Insulating unfinished basement

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BrownT10

Burning Hunk
Jun 1, 2021
187
Massachusetts
I am sure this has already been discussed, but posting anyway. I have a stove in an unfinished basement that previously have batten insulation in the ceiling, some if which I have pulled down to help heat the floor of the living space above. I also have the framed walkout end insulated with batten and the rim joist has been spray foamed. I have exposed concrete walls that obvious allow all of heat loss as well as the concrete floor. I previously had a VC Defiant that put off so much heat that the heat loss wasn't much of an issue because it heated the basement and first floor pretty easily but inefficient and I would need to cold start everyday and house temps would drop in the morning until I got I back up and going again.

I am now burning with an Osburn 3300 and have considered moving on from this to an Woodstock IS but want to give this stove an honest shot first. Burning about 2.5 to 3 cords this winter the stove rarely has been left cold. I am able to keep the house from 68-70 most times heating from the basement, so the temp swings are less than with the Defiant, I could regularly get the house to 75 if I wanted to before, too warm for me though.

Now I am looking for ways to reduce heat loss in the space the stove I in and will never be a finished space. I am trying to to this with minimal cost but I have thought about a couple options. First, foam board, but I don't want to have to cover it that code requires. Second, my father also runs his stove out th3 basement but his walls and floor are painted. I imagine that this cuts down on the heat loss some through porous concrete. His basement is all warmer than mine for sure, I it noticeable. I am not sure if it is the paint or the stove. I have seen thermal paint that supposedly helps reflect heat back towards the room, not sure if anyone has used that or how effective it is. I honestly don't feel I need to go crazy because I have gotten through this winter hardly turning the heat on in the first floor. I think I could increase efficiency with minimal cost. Any suggestions would be appreciated.

Also, considered a blower to add that would get air the the open stairwell quicker. What is the concensus on the effectiveness or a blower on a stove? I personally have not sued one.
 
Paint will not help. Don't waste the time and money. Glue foil-faced sheets of foam insulation to the walls?
 
I would certainly consider that if I don't have to drywall over it. Will need to check on that. Would be alot easier than prep and paint.
 
Make sure it's code legal. If so, be sure to use the right glue for that type of panel.
 
I now have a similar situation as yours. My house is a 1500 sq ft ranch, so my basement is also 1500 sq ft. My old stove was a Hitzer 983 that put out 100,000 btu and had little trouble heating both the basement and living space upstairs. It has been replaced with a Buck model 81 which is a non catalytic stove. So far this year I have burned much less wood, but once it gets below 25 degrees it cannot keep up and my furnace kicks on once or twice an hour. I have researched insulating as well. From what I've learned, if your house was built before 1990 you must first place a vapor barrier against the block or cement wall before adding insulation. Even though mold doesn't grow on Styrofoam, it can grow on the masonry itself. Last thing you want is mold growing where you cannot see. Spray foam is the best alternative but also the most expensive. You can use a plastic for the vapor barrier but all seems must be tapped securely before covering with foam ( boards or spray ).
Do you have a block off plate installed? You could be loosing heat from heating the chimney mass. Adding one did make a noticeable difference for me.
 
The stove is a freestanding stove that vents through the foundation wall via a class a tee. I assume you are talking about a block off plate for a fireplace? That is not my situation.
 
I've heard this type of rigid insulation can be left exposed because it is not as flammable as some other types. It is also what the MassSave contractor used to insulate the rim joist in my basement.


You'd probably want to double check with your local building inspector first to make sure they aren't going to make you frame and sheetrock over it, as you mentioned you're trying to keep the cost down.
 
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Bite the bullet and frame up the walls with 2x4. Then put in your batt insulation. Done. You might be surprised that the lumber may be cheaper than you realize? You can go 24" o.c. for basement walls. I like to put TYPAR directly against the concrete wall. The wording faces in to the wall, keeping the moisture on the concrete side. Tyvec doesn't work as well in this application imo.
Here, we also have a product called comfort board made by Rockwool (formerly roxul) It can be glued or pinned to the wall and left un-sheated . It is available in different thickness.
 
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I've heard this type of rigid insulation can be left exposed because it is not as flammable as some other types. It is also what the MassSave contractor used to insulate the rim joist in my basement.


You'd probably want to double check with your local building inspector first to make sure they aren't going to make you frame and sheetrock over it, as you mentioned you're trying to keep the cost down.
I was looking into this product you mentioned and also R-Tech, which I have confirmed can be left exposed.
 
I am finally looking to add some sort of insulation to my exposed concrete walls and am going g to go with fpil faced rigid foam board. The decision now is to do 1" or 2". I was going to do 2" at R13 or 1" around R6. I would rather do 1" but think I could regret it later then again the 1" is better than the exposed concrete I had. Not sure what difference I would notice either way. Thoughts?
 
I am finally looking to add some sort of insulation to my exposed concrete walls and am going g to go with fpil faced rigid foam board. The decision now is to do 1" or 2". I was going to do 2" at R13 or 1" around R6. I would rather do 1" but think I could regret it later then again the 1" is better than the exposed concrete I had. Not sure what difference I would notice either way. Thoughts?
They used 1” in my basement. No vapor barrier. No air sealing. How are you addressing those two points. I don’t think it would matter much 1 vs2” if it wasn’t well sealed and had a vapor barrier. Then the question is how are you doing your vapor barrier? I think that might be more important than 1 vs 2”. I don’t have the answer. I Just know that it matters.
 
No vapor barrier from my understanding. This coming from a builder. I am simply trying to slow the heat loss from the exposed concrete.
 
It's hard to regret too much insulation. If I was helping you I would still be encouraging you to look at the Rock wool Comfort board.....it's non flammable and will serve your application perfectly,. With TYPAR against the cement wall before applying the comfort board, you would have a very good wall that can be left exposed with no worries.....
 
It's hard to regret too much insulation. If I was helping you I would still be encouraging you to look at the Rock wool Comfort board.....it's non flammable and will serve your application perfectly,. With TYPAR against the cement wall before applying the comfort board, you would have a very good wall that can be left exposed with no worries.....
Yes comfort board is great insulation but it's also really expensive last time I checked
 
Comfortboard r6 = $1.66 sqft

Foil faced iso board r6.5 = $1.53 sqft

Not a huge difference for a much better fire resistance, when there doesn't seem to be any intention on covering a product. Often foil faced is not allowed to be left exposed ,when it burns its a terrible hazard
 
Comfortboard r6 = $1.66 sqft

Foil faced iso board r6.5 = $1.53 sqft

Not a huge difference for a much better fire resistance, when there doesn't seem to be any intention on covering a product. Often foil faced is not allowed to be left exposed ,when it burns its a terrible hazard
Well the price has evened out allot. When I did my basement about 6 years ago the price of comfort board was almost 3x foam board. Then I got lucky and found used foam for really cheap but that doesn't matter here.
 
I was told to not use foil faced in or near damp locations, it's a open cell and will take in moisture and lower the r value. We also have foundation foam that is closed cell, blue, gray, pink colored. 2" is r-10 and will stay that way when damp. Just giving a option, I really like rockwool for everything, it also can hold r-value and drain/dry back out with no ill effects
 
Vapor barrier would be on my must have list. Walls and floor.
Code probably says something like R10 or 14.

I’m trying to solve my moisture issues in my basemen. Half was finished the other was a 2 car garage that is now living space. 1” foam but the 2nd are just shot to block wall with no top wall plate. Don’t do that. I’ve never lived anywhere with a basement that didn’t have moisture/water issues at one time or another. From rain to clogged condensation drain to plumbing, water heater leaks to moister inflation. A dehumidifier has always been needed.

If I was doing a nice finished basement I would use close cell sprayfoam on the walls and up on the sill plate and joist heraldry. . Not super thick. Maybe r5. That would act as my vapor barrier. I really don’t want wood touching the block wall. Then would build a wall with the cheapest mineral wool insulation I could get. Making the bottom foot or two out of pressure treated 2x4 or just the footer.l. And I would not sheet rock down to the floor, but I would make sure I seal it well.

Recommendations. Floor vapor barrier. Even if doing carpet. But I don’t suggest carpet or real or engineered wood products. LVP it tile. If it feels cold get a rug.

From my research there are plenty of well intentioned way to go about building and insulating walls in the basement. Many end up with moisture problems.

Do you have gutters and good drainage? That’s on my list too.

The more I think about my basement the more I want to completely start over rip out the half that’s been finished and do/redo it all. But that’s money and time. So it will sit like like it is until I have money and time.
 
or until it becomes an urgent priority leading to money and time being allocated preferentially.
 
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You always want more closed cell than open, closed is the vapor barrier, but they can't spray thicker than 3" at a time, it's a possible fire Hazzard while it's healing, so they sell you on open cell to finish the job,. To get in and get out
 
First thing to do is get a sheet of plastic and tape a 4x4 section to the wall same to the floor. Give a few days and see how much moisture has collected. This is your starting point. They do make sealer for concret block and floors a bit pricy. the method i have all ways used is to leave apx 1/2" air gap between the concrete and the wall open at top an bottom for circulation (In other words a false wall which makes running electric easy. using solid plastic shims under the2x4from the floor or what ever to elevate the part at least 1/4" to provide circulation. It is best to build a subfloor again elevated over the concrete for any possible water intrusion rather than lay what ever directly on same. that way it is open to a drain. I have had homes that were as dry as as the Sahara desert in the basment and others that were more like standing in vacinity of a waterfall over the years. In one I used a poured epoxy system on the floor that worked well but I got the materials at 1/2 of wholesale- still wasn't cheap - no way could i do that now.
 
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All good info. I can't seem to find the Rockwool panels online with a quick search, will need to look a little more. I have a poured concrete foundation wall that I haven't had moisture or water issues since I built it 12 years ago. I have gutters and good drainage. Honestly, I am not concerned with moisture. Again, this will all be visible since I don't intent to cover whatever insulation I put on the walls. I am simply trying to minimize heat loss through a concrete wall as much as possible without breaking the bank. I have heated with exposed concrete walls for the first 10 years from the basement and kept the house plenty warm. I am trying to minimize the heat loss now because I now have an EPA stove that doesn't throw as much heat as my defiant did, so I want more heat up and not out. Interested in the Rockwool insulation, I assume it is 4x8 sheets like other rigid insulation? How much is a panel? Simply glue to wall or etter to screw?
 
I helped on project for friend using drycore subfoor years ago. I was impressed. Even if the basement has occasion leaks the water just flows under it I have it under my hot water storage tank. Their wall system is pretty impressive.
 
All good info. I can't seem to find the Rockwool panels online with a quick search, will need to look a little more. I have a poured concrete foundation wall that I haven't had moisture or water issues since I built it 12 years ago. I have gutters and good drainage. Honestly, I am not concerned with moisture. Again, this will all be visible since I don't intent to cover whatever insulation I put on the walls. I am simply trying to minimize heat loss through a concrete wall as much as possible without breaking the bank. I have heated with exposed concrete walls for the first 10 years from the basement and kept the house plenty warm. I am trying to minimize the heat loss now because I now have an EPA stove that doesn't throw as much heat as my defiant did, so I want more heat up and not out. Interested in the Rockwool insulation, I assume it is 4x8 sheets like other rigid insulation? How much is a panel? Simply glue to wall or etter to screw?
install

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