We are finishing a poured concrete, "walk out", basement, and installing a Hearthstone "Heritage" stove there. The finished walls are framed, insulated, and drywalled, and a "four season" addition has been added at the "walk out" end of the basement. Anticipating the wood stove, we left a 6 foot section of the exterior concrete wall near the "walk out" end of the basement unframed and uninsulated. With the addition, the concrete wall on the "walk out" end of the basement is now an interior wall, and is also unframed and uninsulated. The stove will sit in the corner, close to the concrete walls, with its back to the exterior wall (about half above grade) and it's right side close to the "interior" concrete wall. When I thought of this placement I was thinking...concrete walls...thermal mass...heat retention...good, good, good. Now I'm beginning to fear that the exterior wall will be more of a heat sink, carrying heat away from the stove and into the ground and the outside air. Is this something I should worry about? Should I consider a heat shield on the back of the stove, or insulating the outside of the basement wall in that section where we didn't insulate the inside? Any advice would be appreciated.
Basement Wood Stove and "Thermal Mass" of concrete walls
- Thread starter normbell
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Do something. That wall is going to suck the heat right out of that room. I know. I heat my unfinished basement office with a wood stove and have to burn the crap out of it because the walls suck up so much heat and deposit into the dirt on the other side of them.
MountainStoveGuy
Minister of Fire
Roospike
New Member
Roospike
New Member
Marty
Feeling the Heat
Roospike said:Ha ..........The "masters of fire" have spoken.
Now the rookies can chime in... poison it, shoot it, stab it, light it on fire, bury it... then insulate it and put a heat sheild on it.
I guess this is where people get into trouble when they think of "thermal mass" Thermal mass when used in the proper setting is great. Numerous studies have pretty much determined that a true thermal mass structure is of limited value, given today's lifestyles, unless placed in a desert. Like in the olden days in the northeast, it was common that a large exposed chimmney (large thermal mass) was placed in the middle of the house. Large thermal mass heated up by the fire, esposed on 2nd story, into a open room allowed people to live comfortably during winter. Mind you it was very common, yrs ago in these situations, to find the entire family sleeping in one room being kept comfortable by the large exposed chimmney. My house built in the late 1860's used this same principle up until 20 yrs ago. The old family which built the place and lived in by the future generations had a pot-belly stove, which heated an exposed, centrally placed brick chimmney. Chimmney is now only used to vent convection oven and microwave. So yes, in those cases, thermal mass did work. Take for instance, the 15 mile circle surrounding NYC, is generally 6 to 9 degrees warmer yr round than further out. All those concrete bulidings and the rivers, and ocean create in essence a heat sink. Great for winter heating bills, bad for summer electricity.
To get to your case, you need to insulate. You describe areas that are 1/2 above grade. Those areas could be covered on the outside with EPS board, and then succoced, sided, bricked, or whatever you like. the interior sheet-rocked and insulated. Especially on the walls that lead into the "all season" room. This is if you want to get the maximum benefit from your stove and allow it to heat the upper stories
To get to your case, you need to insulate. You describe areas that are 1/2 above grade. Those areas could be covered on the outside with EPS board, and then succoced, sided, bricked, or whatever you like. the interior sheet-rocked and insulated. Especially on the walls that lead into the "all season" room. This is if you want to get the maximum benefit from your stove and allow it to heat the upper stories
I have a different point of view you exposure to the concrete is limited one could try out your wood stove and see how it runs. one could use non combustiables in that wall metal studs
non backed fiberglass insulation and wondwe board facing this still would reduce positioning the stove too far into the room.
It is also a good idea to allow free air flow behind that stove. I would keep it out 12" to allow the air flow to extract the heat and dissipate heat from the stove. One does not want to over heat the stove
non backed fiberglass insulation and wondwe board facing this still would reduce positioning the stove too far into the room.
It is also a good idea to allow free air flow behind that stove. I would keep it out 12" to allow the air flow to extract the heat and dissipate heat from the stove. One does not want to over heat the stove
wg_bent
Minister of Fire
reaperman
Member
My question would first be what part of the country do you live in, and what else do you plan on doing with the basement??
It sounds like the walls are finished, but what about the basement floor? Carpet will add insulation to the floor, but without it, the floor will always be cool. Especially near the outside walls where the grade is sloping down and the walkout wall for sure. And what does all of the above mentioned have to do with a non-finished wall you ask? If a protected concrete floor is always cool, imagine what a uninsulated 10" thick concrete wall would feel like, not to mention what it would take to heat. Especially in a cooler state like my very own Minn. Good luck
It sounds like the walls are finished, but what about the basement floor? Carpet will add insulation to the floor, but without it, the floor will always be cool. Especially near the outside walls where the grade is sloping down and the walkout wall for sure. And what does all of the above mentioned have to do with a non-finished wall you ask? If a protected concrete floor is always cool, imagine what a uninsulated 10" thick concrete wall would feel like, not to mention what it would take to heat. Especially in a cooler state like my very own Minn. Good luck
pistonslap
Burning Hunk
I have poured concrete basement walls and a woodfurnace in the basement. Normally I get good radiant heat that goes up my stairwell to my first floor. It will normally get to 75-80 in my basement and 70-72 out of my ductwork. When it gets below 30 outside I still get the 70-72 out of the ducts but it can be anywhere between 58 and 65 in the basement. Concrete and brick are poor insulators.
Martin Strand III
New Member
"Thermal mass" usually refers to a system or material which is designed to "bank heat"; i.e., absorb heat as it is introduced from the source, hold it as permitted by the material's specific heat property and then release the "banked" heat into the room.
Concrete, cement or concrete block are not particularily good thermal mass materials nor are they used in good quality heating appliances for heat in those situations where "thermal mass" heating is desirable, and, to my knowledge, therefore are not referred to as materials associated with thermal mass.
That said, if left uninsulated, they will drain your basement living space of desired heat, albeit not as rapidly as other materials (rock, brick, soapstone or metal), making your wood stove heat output perhaps disappointing.
Aye,
Marty
Concrete, cement or concrete block are not particularily good thermal mass materials nor are they used in good quality heating appliances for heat in those situations where "thermal mass" heating is desirable, and, to my knowledge, therefore are not referred to as materials associated with thermal mass.
That said, if left uninsulated, they will drain your basement living space of desired heat, albeit not as rapidly as other materials (rock, brick, soapstone or metal), making your wood stove heat output perhaps disappointing.
Aye,
Marty
I have an IR camera that used to check the insulation on my house, and conrete (or any rock) is a *lousy* insulator.
Our house (old colonial) has 2 external Chimneys made out of stone. one is used, the other one is filled with rubble & sealed. They peirce the insulation of the house.
The _sealed_ chimney is visibly warmer than the walls.
Our house (old colonial) has 2 external Chimneys made out of stone. one is used, the other one is filled with rubble & sealed. They peirce the insulation of the house.
The _sealed_ chimney is visibly warmer than the walls.
Thank you all for your thoughtful comments on poured concrete basements, insulation, thermal mass, etc. It's certainly got me thinking about potential sources of heat loss for our new wood stove.
Just a couple of additional notes. 95% of the basement walls are well insulated on the inside. It's just that 6 foot section where the stove sits that isn't. We'll see how it goes. If it's a big heat sink, a heat shield on the back of the stove, and insulation on the outside of the wall in that 6 foot section are possibilities.
I'm going to be a little argumentative on the "thermal mass" comments. Poured concrete walls and floors are regarded as good "thermal masses" in "passive" heating applications where you want something that will absorb and store heat when a heat source is present, and radiate that heat when the heat source is absent. I quote Wiikipedia, "Concrete slabs typically have a high thermal mass." If the concrete walls that the stove sits near were very well insulated from heat loss to the outside, then when the stove was really cookin' the walls would be absorbing some of the heat, and when the stove cooled off the walls would radiate some of that heat back into the room. Right?
Just a couple of additional notes. 95% of the basement walls are well insulated on the inside. It's just that 6 foot section where the stove sits that isn't. We'll see how it goes. If it's a big heat sink, a heat shield on the back of the stove, and insulation on the outside of the wall in that 6 foot section are possibilities.
I'm going to be a little argumentative on the "thermal mass" comments. Poured concrete walls and floors are regarded as good "thermal masses" in "passive" heating applications where you want something that will absorb and store heat when a heat source is present, and radiate that heat when the heat source is absent. I quote Wiikipedia, "Concrete slabs typically have a high thermal mass." If the concrete walls that the stove sits near were very well insulated from heat loss to the outside, then when the stove was really cookin' the walls would be absorbing some of the heat, and when the stove cooled off the walls would radiate some of that heat back into the room. Right?
Corie
Minister of Fire
Yep.
If the wall was insulated on the other side HEAVILY, it would serve of something of a thermal mass. Since you have no insulation on its exterior though, it is simply acting as a part of the thermal circuit that takes heat from the stove and moves it into the atmosphere. The greatest temperature differential and the lower thermal resistance (highest thermal conductivity) is the area where most of the heat will be lost from, since heat, like electricity will always take the path of least resistance.
If you installed the stove in the center of the room and surrounded it on three sides with three solid walls of pour conrete which were insulated from contacting the floor, you'd have a pretty good little thermal storage unit.
If the wall was insulated on the other side HEAVILY, it would serve of something of a thermal mass. Since you have no insulation on its exterior though, it is simply acting as a part of the thermal circuit that takes heat from the stove and moves it into the atmosphere. The greatest temperature differential and the lower thermal resistance (highest thermal conductivity) is the area where most of the heat will be lost from, since heat, like electricity will always take the path of least resistance.
If you installed the stove in the center of the room and surrounded it on three sides with three solid walls of pour conrete which were insulated from contacting the floor, you'd have a pretty good little thermal storage unit.
Corie is correct. yes one might say by looking at the numbers concrete is poor for thermal storage. But ya also gotta look at the values: usually in joles/gram of substance. Concrete is on the lower side. However, given its density and cost (especially cost in terms of volume and density, it becomes a viable thermal storage mass. Water is better, but haven't seen a home, that has x-inches of water in between the siding and the interior. However, if ya look at places like International Falls, Minn they take all that snow and pack it up against the side of the house, and just remove it b4 the spring thaw as not to destroy the foundation
Corie
Minister of Fire
Yeah if you could surround the stove with a water jacket, that would be a SWEET thermal storage unit.
RonB
Feeling the Heat
Insulate that 6'section on the outside of the wall (ground side) and then don't use the heat shield, thus allowing the concrete wall to "bank" (absorb) some heat and give it back later. How is that any different than the soapstone stove or other sophisticated masonary wood stoves?-------Alas, I just answered why it won't work. That 6' section is still connected to the other remaining walls and they will draw the heat away and disperse it to the ground. I have block walls that are all insulated on the outside. The section that is behind my stove is not finished but bare and it radiates the heat really nice back into the room.
heydan
New Member
I have a friend who has a stove in an uninsulated basement. He has to burn a lot of wood every year and the ground around his house does not freeze in the dead of winter in MA!
Ah, yes. I'm beginning to get this. Your idea of a "thermal circuit" is very helpful, Corie. Even if I insulate the outside of the 6 ft. section of concrete wall, heat will be transfered along (within) the wall to adjacent areas where the wall is insulated on the inside, and the heat will wind up going out. It seems that the most useful single thing would be a heat shield on the back of the stove to get the heated air moving up and into convection patterns in the interior space. Anyway, thanks for the insights. Tomorrow the stove gets fired up for the first time, and we'll see what happens.
Corie
Minister of Fire
Glad I could.
When I was learning heat transfer I found the easiest way to understand everything was just to equate it all to electricity. In reality, the two are so similar is silly!
When I was learning heat transfer I found the easiest way to understand everything was just to equate it all to electricity. In reality, the two are so similar is silly!
Martin Strand III
New Member
I have a Harman TLC 2000 wood/coal stove in my unfinished basement with concrete floor. It sits right next to the concrete block foundation for the main floor masonry heater and even has outside air coming to it through this block wall. See it here:
https://www.hearth.com/gallery/pics/woodcoal/source/harmanbasement.html
This block wall is not an outside wall but sits near the middle of the basement floor plan. Never the less, it takes several hours of a hot (1000* F stack temp) coal fire to warm the near by concrete floor and adjacent wall before much appreciable heat is noticed in the room. If that block wall were an unfinished outside wall, my feeling is that it would take appreciably longer and heat much less effectively despite it's brute nature.
Now here's my chance to get in another dig at those puny noisey gear driven maintenance laiden rabbit food eating heaters: A pellit stove here would not have a chance.
Aye,
Marty
https://www.hearth.com/gallery/pics/woodcoal/source/harmanbasement.html
This block wall is not an outside wall but sits near the middle of the basement floor plan. Never the less, it takes several hours of a hot (1000* F stack temp) coal fire to warm the near by concrete floor and adjacent wall before much appreciable heat is noticed in the room. If that block wall were an unfinished outside wall, my feeling is that it would take appreciably longer and heat much less effectively despite it's brute nature.
Now here's my chance to get in another dig at those puny noisey gear driven maintenance laiden rabbit food eating heaters: A pellit stove here would not have a chance.
Aye,
Marty
velvetfoot
Minister of Fire
Nobody's talked of the floor. Does it pay to do something there? I'm thinking maybe an inch of foam board and something on top...
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