My wife tells me all winter long, “We need more moisture in our home. This wood burning stove dries everything out!” I have always been skeptical, especially since our humidity gauge reads between 35% – 50% all winter long. I have done some research on this, and here is what I found. (Not that I have to prove her wrong, but…).
Does a wood burning stove dry our home more than other heat sources? Yes, it does, but not for the reason you would expect. There are several reasons that you “feel” drier in winter when burning wood for heat. Here is what I found.
Local Climate
The primary driver of the moisture content in a home or humidity is where you live. The difference between living in Wyoming (the last time we were in Yellowstone in February the average humidity was 14%), and the mid-west USA is massive. No matter how well you insulate and seal your home from the elements, the outside moisture content gets in. Even the house sealing wrap that is applied to new homes to keep the air from blowing through a home allows the moisture to pass in and out.
The inside humidity of a home can be varied but is highly dependent on the outside regional humidity levels.
Wood Heat and Humidity
How does a wood burning stove affect the humidity in a home? There are three ways that wood burning stove can affect the humidity in a home.
Most wood stoves heat a single room to a high temperature, and that very warm room also raises the temperature of the other rooms in a home.
High heat (warm air) will naturally dry the air (think clothes dryer). So if the room that the wood burner is in is 5 to 10 degrees above the other rooms in the house, it will feel dryer because it will be dryer.
The second issue that affects a home with a wood stove has to do with how the fire is fed air. Typically, the air to feed the fire is drawn from the room where the stove is located. The stove draws air out of the room, and that air must be replaced from somewhere. If there is no other air supply for the stove, the air will be drawn from the outdoors through the floor (crawl space), leaky window, or any air gaps the home has. The outside air is dryer in the winter; again, the wood burner seems to produce dry heat.
The third reason a wood heat system is dryer than a furnace system is this. In a home that uses a natural gas or LP gas furnace, a humidifier will normally be added to the duct pipes to add humidity to the home in the winter. This humidifier is not adding moisture to the air if the forced air system is off. Not using this humidifier also creates a dryer home when burning wood.
Remedies
There are remedies for each of these issues if you desire a more humid home while heating with wood in the winter. It will take some planning and a particular stove that has specific air input and air output types. This is what is required.
First, the wood stove should be at the lowest level of the home if you have multiple floors in your home. This allows for heat to naturally rise from the stove and heat the floors and rooms above the stove level.
Second, if the stove has a forced air system (drawing air around the firebox with a blower) connect this output to your existing forced air return using your furnace as an air handler for your wood burner. Then you can run the fan on the furnace system and move warm air throughout the home.
This will also give you the ability to use your humidifier (attached to the furnace duct system) to moisten the air also using your existing ductwork.
Third, and this probably the most valuable tip in the list, would be to add a duct pipe to feed the firebox air from the outdoors.
This makes the burning system a closed loop system, drawing air from outside and expelling air to the outside for the firebox. This will also greatly reduce the air pulled from the outside the home to the inside because of the wood stove system.
Humidity
We feel warmer when the air is more humid and cooler when it is dryer. That is why additional humidity is desired in the winter, and less is better in the summer. There are additional methods to add moisture to a home in the winter.
Setting a cast iron pot on top of the stove can help. Keep the pot full of water to steam the air. I recommend a cast iron, so if it runs dry, the pot will not be damaged or cause an issue to the stove.
If you have an area where you store wood near the stove, keep some green (fresh cut) wood in the room. This will add moisture to the home. The green wood can be burnt once it dries to 10% to 20% moisture content. And then rotate in more green wood.
Finally, a stand-alone humidifier can be run in the room with the wood stove. There are many models that can even be connected to a water supply which will remain full automatically.
A balance must also be achieved. Too much humidity can cause windows to condensate and mold to form on outside walls and in corners. This will be worse in areas where the air is restricted, such as behind furniture and where items may be stored along walls.
Raising the humidity above 55% will generally be too high, especially in homes with less air movement. Keeping an eye on the humidity level will save woodwork from stains or moisture damage and wall from becoming moldy.
Conclusion
A wood burning stove can make a home dryer which in turn “feels” warmer than humid heat. There are remedies that will reduce this effect. Some are simple, some take planning.
Just be aware of the big picture if you burn wood or plan on burning wood. The more efficient your stove is (drawing outside air, for example), the better the system will work and feel (more humid) in the cold winter months.
Research the stove and the method of air draw and/or air handling system it has. This can lead to a wood burning system that will heat your home efficiently and keep your home as warm as you expected it to “feel”!