Humidity questions....

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

Spletz

Member
Apr 30, 2014
123
West Michigan
All-

We're burning 24/7 of late. First year home heating via an FPX insert and loving it! Very warm in, single digits out.

However, bride is concerned with the very low humidity in the home (less than thirty%). We have a humidifier on the propane furnace, which is set to move air constantly (fan only, no propane heat).

Without a freestanding stove, any suggestions to increase humidity? Would the humidifier on my furnace be of any use when the furnace is only set to fan, not heat?

Experimenting with a bowl of water immediately close to the insert on the hearth tonight.

Suggestions?
 
All-

We're burning 24/7 of late. First year home heating via an FPX insert and loving it! Very warm in, single digits out.

However, bride is concerned with the very low humidity in the home (less than thirty%). We have a humidifier on the propane furnace, which is set to move air constantly (fan only, no propane heat).

Without a freestanding stove, any suggestions to increase humidity? Would the humidifier on my furnace be of any use when the furnace is only set to fan, not heat?

Experimenting with a bowl of water immediately close to the insert on the hearth tonight.

Suggestions?
Get a decent stand-alone humidifier with a humidistat.
 
Get a decent stand-alone humidifier with a humidistat.

Yep, and otherwise tighten up your home. Low indoor humidity in the winter means your house is drawing in cold air from outside and losing warm, conditioned air.
 
  • Like
Reactions: fox9988 and Spletz
Yep, and otherwise tighten up your home. Low indoor humidity in the winter means your house is drawing in cold air from outside and losing warm, conditioned air.
You may very well be right! Recently, the weatherstripping was removed from the front door - some 15' away from the insert ( long story). I knew this would require attention, but perhaps sooner than later. Thanks!
 
You may very well be right! Recently, the weatherstripping was removed from the front door - some 15' away from the insert ( long story). I knew this would require attention, but perhaps sooner than later. Thanks!
An offbeat suggestion-- if you have a clothes dryer, get a kit to vent it indoors through a container of water, rather than venting outside. Any time the humidity gets too low, I just do a load of laundry. These inexpensive doobies catch all the lint in the water, so there's no lint flying around even around to the dryer.

A bowl of water next to the insert isn't going to do jack. I have a large steamer on top of my stove, and although it goes through about a gallon-and-a-half a day or more in winter, it only makes a very small dent-- just enough so I don't give myself and the cats an electric shock when I pet them.
 
An offbeat suggestion-- if you have a clothes dryer, get a kit to vent it indoors through a container of water, rather than venting outside. Any time the humidity gets too low, I just do a load of laundry. These inexpensive doobies catch all the lint in the water, so there's no lint flying around even around to the dryer.

A bowl of water next to the insert isn't going to do jack. I have a large steamer on top of my stove, and although it goes through about a gallon-and-a-half a day or more in winter, it only makes a very small dent-- just enough so I don't give myself and the cats an electric shock when I pet them.
That clothes dryer trick only lasts an hour or two.
 
Search this forum or the internet: Essick or Essick Moist Aire

Home Depot, Sears, Lowes or online -Whole house humidifier that has a humidistat, adjustable fan and large cassettes/tanks that are easy to fill once per day in the heavy use time of yr. Different sized units by sq/ft of home. I've used one now for 4 yrs or more, 4 to 5 months per year, and it works as designed, and will replace it with another if it ever fails. Expect to replace the paper filters at least annually ~ 25 bucks per set at HD.
 
An offbeat suggestion-- if you have a clothes dryer, get a kit to vent it indoors through a container of water, rather than venting outside. Any time the humidity gets too low, I just do a load of laundry. These inexpensive doobies catch all the lint in the water, so there's no lint flying around even around to the dryer.

Instead of a clothes dryer I use a drying rack. Why spend money to blow warm, humid air outside when you can keep both inside? The clothes will also last longer. With two young kids we have no shortage of dirty clothes and each load from our old washer certainly puts several pounds of water in the air. Results may not be that impressive with a newer washer that spins at higher speeds.

A bowl of water next to the insert isn't going to do jack. I have a large steamer on top of my stove, and although it goes through about a gallon-and-a-half a day or more in winter, it only makes a very small dent-- just enough so I don't give myself and the cats an electric shock when I pet them.

1.5 gl is pretty sizeable. The small humidifiers from the big-box store can usually do between 2 and 5 gls per day.
 
Yep, and otherwise tighten up your home. Low indoor humidity in the winter means your house is drawing in cold air from outside and losing warm, conditioned air.

Can you explain this a little more ? not doubting you but I always thought that the low humidity was from the wood fire drying the moisture from the air. That's why a humidifier is used to put the moisture back in the air.......If the house is drawing cold moist air from the outside wouldn't it help add to the dry indoor air? [not that anyone wants that]
 
Air humidity is given in relative terms based on how much water it can hold at a given temperature. At 100% the air is saturated at that temperature and any additional water vapor will condense as dew. Air that is at 70 F has a higher capacity to hold water than air at lower temperature. Estimated from this chart: http://en.wikipedia.org/wiki/File:Relative_Humidity.png:

Outside air at 30 F and 50% relative humidity holds about 2 g of water per kg of air. When you bring that air into the house and heat it up to 70 F the amount of water in it does not change. Thus, the 2 g of water will give you only about 15% relative humidity compared to the about 10 g you would need to reach 50% relative humidity. The missing 8 g need to be added artificially if you want the indoor air to also be at 50%. The stove (or any other heat source) dries not out the air. Instead, it raises the temperature which raises the saturation point for the humidity and it pulls in less moist outside air (unless an OAK is installed). That's why people think the stove "dries out the air". Nevertheless, no stove can make water just "disappear". ;)

Modern, airtight homes can actually have problems with accumulating too much moisture due to human activity (showering, cooking, sweating etc.) because they loose much less conditioned air to the outside and therefore pull in less cold air with a low moisture content. That's why mechanical air handlers are often installed in an energy efficient construction to make sure there is enough air exchange and the moisture stays balanced.
 
Yes, be careful about overdoing humidification. There have been many posts on this subject here. In a recent one I referenced an article in the current issue of the Journal of Light Construction (http://www.jlconline.com/mold/petri-dish-house_o.aspx), documenting an extreme example of this. It all comes down to where that added few gallons a day of moisture goes. Not all of it makes it to the outside air; it can accumulate where you don't want it.
 
We have a Aprilaire 700 humidifier on the furnace duct. Anytime the fan comes on, the humidifier (as well as the UV lamps and hepa filtration system) turns on as well. However that is the exception to the rule as the Quad works all day and the furnace comes alive only early in the morning.
I am still looking into a stand alone humidifier. Like the design and features of the Winix, it only uses 16 watts.
 
Last edited:
All-

We're burning 24/7 of late. First year home heating via an FPX insert and loving it! Very warm in, single digits out.

However, bride is concerned with the very low humidity in the home (less than thirty%). We have a humidifier on the propane furnace, which is set to move air constantly (fan only, no propane heat).

Without a freestanding stove, any suggestions to increase humidity? Would the humidifier on my furnace be of any use when the furnace is only set to fan, not heat?

Experimenting with a bowl of water immediately close to the insert on the hearth tonight.

Suggestions?

A pretty normal and healthy range for humidity inside a home is between 30-50%. Above that and you are at greater risk for mold and bacteria, below it things like viruses can thrive and there is the ever annoying static electricity. Also, if you have a house full of hardwood floors like mine, you risk damaging them if the humidity is too low for too long.

Does the FPX insert have an outside air kit? On my Jotul stove, the outside air kit pulls the combustion air from outside the house and I find this makes a night and day difference as to how much humidity stays in the house. I can burn my stove all day long and the humidity doesn't drop. As soon as I fire up my old school masonry fireplace, the humidity starts to drop fast.

I have a whole house humidifier connected to my natural gas furnace too. However, the humidifier only works when the system is in heat mode, not when I am just using the circulation fan. Yours may very well work without the heat being on, so you will have to check. I suspect the heat is required for the humidifier to work since cool air won't hold moisture that well.

If you do need to use a stand alone humidifier, don't cheap out too much or buy something too small. I have a couple of honeywell ones that I bought a while back at a big box store on sale. They are large units and it requires two of them going full blast to make much difference.
 
Further to my last post - how much humidifier you need depends a lot on the size of your house and how air tight it is. At any rate, if the humidifier is rated for 600 sq ft, don't expect it to make a huge difference on its own in a house 3 or 4 times that size.
 
If you can, try installing an Outside Air Kit. When I did, my humidity went from 10-20% to 50-56%. They make your distant rooms warmer and probably save about 3-5% on heating as well -- not much, but in the right direction.
 
If you can, try installing an Outside Air Kit. When I did, my humidity went from 10-20% to 50-56%. They make your distant rooms warmer and probably save about 3-5% on heating as well -- not much, but in the right direction.
That's amazing. I may try this, as your not the first person I've seen post this.
 
Yep, and otherwise tighten up your home. Low indoor humidity in the winter means your house is drawing in cold air from outside and losing warm, conditioned air.
What would you consider acceptable humidity levels in the winter with insert burning 24/7? Would like to get an idea how tight my house is.
 
What would you consider acceptable humidity levels in the winter with insert burning 24/7? Would like to get an idea how tight my house is.

There are so many variables that the tightness of the house will be hard to determine just by humidity levels. My guess is that if it is below 20% it indicates you have a problem but there may well be one already above that. Look into a blower door test to measure how tight your home is. There may be a program in your state that could help with the cost.
 
There are so many variables that the tightness of the house will be hard to determine just by humidity levels. My guess is that if it is below 20% it indicates you have a problem but there may well be one already above that. Look into a blower door test to measure how tight your home is. There may be a program in your state that could help with the cost.
Thank you
 
If you can, try installing an Outside Air Kit. When I did, my humidity went from 10-20% to 50-56%. They make your distant rooms warmer and probably save about 3-5% on heating as well -- not much, but in the right direction.

Exactly right. The key to maintaining higher humidity levels in the winter is to minimize the amount of outside air drawn into the house. An OAK is key to this, as it eliminates the need to supply all that combustion air.
 
Status
Not open for further replies.