as 75%. Also, I find there is a cold air that seems to hang around the ceiling as I put my hand up and walk around the house. Even when the weather is dry, the humidity will be higher inside the house than it is outside. Air conditioning will dry the house, but seems to be a temporary fix. I should also add that the house was built in 1990. Any suggestions?

srini
22 Jul 2008, 01:01

Hi
I live in a fairly hot and humid climate - Chennai, india, on the sea shore. My friend has severe sinus problems and it is recommended that the humidity is around 20% for such cases. SO if the outside temperature is around 30 deg C and humidity is around 70-80%, what should I set the airconditioner to arrive at 20% humidity? PLease let me know the workings also so that i understand it
Thanks.
srini

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