Wood heat issues. Need advice

Long post here but we have a problem and are looking for opinions/advice and I want to give as much details as possible…

Attached are pictures of our wood stove, floor plan and some cold, damp corners of our house. We have a 3 bedroom ranch house in Michigans Upper peninsula. It gets cold here. Like lots of single digit highs most winters and many times we get as cold as -20s at night. We have baseboard heat around most of the house which is fueled by propane. Our first several winters here we were spending well over $2,000 for propane so I installed a Drolet Escape 1800 woodstove. This is our 4th winter primarily heating with wood. I love this stove and it seemed to be doing a great job heating the house besides when we hit streaks of weather that stays below zero. Then the propane kicks in occasionally or Ill just let the stove burn out and run strictly propane until the weather warms a bit.

We’re just coming out of a cold streak and my wife noticed dampness on the back bedroom walls along with a funky smell. We moved some stuff around and found a problematic amount of moisture on walls, baseboards a trim. Some trim is even starting to mold. We do run a small humidifier in our bedroom, and that has the worst moisture, but the other back bedroom has no humidifier and is also damp. The problematic areas are highlighted in yellow in the drawing.

Normally when its pretty cold out, Ill keep the 2 unused bedroom doors shut just so its easier to heat the rest of the house. The basement is about 42 degrees when we’re only heating with the wood stove. Not necessarily an issue in the basement since its just storage. But we have been trying to rid this house of mold for years now and I cant be rotting it because of the way we heat it in winter. Cold bedrooms and basement are fine with me but mold and moisture are not. Aside from some condensation on windows when its really cold out, the kitchen, dining room and living room all stay comfortably warm and dry from the wood stove.

Ideas I have:

Reside the house and add exterior insulation. We have 2x4 walls with aluminum siding. Id like to add insulation and do wood siding but might not happen for a few years

Keep all the bedroom doors open if we’re using the stove.

Use fans to blow some air from the stove down the hallway

Add another layer of insulation around the sill plate

Install a ceiling fan between the dining and living room to distribute heat. Although i dont know how much of an effect that would have on the back rooms.

Add another wood stove into the open concept basement so that the floor is heated more evenly. I could put the stove underneath the bedrooms and theres already a door in the foundation for loading firewood into the basement. Probably could use a smaller stove than whats upstairs and add thermal mass to it as well. Just would need to figure out the best way to do the chimney. And how to get a wood stove down the basement steps…

I love this wood stove. I love doing firewood, tending the fire, watching the flames, heating food and coffee on the stove and drying things out near it. But I cant add more moisture and mold problems to this damn house. Any advice or opinions are appreciated!

I am not an expert, but battled similar problems in a similar house in a similar climate.

i) If the basement is unfinished, insulating the rimjoist is cheap and fairly easy; you can use insulation board and/or sprayfoam.
  Even more than insulation, plugging draft gaps around the rim joist and elsewhere is important; many older houses will have perforations from past cable, plumbing, etc.
ii) Get furniture, books, etc, in away from the walls to allow air circulation; ex. wooden blocks to space out bed headboards from the wall.
iii) Do you have, or could you put, zone control on your propane baseboards to give a little heat in the problematic bedrooms?
iv) Moving air to and from the area with the stove would help, although it can be difficult on a single level house.
Theory says you should push cold air towards the stove; my experience was better pulling warm air from the stove.  Either way the air flow needs a return.  Eyeballing your nice stove, it maybe a little undersized to heat the whole house?
v) If you reside, adding insulation board underneath the new siding, properly installed, will likely help alot, as long as the insulation extends down below the problematic spots.  It was transformative in my similar past house.  But you need to avoid creating a condensation/frost layer within the wall causing hidden rot.
vi) Can you tolerate doing without the humidifier?
vii) You could possibly put insulation board on the problematic inside wall and drywall over that; besure you achieve a vapour barrier so you do not get condensation between layers of the wall.
viii) You may find you 'chase' wet spots around; solve one, the next coldest spot becomes the new condensation spot.
good luck.  Doug

Douglas Campbell wrote:I am not an expert, but battled similar problems in a similar house in a similar climate.

i) If the basement is unfinished, insulating the rimjoist is cheap and fairly easy; you can use insulation board and/or sprayfoam.
  Even more than insulation, plugging draft gaps around the rim joist and elsewhere is important; many older houses will have perforations from past cable, plumbing, etc.
ii) Get furniture, books, etc, in away from the walls to allow air circulation; ex. wooden blocks to space out bed headboards from the wall.
iii) Do you have, or could you put, zone control on your propane baseboards to give a little heat in the problematic bedrooms?
iv) Moving air to and from the area with the stove would help, although it can be difficult on a single level house.
Theory says you should push cold air towards the stove; my experience was better pulling warm air from the stove.  Either way the air flow needs a return.  Eyeballing your nice stove, it maybe a little undersized to heat the whole house?
v) If you reside, adding insulation board underneath the new siding, properly installed, will likely help alot, as long as the insulation extends down below the problematic spots.  It was transformative in my similar past house.  But you need to avoid creating a condensation/frost layer within the wall causing hidden rot.
vi) Can you tolerate doing without the humidifier?
vii) You could possibly put insulation board on the problematic inside wall and drywall over that; besure you achieve a vapour barrier so you do not get condensation between layers of the wall.
viii) You may find you 'chase' wet spots around; solve one, the next coldest spot becomes the new condensation spot.
good luck.  Doug

Thanks for the input!

The rim joists were already insulated but it was stinky and dirty so I replaced it all last summer. Theres room for another layer though so I may add more.

No holes in the wall in those areas, but being corners and wirh aluminum siding, theres definitely a likelihood of some cold air getting into the corners. Ill inspect more closely soon.

Definitely going to rearrange the rooms to keep things away from the outside walls

Not sure about zone control with the boiler but I may look into it.

According to the stoves ratings, it should be slightly oversized for our house. If I keep it ripping all the time the living room is almost unbearable but the back rooms are warmer. I think we need to move that hot air around as best as we can

We will cut the humidifier for the most part. Maybe just use it when it becomes noticeably dry and will monitor the humidity inside now with a hygrometer

Still seems like adding another smaller stove to the basement below that end of the house would be great. But all these other things should help and be quicker and cheaper. Might add ceiling fans to those back rooms too

Your problem is potentially two fold, primary is lack of insulation combined with lack sufficient air flow to keep the interior wall surface from frosting in extreme cold. this is the first.

When the interior warms up enough this frost turns to damp, cycle this enough times and it turns to mold.

The second probable cause is inadequate vapour barrier.  Fiberglass insulation rapidly loses it insulation value if interior vapour can penitrate it.

If poorly installed and or no vapour barrier is present, installing exterior insulation, usually foam, will rot your house from the inside out as it is a vapour barrier itself  and is on the wrong side of the heating surface in this case, will trap moisture within the wall cavity.

Myself, I would take one of your smaller rooms that has an outside wall and rip off the interior surface of it, drywall? Then you will know what you are dealing with.

Bob Hutton wrote:Your problem is potentially two fold, primary is lack of insulation combined with lack sufficient air flow to keep the interior wall surface from frosting in extreme cold. this is the first.

When the interior warms up enough this frost turns to damp, cycle this enough times and it turns to mold.

The second probable cause is inadequate vapour barrier.  Fiberglass insulation rapidly loses it insulation value if interior vapour can penitrate it.

If poorly installed and or no vapour barrier is present, installing exterior insulation, usually foam, will rot your house from the inside out as it is a vapour barrier itself  and is on the wrong side of the heating surface in this case, will trap moisture within the wall cavity.

Myself, I would take one of your smaller rooms that has an outside wall and rip off the interior surface of it, drywall? Then you will know what you are dealing with.

Ive been through the walls in this house in a few places, including the northwest corner which is the coldest, dampest spot and also gets the worst winds. Our walls, from inside out are drywall, fiberglass insulation, plywood sheathing, tar paper then aluminum siding with that backer board. Although that specific corner had a leaking roof valley and wall rot so the backer board was trash. I replaced it with plywood cut to strips that fit behind the aluminum siding panels. The siding corners are aluminum caps with no backing so its cold there. That corner of the bedroom is 33 degrees at the floor right now and in the basement right below its 16 degrees even with fiberglass insulation stuffed around the sill plate.

Should I add another layer of insulation around the sill plate and maybe spray foam behind the siding corner caps?

As of now, we are blowing warm air from the stove down the hallway, bedroom doors are all open, humidifiers are unplugged, trim has been dried off, cleaned and the worst of it is removed. Running air purifiers in the corners and will rearrange the bedrooms so that nothing is pushed up against the outside walls

Hi
I am not familiar with aluminum siding systems.
16F (?) in the basement seems way too cold; there must be air infiltration there?
Maybe through cracks?
For rim joists I made plugs of insulation board sealed in with sprayfoam to generate a vapour barrier.
If the previous fiberglass insulation was wet that suggests condensation; also dirty insulation usually means air has been moving through it.
The wall system seems to rely on the inner surface paint as vapour barrier.
GreenBuildingAdvisor online might have guidance.
As Bob wrote you do not want to bury the condensation surface and create rot within the wall layers.

Brody Ekberg wrote:

Our walls, from inside out are drywall, fiberglass insulation, plywood sheathing, tar paper then aluminum siding with that backer board.

No vapor barrier then?

Hi Brody,
This might be a bigger step than you want to take, but it is worth serious thought.
Currently, you are burning wood in your metal stove (that you dearly love)
To heat the back bedrooms, you must make the living room stifling hot. This is a classic result of trying to heat with metal.
I also suspect you are burning plenty of wood, perhaps more than you would like.

I suggest using bricks for heating instead.
500-1000-plus bricks heated to several hundred degrees will transform your home!
It will be warm throughout the entire living area, and even the basement will benefit from the upstairs warmth.
You will be floored by how warm your house can be! And how much less wood you will use!
Yes, your floor might need extra support. Although it could be built in the basement, mass heaters are best suited to where you live.
Yes, adding exterior insulation and switching to wood siding rather than aluminum will make a huge difference, but not as much as a batchbox core in a double-skin bell.

I have lived in northern Montana with metal wood stoves my entire adult life.
Temperatures here are not nearly as extreme as those you lucky folks receive, but below-zero and single-digit highs are normal for short bursts.
Fire is lit in the fall and remains lit 24 hrs a day until late spring (May-June)
With your kind of temperatures, wood use is substantial.
There is always the troubling thought in the back of your head about chimney fires...
With a mass heater, even where you live, you will not need any fire at all overnight!  Think about that, no stoking before bed, no stoking at dark thirty.
And the very best part in my mind is strolling to the bathroom at dark thirty with no robe because it is that warm!!!
Your fire will be out quite a bit because you just don't need one.
Your wood use will realistically be cut in half, and your propane baseboard heat will hardly run.

Building yourself, with all new materials, you may spend $1200-$1500.
Locate used brick, and your cost could plummet to $500 or less.

Yep, there is a fair bit of labor needed to build one, while you are laboring, think about the firewood you will not be laboring to get...

Two loose ideas: 1. warm air moves from the stove up to the ceiling and then out to the outside walls, cools and drops and is sucked back toward the stove along the floor.  Just having fans here and there, especially on the floor blowing out, is working against this natural flow. What we have are small fans that mount near the top of doorways or in corners where wall meets ceiling, to push warm air out, and then a box fan on the floor blowing cool air back toward the stove, so as to speed up the natural cycle that's already there.
2. As a stopgap measure while you pursue the mold and moisture issues, remember borax and boric acid are your friends.  Dissolve either or both in boiling water to saturation and then paint onto any moldy or half rotted surface of wood, drywall, etc. and let it dry and crystallize. This will kill and prevent all kinds of mold and rot.  Once it dries you can wipe off the dry crytals and paint over it if you like.  

generally speaking from my experience burning wood in stove or fireplace dries everything out. propane heat creates all kinds of moisture and condensation unless if it is a system where propane heats boiler and steam or hot water go through radiators or other such devices or in floor piping

Douglas Campbell wrote:Hi
I am not familiar with aluminum siding systems.
16F (?) in the basement seems way too cold; there must be air infiltration there?
Maybe through cracks?
For rim joists I made plugs of insulation board sealed in with sprayfoam to generate a vapour barrier.
If the previous fiberglass insulation was wet that suggests condensation; also dirty insulation usually means air has been moving through it.
The wall system seems to rely on the inner surface paint as vapour barrier.
GreenBuildingAdvisor online might have guidance.
As Bob wrote you do not want to bury the condensation surface and create rot within the wall layers.

The 16 degrees was surface temperature checked with an infrared camera on the inside of the rim joist area in the basement. But theres definitely some air infiltration. It faces our prevailing winds and is a corner. I dont know how air wouldn’t infiltrate that, especially since the siding corner caps are just hollow.

The previous insulation was dirty because the basement had a layer of black mold, was way too humid, had carpenter ants and roof leaks when we moved in. All of those problems have been addressed since.

Michael Helmersson wrote:

Brody Ekberg wrote:

Our walls, from inside out are drywall, fiberglass insulation, plywood sheathing, tar paper then aluminum siding with that backer board.

No vapor barrier then?

Not unless the fiberglass insulation backing or tar paper counts. And actually our walls arent just drywall. They seem to be 1” thick made of 2 separate layers. The layer closest to the outside seems like drywall but the layer we can see inside the house seems different. Its harder than regular drywall. Can’t pound a nail in without busting chips out. Its like drywall but harder. And not all uniform thickness. The 2 attached pictures were taken from a single piece I cut out of the wall and theres almost 1/8” different in thickness

thomas rubino wrote:Hi Brody,
This might be a bigger step than you want to take, but it is worth serious thought.
Currently, you are burning wood in your metal stove (that you dearly love)
To heat the back bedrooms, you must make the living room stifling hot. This is a classic result of trying to heat with metal.
I also suspect you are burning plenty of wood, perhaps more than you would like.

I suggest using bricks for heating instead.
500-1000-plus bricks heated to several hundred degrees will transform your home!
It will be warm throughout the entire living area, and even the basement will benefit from the upstairs warmth.
You will be floored by how warm your house can be! And how much less wood you will use!
Yes, your floor might need extra support. Although it could be built in the basement, mass heaters are best suited to where you live.
Yes, adding exterior insulation and switching to wood siding rather than aluminum will make a huge difference, but not as much as a batchbox core in a double-skin bell.

I have lived in northern Montana with metal wood stoves my entire adult life.
Temperatures here are not nearly as extreme as those you lucky folks receive, but below-zero and single-digit highs are normal for short bursts.
Fire is lit in the fall and remains lit 24 hrs a day until late spring (May-June)
With your kind of temperatures, wood use is substantial.
There is always the troubling thought in the back of your head about chimney fires...
With a mass heater, even where you live, you will not need any fire at all overnight!  Think about that, no stoking before bed, no stoking at dark thirty.
And the very best part in my mind is strolling to the bathroom at dark thirty with no robe because it is that warm!!!
Your fire will be out quite a bit because you just don't need one.
Your wood use will realistically be cut in half, and your propane baseboard heat will hardly run.

Building yourself, with all new materials, you may spend $1200-$1500.
Locate used brick, and your cost could plummet to $500 or less.

Yep, there is a fair bit of labor needed to build one, while you are laboring, think about the firewood you will not be laboring to get...

Ive wanted a rocket mass heater since Ive learned of them but as far as i know, they arent legal here. But if I were to put a small wood stove in the basement I would certainly add mass around it one way or another. We really dont burn much wood. This is winter #4 and Im keeping track, but the first 3 winters we used 2-3 cords of wood. Really isnt bad at all compared to what most people I know burn in a winter.

Also, we have rigged up a couple fans blowing warm living room air down the hallway and its made quite a difference. The living room is more comfortable, about 65 and the hallway and back bedrooms are noticeably warmer.

Alder Burns wrote:Two loose ideas: 1. warm air moves from the stove up to the ceiling and then out to the outside walls, cools and drops and is sucked back toward the stove along the floor.  Just having fans here and there, especially on the floor blowing out, is working against this natural flow. What we have are small fans that mount near the top of doorways or in corners where wall meets ceiling, to push warm air out, and then a box fan on the floor blowing cool air back toward the stove, so as to speed up the natural cycle that's already there.
2. As a stopgap measure while you pursue the mold and moisture issues, remember borax and boric acid are your friends.  Dissolve either or both in boiling water to saturation and then paint onto any moldy or half rotted surface of wood, drywall, etc. and let it dry and crystallize. This will kill and prevent all kinds of mold and rot.  Once it dries you can wipe off the dry crytals and paint over it if you like.  

We put a fan on a shelf near the wood stove aiming down the hallway and another fan on a shelf in the corner of the living room blowing towards the hallway. Its made a noticeable difference in warming up those back rooms. Also, hallway has space above the entrance like a door would have. We have considered opening that up and mounting some sort of fan in there but dont know if its structural or hollow in there or what. Not even sure how to find out besides opening it up.

Didnt know that about borax but thanks for the information, Ill try to remember that!

]

Brody Ekberg wrote: And actually our walls arent just drywall. They seem to be 1” thick made of 2 separate layers. The layer closest to the outside seems like drywall but the layer we can see inside the house seems different. Its harder than regular drywall. Can’t pound a nail in without busting chips out. Its like drywall but harder. And not all uniform thickness. The 2 attached pictures were taken from a single piece I cut out of the wall and theres almost 1/8” different in thickness

Sounds like thermal mass.

bruce Fine wrote:generally speaking from my experience burning wood in stove or fireplace dries everything out. propane heat creates all kinds of moisture and condensation unless if it is a system where propane heats boiler and steam or hot water go through radiators or other such devices or in floor piping

our experience is the same. The house is dry as hell unless we add moisture in winter. December was rough so I put a kettle on the stove and started running 2 small humidifiers, one in the dining room and one in our bedroom. Think I overcompensated because the humidity got up to 50-60%…

And our propane does heat a boiler that pumps hot water through radiators. So probably no added moisture there

Where you have known cold spots that are getting damp issues you need to guarantee good air circulation. Pull back furniture away from walls, remove fabric like curtains etc...

The problem is that the cold spots are at a lower temperature (at least some of the time) than the air in the room. The warm air in your living space holds lots of moisture, as that circulates through the house it cools and becomes saturated, then condenses out in the cold spots.

You can address the cold spots directly by insulating as you have already suggested.

Otherwise you need to address the humidity in the air itself. In our case we installed a powerful dehumidifier upstairs on the landing, in the cooler part of the house. It runs through the damp UK autumn when the relative humidity is high. We were emptying about 4 litres a day from it to start with. The fabric of the building holds a lot of moisture in the timber, plaster work etc... This has the advantage of making the house both feel warmer and then be easier to heat as well.

Michael Cox wrote:Where you have known cold spots that are getting damp issues you need to guarantee good air circulation. Pull back furniture away from walls, remove fabric like curtains etc...

The problem is that the cold spots are at a lower temperature (at least some of the time) than the air in the room. The warm air in your living space holds lots of moisture, as that circulates through the house it cools and becomes saturated, then condenses out in the cold spots.

You can address the cold spots directly by insulating as you have already suggested.

Otherwise you need to address the humidity in the air itself. In our case we installed a powerful dehumidifier upstairs on the landing, in the cooler part of the house. It runs through the damp UK autumn when the relative humidity is high. We were emptying about 4 litres a day from it to start with. The fabric of the building holds a lot of moisture in the timber, plaster work etc... This has the advantage of making the house both feel warmer and then be easier to heat as well.

We moved everything out of the way of those cold damp corners and have been running air purifiers nearby and thats helped a lot. Plus we have a couple fans blowing warm wood stove air down the hallway towards the bedrooms and have been leaving the bedroom doors open. Turned off the 2 humidifiers and let the kettle on the stove run dry and now the back rooms are down to high 40% humidity range. I guess thats good for the house but its drying my wife and I out…

What should I insulate the aluminum siding corner caps with? Im hesitant to use spray foam as its almost permanent but my only other idea is fiberglass.

Be careful with sprayfoam under aluminum corner caps.
The foam expansion may blow the caps off (I once had similar (?) aluminum corner caps on horrible 'beaverboard' press wood siding).
And spray foam is a vapour barrier so you could create condensation/rot pockets under the foam.

Maybe think of insulating the corners from  the inside, sort of like a vertical cap, like a crown moulding?

Brody Ekberg wrote:

Michael Helmersson wrote:

Brody Ekberg wrote:

Our walls, from inside out are drywall, fiberglass insulation, plywood sheathing, tar paper then aluminum siding with that backer board.

No vapor barrier then?

Not unless the fiberglass insulation backing or tar paper counts. And actually our walls arent just drywall. They seem to be 1” thick made of 2 separate layers. The layer closest to the outside seems like drywall but the layer we can see inside the house seems different. Its harder than regular drywall. Can’t pound a nail in without busting chips out. Its like drywall but harder. And not all uniform thickness. The 2 attached pictures were taken from a single piece I cut out of the wall and theres almost 1/8” different in thickness

I admjt to being lazy about reading this whole thread, ans this might already have been answered, but it looks like plaster over rocklath. I have it too. It was kind of a intermediate step between drywall and plaster, with all the advantages, and disadvantages of both. I actually really like it (when I am not trying to hang something from the wall).

Very off topic but to pound a nail, predrill. Cut any holes with a diamond tipped saw and expect a ton of dust. Do not use drywall anchors. To find studs, buy a 'Stud Pop's magnetic stud finder. The rocklath is secured by nails over the studs.

Back to your actual question...

My solution to uneven heat in a house I try to spot heat with a cheaper source, (pellets/wood), while keeping cold and moisture in check, is to run my boiler for a few hours each day, usually first thing in the morning to bring the house up to temp after I let it cool off overnight and restart the stove. In my case, I do it to prevent freeze, but it would also likely help your moisture issues. I dramatically lower my oil consumption by doing this, vs. running just oil, and IMO the house is more comfortable. Seeing those pics, I wonder if the discolouration in the floors of the two back bedrooms is from the previous people doing what you were doing...

Long term, I plan to add mini split heating to that side of the house, but this works for now and is cheaper than mold issues or a frozen pipe in my basement.  If I were you, and considering installing a basement woodstove, I would put it on the opposite side of the house from the upstairs stove - I have one in the basement and one on the main floor, both on the same side, which STILL leaves the back bedrooms cold even when I run both.

Also - for circulation with fans, push cold air along the floor towards the stove, with fans at floor level, not towards the bedrooms. For warm air, run ceiling fans to wash it down the walls, or fans in the top corners of doorways, pushing warm air to the bedrooms, which, as it cools and sinks, gets returned by the lower fans. You want to create a circulation pattern of air.

I'm also considering insulating my rim joists. I've been mulling just Rockwool, since I also have concerns about spray foam and rot in a humid climate with a house with no vapour barrier... Plus, Rockwool is inflammable and doesn't offgas. Other sources say my plan will CAUSE rot because it causes condensation on the surface of the joist, so I keep mulling it and haven't done it. So this is certainly not advice.

Probably not the case, but you mention having a propane baseboard heating system as well. Are there any pipes of any kind going through there? If you do, you might have had a frozen pipe and the baseboard heating system is leaking, other plumbing is leaking including drain lines that might have froze, or even water infiltration from the siding or roof. Water travels a lot longer than what people give it credit for including water that travels uphill from wind and capillary action.

By your description it sounds like it came on suddenly. That's not typically a moisture problem in a system that has been in place for four years.

You might want to rule those water leaks out before thinking it is a moisture issue.

Douglas Campbell wrote:Be careful with sprayfoam under aluminum corner caps.
The foam expansion may blow the caps off (I once had similar (?) aluminum corner caps on horrible 'beaverboard' press wood siding).
And spray foam is a vapour barrier so you could create condensation/rot pockets under the foam.

Maybe think of insulating the corners from  the inside, sort of like a vertical cap, like a crown moulding?

Maybe Ill just use fiberglass insulation. I could just pull a handfull off of the paper backing and shove it under the caps. For this winter, Ive just piled snow up on the area and that should insulate better than anything else until it melts

Catie George wrote:

Brody Ekberg wrote:

Michael Helmersson wrote:

Brody Ekberg wrote:

Our walls, from inside out are drywall, fiberglass insulation, plywood sheathing, tar paper then aluminum siding with that backer board.

No vapor barrier then?

Not unless the fiberglass insulation backing or tar paper counts. And actually our walls arent just drywall. They seem to be 1” thick made of 2 separate layers. The layer closest to the outside seems like drywall but the layer we can see inside the house seems different. Its harder than regular drywall. Can’t pound a nail in without busting chips out. Its like drywall but harder. And not all uniform thickness. The 2 attached pictures were taken from a single piece I cut out of the wall and theres almost 1/8” different in thickness

I admjt to being lazy about reading this whole thread, ans this might already have been answered, but it looks like plaster over rocklath. I have it too. It was kind of a intermediate step between drywall and plaster, with all the advantages, and disadvantages of both. I actually really like it (when I am not trying to hang something from the wall).

Very off topic but to pound a nail, predrill. Cut any holes with a diamond tipped saw and expect a ton of dust. Do not use drywall anchors. To find studs, buy a 'Stud Pop's magnetic stud finder. The rocklath is secured by nails over the studs.

Back to your actual question...

My solution to uneven heat in a house I try to spot heat with a cheaper source, (pellets/wood), while keeping cold and moisture in check, is to run my boiler for a few hours each day, usually first thing in the morning to bring the house up to temp after I let it cool off overnight and restart the stove. In my case, I do it to prevent freeze, but it would also likely help your moisture issues. I dramatically lower my oil consumption by doing this, vs. running just oil, and the house is more comfortable. Seeing those pics, I wonder if the discolouration in the floors of the two back bedrooms is from the previous people doing what you were doing...

Long term, I plan to add mini split heating to that side of the house, but this works for now and is cheaper than mold issues or a frozen pipe in my basement.  If I were you, and considering installing a basement woodstove, I would put it on the opposite side of the house from the upstairs stove - I have one in the basement and one on the main floor, both on the same side, which STILL leaves the back bedrooms cold even when I run both.

Also - for circulation with fans, push cold air along the floor towards the stove, with fans at floor level, not towards the bedrooms. For warm air, run ceiling fans to wash it down the walls, or fans in the top corners of doorways, pushing warm air to the bedrooms, which, as it cools and sinks, gets returned by the lower fans. You want to create a circulation pattern of air.

I'm also considering insulating my rim joists. I've been mulling just Rockwool, since I also have concerns about spray foam and rot in a humid climate with a house with no vapour barrier... Plus, Rockwool is inflammable and doesn't offgas. Other sources say my plan will CAUSE rot because it causes condensation on the surface of the joist, so I keep mulling it and haven't done it. So this is certainly not advice.

I sent the pictures to a few local contractors and they agreed its plaster over drywall. And yes, stud finding is tricky!

As for the boiler running daily, it tends to anyway since my wife and I are both gone enough during the day for the house to cool down enough to the point that it needs to kick on. Usually it isnt for long enough to actually heat up though because as soon as I get home I get the stove ripping again. I think long term, Id like to add another small stove directly under those cold rooms, insulate the outside of the house when residing and add ceiling fans to the bedrooms.